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PT6A-27/28/34 TRAINING MANUAL
Pratt Wh,itney Canada
PT6A-27 / 34 Series Turboprop
TRAINING MANUAL
June 1999
PRATT & WHITNEY CANADA
C) 1999 Pratt & Whitney Canada, Inc
Printed in Canada
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION I
INTRODUCTION
PT6A-27 / 34
0 0 ,.., ,w ...)
TRAINING USE ONLY
INTRODUCTION
000000000000Q0U000000000Q000QUO000000 9,
Pratt & Whitney Canada
This publication is issued by the CUSTOMER TRAINING CENTRE, Pratt & Whitney Canada, Longueuil, Quebec, Canada.
This document is to be used FOR TRAINING USE ONLY. The data contained herein does not replace or supersede the information
contained in the appropriate airframe or engine maintenance manuals or other official publications.
For information concerning this manual, contact the P&WC customer training centre,
Tel.: 1-450-468-7774 or Fax : 1-450-468-7834.
For technical queries, contact the P&WC technical support HELP DESK. (24 HOURS SERVICE)
TEL.: USA & CANADA
OVERSEAS
FAX
1-800-268-8000
1-450-647-8000
1-450-647-2888
Pratt & Whitney Canada on Internet : http://www.pwc.ca/
There is a page for technical support and then a page for Customer training with schedule and enrolment forms.
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION
PT6A SERIES TURBOPROP
HEAVY MAINTENANCE COURSES
TC267-94-03
STUDENT SCHEDULE:
Course duration:
Breaks:
Lunch period:
7 days (42 hours)
Classes 8:30 to 16:10
20 minutes at 10:15 & 14:45
12:00 to 13:00
STUDENT HANDOUTS:
The appropriate training manual is given to each student.
COURSES AVAILABLE:
PT6A-20
PT6A-15/21/27/28/34/36/1 12/1 14/135
PT6A-41/42/45
PT6A-50
PT6A-60/61/64/65/66/67
PT6A-68
COURSE OBJECTIVES:
To teach the fundamentals and skills necessary to operate and maintain the engine. At the end the student should be in a
position to perform all Maintenance operations covered during the course.
NUMBER OF STUDENTS:
6-8
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION IV
LOOLL-,..)000000C)0000000000000000Ü000000Ü00C)00000
TABLE OF CONTENTS
INTRODUCTION:
Scope of Course
Publications
Service Bulletins / Compliance Codes
Course Syllabus
Engines Covered
Powerplant Aircraft Applications
VIII
IX
XIII
XIV
XXI
XXIII
CHAPTER 1: Engine Overview
Abbreviation
Features
Right Front View
Right Rear View
Left Rear View
Left Front View
Engine Operation
Stations
Bearings and Flanges
Externals
1.4
1.6
1.8
1.9
1.10
1.11
1.12
1.14
1.16
1.18
CHAPTER 2: Compressor Section
Inertial Separator
Inlet Case
Compressor Rotor Assembly
Compressor Bleed Off Valve
PT6A-27 / 34
Gas Generator Case
Compressor Wash
Compressor Section Troubleshooting Chart ...
2.10
2.12
2.14
CHAPTER 3: Hot Section
Operation
Combustion Chamber Liner
A27 - Exit Ducts - Small & Large
A27 - Compressor Turbine Vane Assembly ...
A34 - Exit Ducts - Small & Large
A34 - Compressor Turbine Vane Assembly ...
Compressor Turbine
Power Turbine Vane Ring Area
Power Turbine Stator Housing
Power Turbine
Exhaust Duct
Number 3 & Number 4 Bearing Area
Hot Section Troubleshooting Chart
3.2
3.4
3.6
3.8
3.10
3.12
3.14
3.16
3.18
3.20
3.22
3.24
3.26
CHAPTER 4: Gearboxes
2.2
2.4
2.6
2.8
Reduction Gearbox (RGB)
Accessory Gearbox (AGB)
Accessory Gearbox Input Drive
TRAINING USE ONLY
4.2
4.4
4.6
INTRODUCTION V
CHAPTER 5: Oil System
Oil System Description
Oil System Servicing
Oil Pressure Regulation & Filtration
Troubleshooting Chart
5.2
5.4
5.6
5.8
CHAPTER 6: Secondary Air System
Secondary Air System Description
Accessory Gearbox Breather
Bearing Sealing
6.2
6.2
6.2
7.2
7.4
7.6
7.8
7.10
CHAPTER 8: Ignition
8.2
8.4
Glow Plugs
Igniter Plugs
CHAPTER 9: Performance
Performance Check
ECTM (Engine Condition Trend Monitoring)
Engine Troubleshooting
HSI & TBO
Rotor Components - Service Life
PT6A-27 / 34
C)
Fuel Management
Engine Fuel System
Fuel Heater
Fuel Pump
Fuel Control Unit (FCU) Hydraulic Section
Fuel Control Unit (FCU) Pneumatic Section
Fuel Control Operation
Starting Flow Control
Flow Divider & Dump Valve
Fuel Nozzles
Fuel control Unit manual Override
Fuel Control Unit (FCU) Adjustments
Fuel Control Unit Troubleshooting Chart
10.2
10.4
10.6
10.8
10.10
10.12
10.14
10.16
10.18
10.20
10.22
10.24
10.28
9.2
9.4
9.9
9.10
9.12
TRAINING USE ONLY
J
9.14
9.15
9.16
9.17
9.18
9.19
9.20
9.21
9.22
9.23
CHAPTER 10: Fuel System
CHAPTER 7: Engine Indicating System
Description
T5 Indicating System
T5 Troubleshooting Chart
Torque System Description
Chip Detector
Operating Limits
PT6A-21- Operating Chart
PT6A-27- Operating Chart
PT6A-28- Operating Chart
PT6A-34 / 34B / 34AG - Operating Chart
PT6A-36 - Operating Chart
PT6A-114 - Operating Chart
PT6A-114A - Operating Chart
PT6A135 - Operating Chart
PT6A-135A - Operating Chart
0 0 0 0 0 0 (.) 0 0
0 0 (.)
INTRODUCTION VI
C) 0 0 0 Li JUO U
C) 0 U
CHAPTER 11: Propeller System
Description
Governing Mode
Forward Beta Mode
Reverse Beta Mode
Primary Blade Angle (PBA) Check
Feathering
Overspeed Protection
Governor Adjustment
Reversing Cam
Propeller System Troubleshooting Chart
11.2
11.4
11.6
11.8
11.10
11.12
11.14
11.16
11.18
11.20
CHAPTER 12: Maintenance Practices
Hot Section Inspection
Borescope Inspection
Hot Section Tools
CT Tip Clearance Measurement
HSI Inspection
Shroud Segment Grinding
Fuel Nozzle Check
T5 Check
Basic Engine Rigging
Rear Linkage Rigging
Front Linkage Rigging
Fuel Lever and Propeller Lever Rigging
Post Run Up Adjustments
Summary of Controls
PT6A-27 / 34
12.2
12.4
12.6
12.8
12.10
12.13
12.14
12.15
12.16
12.18
12.20
12.22
12.24
12.26
TRAINING USE ONLY
INTRODUCTION VII
SCOPE
This training manual contains information pertaining to the description, operation, maintenance and troubleshooting of the
PT6A-27/34 engines. This training manual is intended for classroom use only and includes cross section drawings,
schematics and text.
A basic understanding of jet engine principles would be an asset. This manual may be used for Line Maintenance or Hot
Section Maintenance training.
Line Maintenance: Includes engine description, operation and "on-aircraft" maintenance.
Hot Section Inspection: Includes removal, inspection, and refurbishment of hot section parts as per Maintenance
Manual procedures.
PT6A-27 / 34
QU
TRAINING USE ONLY
INTRODUCTION Vill
Id JQO)OOOOOOOOJOQOOOOOOQOOOOQQOOOQOO OQ
P&WC Publications :
Pratt and Whitney Canada publish various documents and manuals to support all the engines in service. This is a brief
description of the documents:
Illustrated Parts Catalogue (IPC):
Contains all part numbers and parts history information along with identifying drawings for an engine series. To be used
for ordering parts.
Maintenance Manual (MM):
The manual defines all the line and heavy maintenance tasks that can be done on the engine as well as various tests and
adjustments.
Service Bulletin (SB):
Service bulletins are published to introduce new parts, modify existing parts to improve the product.
Spare Parts Bulletins (SPB):
Spare parts bulletins are published to advise for new parts, fully interchangeable with existing parts.
Commercial Support Program Notification (CSPN):
Program issued to assist operators in the accomplishment of SB's.
Airworthiness Directive (AD):
Issued by Governmental Aviation Regulatory Agencies. Requires compliance to rectify potential problems affecting the
airworthiness of the aircraft. AD's refer to applicable SB's for accomplishment instructions.
Special Instruction (SI):
Special instructions are produced by Customer Support to provide specific maintenance information to specific
Customers.
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION
, LR)
Service Information Letter (SIL):
Service information letters are produced by Customer Support to inform all operators on new techniques, new
Products and other general information.
Aircraft Gas Turbine Operation Information Letter (AGTOIL):
AGTOIL's provide general information on technical issues such as temperature measurements, torque measurement, etc.
Training Manual:
Training manual are published by the Customer Training Centre to assist the instructors in class.
Publication price list:
The publication price list contains the prices of all P&WC publications and training material available to customers.
For more information on Pratt & Whitney Canada publications contact:
Supervisor, Publications Customer Services (01CA4)
1000 Marie Victorin
Longueuil, Quebec
Canada J4G 1A1
Telephone: 1-450-647-2705 Fax: 1-450-647-2702
Publication Standards
General:
The engine manuals are published following the ATA 100 revision 15
Chapters:
ln relation with the documentation used on an aircraft the chapter 71 is the POWERPLANT Chapter, and chapter 72 is the
ENGINE Chapter.
TRAINING USE ONLY
PT6A-27 / 34
0 C)
4J 00(>00 0 QO U U C)
INTRODUCTION X
0 C>
0 C)
The basic engine chapters are:
72 - 00 ENGINE (GENERAL)
73 - 00 ENGINE FUEL AND CONTROL (
74 - 00 IGNITION
75 - 00 AIR
76 - 00 ENGINE CONTROLS
77 - 00 ENGINE INDICATING
79 - 00 OIL
Component parts:
Component parts are treated under engine section number as follows:
72 — 00 - 01 &
72 — 12 - 01 &
72 — 22 - 01 &
72 — 32 - 01 &
72 — 42 - 01 &
72 — 52 - 01 &
72 — 62 - 01 &
ENGINE EXTERNALS
POWER SECTION ASSEMBLY
COMPRESSOR
GAS GENERATOR COMPONENTS
COMBUSTION CHAMBER LINER
TURBINES
AGB COMPONENTS
Example:
A basic Chapter will be identified as:
Indicates engine chapter:
Indicates combustion section:
Indicates combustion chamber liner:
PT6A-27 / 34
72 - 42 - 41
1
TRAINING USE ONLY
INTRODUCTION Xl
Pages :
The pages block number inside each chapter is used for breaking the subjects within the manual to small topics for ready
reference and ease of use.
The standard page blocks are as follows :
Description and Operation
Fault isolation
Maintenance Practices
Servicing
Removal/Installation
AdjustmentfTest
Inspection/Check
Cleaning/Painting
Approved Repairs
1 to 99
101 to 199
201 to 299
301 to 399
401 to 499
501 to 599
601 to 699
701 to 799
801 to 899
Example :
On page 73 - 12 - 45, page 201 you will find the Maintenance practice of the fuel nozzles.
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION XII
0 1.) 00 00000 00 0 0000Q U U0O U JO0000 00 09
Service Bulletins ('s) Compliance Codes :
SB's are now available on P&WC's Intranet: http://www.pwc/d8200/d8400/index/index.htm
Category 1 Do before the next fliaht.
Category 2 Do the first time the aircraft is at a iine station or maintenance base that can do the procedure.
Category 3 Do before xxx hours or xxx cycies. This Category may be expanded as required, to specify a minimum
andlor a maximum and/or repetitive intervailinspection.
Category 4 Do this SB the first time the engine or module is at a maintenance base that can do the procedures,
regardiess of the scheduled maintenance action or reason for engine removal.
Category 5 Do this SB when the engine is disassembled and access is available to the necessary sub-assembiíes. Do
all spare part assemblies.
Category 6 Do this SB when the sub-assembly is disassembled and access is available to necessary part.
Category 7 Do this SB when the supply of superseded parts is fully used.
Category 8 Do this SB if the operator thinks the change is necessary because of what he knows of the parts history.
Category 9 Spare parts information only. Old and new parts are directly interchangeable and operators can mix old and
new parts.
Category CSU: Used to evaluate new parts before final introduction in commercial service. Operators who participate
should include this SB at the next maintenance or overhaul of the engine.
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION X111
COURSE SYLLABUS
Time Allowed
Hours
DAY 1 AND II
INTRODUCTION:
- Registration and Orientation
Video Presentation
1.5
0.5
GENERAL INFORMATION:
Introduction To The Engine
Main Features
Glossary Of Terms (Abbreviations)
Engine Rating
Stations And Flanges
Bearing Locations
External Views
0.5
0.5
ENGINE CONSTRUCTION:
Compressor Inlet Case
Compressor
Compressor Bleed Valve
Cold Section Performance
Compressor Wash
1.5
DAY II
Gas Generator Case
Combustion Chamber Liner
Compressor Turbine Vane Ring
Compressor Turbine
Temperature Indicating System (T5)
Exam 1
PT6A-27 / 34
TRAINING USE ONLY
1.0
1.0
0.7
INTRODUCTION XIV
-,...)000000000000000(,)00000000U0000,J001M)00
DAY II (continued)
Exhaust Case
Power Turbine Vane Ring
Power Turbine
Reduction Gearbox
Torquemeter
Accessory Gearbox
Troubleshooting
Turbine Engine Disk Life
Overhaul / HSI Frequency
0.7
1.0
0.5
0.2
DAY III (AM)
AIR SYSTEM:
General
Bearing Compartment Sealing
Turbine Cooling
Compressor Bleed Valve
1.0
General
Engine Lubrication Circuit
Oil Filter And By-Pass Valve
Check And Relief Valves
Fuel Heater
Troubleshooting
1.2
LUBRICATION SYSTEM:
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION XV
DAY III — AM (continued)
IGNITION SYSTEM:
General
Ignition Exciter Unit
High Tension Leads
Igniter Plugs
Exam 2
0.5
1.0
DAY III (PM) TROUGH DAY V
PRACTICAL TRAINING:
During this period every student will have the opportunity to perform maintenance, inspection and repair included in the
PT6A Maintenance Manual. This portion of the course is done in the Training Center shop on a production like engine.
LINE MAINTENANCE:
Bleed Valve Replacement
Filters Inspection
Accessory Gearbox Seals Replacement
Removal And Installation Of External Accessories
Adjustments
Borescope Inspection
Hot Section Inspection
TRAINING USE ONLY
PT6A-27 / 34
(...)
J
(..) C?
t) 0 0 U 0 0 0 0 0 0 0 (.) 0
3.0
8.1
INTRODUCTION XVI
C.) (.> -) 1.) 0 0 0 C.)
0
HEAVY MAINTENANCE:
Accessory Gearbox Removal and Installation
Carbon Seal Replacement
Starter Generator Gearshaft Replacement
Shroud Segments Replacement and Grinding
2.5
0.7
0.5
1.5
Fuel Management
Fuel System General
Fuel Pump
Fuel Control Unit
Flow Divider (Starting Flow Control)
Fuel Nozzles
Adjustments
Troubleshooting
Exam 3
0.7
DAY VI AND VII
FUEL SYSTEM:
0.5
2.5
0.7
1.0
0.5
0.5
PROPELLER SYSTEM:
General
Constant Speed Unit
Governing
Beta
Reverse
Overspeed Protection
Adjustment
Troubleshooting
Control Exam
Rigging
0.5
2.5
0.5
0.5
2.0
EXAMS:
Four comprehensives multiple choice exams are administered duríng the course and the student must maintain an overall
average of 70% on each exam to obtain a Heavy Maintenance certificate.
PT6A-27 / 34
TRAINING USE ONLY
INTRODUCTION XVII
ENGINES COVERED IN THIS GUIDE
Derivativ
Reference model
PT6A-11
PT6A-28
PT6A-34AG
PT6A-114 / 114A
PT6A-27
PT6A-34
PT6A-11AG
PT6A-110
PT6A-34B
PT6A-135 / 135A
le
PT6A-21
PT6A-1 12
PT6A-36
MAJOR DIFFERENCES BETWEEN THE ENGINES COVERED IN THIS GUIDE
The PT6 engines covered in this guide can be divided in two major groups.
PT6A-27, A-11, A-11AG, A-21, A-28, A-110, A-112
PT6A-34, 34AG, A-34B, A-36, A-1141114A, A-135/135A
.,.......:.....:..-
..:::::::.,...1:
.:..
Group
1: PT8A-27, 1 11AG, 21, 21110, 112
. . „.
i
..
Group 2:
PT6A-34, 34AG, 36, 114/114A, 135/135A
PT6A-27: Reference Model
PT6A-34: Reference Model
PT6A-21: A-27 with A-20 fuel and starting systems and first stage
PT6A-36: Identical to a A-34 except for higher take-off power
rating.
reduction gearing
PT6A-28: Cruise rating increased through coated small and large
exit ducts.
PT6A-114: derivative of a A-36 with single port exhaust and a
1900 rpm low speed reduction gearbox.
PT6A- 11: Mechanically identical to PT6A-21 but is torque limited
to 500 SHP at 2200rpm.
PT6A-114A: Mechanically similar to a PT6A-114 except for
incorporation of the PT6A-135A compressor.
PT6A-10: Mechanically identical to PT6A-11 but is torque limited
to 475 SHP at 2200 rpm.
PT6A-135: A-34 with 1900 rpm low reduction gearbox and
improved hot end for higher cruise power rating.
PT6A-110: Mechanically identical to PT6A-10 but with a 1900
rpm low speed reduction gearbox.
PT6A-112: Mechanically identical to PT6A-11 but with a 1900
rpm low speed reduction gearbox.
PT6A-27 / 34
PT6A-135A: Mechanically similar to PT6A-135 but with PT6T-3B first
stage compressor blades and long inducer impeller. Single
line fuel system.
TRAINING USE ONLY
00 0 0 0 C) C) 0 0 0 0 Q 0 C) 0 0 0 0 0 0 0
INTRODUCTION XVIII
C) () 0 C.1 0 0 0 0 0
POWERPLANT AIRCRAFT APPLICATIONS
ENGINE MODEL
SHP / SHAFT RIVI
PT6A-11
550 / 2200
PT6A-11AG
550 / 2200
PT6A-15AG
680 / 2200
PT6A-27
680 / 2200
PT6A-28
680 / 2200
PT6A-34134AG
750 / 2200
PT6A-27 / 34
AIRCR
. .:.
1"
Piper Cheyenne IA
Piper T1040
Air Tractor AT 402A/402B
Weatherly 620 TP
Air Tractor AT 402A/402B
AASI Jetcruzer
AVIC/HAMC Y-12
deHavilland Twin Otter Series 300
LET L410
Embraer Banderirante EMB-110
Pilatus Turbo Porter PC-6
Raytheon Beech 99A
Raytheon Beech B99
Raytheon Beech 99A
Raytheon Beech king Air A100
Raytheon Beech king Air E90
Air Tractor AT 502
Ayres Turbo Thrush T-34
CROPLEASE Fieldmaster
Embraer Banderirante EMB-110
Embraer Banderirante EMB-111
Embraer Caraja / Frakes Mallard
Frakes Turbo Cat Model A/B/C
Pacific Aero Cresco 750
PZL — Okecie PZL-106 Turbo-Kruk
Raytheon Beech T-44A
Scheweizer G-164B AG-Cat Turbine
Scheweizer G-164D AG-Cat Turbine
TRAINING USE ONLY
INTRODUCTION XIX
POWERPLANT AIRCRAFT APPLICATIONS (continued)
_
Fairchild Dornier 128-6 Turbo Skyservant
Cessna Conquest I
Reims F406 Caravan II
Cessna 208 Caravan I
Cessna 208B Caravan I
PT6A-110
PT6A-112
500 / 1900
PT6A-114
600 / 1900
PT6A-114A
675 / 1900
PT6A-135A
PT6A-27 / 34
OO0 0 (.) () 0 0 0
Soloy Pathfinder 21
Cessna Conquest I
C. Dornier Seastar
Embraer EMB-121 XINGU II (PT6A-135)
Piper Cheyenne II XL
Raytheon Beech King Air F90-1
Vazar Dash 3 Turbine Otter
750 / 1900
TRAINING USE ONLY
t.) 0 (-.) 0
INTRODUCTION XX
J OQUOUUJOU 0 000 UOU (4)
ENGINE OVERVIEW
TRAINING USE ONLY
ENGINE OVERVIEW 1.1
PT6A-27/34
TRAINING USE ONLY
ENGINE OVERVIEW 1.2
0000t.../..WOUQ0000000000000000000000CR/J000J0k..,30
FRONT
LEFT
RIGHT
REAR
ENGINE ORIENTATION
PT6A-27/34
0101 PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.3
ABBREVIATIONS
Ag
AGB
AMM
BOV
CW
CCW
CSU
CT
ECTM
ESHP
FCU
Fl
FOD
GI
HSI
IAS
ISA
ITT
WM
MOP
MOT
Nf
Ng
Np
OAT
PO
Agricultural (PT6A-15Ag)
Accessory Gearbox
Airframe Maintenance Manual
Bleed Off Valve
Clockwise
Counterclockwise
Constant Speed Unit
Compressor Turbine
Engine Condition Trend Monitoring
Equivalent Shaft Horsepower
Fuel Control Unit
Flight Idle (high idle)
Foreign Object Damage
Ground Idle (low idle)
Hot Section Inspection
Indicated Air Speed
International Standard Atmosphere
Interturbine Temperature (T5)
Maintenance Manual
Main Oil Pressure
Main Oil Temperature
Free turbine speed
Gas generator speed
Propeller speed
Outside Air Temperature
Bypass (spill) fuel pressure
PT6A-27/34
P1
P2
P3
Palt
Pamb
PBA
PLA
PPH
PSI
PSIA
PSID
PSIG
PT
RGB
S/L
S/N
SB
SIL
SFC
SHP
T/O
T5
TBO
Tq
Wa
Wf
Fuel pump delivery pressure
Metered fuel pressure
Compressor discharge pressure (station 3)
Pressure altitude
Ambient air Pressure
Primary Blade Angle
Power Lever Angle
Pounds Per Hour (Lb/hr)
Pounds per Square Inch
Pounds per Square Inch Absolute
Pounds per Square Inch Differential
Pounds per Square Inch Gauge
Power Turbine
Reduction Gearbox
Sea Level
Serial Number
Service Bulletin
Service Information Letter
Specific Fuel Consumption
Shaft Horsepower
Take-Off
Interturbine Temperature (ITT)
Time Between Overhaul
Torque
Air mass flow
Fuel flow
TRAINING USE ONLY
ENGINE OVERVIEW 1.4
Uu,-JOUOUUOUOU00000000000000U00( JU00000J0
TURBOPROP ENGINE SYMBOLS
PT6A-27/34
01020 PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.5
ENGINE FEATURES
450 to 750 SHP.
Free turbine, reverse flow inlet configuration.
Reverse flow combustion system.
Two sections: gas generator, power section.
Two stage planetary reduction gearbox.
Variable speed propeller.
Reverse thrust capability.
Hydro pneumatic fuel control unit.
Hydraulic torque measurement system.
Three lever power management.
Fuel control with manual override.*
Notes:
*On certain single engine aircraft only.
PT6A-27/34
TRAINING USE ONLY
ENGINE OVERVIEW 1.6
tiVoL C)00QUI>0000000004>QUOU JG10 .000t.i _)000QUOU00
POWER SECTION
ENGINE FEATURES
TWO STAGE
PLANETARY
REDUCTION
GEARBOX
ACCESSORY
GEARBOX
GAS GENERATOR
PT6A-27/34
0103 PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.7
TORQUE
TRANSDUCER
OUTPUT
PyLINE
PROPELLER
GOVERNOR (C.S.U.)
PROPELLER
SHAFT
MOUNTING PAD
RGB MAIN OIL
PRESSURE
RGB SCAVENGE
SCREEN
RIGHT FRONT VIEW
PT6A-27/34
k,-)J3
0104HT PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.8
OU4J(JUOUQUOQUQUO000000000000ü .,0000UC)k.
FUEL HEATER
OIL RETURN
OIL COOLER
CAM BOX
FUEL PUMP
OIL PRESSURE
SENSOR
STARTING FLOW
CONTROL UNIT
(NONE IF FLOW DIVIDER)
PT6A-27/34
0105HT PT6A 27-34
P3 LINETO F.C.U.
(SOME APPS. FILTER)
OILTEMPERATURE SENSOR
RIGHT REAR VIEW
TRAINING USE ONLY
ENGINE OVERVIEW 1.9
OIL TANK VENT
(VENT AIR TO AGB)
P3 AIR CABIN
SERVICES
OIL FILLER CAP
& DIP STICK ASSY
STARTER
DRIVE PAD
NG TACHO
PAD
AIRFRAME
ACC.
RGB SUMP
SCAVENGE OIL
(OUTTO AIRFRAME)
NO. 3 & NO. 4 BRG
SCAVENGE OIL
(INTERNAL AGB
TO SEPERATE
OIL / AIR SEALS)
OIL OUTTO
AIRFRAME
OIL COOLER
INLET SCREEN
SCAVENGE
NO. 2 BEARING
(TO AGB)
EXTERNAL
SCAVENGE
PUMP
LEFT REAR VIEW
PT6A-27/34
0106HT PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.10
)UU0000L JOU0000000QUQUUQUQUUU4JUOUtItJOU00
RGB STATIC
PRESSURE PORT
BETA LEVER
OVERSPEED
GOVERNOR PAD
IGNITION
EXCITER
BOX
BLEED
VALVE
CHIP DETECTOR
IGNITERS x 2
(9 O'CLOCK
4 O'CLOCK)
CENTER
FIRE SEAL
IGNITION
CABLES
LEFT FRONT VIEW
PT6A-27/34
0107HT PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.11
BASIC PT6A ENGINE
Engine Operation:
Design of the PT6 started in 1958. Production began in 1963 with
the 550 SHP PT6A-6. Over 50 different PT6A models are now in
operation, ranging from 500 SHP (PT6A-112) to 1424 SHP (PT6A67R). Over 24,000 engines were delivered with over 164,000,000
hours accumulated, the PT6A's are used in 145 different countries.
The generated hot gases are then directed to the turbine area and
assist the starter in accelerating the compressor to idle speed.
The PT6A-34/42 engine series are lightweight turbine engines
driving a propeller shaft via a two-stage reduction gearbox. Two
major rotating assemblies compose the heart of the engine. One
assembly consists of the compressor turbine and the compressor.
The other one consists of the power turbine(s) and the power turbine
shaft. The two rotating assemblies are not connected together and
turn at different speeds and in opposite directions. This design is
referred to as a "Free Turbine Engine".
The hot expanding gases accelerate through the compressor turbine
vane ring and cause the compressor turbine to turn. The gases
leaving the compressor turbine are accelerated again as they
expand through the power turbine vane ring(s). The power turbine(s)
provide rotational energy to drive the propeller. The reduction
gearbox reduces the power turbine speed (33,000-rpm) to one
suitable for the propeller (1700 to 2200 rpm).
This configuration allows the power turbine and propeller to rotate at
constant speed while the fuel control system schedules compressor
speed (Ng) according to the power demand.
Starter cranking torque is low since only the compressor rotates on
start. Engaging the starter mounted on the accessory gearbox starts
the engine. The compressor draws air into the engine via an annular
plenum chamber (inlet case), increases its pressure across 3 axial
stages and one centrifugal impeller and delivers it to the combustion
chamber.
Air enters the combustion chamber through small holes. At the
proper compressor speed, fuel is introduced into the combustion
chamber. Two igniters located in the combustion chamber ignite the
air-fuel mixture.
PT6A-27/34
At this point, ignition and starter are turned off as the self-sustained
combustion is now able to drive the compressor.
Gases leaving the power turbine are expelled into the atmosphere by
the exhaust duct. Engine shutdown is accomplished by cutting fuel
going to the combustion chamber.
Engine oil is supplied from an integral oil tank located in the inlet
case rear section. The oil cools, lubricates and cleans all bearings
and gears.
A hydro-pneumatic fuel control unit, mounted on the fuel pump,
regulates compressor speed by metering fuel flow to the nozzles, in
response to the power lever angle and flight conditions.
The propeller governor controls the power turbine / propeller speed
by varying the propeller blade angle in response to the propeller
speed control lever, engine power and flight conditions.
TRAINING USE ONLY
ENGINE OVERVIEW 1.12
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ENGINE CROSS-SECTION & AIRFLOW
PT6A-27/34
0108C PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.13
STATIONS
_
1
2
2.5
3
4
5
6
7
Ambient
Compressor Inlet
Interstage Compressor
Compressor Discharge
Turbine
Inter Turbine
Turbine Exit
Exhaust
15°
16°
110°
280°
934°
690°
565°
551°
14.7
14.7
26.4
103
101
35
16
15.5
Note: Temperatures and pressures taken at take-off power, 15°C and at sea level.
PT6A-27134
TRAINING USE ONLY
1,QUOOU'UOVUOUQUQUOQUOU 0000,..,004>‘)
ENGINE OVERVIEW .14
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MAIN STATIONS
PT6A-27/34
0109 PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.15
FLANGES
BEARINGS
Flanges: Mating faces where components are joined
together.
Bearings: They support major rotating assemblies. There
are six main bearings on the PT6 engine: three roller bearings
and three ball bearings. The ball bearings withstand the
following thrusts:
Attaches the RGB front & rear housings to the exhaust
case.
No. 1 bearing : Compressor thrust (rearward).
No. 4 bearing : Power turbine thrust (forward).
Attaches the RGB rear housing to the No 3 bearing
housing.
No. 6 bearing : Propeller thrust (forward).
Attaches the exhaust case to the gas generator case.
Attaches the PT vane assembly to the exhaust case.
Bearings number 2, 3 and 5 are roller bearings. They support
radial loading and permit axial rotor movement required for
thermal expansion.
Joins the CT vane assembly together.
otor
Attaches the inlet case to the gas generator case.
-G-
No. 1 Ball
No. 2 Roller
No. 3 Roller
No. 4 Ball
No, 5 Roller
No. 6 Ball
Compressor shaft
Attaches the AGB to the inlet case.
Power Turbine Shaft
Propeller Shaft
Maintenance:
None on the bearings. Preventive maintenance consists of
periodic oil level checks and inspection of filter. Ensure oil
pressure is kept within limits.
PT6A-27/34
TRAINING USE ONLY
000000000000000000 Jto
ENGINE OVERVIEW 1.16
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FLANGES & BEARINGS
PT6A-27/34
0110 PT6A 27-34
TRAINING USE ONLY
ENGINE OVERVIEW 1.17
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COMPRESSOR SECTION
PT6A-27/34
TRAINING USE ONLY
COMPRESSOR SECTION 2.1
INERTIAL SEPARATOR (AIRFRAME)
Purpose:
Protect the engine from ingesting foreign objects such as:
stones, ice, sand, snow, rain, etc.
Operation:
Deployment of the inertial separator to the bypass (icing)
position force air in the nacelle to execute a sharp turn
before entering the engine. Water droplets, ice crystals or
snow, because of their inertia, tend to maintain their
original high velocity path and are discharged overboard
through the separator bypass duct.
Note:
The inertial separator is an airframe supplied item. Not
using the inertial separator in icing conditions could result
in costly damage to the compressor blades. Ensure
separator operates freely. Erratic movement of the
separator vane may cause engine parameter fluctuation.
For specific maintenance action, refer to the Airframe
Maintenance Manual.
PT6A-27/34
TRAINING USE ONLY
COMPRESSOR SECTION 2.2
000LJOUOU00000G 000090000000U00Q OQUOC JOUU
BYPASS (ICING) POSITION
NORMAL (NON-ICING) POSITION
AIR INLET INERTIAL SEPARATOR
TYPICAL
PT6A-27/34
0201 PT6A 27-34
TRAINING USE ONLY
COMPRESSOR SECTION 2.3
INLET CASE
Operation:
Purpose:
Directs air into the compressor.
Support #1 bearing.
Support the AGB.
Forms the oil tank.
Inlet screen (1/4 inch mesh) prevents objects from
entering the compressor.
The annular configuration of the P16 inlet case facilitates
the protection against Foreign Object Damage. Because
the compressor rotor intake is not in line with the flight
path, air coming into the PT6 makes a sharp turn prior to
entering the inlet case. This configuration is combined
with the inertial separator for maximum protection against
FOD. The shape of the air inlet also contributes to the
silent operation of the engine.
Construction:
Inlet case struts anti-icing is provided by heat conduction
from the oil contained in the tank.
One piece aluminum casting protected against corrosion
with aluminized epoxy paint.
Maintenance / Inspection:
Inspect inlet screen for damage and cleanliness. Wire
mesh damage is not acceptable.
Inspect inlet screen rubber sealing rims for damage.
Repair damage as per Engine Maintenance Manual
instructions.
Inspect inlet case for cracks in the strut area, refer to
maintenance manual for limits.
PT6A-27/34
TRAINING USE ONLY
COMPRESSOR SECTION 2.4
000000000000000000000000000000 J00000‘ 0009
OIL TANK VENT
OIL RETURN FROM COOLER
OIL TANK
AIR INLET
DATA P LATE
OIL FILTER
HOUSING
LOCATION
OIL RETURN
FROM NO.1 BEARING
NO.2 BEARING
SCAVENGE
RETURN
INLET CASE
PT6A-27/34
Yiwami: OIL TANK DRA1N
0202C PT6A 27-34
TRAINING USE ONLY
COMPRESSOR SECTION 2.5
COMPRESSOR ROTOR ASSEMBLY
Operation:
Purpose:
The compressor rotor assembly has three axial stages plus a
single stage centrifugal impeller. Each axial stage accelerates
the air, which is then decelerated through divergent stator
vanes, thus increasing the air pressure. The same process is
repeated throughout all the compressor stages.
Directs air into the compressor and provide the combustion
chamber with the correct airflow at the required pressure.
Supplies air under pressure for aircraft pneumatic needs.
Construction:
The compressor rotor assembly consists of 3 axial stages and
one centrifugal impeller joined together by 6 tie rods and
interstage spacers. It rotates within a stator assembly.
The impeller and first stage blades are made of titanium. The
remaining parts are steel.
The compressor rotor is supported by the #1 ball bearing and
by the #2 roller bearing.
The #1 bearing is supported by the compressor inlet case via
a flexible housing. Compressor unbalance caused by normal
engine wear produces vibrations that are absorbed by the
number 1 bearing flexible housing, reducing vibrations
transmitted to the engine mounts and aircraft.
The compressor stator assembly consists of 3 axial stationary
stages bolted together to an impeller housing.
The dynamic pressure (air velocity) generated by the
centrifugal impeller speed is converted into static pressure by
the diffuser pipes divergent shape which reduce the air speed
and increase the compressor discharge pressure (P3).
ompression rat110:
powor
vot
1.22 : 1 (each stage)
Axial:
1.80 : 1 (Axial total)
Centrifugal:
3.9 : 1
Total ratio:
7.0 : 1
Mass airflow (take-off power sea level ISA): 6.5 lbs./sec
0111:
Maintenance / Inspection:
' Check for FOD on first stage blades every time the inlet
screen is removed.
Blend repair first stage blades. Refer to the Engine
Maintenance Manual for procedure.
/ Wash and rinse compressor at regular intervals.
The gas generator case and the inlet case support the
assembly. The 3rd stage stator shroud incorporates bleed air
slots for bleed valve operation.
PT6A-27/34
TRAINING USE ONLY
COMPRESSOR SECTION 2.6
1 00000000 000000000 JOGWOO UOUUU
NO.1 BEARING
OIL PRESSURE
NOZZLE
COMPRESSOR INTERSTAGE
AIR BLEED (P2.5)
NO.1 BEARING
COMPRESSOR FRONT
STUB SHAFT
COMPRESSOR ROTOR
& NO.1 BEARING AREA GAS GENERATOR CASE
PT6A-27/34
0203C PT6A 27-34
TRAINING USE ONLY
COMPRESSOR SECTION 2.7
COMPRESSOR BLEED VALVE
Maintenance / Inspection:
Purpose:
Check for air losses at sealing faces and mating surface. Bleed
valve piston sticking. Seat or piston damage.
Diaphragm changing.
Diaphragm pressure check.
; Clean orifices.
Prevent compressor stalls at RPM's below 91% Ng.
Description:
Pressure operated piston sliding on a guide pin.
Piston discharges P2.5 to atmosphere at low Ng speed.
A rolling diaphragm mounted on the valve piston prevents
leakage between P2.5 and the P3 chamber.
Pressure check:
Purpose:
Verify the integrity of the bleed valve rubber diaphragm.
Operation:
Two forces act on the bleed valve piston. Modified P3 air (P3 mod)
pressure pushes to close the valve and P2.5 air pressure, from the
interstage compressor area, pushes to open it.
P3 air flows through a primary metering orifice and is directed to the
top of the piston and to atmosphere via a convergent divergent
The valve closing point is achieved during engine
orifice.
acceieration when the pressure acting on the valve diaphragm (P3
mod) is sufficient to overcome the compressor interstage pressure
(P2.5).
Description:
Remove bleed valve spring pin.
Seal valve seat on a rubber sheet and secure in position.
Remove two plugs on bleed valves and install appropriate
equipment as per Maintenance Manual instructions.
Apply required pressure to valve and check that leakage rate is
within limits.
As the compressor speed increases, P3 rises faster than P2.5, thus
increasing the pressure acting on the piston to gradually close it.
The speed (Ng) at which the valve closes is a function of the primary
and convergent divergent orifice sizes. A larger primary orifice
requires less Ng speed (less P3 pressure) to close the valve.
Note: The primary orifice is matched to the bleed valve and is not
field replaceable.
PT6A-27/34
000 0 0 Q t) Q 0 0 0
TRAINING USE ONLY
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COMPRESSOR SECTION 2.8
PISTON
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CLOSED POSITION
COMPRESSOR BLEED VALVE
PT6A-27/34
02040 PT6A 27-34
TRAINING USE ONLY
COMPRESSOR SECTION 2.9
GAS GENERATOR CASE
Operation:
Purpose:
Impeller air enters the diffuser tangentially. The diverging
diffuser pipes redirect the air axially and transform the high
velocity into static pressure.
The gas generator case is the engine main structural
component and has multiple functions such as:
Support the engine on the aircraft via engine mount pads.
Support the power section, inlet case and accessory
gearbox.
Contain the air pressure coming from the compressor.
Provide housing for the combustion chamber and the
compressor turbine stator assembly.
Support the #2 bearing.
Provide oil supply and scavenge for the #2 bearing.
Support 21 diverging diffuser pipes.
Support the fuel nozzles and the igniter plugs.
Support the compressor bleed valve.
Two spring loaded drain valves are located under the case. P3
air pressure closes them soon after combustion initiation
(approx. 2 PSIG). They open after shutdown to drain residual
fluids from the case.
Maintenance / Inspection:
Inspect case for cracks, distortion, corrosion and evidence
of overheating.
• Inspect engine mount threads.
• Inspect P3 air supply holes at CT vane flange for blockage.
I Inspect diffuser pipes for cracks and fretting wear.
• Inspect shanknuts at CT vane flange for security.
Description:
The gas generator case is a welded assembly of steel alloy
machined parts and sheet metal coated with diffused
aluminide process treatment for increased resistance to
corrosion. The rear inner section provides a housing for the
compressor assembly while the front section forms the outer
housing for the combustion chamber liner.
Diffuser tubes, brazed inside the center section of the case,
increase the static pressure of the compressor discharge air
and direct it to the combustion area.
PT6A-27/34
41)U kJUQCO Q ,„
TRAINING USE ONLY
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P3 PRESSURETUBE SUPPLYING
FUEL CONTROL UNIT
NO.2 BRG. SCAVENGE
OIL TUBE
FLANGE "F"
DIFFUSER PIPE
P3 SUPPLY FOR
BLEED VALVE
°
NO.2 BRG. PRESS. OIL TUBE
FLANGE "C"
STRAIGHTENING VANE
BLEED VALVE VANE
GAS GENERATOR CASE
PT6A-27/34
0205 PT6A 27-34
TRAINING USE ONLY
COMPRESSOR SECTION 2.11
COMPRESSOR WASH
Desalination wash:
Procedure:
This method of washing is used to remove salt deposits from the
compressor section of the engine to minimize corrosion. The
washing medium is normal drinking water. When the temperature is
below 2°C (36°F), methanol must be added to the water to prevent
freezing (refer to the Engine Maintenance Manual for proper
mixtures).
Refer to the Maintenance Manual for compressor wash procedure,
approved detergents and equipment's used.
40 minutes minimum cooldown period before washing.
Remove the P3 line going to the FCU.
Ensure cabin bleed is off.
Ensure ignition is off.
Respect starter limitations.
Aircraft fuel boost pumps should be "on".
Turn starter on.
At 5°/0 Ng start flowing solution.
Motor for 30 seconds.
Stop starter, stop flow as Ng drops to 5°/0.
Soak for 15 to 30 minutes (when washing only).
Rinse compressor, twice, as there might still be soap on the
compressor, using water or water methanol mix.
If water / methanol mix was used, motor for 30 seconds.
Reconnect P3 line to the FCU.
Run engine at 80°/0 Ng for one minute minimum
Check engine acceleration time.
lt is strongly recommended that this procedure be carried out when
operating in a salt laden atmosphere. The washing mixture is
injected into the compressor section using the wash
ring mounted over the inlet screen.
Performance recovery wash:
This method of washing consists of injecting a water based cleaning
agent into the compressor section via the wash ring while motoring
(starter only). It restores the compressor efficiency by removing dirt
Approved chemical
deposits from the compressor gas path.
additives are used to remove stubborn dirt deposits, which cannot be
removed using water only. When the temperature is below 2°C
(36°F), methanol and kerosene must be added to the cleaning
solution to prevent freezing. Refer to the Engine Maintenance
Manual for washing mixtures and procedures.
TURBINE WASH:
Purpose: Remove salt deposits from the turbine section of the
engine to minimize blade sulphidation attack.
A 15-20 minute period is allowed for the cleaning agent to soak in,
followed by one or two rinse cycles (water). This method of washing
should be carried out on a regular basis based on the flying
environment. Compliance with these guidelines and Maintenance
Manual instructions will promote parts life and reduce potential
overhaul costs.
PT6A-27/34
Method: Motoring wash with turbine wash nozzle inserted in one of
the igniter port.
Note: The procedure to perform the turbine wash is very similar to
the compressor desalination wash. Refer to the Engine Maintenance
Manual chapter 71 for more details.
TRAINING USE ONLY
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COMPRESSOR WASH SCHEMATICS
PT6A-27/34
0206 PT6A 27-34
TRAINING USE ONLY
COMPRESSOR SECTION 2.13
COMPRESSOR SECTION PROBLEMS
SYMPTOMS AT CONSTANT POWER
Wf
Ng
T5
PROBLEM
Restricted inlet screen.
Up
Up
Up
Dirty compressor.
Up
Up
Up
Damaged compressor
= blades.
Up
Up
Up
Bleed Valve stuck open.
Up
Up
Up
External P3 air leaks.
Same or Up
Up
Up
Up
Up
Up
.
Inertial separator in
bypass position.
Bleed valve closing point
out of limit.
,Bleed Valve stuck closed.
Compressor stalls.
Possible hooting noise.
Compressor stalls.
Compressor unbalance.
Vibration or humming noise
ACTION REQUIRED
Clean and/or remove obstruction
Perform compressor wash / revise
schedule
Return to an authorized overhaul
facility if damage is beyond limit.
Ensure P3 is not leaking between
bleed valve and gas generator
case.
Replace bleed valve.
Check for external leaks on gas
generator.
Verify sealing surfaces at next HSI
Return separator vanes to normal
position.
Replace bleed valve if found
defective.
Replace bleed valve
Inspect first stage compressor
blades for FOD.
Note: Compressor section problems are always characterized by a higher T5 and Wf. Ng usually goes up,
PT6A-27/34
000, 1 00
TRAINING USE ONLY
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COMPRESSOR SECTION 2.14
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HOT SECTION
TRAINING USE ONLY
HOT SECTION 3.1
HOT SECTION
Operation:
This chapter covers the construction and operation of hot
section components. Inspection, maintenance and
troubleshooting are covered in Chapter 9.
The hot section of the engine comprises of components
down stream of the gas generator. Hot expanding gases
leaving the combustion chamber are directed towards the
compressor turbine blades by the compressor turbine
vane ring.
Purpose:
Thereafter, gases travel across the power turbine vane
ring and hit the power turbine blades. Turbine rotation is
transmitted to the propeller via the power turbine shaft
and the reduction gearbox.
Extract energy from the hot expanding gases to:
Drive the compressor turbine
Drive the power turbines and the propeller
Gases leaving the power turbine are expelled to the
atmosphere through the exhaust duct.
Topics covered:
Combustion Chamber.
Compressor Turbine Vane Ring.
Compressor Turbine.
Power Turbine Vane Ring.
Power Turbine.
Exhaust Duct.
Sealing of the Hot Section.
PT6A-27/34
TRAINING USE ONLY
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PT6A-27/34
0301 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.3
COMBUSTION CHAMBER LINER
Purpose:
Operation:
The combustion chamber provides an area for the
combustion of the fuel/air mixture.
Air enters the primary zone, through holes and cooling
rings, in the dome end, allowing incoming fuel to be
continuously mixed and recirculated. This permits the
flame to be self-sustaining and to distribute the heat from
each nozzle evenly.
Description:
• Annular, reverse flow type combustion chamber made
of heat resistant nickel alloy (Inco 625).
Supported by the small and large exit ducts at the
rear and by the fuel nozzles at the front end.
14 fuel nozzle adapter bosses.
2 spark igniter bosses.
Gapped cooling rings maintain a layer of cooling air to
protect the combustion chamber walls from the flame.
Provides a primary zone for mixing incoming fuel and
air.
Provides a secondary zone for completing the
combustion process and establishes the 15:1 air to
fuel ratio.
Provide a dilution zone for cooling the gases to a
temperature suitable for the turbine operation.
Corrugated strip ensures a gap between liner and
large exit duct.
PT6A-27/34
The primary zone is, however, a fuel rich area and more
air is needed, downstream, to complete the combustion
process.
More air enters the liner through larger holes on the inner
and outer walls in the secondary zone. This completes
the combustion process and establishes the ideal 15:1
air/fuel ratio.
The dilution zone allows more air in to cool the hot gases
for an acceptable turbine entry temperature. The open
side of the liner and the exit ducts forms it.
Maintenance / Inspection:
Visually inspect the liner for evidence of burning,
cracking, buckling or metal to metal fretting wear.
Regap cooling rings if they are distorted.
Stop drilling of cracks and welding may be required
(refer M/M for limits).
TRAINING USE ONLY
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PT6A-27/34
0302 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.5
A-27 SMALL AND LARGE EXIT DUCTS:
Maintenance / Inspection:
Purpose:
•
Form an envelope that changes the direction of the gas
flow 180 0 and complete the dilution process of the
combustion gases.
•
Inspect the small and large exit ducts for evidence of
burning, cracking, buckling, coating loss or metal to
metal fretting wear.
Stop drilling of cracks may be required (refer M/M for
limits).
Description:
Double layer of heat resistant nickel alloy.
PT6A-27/34
TRAINING USE ONLY
HOT SECTION 3.6
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PT6A-27/34
0303 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.7
A-27 COMPRESSOR TURBINE VANE ASSEMBLY
Vane ring:
Changes the combustion gases into velocity, at the optimum
angle to drive the compressor turbine.
Supports the small exit duct and the shroud housing
Exit area is classed.
Effect of CT vane area on T5 & Ng at constant power:
Ng nio , T5 t
Increase area =
Decrease area =
Ng t, T5 9
Shroud housing:
Support and locates the shroud segments.
Shroud segments: (16 segments)
Class selection and grinding of segments provide adequate
turbine blade tip clearance to minimize gas leakage and to suit
compressor turbine wheel diameter.
Note: If you change the CT vane ring, use another one of the same
class.
Maintenance/ Inspection:
Vane ring:
Inspect vane ring for evidence of burning, cracking and coating
loss.
Insure proper sliding fit (lugs to slots) with mating parts.
Interstage sealing ring:
Prevents P3 air leakage to station 5.
#2 bearing cover:
Supports the Compressor Turbine vane assembly with a lug to
slot fit arrangement.
Serves as a baffle to control cooling air to Compressor Turbine
disk.
Lockpiate:
Secures the Compressor Turbine vane assembly to the gas
generator case and provides a sealing surface.
Shroud housing:
lnspect shroud housing for cracks, blockage of cooling air holes,
fretting wear at sealing ring contact area.
Shroud segments:
Inspect shroud segments for cracks, burning distortion and metal
buildup.
Interstage sealing ring:
Inspect sealing ring(s) for fretting wear on sealing diameter and
face. Fit ring on sealing diameter for full contact.
TRAINING USE ONLY
PT6A-27/34
0000QuOUU ti
Operation:
Expanding gases, accelerated through classed vanes are directed at
the turbine blades. The vane exit area determines the vane ring
class. A smaller vane ring class (smaller area) accelerates the air
more and therefore increases the compressor turbine speed (Ng). A
higher Ng speed provides more air to the engine, more cooling and a
lower T5.
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HOT SECTION 3.8
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C.T. SHROUD HOUSING
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INTERSTAGE
SEALING RING
VANE RING
SMALL EXIT DUCT
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TIP CLEARANCE
LARGE EXIT DUCT
SHROUD SEGMENT
LOCK PLATE ------*
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-
NO.2 BEARING COVER
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COMPRESSOR TURBINE
A-27 COMPRESSOR
(---,-r
TURBINE VANE ASSEMBLY
PT6A-27/34
0304C PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.9
A-34 SMALL AND LARGE EXIT DUCTS:
Purpose:
Maintenance / Inspection:
Form an envelope that changes the direction of the gas
flow 180 0 and complete the dilution process of the
combustion gases.
Inspect the small and large exit ducts for evidence of
burning, cracking, buckling, coating loss or metal to
metal fretting wear.
Description:
Stop drilling of cracks may be required (refer M/M for
limits).
Double layer of heat resistant nickel alloy.
PT6A-27/34
TRAINING USE ONLY
HOT SECTION 3.10
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LARGE EXIT DUCT
COMBUSTION
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LINER
SMALL
EXIT DUCT
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A34 SMALL & LARGE EXIT DUCTS
PT6A-27/34
0305 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.11
Operation:
A-34 COMPRESSOR TURBINE VANE ASSEMBLY
Expanding gases, accelerated through classed vanes are directed at
the turbine blades. The vane exit area determines the vane ring
class. A smaller vane ring class (smaller area) accelerates the air
more and therefore increases the compressor turbine speed (Ng). A
higher Ng speed provides more air to the engine, more cooling and a
lower T5. Cooled vanes have P3 air circulating in individual core
passages.
Vane ring:
Changes the combustion gases into velocity, at the optimum
angle to drive the compressor turbine.
Supports the small exit duct and the shroud housing.
Passages allow P3 air to cool each vane.
Exit area is classed.
Effect of CT vane area on T5 & Ng at constant power:
Shroud housing:
Support the shroud segments and interstage sealing ring.
Increase area = Ng 40 , T5 t
Decrease area = Ng 41, T5 40
Shroud segments: (9 segments)
Class selection and grinding of segments provide adequate
turbine blade tip clearance to minimize gas leakage and to suit
compressor turbine wheel diameter.
Note: If you change the CT vane ring, use another one of the same
class.
Interstage sealing ring:
Prevents P3 air leakage to station 5.
Maintenance / Inspection:
Vane ring:
#2 bearing cover:
Supports the Compressor Turbine vane assembly with a lug to
slot fit arrangement.
Serves as a baffle to control cooling air to Compressor Turbine
disk.
Inspect vane ring for evidence of burning, cracking and coating
loss.
Insure proper sliding fit (lugs to slots) with mating parts.
Check air-cooling holes for blockage. (A-34 series only).
Shroud housing:
Lockplate: Secures the Compressor Turbine vane assembly to
the gas generator case and provides a sealing surface.
Inspect shroud housing for cracks, blockage of cooling air holes,
fretting wear at sealing ring contact area.
CT blade tip clearance:
Tip clearance is the gap between the tip of the compressor
turbine blade and the shroud segment. Tip clearance
deterioration reduces engine performance
Shroud segments:
Inspect shroud segments for cracks, burning distortion and metal
buildup.
Interstage sealing ring:
Inspect sealing ring(s) for fretting wear on sealing diameter and face.
Fit ring on sealing diameter for full contact.
tAr (.1
HOT SECTION 3.12
TRAINING USE ONLY
PT6A-27/34
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INTERSTAGE SEALING RING
SHROUD SEGMENT
C.T. SHROUD HOUSING
SMALL EXIT DUCT
LARGE EXIT DUCT
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TIP CLEARANCE
P3 COOLING
LOCK PLATE
NO.2 BEARING COVER
\
COMPRESSOR TURBINE
A-34 COMPRESSOR
TURBINE VANE ASSEMBLY
PT6A-27/34
0306C PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.13
COMPRESSOR TURBINE
Purpose:
Extract energy from the hot gases to drive the compressor rotor unit.
Construction:
At maximum speed, each blade pulls on the disk with a force of
approximately one ton (2000 lbs.).
The compressor turbine is a two-plane balanced disk assembly,
the disk is a machined nickel alloy forging with firtree serration's
that provide a firm attachment as well as allowing for thermal
expansion differences between the blades and the disk. Rivets
are used to axially retain the 58 blades on the disk.
Compressor turbine blades are cast from a nickel-based alloy,
tapered airfoil design or squealer tip construction, firtree
retention, and corrosion resistant protective coating.
The turbine is secured to the compressor stubshaft by a single
bolt locked by a cupwasher. A master spline ensures
reinstallation of the turbine in its initial position on the
compressor stub shaft during maintenance.
SB: 1439 / 12082
The Compressor turbine is dynamically balanced on two planes
with counterweights and a master spline ensures reinstallation of
the turbine in its initial position on the compressor stub shaft
during maintenance. This feature allows for compressor turbine
replacement in the field.
Operation:
Expanding gases, accelerated through the vane ring hit the turbine
blades. The energy available in the gases is converted into
rotationai movement to drive the compressor and the engine
accessories.
PT6A-27/34
‘,1 0 0 0 ü
Nearly 2/3 of all the energy available from the products of
combustion is needed to drive the compressor. The 1/3 remaining is
used to drive the propeller via the power turbine.
Ng at 100% = 37500 rpm
Max Ng at 101.5% = 38,100
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Maintenance / Inspection:
Inspect CT blades for: tip rub, cracks, sulphidation, erosion,
burning and coating loss.
Inspect CT disk for damage.
Wash turbine blades based on past sulphidation experiences.
CT tip clearance:
Tip clearance is the gap between the tip of the compressor turbine
blade and the shroud segment. lt is one of the most important
factors affecting engine performance. lt limits the gas leakage at the
tip of the compressor turbine blades. When the turbine tip clearance
is too large, more gases leak, preventing the turbine from extracting
the power it needs to drive the compressor. To maintain power, fuel
flow and ITT will increase, but Ng remains below normal because of
the less efficient turbine.
Effect of CT tip clearance at constant power:
Increase clearance = T5 t, Wf +, Ng 9
TRAINING USE ONLY
HOT SECTION 3.14
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MASTER
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POWER TURBINE (REF.)
17\---".
INTERSTAGE BAFFLE
ASSEMBLY (REF.)
RETAINING
BOLT
POWER TURBINE
STATOR (REF.)
COMPRESSOR TURBINE
PT6A-27/34
0307 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.15
POWER TURBINE VANE RING AREA
Maintenance / Inspection:
Power turbine vane ring:
Redirect the combustion gases toward the power
turbine at optimum angle and speed.
Supported by the power turbine stator housing, it
consists of a nickel alloy casting with a riveted sheet
metal center baffle. A lug to slot arrangement
centralizes and prevents movements of the vane ring.
The exit area of the vane ring is classified.
Inspect vane ring for evidence of burning, cracking
and coating loss.
Ensure proper sliding fit (lugs to slots) with PT stator
housing.
Damage to the power turbine vane ring is not
common unless bad fuel nozzles caused damage to
CT area.
Effect of PT vane area on ITT & Ng at constant power:
Power turbine containment ring:
Supported by flange D of the exhaust case, it provides
containment of power turbine blades in case of
separation from the PT disk.
Machined nickel alloy forging, supported by flange D.
Increase area =
Decrease area =
9
Ng, t T5
(Ng Limited)
Ng, 44 T5 t (T5 Limited)
Compressor stall margin is also lost when using a smaller
area PT vane.
Operation:
Gases exiting the compressor turbine are accelerated
through the power turbine vane ring and cause the power
turbine to rotate.
Note: If you change the PT vane ring, use another one
of the same class.
The vane ring is held in piace by lugs fitted in the power
turbine stator housing. The riveted inner baffle directs aír
close to the power and compressor turbine disks for
cooling. During engine assembly, selection of the correct
vane ring class (area) will allow to get optimum Ng and
ITT parameters at engine test.
PT6A-27/34
TRAINING USE ONLY
HOT SECTION 3.16
POWER TURBINE
\..,._
INTERSTAGE BAFFLE
ASSEMBLY (REF.)
SEALING RING
PT6A-27/34
0308 PT6A 27-34
POWER TURBINE VANE RING
TRAINING USE ONLY
HOT SECTION 3.17
POWER TURBINE STATOR HOUSING
Purpose:
Supports the power turbine vane ring, the 15 harness
and thermocouple probes.
Interface with the gas generator section via a seal
ring.
Machined stainless steel, inner lugs for PT vane
support, 8 - T5 thermocouple bores.
PT6A-27/34
(,)
TRAINING USE ONLY
1•1 U QU Q UVUt,..„Ut, (.>
HOT SECTION 3.18
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1.)
POWER TURBINE STATOR HOUSING
PT6A-27/34
0309 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.19
POWER TURBINE
Operation:
Power turbine:
Extracts the remaining energy from the combustion
gases to drive the propeller through the reduction
gearbox.
Single stage disk assembly, made of nickel alloy and
splined to the power turbine shaft. A master spline
ensures that the turbine can only fit in one position on
the turbine shaft.
There is no mechanical link between the power
turbine and compressor turbine thus the power
turbine is "Free" to turn independent of the
compressor turbine operation.
The blades are shrouded at the tip to form a solid
outer rim and reduce blade vibrations. A labyrinth type
shroud achieves gas sealing at the tip of the blade
which provide a two step double knife-edge. The 41
blades are retained in the firtree serrations with rivets.
Expanding gases, accelerated through the PT vane ring
hit the turbine blades. The energy available in the gases
is converted into rotational movement to drive the
propeller. Nearly one third of the energy available from
the combustion is used to drive the propeller.
Max Nf at 100`)/0 = 33,000 rpm.
Rotation CW viewed looking forward.
Maintenance / Inspection:
Inspect the turbine for: cracks, burning, coating loss,
corrosion, impact damage and blade shift
Return the power section to an authorized overhaul
facility if the turbine needs to be replaced
Removal of the power turbine is permissible at field
level if an operator wants to inspect the area beneath
the turbine.
Balancing of the power turbine is done with the power
turbine shaft and the no. 3 and 4 bearings altogether
and for that reason the power turbine is not field
replaceable.
It is secured to the PT shaft by a single locking bolt.
PT6A-27/34
TRAINING USE ONLY
HOT SECTION 3.20
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BALANCING ASSEMBLY
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POWER TURBINE
INTER-STAGE
BAFFLE
POWER TURBINE
PT6A-27/34
0310 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.21
EXHAUST DUCT
Maintenance / Inspection:
Exhaust duct:
•
•
•
•
•
Direct the exhaust gases to ambient atmosphere.
Support the RGB and power turbine, flanges A, B & D
Dual port (A-27/34) or single port case (A-114).
Ski jump helps evacuate the exhaust gases.
Nickel alloy sheet metal and welded machined
flanges.
•
•
•
•
Inspect the case for general condition.
Check the case for cracks near the flanges.
Inspect inner ski jump area for wear caused by #3
bearing cover.
Inspect flange -D- area for cracks around PT shroud.
Insulation blanket:
Reduce heat transmission between exhaust gases
and RGB.
Fire resistant fiber, sandwiched between 2 nickel alioy
sheets.
TRAINING USE ONLY
PT6A-27/34
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HOT SECTION 3.22
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FLANGE C
FLANGE D
FLANGE A
EXHAUST DUCT
PT6A-27/34
0311 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.23
NO. 3 & NO. 4 BEARING AREA
Maintenance / Inspection:
Purpose:
Support the power turbine shaft.
Form a cavity for #3 and #4 bearings.
Sheet metal steel cylinder, supported by flange B of
the RGB.
Contains oil passages to lubricate and scavenge #3 &
4 bearings.
With a suitable light or borescope, inspect inner ski
jump area for any looseness or wear caused by #3
bearing cover rotation.
#3 Bearing Cover:
Reduce heat transmission between exhaust gases
and RGB.
Sheet metal nickel alloy baffle with a machined inner
ring.
Latest exhaust cases have an integral welded cover
(post SB 1430).
Power Turbine Shaft:
Supports the power turbine and transmits the power
to the 1st stage reduction sun gear.
Consists of a machined forged steel shaft.
PT6A-27/34
TRAINING USE ONLY
HOT SECTION 3.24
UQUOQU Q U Q U Q UUOUQ U OUQUQ C) UUQUOQUO C.) t.) 0 (.1
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OIL STRAINER
REDUCTION GEARBOX
REAR CASE
POWER TURBINE
SHROUD
POWER
TURBINE
TORQUEMETER
CONTROL VALVE -----.,_____._,_____o
OIL NOZZLE
ASSEMBLY
PT6A-27/28
NO.3 BEARING
PT6A-34
LABYRINTH
SEAL
POWER TURBINE
SHAFT HOUSING
NO.4 BEARING
POWER TURBINE
VANE RING
SCAVENGE OIL TUBE
POWER TURBINE SHAFT
POWER TURBINE NO.3 & NO.4 BEARING AREA
PT6A-27/34
0312 PT6A 27-34
TRAINING USE ONLY
HOT SECTION 3.25
HOT SECTION PROBLEMS
PROBLEM
Seal ring leak.
Gas leakage at junction between
small exit duct and vane ring.
Burnt vane ring (larger throat
area).
SYMPTOMS AT CONSTANT POWER
Ng
T5
Wf
Same
Up
Up
Same
Up
Up
Down
Up
Up
High CT tip clearance.
Down
Up
Up
Eroded compressor turbine
blades.
Down
Up
Up
ACTION REQUIRED
Reposition or replace seal ring.
Verify seal ring groove and replace
shroud housing if necessary.
Lap sealing faces. Replace parts if
distorted.
Replace vane ring.
Replace shroud segments to
restore clearance.
Replace turbine if blades are worn
out.
Send assembly to an authorized
facility for blade replacement.
Note: Hot section problems are always characterized by a higher T5 and Wf. Ng usually goes down or remains constant.
PT6A-27/34
TRAINING USE ONLY
HOT SECTION 3.26
GEARBOXES
TRAINING USE ONLY
GEARBOXES 4.1
REDUCTION GEARBOX
Operation:
Purpose:
Reduce the power turbine speed to a speed suitable for propeller
operation.
Provide drive, for the Prop. governor, Overspeed governor, and
Np tachometer.
Provide a system to indicate engine torque
Provides a sump area for the RGB scavenge oil to de aerate
Construction:
The PT6 engines use a planetary type reduction gearbox system
with two stages of reduction. The first stage consists of a sun gear
meshing with three planet gears mounted in a carrier. The three
planet gears mesh on the outside with a ring gear splined into the
reduction gearbox casing. The first stage gear carrier drives the
second stage sun gear through a flexible coupling arrangement.
Provision to measure torque is provided by the first stage reduction
system.
The second stage reduction system is similar to the first stage but
uses five planet gears instead of three. The second stage carrier is
splined onto the propeller shaft. A bevel gear, mounted on the
propeller shaft drives three gears for:
Two stage planetary reduction system.
Light alloy front and rear housing.
2 main bearings (No. 5 & 6).
1 chip detector.
Prop governor (CSU).
Propeller Overspeed Governor (OSG).
Np Tach Generator.
.•.•.•.•
Input Nf, 100°/0, CW
First Stage
Second stage
Output, 100°/0, CW
OVERALL RATIO:
33,000
5.000:1
3.000:1
2200
15.000:1
33,000
5.000:1
3.473:1
1900
17.368:1
Propeller Governor / Np tach /
4171 rpm
CW
4201 rpm
CW
RGB Line Maintenance:
Propeller shaft oil seal replacement: Replace seal on condition.
Visually inspect the seal runner for damage.
Np tach oil seal replacement: Replace seal on condition.
Overspeed governor
Propeller governor replacement: Replace on condition.
Note: There are no repairs or accesses inside the reduction gearbox
at field level.
PT6A-27/28
TRAINING USE ONLY
GEARBOXES 4.2
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ACCESSORY DRIVES (3)
FIRST STAGE RING GEAR
FIRST STAGE PLANET GEAR
FIRST STAGE SUN GEAR
0
SECOND STAGE SUN GEAR
SECOND STAGE PLANET GEAR
SECOND STAGE RING GEAR
REDUCTION GEARBOX
PT6A-27/34
0401C PT6A 27-34
PROPELLER SHAFT OIL SEAL DETAIL
TRAINING USE ONLY
GEARBOXES 4.3
ACCESSORY GEARBOX
AGB line maintenance:
Purpose:
To drive the fuel pump/fuei control unit, starter / generator,
pressure and scavenge oil pumps, Ng tachometer and airframe
accessories.
Support the oil filler neck, oil level dipstick and cap.
Provides a sump area for the #1, 2, 3 and 4 bearings scavenge
oil to de aerate
Provides a centrifugal air oil separator breather impeller
Two light allow casings support the drive gears
The casings are bolted to the inlet case
The front casing (diaphragm) separates and seals the AGB from
the oil tank.
Hardened carbon steel gears
Wet splines on starter, fuel pump and air conditioning gearshafts.
Plain aluminum bearing on oil pump gearshaft, roller bearings on
all other gearshafts.
5.11
PT6A-27/28
AGB scavenge pump inlet screen: lf carbon is found on main oil
filter, inspect and clean screen via AGB drain plug.
AGB accessory oil seal replacement: Replace seals on condition.
AGB removal: There are three reasons for removal and splitting the
AGB: (heavy maintenance)
Construction:
Input Ng:
Starter / Generator:
Fuel Pump / FCU:
Ng Tach:
External Scavenge Pump:
Optional, High Speed:
Optional, Low Speed:
Starter generator gearshaft spline wear check: inspect whenever
the starter is removed for maintenance.
37,500 rpm CCW
10,991 r m CW
6,262 rpm CCW
4,203 rpm CW
3,821 rpm CCW
12,028 rpm CW
7,654 rpm CCW
Carbon seal replacement.
Starter generator gearshaft replacement.
Oil pump gearshaft lip seal replacement.
Carbon seal replacement: Required when excessive oil is coming
out of the overboard breather, for reasons other than over servicing.
Inspect starter gearshaft seal face for damage. lt should be a mirror
finish. Replace if necessary.
Starter gear replacement: Replace starter generator gearshaft if
inspection reveals worn out splines. Remove and reuse breather
impeller.
Oil pump gearshaft lip seal replacement: A bad seal may cause
static oil leak into the accessory gearbox.
Note: Always wear gloves when handling AGB internal components.
TRAINING USE ONLY
GEARBOXES 4.4
00Q0k.90QUUOUQUOUU0(,) (>1..,(..„JUQUQUQUO t, 0()U0( ,)U0
CENTRIFUGAL BREATHER &
STARTER GENERATOR GEAR
FUEL PUMP & FCU GEAR
CARBON FACE SEAL
OIL TANK
CENTRIFUGAL
BREATHER
IMPELLER
ACCEESSORY
DRIVES
OPTIIONAL
GEARBOX INPUT
GEARSHAFT
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BALL
LOCK
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EXTERNAL OIL SCAVENGE &
OPTIONAL VACUUM PUMP REAR
SCAVENGE
OIL PUMPS
PT6A-27/34
0402 PT6A 27-34
TRAINING USE ONLY
INTERNAL OIL SCAVENGE,
PRESSURE PUMP &
TACHO-GENERATOR
ACCESSORY GEARBOX
GEARBOXES 4.5
AGB INPUT DRIVE ARRANGEMENT
Purpose:
To lock the input driveshaft to the compressor rear hub.
Construction:
1 Ball.
1 "C" shape expander spring.
2 Locating plates.
1 Key pin.
1 Retaining ring.
2 Piece input gearshaft.
Ball lock system disassembly:
Ensure ball is at 12 o'clock position before unlocking
(key at 3 o'clock) (see view A) when viewed from rear
of engine. Position ball by rotating compressor slowly.
Unlock ball by pulling the input shaft using the pullerpusher tool.
Do not rotate compressor during disassembly.
Remove the accessory gearbox.
Replace expander spring and ball lock.
PT6A-27/28
TRAINING USE ONLY
GEARBOXES 4.6
ACCESSORY GEARBOX HOUSING
ACCESSORY GEARBOX DIAPHRAGM
VIEW A
g
INLET CASE
PLUG
FLANGED ROLLER
BEARING
OIL TRANSFER TUBE
GEARBOX INPUT
DRIVESHAFT
REAR HUB
COMPRESSOR ASSY.
PRESSURE PUMP
ACCESSORY GEARBOX INPUT DRIVE ARRANGEMENT
PT6A-27/34
0403 PT6A 27-34
TRAINING USE ONLY
GEARBOXES 4.7
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OIL SYSTEM
TRAINING USE ONLY
OIL SYSTEM 5.1
OIL SYSTEM DESCRIPTION
Supplies oil to the engine in order to cool, clean and lubricate
bearings & gears.
Provides oil to the prop governor (CSU) to allow propeller pitch
and speed control.
Provides oil pressure for torquemeter indication.
Description: The PT6 lubrication system provides a constant
supply of clean oil to the engine bearings, reduction gears,
accessory drives, torquemeter and propeller governor. The oil tank
is integrated in the engine air inlet casing. The oil lubricates and
cools the bearings and carries any extraneous matter to the oil filter
where it is precluded from further circulation. The oil is also an anti
corrosion agent for the steel bearings and gears. A chip detector is
located in the reduction gearbox to detect metal particles and warn
operators of metal contamination.
Pressure system flow: Oil is drawn from the oil tank and pumped
through a gear type pump and is then delivered to the oil filter. At
the filter outlet, oil separates into several paths.
The no. 1 bearing and accessory input drives are lubricated with
pressure oil directed through cored passages and transfer tubes.
Pressure oil is sent to the fuel heater via a minimum pressure valve
at 2 o'clock position on the inlet case.
A single tube located at the bottom, right hand side of the engine
delivers oil to lubricate the no. 2, 3 and 4 bearings, the reduction
gearbox, front accessories and supply the propeller system.
PT6A-27/34
(-)
Scavenge oil system flow: The scavenge system returns used oil
back to the tank. It consists of 2 oil sumps, one in the AGB, and one
in the RGB. The sumps allow the oil to be collected and deareated
before it returns to the tank.
Four gear type pumps assembled in two double elements form the
scavenge system. Two pumps are located inside the accessory
gearbox, the other two are mounted externally at the left rear side of
the accessory gearbox.
#1 bearing scavenges into the accessory gearbox by gravity. #2
bearing scavenges through an external tube mounted underneath
the engine. At high power a relief valve mounted at the #2 bearing
scavenge pump inlet allows air/oil from the bearing cavity to bleed
into the accessory gearbox, preventing flooding of the #2 bearing
cavity.
#3 & 4 bearing area scavenges into the accessory gearbox via a
scavenge tube mounted on the left-hand side of the engine. Oil is
scavenged by one of the pumps located at the rear of the accessory
gearbox.
The reduction gearbox and the propeller system oil scavenge
through an external tube located along the #3 and #4 bearing
scavenge tube. The oil is pumped by the externally mounted
scavenge pump and goes directly to the airframe oil cooler.
Oil from the AGB sump (from #1, 2, 3 & 4 bearings) is returned to the
oil cooler by a scavenge pump located at its bottom.
OIL SYSTEM 5.2
TRAINING USE ONLY
0 QUOGUOQU Q UOQU QU QUO
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0
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TrA LUBRICATION SCHEMATIC
(REAR)
CHECK
VALVE
CENTRIFUGAL
BREATHER
OIL
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FILTER
BYPASS
VALVE
RELIEF
VALVE
PRESSURE TRANSMITTER
TEMP. BULB
ACC. G/B
DRAIN
OIL SUPPLY TO PROPELLER & REDUCTION G/E1
PT6A-27/34
0501C (A) PT6A 27-34
OIL TANK DRAIN
TRAINING USE ONLY
OIL SYSTEM 5.3A
TaiLlYe)75,
LUBRICATION SCHEMATIC (FRONT)
CSU
PROPELLER
GOVERNOR
TORQUE OIL
CONTROL VALVE
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INTERNAL
PASSAGE
CHIP DETECTOR
DRAIN
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PRESSURE
INDICATOR
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PT6A-27/34
0501C (B) PT6A 27-34
OIL SUPPLYTO PROPELLER & RE'DUCT1ON Gli3
TRAINING USE ONLY
OIL SYSTEM 5.3B
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OIL SYSTEM SERVICING
Servicing:
Max oil consumption:
•
•
•
•
•
•
•
•
Use approved synthetic oil listed in proper service
bulletin (SB 1001).
No intermixing of different oil brands in an engine.
Check oil level within 15 - 20 minutes after shut down.
If engine has been shut down for more than 30
minutes and the oil level indicates lower than average,
run engine before checking oil level.
Oil changes required as specified by the Airframe
Maintenance ManuaL
Ensure that oil pressure is within limits (approx. 80105 PSIG). Check with Ng above 72%.
Inspect oil filter every 100 hours, discard every 1000
hours.
Uti.
. on. :.If . filt01.:
rasonically cleaned, it hasté e
EE-tértioloil:::aticktótá
0.2 lb./hr max oil consumption.
(For better accuracy, consumption should be
monitored on a 10 hour period.) (r) (2 lb/10 hrs).
[Ref: 2 lbs, = 1 US quart (approx.)].
Dipstick:
•
Shows oil quantity needed to keep the tank full,
normal cold oil level is "MAX COLD".
Locking cap:
•
Seals oil tank when closed by a latch.
ut
major . ,cause
. loss of oil OrtssureiI. an improperly I ocked.ollan
Oil system flushing:
Flush oil system if new brand or type of oil is to be
used. Refer to Engine Maintenance Manual for
flushing procedure.
Flush system if oil is contaminated.
ip!ution: If ari engine is rernovedialgto me
con tamination.
the prOp011er, all Ottfitjés ark.
.„„...
ould be flushed, and theioit:coolért
Chip detector maintenance:
Check for metal pickup (continuity check) at every 100
hrs.
Check for function of the chip detector's internal wiring
by bridging the 2 poles checking continuity at 600 hrs
or 12 months.
RGB oil strainer maintenance:
Check RGB scavenge strainer for blocked passages
and non ferrous metal contamination.
PT6A-27/34
TRAINING USE ONLY
OIL SYSTEM 5.4
OVERBOARD BREATHER VENT
OIL TANK FILLER CAP
AND DIPSTICK
OIL PRESSURE
RELIEF VALVE
ACCESSORY
GEARBOX
HOUSING
FILTER ELEMENT
OIL FILTER
COVER
FILTER CHECK VALVE
FILTER
HOUSING
OIL PRESSURE REGULATOR
PT6A-27/34
05020 PT6A 27-34
AGB DRAIN PLUG
TRAIN1NG USE ONLY
PRESSURE OIL
TO REDUCTION GEARBOX
AND POWER SECTION
OILSYSTEM 5.5
000 J0U0UO000009(>0000000 *194,><>99000000 )0UUVU
OIL PRESSURE REGULATION AND FILTRATION
Operation:
Oil Pressure Pump:
Sends oil pressure to the bearings, gears, fuel heater and
propeller.
Gear type pump located in the oil tank and contained in a light
alloy housing also supporting the oil filter housing and pressure
relief valve.
Pressure Relief Valve:
Maintains engine oil pressure within specified limits.
Consists of a sleeve, valve, adjusting spacers, spring and spring
seat, guide and retaining ring. Accessible through the oil filter
housing boss. Refer to Performance Section (9) for limits.
Oil is fed to the pump inlet by the positive static air pressure in the
tank. The oil is then displaced around the pump gears and delivered
simultaneously to the PRV and the filter.
Pump oil pressure is sensed above the pressure relief valve piston.
When oil pressure increases over the limit set by the PRV spring
tension, the valve moves in, opening a passage to the tank, thereby
limiting the oil pressure.
The oil that goes to the filter opens the check valve, exits the
cartridge through holes then enters the filter element. Clean oil flows
out the filter center, to the cover, back in the inlet case bore and is
distributed to the system.
The Teflon washer inside the cover loads the filter against the
bypass valve.
Check Valve:
Allows oil filter removal without draining the oil tank.
Prevents oil gravity flow in static condition.
Spring loaded piston, opens when pump outlet pressure reaches
15 PSI.
Bypass Valve:
If the filter gets contaminated, a bypass valve is provided to allow oil
to flow to the system. The valve senses filtered and unfiltered oil
pressure. Should the delta P exceed a preset limit. the valve will
move away from the filter and oil will flow through the center of the
filter, bypassing the main element. A 40-micron strainer will however
still filter the oil.
Allows unfiltered oil to flow through the engine if the filter was
blocked. Opens when the pressure drop across the filter reaches
25 PSID.
Consists of a piston, a "V" seal. and a spring.
Filter:
Cleans the oil system by trapping any foreign matter on its outer
surface.
Cartridge type 15 micron fiber main element.
Secondary 40 micron internal strainer element.
Filter is marked "THIS SIDE IN", "THIS SIDE OUT" and
"NON CLEANABLE", for proper handling of filter.
PT6A-27/34
Note:
Earlier, all steel filters are still in use today. Refer to the
Maintenance Manual for cleaning instructions and servicing.
TRAINING USE ONLY
OIL SYSTEM 5.6
OIL PUMP HOUSING OIL FILTER HOUSING
FILTER ELEMENT
INLET CASE
COVER
CHECK VALVE SEAT
111;00.
‘IN
GD
C)
0
0 L.1 0
000
0
000
CD
0
C'
CHECK VALVE
BY•PASS
CHECK VALVE SPRING
BY-PASS VALVE
SECONDARY FILTER
FILTER HOUSING & CHECK VALVE
PT6A-27/34
0503C PT6A 27-34
TRAINING USE ONLY
000 JOC)._,JUO(w.J JOQUUQ0000tiv...,
OIL SYSTEM 5.7
..)04)000U0OUGUQUOU
OIL SYSTEM TROUBLESHOOTING
POSSIBLE CAUSE AND FIX
SYMPTOMS
• Check oil level.
Low oil pressure:
(indication may follow power lever setting)
High oil pressure.
Oil pressure fluctuation.
•
•
•
•
•
•
•
•
•
•
•
•
High oil temperature.
•
•
•
PT6A-27/34
Check Indicating system / Aircraft 28V.
Check / Replace oil filter.
Check / adjust pressure regulating valve.
Check pump housing for cracks.
Check Indicating System.
Adjust / verify pressure regulating valve.
Check indicating system.
Check oil level.
Check / Replace oil filter.
Check / Replace or clean pressure regulating valve.
Check oil level.
Excessive operation with propeller feathered.
Check oil temperature indicating system.
Check airframe oil cooler.
AGB scavenge pump inlet screen for blockage.
TRAINING USE ONLY
OIL SYSTEM 5.8
OIL SYSTEM TROUBLESHOOTING
POSSIBLE CAUSE AND FIX
SYMPTOMS
•
•
•
•
•
Excessive oil consumption.
•
•
•
•
Oil venting out from AGB breather.
Static oil leakage:
Oil level is found low after a period of engine inactivity.
(Static internal oil leak, oil might leak out from
compressor inlet).
PT6A-27/34
Q000000000UUQUV JOO
•
•
•
•
Oil level kept too high.
Internal static leakage problem.
Oil venting out from AGB breather.
Check for oil leaks.
Check exhaust, bleed valve and inlet case for oil.
Fuel heater internal leakage.
Oil level kept too high.
Internal static leakage problem.
Verify / replace breather carbon seal.
AGB scavenge pump inlet screen blockage.
Oil filter check valve, lap valve seat or replace 0-ring
(depending on configuration).
0-ring and plastic ring on oil filter housing, replace.
0-rings in oil tank.
Oil pressure pump shaft seal.
TRAINING USE ONLY
OIL SYSTEM 5.9
QUO 4,,?‘><>1>OOGJOU JUt>00,_,
SECONDARY AIR SYSTEM
PT6A-27/34
TRAINING USE ONLY
SECONDARY AIR SYSTEM 6.1
SECONDARY AIR SYSTEM
General: The secondary air system consists of engine airflow used
for other means than producing power.
Of all the air entering the compressor, approximately 25`)/0 is used in
the combustion process, 65°/0 is used to cool the combustion gasses,
5% is allowed for airframe services and the 5% remaining is used by
the secondary air system.
.....:._
...
...... • ur • •
of air us . . -......• ..' • - .. •titts
._
P3
Ensure holes in the number 2 bearing area of gas generator are
not blocked (during HSI)
Ensure overboard breather line is unobstructed
.::::111:11:::1
#1 Bearing
Use
Air Source
P2.5
em
.
Maintenance / Inspection: No repair possible at field level
Bleed off from compressor bleed valve.
Seal No. 1 bearing labyrinth seal.
Cooling of hot section components.
Seal No. 2 & No. 3 bearing labyrinths seals.
Bleed Valve closing.
Fuel Control Unit operation.
#2 Bearing Rear
#2 Bearing Front
#3 Bearing
Bearing compartment sealing: Prevent oil from leaking outside the
bearing cavities.
Description: Air pressure is used to keep oil into the bearing
cavities. The air seal (labyrinth seal ) consists of two separate parts,
one stationary and one rotating with the bearing. One of the two
parts is machined with grooves and a small clearance is maintained
between the two. Pressure air is allowed to flow between them to
create the required sealing.
Oily inlet, bleed valve and compressor.
Oil smell and / or smoke in the cabin.
Oil smell and / or smoke in the cabin.
Coked oil around CT Disk and #2 Bearing
Area.
Possible smoke in exhaust at start and
shutdown.
Coked oil around PT disk and #3 Bearing area.
Oil traces in exhaust ei ees.
Possible smoke in exhaust at start and
shutdown.
NOTE: Contact a P&WC representative if you notice persisting oil
smell in the cabin or suspect any labyrinth seal problems.
Air that flows into bearing compartments are evacuated via the oil
scavenges system and discharged overboard through the centrifugal
breather impeller located in the accessory gearbox.
PT6A-27/34
0000
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SECONDARY AIR SYSTEM 6.2
TRAINING USE ONLY
0 4.)
ti# (I> Q
)
11.
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-
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ri
_
BEARING COMPARTMENT SEALS
TURBINE COOLING & AIR BLEED SYSTEM
PT6A-27/34
0601C PT6A 27-34
TRAINING USE ONLY
SECONDARY AIR SYSTEM 6.3
nnnonnnoe5nnnon~nnnonononor y nn^‹~nonoonnon
ENGINE INDICATING SYSTEM
PT6A-27/34
TRAINING USE ONLY
ENGINE INDICATING SYSTEM 7.1
ENGINE INDICATING SYSTEM
Purpose:
Provide the pilot with indications concerning the
engine parameters during flight.
Provide the required data for engine condition trend
monitoring and performance check on the ground.
Page 7.3 of this chapter shows typical airframe indicating
systems:
Compressor speed.
Oil temperature indication.
Oil pressure indication.
Propeller speed.
Description:
Different systems are designed into the engine to
transmit signals such as torque, propeller speed,
interturbine temperature, compressor speed, etc. All
these signals are sent electrically to the instrument panel
in the cockpit.
PT6A-27/34
Pages 7.4 to 7.10 describe the indicating system built in
the PT6:
• Inter Turbine Temperature system (T5).
Torque Indication System.
Chip Detector.
TRAINING USE ONLY
t> 1.) U 4,) U (4) L1 UOUUUQUOUU
,
41)
ENGINE INDICATING SYSTEM 7.2
L> U
UOUVUU 4) 11
OIL TEMPERATURE
& PRESSURE
WF
PT6A-27/34
0701 PT6A 27-34
TRAINING USE ONLY
ENGINE INDICATING SYSTEM
ENGINE INDICATING SYSTEM 7.3
T5 INDICATING SYSTEM
Purpose: Provide the pilot with an indication of the
engine combustion temperature. That temperature is
ádritiOl gáletween the compressor turbine exit and the
power turbine vane inlet.
Construction:
An external T1 trim probe provides trim compensation, to
the T5 signal, to compensate for temperature profile
sampling errors.
A classed trim probe located at 2
o'clock over the inlet case is connected ín parallel with
the 8 thermocouples to bias the average temperature
reading. This temperature (T5c) is read in the cockpit.
Operation: As heat is sent to the thermocouples,
The amount of trimming is a function of the trim probe
internal resistance. The higher the trim resistance, the
lower the down trim (higher T5). The resistance is
established at engine test to match the required
temperature trim.
Because the amount of trim
compensation required vary from engine to engine, the
trim stick class is specified in the engine test certificate
provided with the log book.
voltage is generated at the tip of each Chromel / Alumel
probe.
T5 system tests:
8 individual thermocouples (Chromel-Alumel).
1 positive bus bar (Chromel, small thread terminals).
1 negative bus bar (Alumel, large thread terminals).
1 trim probe,
f T5 wiring harness with terminal block.
P-(9-P'.524\-vD
To obtain an average reading, the thermocouples are
connected in parallel. T5 is the average temperature at 8
specific locations (thermocouple tips) within the gas patiVÇ
and iiiárldrje" does not represent the exact average
Or
templáttiVé
at station 5.
The actual T5 is calculated at engine test and is used to
determine engine acceptance.
Trimming: Uneven heat distributíon within the gas path
causes individual thermocouples to see different
temperatures and generate different voltages.
PT6A-27/34
0 0 ‘,.)
tin.) (1 0 0 0 t)
Loop (continuity)
Ensu res
continuity and proper resistance in the T5 probes,
busbars, wires and terminals.
Insulation (ground) resistance check: Ensures that
neither Alumel nor Chromel contact the casing.
Heat response (T5 probe functional) check: Ensures
T5 probes response to heat. Test is done when engine is
open at "C" flange.
TRAINING USE ONLY
U 0 t)
resistance check:
C.)
ENGINE INDICATING SYSTEM 7.4
U U 0 0 Q 0 tlib tok 4) 0 (i>
Q
TERMINAL BLOCK
TERMINAL LUG
CHROMEL TERMINAL
PROBE
RETAINING NUT
CAP SCREW
BUS-BAR
MOUNTING
SCREW
ALUMEL
TERMINAL
TERMINAL
STRAPS
PROBE ASSEMBLY
CHROMEL
BUS-BAR
ALUMEL BUS-BAR
TRIM THERMOCOUPLE
SEAL RING
RETAINING PLATE
T5 INTERTURBINE TEMPERATURE THERMOCOUPLE ASSEMBLY
PT6A-27/34
0702 PT6A 27-34
TRAINING USE ONLY
ENGINE INDICATING SYSTEM 7.5
T5 SYSTEM TROUBLESHOOTING
SYMPTOMS
Lower T5 indication than
normal.
POSSIBLE CAUSE
Cockpit gage calibration.
Calibrate or change cockpit gage.
Airframe loop resistance too high.
Adjust (ref. Aircraft Manual).
Dirt or corrosion on connections to cockpit gage.
Cockpit gage calibration.
Airframe loop resistance too low.
Clean or replace as required.
Replace with proper trim stick class.
Do an insulation check.
Do continuity or a heat response test.
Replace defective T5 probes.
Calibrate or change cockpit gage.
Adjust (ref. Aircraft Manual).
Broken or wrong class trim stick (high class).
Replace trim stick.
Wrong class trim stick.
Grounded system.
Burnt or broken T5 probes.
Higher T5 indication than
normal.
CORRECTIVE ACTION
Dirt or corrosion on trim stick terminals.
Clean or replace as required.
Do continuity or a heat response test.
Burnt or broken T5 probes.
Replace defective T5 probes.
Open circuit between T5 probes and cockpit gage.
Verify / Clean / replace or Tighten to specification.
No T5 indication
Loose, corroded or dirty connectors on terminals.
Verify / Clean / replace or tighten to specification
System grounded.
Erratic T5 / T5 fluctuations
Verify ceramic insulation, ensure wires are not
grounded to case.
Broken / chafed wires.
ONLY,
if
other
parameters
are
also
off,
refer to engine performance troubleshooting.
In
all
cases,
ensure
the
problem
is
T5related
Note:
PT6A-27/34
1)0uk.M..4 UU0410419U4)04194#
TRAINING USE ONLY
Il sOU gho
ENGINE INDICATING SYSTEM 7.6
UULktivu
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PT6A-27/34
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TRAINING USE ONLY
ENGINE INDICATING SYSTEM 7.7
TORQUE SYSTEM
Purpose:
Provide a representation of the shaft horsepower
produced by the engine by indicating the torque applied
to the propeller.
Static air pressure inside the reduction gearbox produces
a force on the torquemeter piston and can cause wrong
torque reading.
For this reason, that same static
pressure is sent to the opposite side of the transducer
and subtracted from the torque reading.
Description:
The torque is a force felt between the driving (power)
turbine and the driven propeller. The system is a hydromechanical unit comprising:
Floating first stage ring gear with helical splines.
Piston and seals.
Cylinder.
Spring loaded oil control valve.
Airfranne:
Torque applied to the propeller induces a small
rotational and rearward reaction movement of the first
stage ring gear. This movement is due to the helical
splines on the ring gear. The piston and the control
valve are pushed by the ring gear and always follow
it.
0000L JUQUU004.1041000
PT6A-21
PT6A-27/28
PT6A-34/34B/34Ag
PT6A-114
"" TÓrC
1315 Lb.-Ft
42.5Psi g)
1628 Lb.-Ft
53.3Psi g)
1970 Lb.-Ft
64.5Psi q)
1980 Lb .-Ft
56.2Psi g)
Maintenance:
Operation:
RT6A-27/34
Engirle Model
Calibrate transducer as per Airframe Maintenance
Manual instructions.
Replace faulty transducers.
Engine: No maintenance at field level.
TRAINING USE ONLY
ENGINE INDICATING SYSTEM 7.E
000 IJUOU
OUVO 14+Jt,
ELECTRIC
TORQUE
SIGNAL
TORQUE PRESSURE
TRANSMITTER
(AIRFRAME)
FIRST STAGE
PLANET GEAR
REDUCTION GEARBOX
STATIC PRESSURE
t
1ST STAGE
RING GEAR
TORQUE OIL
PRESSURE
CONTROL
VALVE
TORQUE PISTON
LOW POWER
PT6A-27/34
0703C PT6A 27-34
TORQUE SYSTEM
TRAINING USE ONLY
CYLINDER
METERING ORIFICE
HIGH POWER
ENGINE INDICATING SYSTEM 7.9
TORQUE SYSTEM TROUBLESHOOTING
Note: in all cases, ensure the problem is torque related only, if other parameters also appear faulty, such as Np, the
problem is possibly propeller control system related. Often, a faulty torque system indication will make all engine
parameters read higher or lower than normal. This is easy to understand, as the pilot sets engine power using torque as
reference.
te
H igh Tarque ind icatiori
ua t
•
•
•
•
•
•
•
•
•
•
•
•
Too low main engine oil pressure.
Indicating system problem
Torque piston is stuck.
RGB static line leaking (-2psi)
Indicating system problem.
Control valve stuck.
Piston seals could be worn.
Excessive internal oil leakage.
Control valve stuck open.
Torque pressure tramsmitter.
Indicating system problem.
RGB static line loose.
PT6A-27/34
()(.)(J.,uuv.it/fibto gh0Vii#VV‘OV
TRAINING USE ONLY
•
•
•
•
•
•
•
•
•
•
•
Increase oil pressure within limits.
Check or calibrate transducer or gage.
Return power section to overhaul shop.
Check and fix RGB static pressure line.
Check or calibrate transducer or gage.
Contact your PWC representative.
Increase oil pressure within limits.
Return power section to overhaul shop.
Contact your PWC Representative.
Test wiring.
Test and/or replace transmitter.
ENGINE INDICATING SYSTEM 7.10
1.)Vvit0WV‘év )VVVw
)1.)
TRAINING USE ONLY
ENGINE INDICATING SYSTEM 7.11
CHIP DETECTOR
Purpose:
Operation:
Provide an indication of metal particie contamination of
the engine oil system.
When metal particles accumulate on the two magnetic
poles and bridge the existing gap, the normally open
circuit closes.
Description:
On some installations a light illuminates in the cockpit to
indicate the contamination. On other models, visual
inspection and continuity check of the chip detector that
will detect contamination. Particles found on the chip
detector can be analyzed and identified. Refer to Chapter
71 of the Engine Maintenance Manual.
Two magnetic poles.
Normally open circuit.
Wired to a light in the cockpit.
Self closing valve allows chip detector verification
without draining the RGB.
Maintenance:
Check threads for damage.
Check if continuity exist when the two poles are
shorted.
Check that wires going to cockpit are in good
condition.
Check area of chip detector underneath 0-Ring for
wear and cracks.
Check for security of terminal pins.
PT6A-27/34
UUUL)
.11
TRAINING USE ONLY
ti> UVUUUU t> t.# 4h) VUVU
ENGINE INDICATING SYSTEM 7.12
4.1 V 4,0 4.0 tibM SJ 4.1 ‘,4
0 t> 0
MAGNETIC POLES
PREFORMED
PACKING
MAGNETIC
CHIP
DETECTOR
LOCKWIRE
SECURING LUG
INSULATION
ELECTRICAL
CONNECTOR
CHIP DETECTOR
PT6A 27/34
0704 PT6A 27 34
TRAINING USE ONLY
ENGINE INDICATING SYSTEM 7.13
"nonn000nnononononeloonononnnonennes,00mononn
IGNITION
TRAINING USE ONLY
IGNITION 8.1
IGNITION SYSTEM (GLOW PLUGS)
Maintenance / Inspection:
Purpose: Provide the heat source to ignite the fuel/air
mixture.
Inspect for carbon build up and clean.
inspect cables for chaffing, replace if necessary.
Inspect coil end for fused areas.
Refer to Engine Maintenance Manual for limits.
Carry out functional test every minor airframe inspectior
glow plugs should reach an acceptable orange-yellow
color within 8 seconds.
Proceed by elimination to find faulty components.
Glow ignition components life 'on condition'.
Voltage regulator and ballast tubes are replaceable.
Description: The glow plugs ignition system consist of an
engine mounted current regulator (left-hand side of the
accessory gearbox), two high tension cables and two glow
plugs. The system is energized only during engine start up.
Current regulator box: Comprise two sets of ballast tubes
which keep the amount of current constant to the glow plugs
over a wide range of input voltages. The electrical circuitry is
designed to provide a selection of either glow plug on start
(A/F option).
Ignition Cables: Two cables carry the electrical energy from
the current regulator to the glow plugs. Each cable consists of
an insulated electrical lead contained in a flexible metal
braiding.
Glow plugs: Located at 4 and 9 o'clock positions on the gas
generator case, the glow plugs are in the form of threaded
plugs with a central coil. When the current reaches a certain
level, the coil element glow which ignite the fuel mixture.
NOTE 1: When starting an engine with a glow plug systn,
wait an additional 5 seconds after Ng has stabilized pricto
introduce fuel. (this delay will give more time for the plugto
reach full glow).
Current regulator specifications:
NOTE 2: SB1196 introduced the spark ignition system orall
new small PT6A's.
17-28 VDC.
Input voltage:
Coil temperature: 1200°c to 1300°c.
7-8 amp.
Output current:
PT6A -27/34
SB 1103: B-B = 1230°c.
A-B = 1320°c.
DO NOT use A-A = it's too hot.
TRAINING USE ONLY
0000000Q0004)UOUG0000 04?
1GNITION .2
J0UOGC>Q0 00() QUO
A
LEFT
CLOCK
POSITION)
s
(9 O
IGNITION GLOW PLUGS
A RIGHT
(4 CYCLOCK POSITION)
UPPER INPUT CONNECTOR
CENTER
OUTPUT CONNECTOR
LOWER
OUTPUT CONNECTOR
A
4-0
(
3
--0-1
06
,
NO. 3
NO. 4 COMMON
7 & 8 COMMON
CURRENT REGULATOR UNIT CIRCUIT & GLOW PLUG
PT6A-27/34
0801 PT6A 27-34
TRAINING USE ONLY
IGNITION 8.3
IGNITION SYSTEM (SPARK IGNITERS)
Purpose: Provide the spark to ignite the fuel/air mixture.
Exciter box specifications:
Description:
•
The spark ignition system consist of an airf rame mounted
ignition exciter, two high tension cables and two spark igniters.
The system is energized only during engine start up.
•
•
•
Input voltage:
9-30 VDC.
Spark rate 10 VDC: 1 spark/sec.
Spark rate 30 VDC: 4 sparks/sec.
8000 volts.
Output voltage:
Maintenance / Inspection:
Exciter Box:
Sealed unit which transfers a DC low voltage input into a high
voltage output. When the unit is energized, a capacitor is
progressively charged until the energy stored is sufficient to
ionize a spark gap, then the capacitor discharges through the
igniter plugs.
Ignition Cables:
Two cables carry the electrical energy from the exciter box to
the igniters. Each cable consists of an insulated electrical lead
contained in a flexible metal braiding.
Inspect cables for chafing, replace if necessary.
inspect cooling holes of spark igniters for blockage.
inspect igniter shell and electrode for erosion.
Refer to Engine Maintenance Manual for limits.
Carry out functional test every minor airframe inspection by
disconnecting one ignition cable at the exciter box, switch
ignition on and listen for the spark.
Proceed by elimination to find faulty components..
Spark ignition components life 'on condition'.
Do not clean carbon at plug tip.
No thread lubricant is allowed.
Spark Igniters:
Located at 4 and 9 o'clock positions on the gas generator
case, the spark igniters are in the form of threaded plugs with
a central electrode enclosed in an annular semi-conducting
material. When the voltage reaches a certain level, the air
between the central electrode and the plug outer shell ionizes
and allow a high energy spark to discharge from the centre
electrode.
PT6A-27/34
)0 0
TRAINING USE ONLY
i0000000 , 404 , 00
IGNITION 8.4
()000UU0J
0009
COMBUSTION CHAMBER
EXHAUST DUCT
N
rr
~ COOLING AIR PASSAGE
SPARK IGNITER
GAS GENERATOR CASE
IGNITION SYSTEM
PT6A-27/34
0802 PT6A 27-34
TRAINING USE ONLY
IGNITION 8.5
nonnoneonnonnonnneonononnononononeenoonnnnn
PERFORMANCE
TRAINING USE ONLY
PERFORMANCE 9.1
PERFORMANCE CHECK
Procedure:
Purpose:
Determine Outside Air Temperature (OAT).
Permits verification of engine condition over a wide range
of ambient temperatures without exceeding torque or T5
limits.
The performance check run allows the operator to check
T5, Ng and Wf margin. Periodically, the engine is ran and
checked against an Airframe supplied performance chart to
see what remains of this margin. The interval is at
operator's discretion.
Determine Pressure Altitude (Pa) or Barometric
Pressu re.
3. From appropriate curves, determine:
Target Torque.
T5 Limit.
Ng Limit.
Fuel Flow (Wf) Limit.
4. Determine parameter limits using tolerance from the
Airframe Maintenance Manual applied to the graph
values.
Schedule:
Performance check should be performed:
Start engine and stabilize at idle for 5 min. During
check, generator and P3 air supply must be switched
off.
After engine installation.
Before and after hot section inspection (HSI).
At regular interval.
Increase power until specified propeller speed and
target torque is reached.
Allow engine and
instrumentation to stabilize.
Description:
The performance check curves establishes engine
parameter limits of an acceptable engine for different
atmospheric conditions. The check is performed at a given
power (Tq and Np constant) and the values obtained for
Ng, T5 and WF are compared to the limits obtained from
the curves on the chart.
Record actual T5, Ng and Wf.
Compare recorded values of T5, Ng and Wf to chart
parameters.
lf values deviate from chart limits,
troubleshooting action should be undertaken to restore
engine performance.
Note: Ensure gauges are properly calibrated.
PT6A-27/34
TRAINING USE ONLY
000000000GIUOUGIC)00_ JO
PERFORMANCE 9.2
00004)4000041
00
,
FIELD BAROMEI TRIC PRÉSSURE
48.0
2000
a, 1800
72. 1600
1400
<:?,, 1200
100
800
600
a
500
cc 450
400
350
300
114,000 FT
250
-12'°1 COOOFTO FT
— 8000 FT
200
3100 Hg
2992
46 0
2900
1- 44.0
2800
L"--
2700
42,0
2600
40.0
2500
o 38.0
2400
360
2300
2200
340
360 —
FILED BAROMETRI
3100
C PRESSURE
2992
2900
2800
2700
2600
2500
2400
2300
2200
cc 340
59 320
53 300
280
102
100
98
96
94
92
90
790
770
750
730
o
710
690
ir)
670
650
630
610
590
260
240
CZI LLI
LLI W5
LU
1.05
au)
* .°2
1.00
CD
,a)
0.95
c
NOTES 1 PROP SPEED . 2000 RPM -A27
2 STATIC CONDITIONS
3 NO INSTALLATION LOSSES AIR
BLEED OR POWER EXTRACTION
4 TORQUE LBS FT .30-57 PSI
c> 700
-
P
600
Eb
cc
i s p1/4.211 01 \
?
---1
k-z
80
__+__
-I---
SEA LEve.
-I 2000 Fr
4000 p.i.
—I 8000 Fr'e000 F7.1_
io,000 Fr
i
112.0ooFri
___i____
__n__.
50
60
14.000 pr
nffitm.i
0
-1----
14,000 FlT
12,000 FT
10,000 FT
. ,1111,,1~
. .n ,..i~. 4
imi
,~
—41~~1021111.1111111r
'151'
-"--4°
tO
<<,
%•
-40
" p41 0 \
so
200
-30
-20
-10
0
10
20
30
40
STATIC CONDITIONS / NP = 2000 RPM
500
?0
-10
0
10
20
30
40
AIR INLETTEMPERATURE °C
PERFORMANCE CHART (TYPICAL)
PT6A-27/34
0901 PT6A 27-34
TRAINING USE ONLY
PERFORMANCE 9.3
ENGINE CONDITION TREND MONITORING (ECTM)
Data acquisition:
Purpose:
The accuracy of the ECTM process depends on the quality
of the data entered in the computer program. ECTM Data
is collected in cruise flight since it is the operating
environment where engine performance is most
predictable.
ECTM is a maintenance tool which allows the user to
monitor the engine performance and:
Permit early detection of engine deterioration.
Help determine source of problems.
Increase dispatch reliability.
Perform repairs at the most economical time.
Do HSI's on condition.
The data will be valid when the following restrictions are
applied:
Record data daily, or every 6-flight hours, select the
flight with the longest cruise portion that is at a
representative altitude and airspeed.
Allow the engine to stabilize 3 to 5 minutes without
ANY lever movements.
The same flight configuration should be repeated (i.e.
electrical load, bleed air extraction).
Record data within a reasonable time frame.
Up-date entry in ECTM.
Description:
ECTM is a process involving repetitive recording of engine
and aircraft instrument parameters and comparing them to
a computer reference model.
Under specific ambient conditions, engine parameters
such as compressor speed (Ng), interturbine temperature
(T5) and fuel flows (Wf) are predictable. The difference
between the actual engine parameters and the computer
model values will be plotted as 3 deltas using a graphical
chart method.
Once a trend is established by the plotting of these deltas,
any deviation would indicate some degree of engine
deterioration. Analysis of the trend reveals extent of
deviation and possible need for corrective action.
Note: Service Information Letter Gen 010 provides
generic information in regard to engine trend analysis.
PT6A-27/34
000
00
Data entry and calculation:
IBM PC with PWC supplied ECTM IV Version 2
program. (ECTM III discontinued)
Plotting and Trend Analysis:
Once the deltas are calculated, the computer does the
plotting and dispiays the result on the screen or sends it to
a printer. Analysis of the trend reveals extent of deviation
and possible need for corrective action.
TRAINING USE ONLY
100000000 1
1.1, n••.,
)
0
PERFORMANCE 9.4
OUVOGju0000
ECTM
PT6A-27/34
0902 PT6A 27-34
TRAINING USE ONLY
PERFORMANCE 9.5
ENGINE CONDITION TREND MONITORING (Continued)
GUIDELINES:
PLOTTING
Following computation, DELTA Ng, DELTA T5, and
DELTA Wf are plotted on a continuous sheet. Flight log
number may be used as the abscissa, although the trend
could also be recorded as a function of date or, preferably,
as a function of engine running time in hours.
Delta T5
Net change of 5 to 10°C: Early signal of some
deterioration that should be investigated when
convenient.
Interpretation of Trend
Net change of 20 to 25°C: Deterioration becoming
more serious. Further running could result in high cost
component replacement (Ex: Compressor turbine vane
ring, compressor turbine blades, etc). Action should be
taken as soon as possible.
Definition of Terms:
Base Line: Delta values, for a particular engine with
known conditions. Known conditions include a recently
completed HSI, inspection of compressors and a
compressor wash. New or newly overhauled engines
also meet these conditions.
Net Change: The change from the base line to a line
passing through a delta point at a specific location on
the graph.
Net change of 50°C: At this level, whether or not T5 is
redlined, deterioration has progressed to a point where
serious engine damage is imminent.
Delta Ng
Revision of Base Line: In the event the position of the
initial base line is improperly estimated a fault or
change in the calibration of instrumentation often
causes (this), a revision of the base line values needs
to be carried out.
Net change of 1.5 to 2% : Action should be taken as
soon as possible.
Analysis: The analysis of the trend graph should be
carried-out on a daily basis if possible, but not deferred
for more than five days.
NOTE: Courses on ECTM are available, please contact
P&WC Customer Training department for the schedule.
PT6A-27/34
0 0 C, 0 0
Net change of .75 to 1% : Early signal of some
deterioration.
PERFORMANCE 9.6
TRAINING USE ONLY
0 41
0U
0
t)
4) 0
t.*
(i) tá
0
COMPRESSOR CONTAMINATION
I
I
4
cS-5-1
17)
2
2
o
I
< 2
4
i
50
i
25
0
25
50
20
=c:. 10
/\A
cl_
0
I 10
< 20
TIME UNIT ----/-
SAMPLE PLOT
PT6A-27/34
0903 PT6A 27-34
TRAINING USE ONLY
PERFORMANCE 9.7
HOT SECTION CONTAMINATION
4
2
CS)
0
-2
-4
20
10
O
-10
-20
TIME UNIT
SAMPLE PLOT
PT6A-27/34
C) 0 0 0 0 Q
PERFORMANCE 9.8
TRAINING USE ONLY
0904 PT6A 27-34
)00
0
0 0 GO tw
0 ,
ENGINE TROUBLESHOOTING
Effective troubleshooting implies monitoring engine
parameters on a regular basis, using performance
check and Engine Condition Trend Monitoring.
Effective troubleshooting may be divided into four
steps:
Evaluate the symptom.
Logically isolate the possible cause of the
problem.
Try quick fixes when possible.
Determine the corrective action required to resolve
the problem.
Remember that troubleshooting is done by comparing
engine parameters with a set of reference valves for a
good engine or by looking at the trend of the
parameters of one engine over a period of time.
PT6A-27/34
TRAINING USE ONLY
PERFORMANCE 9.9
HOT SECTION INSPECTION AND TIME BETWEEN
OVERHAUL
HSI and TBO are defined under the following Service
Bulletins:
TBO escalation Program:
Operators desiring TBO extension should submit a
formal request in writing together with details of
sample engine log book to:
Pratt & Whitney Canada Inc.
ATTN: Manager, Technical Support
P16 Engines.
SB 1003 for PT6A-21 / 27 /28 / 34B / 114 /114A /
116 / 135 / 135A
SB 1303 for PT6A-34AG
SB 1403 for PT6A-34 / 36
ENGINE
TBO Industry: PWC recommended TBO applicable
to all operators.
TBO Fleet: TBO attained by individual operators for
engines of the same model in their fleet only.
Compressor turbine blades must be submitted to an
overhaul type inspection first at 5000 hours and then
every 3000 hours. Such inspection must include Non
Destructive Testing (NDT) inspection and blade
stretch measurement in accordance with Overhaul
Manual Instructions.
PT6A-27/34
000C JUU411_ JOUGIU000
BASIC TBO
BASIC HSI*
3500
1750
3500
4000
1750
1250
PT6A-21 / 27 /28 /
34B / 114 / 114A /
116 / 135 /135A
PT6A-34AG
PT6A-34/36
*
HSI interval may be based on Engine Condition
Trend Monitoring as per:
Analytical Guide. Ref: SIL PT6A-036
TRAINING USE ONLY
1 00
PERFORMANCE 9.10
U00410000
Notes:
PT6A-27/34
TRAINING USE ONLY
PERFORMANCE 9.11
ROTOR COMPONENTS — SERVICE LIFE
Accumulated (Abbreviated) Total Cycles =
Description:
Certain rotating components are subject to low cycle
fatigue due to cyclic operation of the engine.
Additionally, other factors such as high frequency
fatigue and metallurgical changes related to time
rather than flight cycles are considered. As a result,
these parts must be removed from service when the
total cycle limit of the hourly limit is reached.
Airworthiness regulations require the operator to log
engine hours, engines starts and aircraft flights. it is
also the responsibility of the operator to calculate and
record these hours and cycles.
# of starts +
# of flights - # of starts
Abbreviated cycle factor
]
X Flight count factor
Example: Refer to Service Bulletin 1002
Part No.
3013111
(PT6A-27 / 34 1 st stage compressor hub. Life = 1900 cycles)
Abbreviated Cycle factor
No. of Starts
No. of Flights
Flight Count Factor
2
850
1910
1
Operators having missions which include many touchand-go flights, or a frequency of scheduled in-flights
shutdowns (such as used during pilot training) or
which include more than 10 flights per hour should
submit their mission profiles to Pratt & Whitney
Canada for life cycle analysis.
[850 + (1910 — 850)] x 1
2
Rotor components must be retired from service when
the "Hour Limit" or "Cycle Limit" is reached, which
ever occurs first.
The l st stage compressor hub has accumulated 1380
cycles.
Component life is calculated using the following
formula:
[850 + 530] x 1
[1380] x 1 = 1380
Note: Rotor components must be retired from service
when the cycle limit is reached, regardless of the TBO
life of the engine.
Accumulated Total Cycles =
Number of flights X flight count factor
PT6A-27/34
TRAINING USE ONLY
PERFORMANCE 9.12
VUUL UUW 410 4# 41) 4# 41 U 41h 11 4# 11 4) UUUVUOU404.1 400 11 V V 40
UUV
TAKE-OFF
IDLE -
TAXI
T.O.
CLIMB CRUISE
LET DOWN REVERSE
TAXI
STOP
TYPICAL GAS GENERATOR RUNNING MAP
PT6A-27/34
0913 PT6A 27-34
TRAINING USE ONLY
PERFORMANCE 9.13
OPERATING LIMITS
The operating limits define, for each specific engine
model, the upper and lower boundaries, where
applicable, for all engine parameters observed in the
cockpit during normal operation.
Excursion beyond these limits may accelerate engine
wear and possibly lead to component failure.
For current operating limits, refer to applicable Engine
Maintenance Manual (chapter 71).
Operating limits are listed here for the: A-27, A-28,
A-34/34B/34AG, A-36, A-114, A-114A, A-135,
A-135A, A-21 for reference only.
S.0.1. (Specific Operating Instructions)
ENGINE RATINGS
Take-off: This rating is the maximum power
permissible and corresponds to the applicable model
SHP at sea level up to their respective temperature.
The torque pressures for the various air inlets
temperatures and barometric pressures to give this
rating re shown within their respective charts. The
maximum allowable output torque must not be
exceeded.
PT6A-27/34
UUl.) UUVUU4k41414>OUUOUU
Maximum Continuous / Enroute Emergency: This
rating is intended for emergency use at the discretion
of the pilot. Use of this rating is also authorized for
aircraft certification where flight at maximum
continuous power is called for.
Maximum Climb / Maximum Cruise: ls the
maximum power approved for normal climb and
cruise.
Hi-Idle: Hi-idle is obtained by placing the starting
control lever in the Hi-idle position (approximately 26,
000 rpm) as defined by the aircraft manufacturer.
Idle: Idle power is obtained by placing the power
control lever in the Idle position with the stating control
lever in the Run position. This power corresponds to
that obtained at approximately 20, 000 gas generator
rpm.
Reverse: Either full or partial reverse is obtained by
moving the power control lever to any position below
idle.
TRAINING USE ONLY
)1.11> wirb
PERFORMANCE 9.14
U41400%.0
)41/U0
it)U0
OPERATING LIMITS
PT6A-21
CONDITION
TORQUE
POWER SETTING
SHP
Takeoff and
Maximum / Enroute
Continued
Emergency
Maximum Climb
Maximum Cruise
OPERATING LIMITS
Ng
ITT° C
MAXIMUM
RPM
°/0
OBSERVED
LB.FT
.PSIG
550
32 8° C
(91° F)
1315
42.5
695
38,100
620
20.6° C
(69° F)
1628
42.5
695
38, 100
Lo-Idle
660
Starting
1090
Acceleration
Maximum Reverse
PT6A-27/34
500
32.8° C
(91° F)
101.5
Np
OIL
RPM
PRESSUR
E PSIG
2200
80 — 100
2200
80 — 100
40 (Min.)
1500
48.5
825
38, 500
102.6
2420
1315
42.5
695
38, 100
101.5
2112
2068
TRAINING USE ONLY
TEMP. °C
,
10 to 99
150° to 210°F)
0 to 99
(32° to 210° F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
0 to 99
(32° to 210° F)
80 -100
,
0 to 99
(32° to 210° F)
PERFORMANCE 9.15
OPERATING LIMITS
PT6A-27
SHP
LB.FT
PSIG
OPERATING LIMITS
ITT° C
Ng
MAXIMUM
NOMINAL OBSERVED
RPM
°/0
680
21.7° C
(71° F)
1628
53.3
725
38,100
101.5
2200
100
80 — 100
620
20.6° C
(69° F)
1628
53.3
695
38, 100
101.5
2200
100
80 — 100
(32° to 210° F)
40 (Min.)
-40 to 99
CONDITION
POWER
SETTING
Takeoff and
Maximum /
Enroute
Continued/
Emergency
Maximum
Climb
Maximum
Cruise
Lo-Idle
Starting
Acceleration
Maximum
Reverse
TORQUE
675
Np
Nf
RPM
%
660
925
620
1090
2100
68.7
825
38, 500
102.6
1628
53.3
725
38, 100
101.5
2420
2112
2068
110
96
94
f
) )
TEMP. °C
10 to 99
(50° to 210°F)
0 to 99
(-40° to 210° F)
-40 (Min.)
0 to 99
(32 0 to 210° F)
80 -100
, 0 to 99
(32° to 210° F)
PERFORMANCE 9.16
TRAINING USE ONLY
PT6A-27/34
UU UULi ka 4h$ 11 4) 0 0 0 0 f)
OIL
PRESSURE
PSIG
) .f) tiO
1) U kk ) U UUO
OPERATING LIMITS
PT6A-28
CONDITION
POWER
SETTING
TORQUE
OPERATING LIMITS
Ng
ITT° C
MAXIMUM
RPM
%
NOMINAL OBSERVED
SHP
LB.FT
PSIG
Takeoff and
Maximum /
Enroute
Continued/
Emergency
680
21.7° C
(71° F)
1628
53.3
750
38,100
Normal
Cruise
620
20.6° C
(69° F
1628
53.3
695
38,100
Maximum
Climb
Maximum
Cruise
620
20.6° C
(69° F)
1628
53.3
750
38100
925
Starting
Acceleration
PT6A-27/34
101.5
620
OIL
Nf
RPM
%
PRESSURE
PSIG
2200
100
80 — 100
2200
100
80 — 100
2200
100
80 — 100
40 (Min.)
660
Loldle
Maximum
Reverse
101.5
Np
68.7
850
38,500
102.6
2420
110
1628
53.3
750
38, 100
101.5
2090
95
TRAINING USE ONLY
10 to 99
(500 to 210°F)
0 to 99
(32° to 210° F
0 to 99
(320 to 210° F)
-40 to 99
(-40 0 to 210° F)
-40 (Min.)
0 to 99
1090
2100
TEMP. °C
(32° to 210° F)
80 -100
0 to 99
(32° to 210° F)
PERFORMANCE 9.17
OPERATING LIMITS
PT6A-34 / 34B / 34AG
CONDITION
SHP
LB.FT
PSIG
750
31.000
(87° F)
1970
64.5
790
38,100
101.6
2200
100
85-105
A-34134B
A-34/34B
765
38, 100
101.6
2200
100
85 — 105
740
38,100
101.6
2200
100
85 - 105
Idle
685 (6)
19,750
52.6
Starting
Momentanj
Acceleration
Maximum
ReVerse
1090
POWER
SETTING
Takeoff and
Maximurñ /
Enroute
Continued/
Emerúency
Maximum
Climb
Maximum
Cruise
700
28 3° C
(83° F)
700
19.4° C
F)
750
1970
64.5
A-34AG
A-34AG
1840
60.2
1840
60.2
4.#
Nf
OIL
RPM
%
RPM
°/0
PRESSURE
PSIG
40 (Min )
2100
68.4
850
38, 500
102 6
2420
110
85 to 105
1970
64.5
790
38, 100
101.6
2100
95±1%
85 to 105
PT6A-27/34
UOU L•
OPERATING LIMITS
Ng
Np
ITT° C
MAXIMUM
OBSERVED
TORQUE
ly) 411 41 410 ti# OVUOU
TRAINING USE ONLY
itá gh, V VVU 41, 41 0
TEMP. °C
10 to 99
(500 to 210°F)
0 to 99
(32° to 210° F)
0 to 99
(32° to 210° F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
0 to 99
(32° to 210° F)
0 to 99
(32° to 210° F)
PERFORMANCE 9.18
fiá Vtlá gJ V 410 U 4.1 4,4 U
OPERATING LIMITS
PT6A-36
CONDITION
POWER
SETTING
LB.FT
PSIG
ITT° C
MAXIMUM
OBSERVED
1970
64.5
1970
TORQUE
SHP
OPERATING LIMITS
Ng
Np
OIL
RPM
%
RPM
PRESSURE
PSIG
805
38,100
101.6
2200
85 — 105
64.5
805
38,100
101.6
2200
85 — 105
64.5
765
38, 100
101.6
2200
85 — 105
0 to 99
(32° to 210° F)
60.2
740
38,100
101.6
2200
85 - 105
0 to 99
(32° to 210° F)
Idle
685
19,750
52.6
Starting
1090
Takeoff and
Max. Cont.
Takeoff Wet
Maximum Climb
Maximum Cruise
750
36.1° C
(97° F)
750
47.8° C
(118° F)
700
28.3° C
(83° F)
700
19.4° C
1970
1840
(67° F)
Acceleration
Maximum
Reverse
PT6A-27/34
750
40 (M n.)
2100
68.4
865
38, 500
102.6
2420
85 to 105
1970
64.5
805
38, 100
101.6
2100
85 to 105
TRAINING USE ONLY
TEMP. °C
10 to 99
(50° to 210°F)
10 to 99
(50° to 210°F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
0 to 99
(32° to 210° F)
0 to 99
(32° to 210° F)
PERFORMANCE 9.19
OPERATING LIMITS
PT6A-114
CONDITION
POWER
SETTING
LB.FT
PSIG
ITT° C
MAXIMUM
.-OBSERVED
1980
56.2
1980
TORQUE
OPERATING LIMITS
Ng
Np
OIL
RPM
%
RPM
PRESSURE
PSIG
805
38 ,100
101.6
1900
85 — 105
56.2
765
38, 100
101.6
1900
85 — 105
56.2
740
38,100
101.6
1900
85 - 105
Idle
685
19,500
52.0
Starting
1090
Takeoff and
Max. Cont.
Maximum Cliirb
Maximum Cruise
Transient
Maximum
Reverse
SHP
750
57.8° C
(136° F)
600
40° C
(104° F)
600
31.1° C
(88° F)
600
1980
40 (Min.)
2400
68.2
865
38, 500
102.6
2090
85 to 105
1980
56.2
805
38, 100
101.6
1825
85 to 105
PT6A-27134
UUUU0 434 )00#)00000 (1.- ) 0 0
TRAINING USE ONLY
TEMP. °C
10 to 99
(50° to 210°F)
0 to 99
(32° to 210° F)
0 to 99
(32° to 210° F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
104
(219° F) (10)
0 to 99
(32° to 210° F)
PERFORMANCE 9.20
04) 1 , ff Off 4411) f)Oft f If#Iff 15 ,-a f It440
OPERATING LIMITS
PT6A-114A
CONDITION
TORQUE
POWER
SETTING
SHP
Takeoff and
Max. / Enroute
Cont'd /
Emergency
675
61.1° C
(142° F)
675
47.2° C
(117° F)
675
38.9° C
(102° F)
LB.FT
PSIG
ITT° C
MAXIMUM
OBSERVED
1980
56.2
1980
OPERATING L1MITS
Ng
OIL
Np
RPM
°A9
RPM
PRESSURE
PSIG
805
38,100
101.6
1900
85 — 105
56.2
765
38, 100
101.6
1900
85 — 105
56.2
740
38,100
101.6
1900
85 - 105
Idle
685
19,500
52.0
Starting
1090
Maximum Climb
Maximum Cruise
Acceleration
Maximum
Reverse
PT6A-27/34
675
1980
40 (M n.)
2400
68.2
865
38, 500
102.6
2090
85 to 105
1980
56.2
805
38, 100
101.6
1825
85 to 105
TRAINING USE ONLY
TEMP. °C
10 to 99
(50° to 210°F)
0 to 99
(320 to 210° F)
0 to 99
(32° to 210° F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
104
(219° F) (10)
0 to 99
(32° to 210° F)
PERFORMANCE 9.21
OPERATING LIMITS
PT6A-135
CONDITION
TORQUE
POVVER
SETTING
SHP
Takeoff and
-Max. / Enroute
750
29.5° C
(85° F)
700
36.7° C
(98° F)
700
36.7° C
(98° F)
LB.FT
PSIG
ITT° C
MAXIMUM
OBSERVED
2080
59.1
1940
1940
OPERATING LIMITS
Ng
Np
OIL
RPM
%
RPM
PRESSURE
PSIG
805
38,100
101.6
1900
85 — 105
10 to 99
(50° to 210°F)
55.1
805
38, 100
101.6
1900
85 — 105
0 to 99
(32° to 210° F)
55.1
805
38,100
101.6
1900
85 - 105
Idie
685
19,750
52.6
Starting
1090
Cont'd /
Emergency
Maximum Climb
Maximum Cruise
Acceleration
- Maximum
Reverse
PT6A-27/34
720
40 (Min.)
2400
68.2
865
38, 500
102.6
2090
85 to 105
2080
59.1
805
38, 100
101.6
1825
85 to 105
TRAINING USE ONLY
TEMP. °C
0 to 99
(32° to 210° F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
0 to 99
(32° to 210° F)
0 to 99
(32° to 210° F)
PERFORMANCE 9.22
4.)000(. Jkl#4,4>UUU0414>U4kUtilibbkOVIJUV41#004M1Vt.k.400JUU4,404U4J4
OPERATING LIMITS
PT6A-135A
CONDITION
TORQUE
POWER
SETTING
SHP
Takeoff and
Max. / Enroute
Cont'd /
Emergency
750
33.9° C
(93° F)
Maximum Climb
700
40.6° C
(105° F)
700
40.6° C
(105° F)
LB.FT
PSIG
ITT° C
MAXIMUM
OBSERVED
2080
59.1
805
1940
55.1
55.1
OPERATING LIMITS
Ng
Np
OIL
%
RPM
PRESSURE
PSIG
38,100
101.6
1900
85 — 105
805
38, 100
101.6
1900
85 — 105
805
38,100
101.6
1900
85 - 105
Idle
685
19,750
Starting
1090
Maximum Cruise
Acceleration
Maximum
Reverse
PT6A-27/34
720
1940
RPM
40 (Min.)
2200
68.2
880
38, 500
102.6
2090
85 to 105
2080
59.1
805
38, 100
101.6
1825
85 to 105
TRAINING USE ONLY
TEMP. °C
10 to 99
(50° to 210°F)
0 to 99
(32° to 210° F)
0 to 99
(32` to 210° F)
-40 to 99
(-40° to 210° F)
-40 (Min.)
0 to 99
(32° to 210° F)
0 to 99
(32° to 210° F)
PERFORMANCE 9.23
ononnononnonoonnoononoonnonononoennnoonorno
FUEL SYSTEM
PT6A-27/34
TRAINING USE ONLY
FUEL SYSTEM 10.1
FUEL MANAGEMENT
The PT6A is operated by using three cockpit levers:
1. Power lever:
The power lever is used for controlling the compressor
speed (Ng) and to control the propeller pitch in reverse.
The lever is connected to a cam box located on the
accessory gearbox. The cam box transmits power lever
movement to the fuel control unit (FCU) which controls
fuel flow to the engine, therefore Ng.
1n the forward operation mode, the power lever controls
Ng speed only and has no effect on the beta valve.
The shut-off position stops fuel flow to the combustion
chamber and causes an engine to shut down.
From low idle to high idle (optional), the fuel lever rotates
the fuel control unit input lever to increase Ng up to a
specified value. This value is the minimum compressor
speed allowed for flight operation and is also used for
cross generator starts.
3. Propeller lever:
From idle to full reverse position, the power lever
increases Ng and also moves the beta valve to change
propeller blade angle into reverse pitch. This range of
operation is referred to as beta mode. Taxiing the aircraft
is accomplished in this mode.
The propeller lever is connected to the speed lever on
the top of the propeller governor (CSU). lt is used for two
purposes:
2. Fuel lever (condition lever):
Control the propeller speed in the governing mode
(cruise)
To start the engine, the condition lever is moved to low
idle position when the correct Ng is reached. This allows
fuel to the sent to the combustion chamber.
Allows the pilot to feather the propeller on the ground
prior to shut down of the engine or during flight, in the
event of an in-flight shutdown.
PT6A-27/34
OUU JUVUO041410UUG1414V
TRAINING USE ONLY
4) 41)
FUEL SYSTEM 10.2
04.00U.
000
POWER LEVERS
MIN. POWER
MAX
REVERSE
TAXI
RANGE
POWER
RANGE
FUEL CONDITIONS
LEVERS
MAX. POWER
BETA-P-
MIN. RPM
FEATHER
POWER
LEVER
CAM ASSY
(POWER CONTROL
LEVER)
PROPELLER SPEED
CONTROL LEVERS
MAX. RPM
LEVER LOCKS
PROPELLER
LEVER
PROPELLER GOVERNOR
(PROPELLER LEVER)
LOW IDLE
SHUT-OFF
HIGH IDLE
FUEL
LEVER
PT6A-27/34
ENGINE MANAGEMENT
1001 PT6A 27-34
TRAINING USE ONLY
FUEL SYSTEM 10.3
ENGINE FUEL SYSTEM
Purpose: Provide the engine with clean fuel at the
required pressure and flow to permit control of engine
power.
Fuel Drain Valves (2): They drain residual fluids from
the gas generator case
Fuel and additives: Refer to Service Bulletin of specific
engine model for complete listing of approved fuel and
additives. (SB1244).
The fuel system components control the following
features:
Proper fuel flow at minimum fuel introduction speed
(12°/0 Ng and above)
Sequencing fuel distribution to the proper nozzles
during start
Controlling a ground idle speed
Providing a strong surge free acceleration
Limiting a maximum compressor speed (Ng)
Providing a rapid deceleration without extinguishing
the combustion
Providing fuel shut off and fuel dump after shut down
Components:
Fuel Pump: Made by Sundstrand or Argo-Tech
(TRW), sends fuel flow at high pressure to the FCU
Fuel Control Unit: DP-F2 Hydro pneumatic unit
made by Allied Signal (Bendix) . Controls the proper
fuel burn flow at all power ranges, acceleration and
deceleration
Flow Divider: (PT6A-21/36/114/135A) Made by
Allied Signal (Bendix)
Start Flow Control Unit: (PT6A-27/28/34/135) made
by Lucas aerospace
Use of Aviation Gasoline (AVGAS) is limited to 150 hour
per engine between overhaul periods (TBO)
Description: Fuel from the aircraft tanks is sent to the
fuel heater via airframe boost pumps. Heated fuel then
flows to the engine driven fuel pump. Hi pressure fuel
now goes to the FCU via an external hose. The FCU will
determine the correct fuel flow for combustion and return
he unused fuel to the pump inlet.
Metered fuel exiting the FCU flows to the flow divider
(PT6A-112/114) or the start flow control (PT6A-27/34)
which sequence the fuel distribution between the primary
and secondary manifolds. Fuel is then atomized by the
14 nozzles for best combustion characteristics.
Inputs required:
Primary inputs (to operate the system):
Power lever position (PLA)
Ng (compressor speed)
P3 (compressor discharge pressure)
Fuel Nozzles: Made by Delevan or Parker Hannifin,
PT6A-27/34
OGIU0000
TRAINING USE ONLY
000090000,
)0
FUEL SYSTEM 10.4
OUUCI I OGI,
IOUU
FUEL NOZZLE
STARTING FLOW CONTROL
DUMP
MIN. PRESSURE
VALVE
MIN.
ACCEL.
FLOW
STOP /ADJ.
DRAIN
DRAIN
FCU
ENGINE FUEL SYSTEM
CUT-OFF
PLUNGER
GOVERNOR
BELLOWS
PROPELLER
GOVERNOR
TRANSFER
VALVE
BYPASS
VALVE
BLEED TO TANK
„-r r
RESET
ARM
MINIMUM
GOVERNOR
ADJUSTMENT
I
FUEL
PUMP
es\
,
MAX.
FLOW
STOP
ACCEL.
BELLOWS
(EVACUATED)
FILTER
BYPASS
VALVE
PRESSURE
REL1EF
VALVE
IDLE SPEED
ADJ.
10
MICRON
FILTER
rirs
TO POWER
LEVER
—W•1111
Illr
P1 PUMP DELIVERY FUEL
P2 METERED FUEL
Po BYPASS FUEL
SECONDARY FUEL
P3 COMPRESSOR DISCHARGE
Px ACCELL. PRESSURE
Li Py GOVERNING PRESSURE
PT6A-27/34
10020 PT6A 27-34
Ii
DRAIN
7.11111
Ng GOVERNOR
Px METERING ORIFICE
P3 AIR
P3 FILTER
TRAINING USE ONLY
Il
COUPLING
Pa
BYPASS
PRESSURE
REG. VALVE
74 MICRON
STRAINER
FUEL INLET
FUEL SYSTEM 10.5
FUEL HEATER
Purpose:
Specification:
Heat the fuel to prevent ice crystal formation
Outlet fuel temperature control range is 21 to 32°C.
Min oil temp for proper fuel heater operation = 55°C.
Description:
Troubleshooting:
The fuel heater is a heat exchanger using thermal energy
contained in the oil to heat fuel. A thermal element
reacts to fuel temperature and moves a sliding valve to
control the amount of oil flowing into the heat exchanger.
Internal failures of fuel heater may cause high oil
consumption when engine is running. Internal failure
may also cause fuel to transfer into the oil tank in static
conditions.
Operation:
Maintenance / Inspection:
Cold fuel from the aircraft boost pump enters the fuel
The
heater and surrounds the thermal element.
thermostatic element contracts and allows oil to travel
across the heat exchanger. Heat from the oil transfers to
the fuel and fuel temperature starts to rise. At 21°C the
thermal element begins to expand and push the sliding
valve out. ln this position, oil progressively bypasses the
fuel heater and fuel temperature begins to stabilize.
Verify for proper operation by touching fuel filter bowl
after shutdown. Should be warm but comfortable to
touch.
Replace unit if internal problems are suspected.
A spring located at the back of the sliding valve returns it
back in (heating position) when fuel temperature drops.
During operation, the thermal element constantly reacts
to adjust fuel outlet temperature.
PT6A-27/34
TRAINING USE ONLY
UU0uU4,14.00U0004104bUUVUO
)10U
FUEL SYSTEM 10.6
)411)U JW.
)0(.14J
FUEL INLET
THERMAL
ELEMENT
FUEL
OUTLET
FUEL
OUTLET
1
<11
"
'Or
OIL
OIL INLET OIL OUTLET
OIL
BYPASS
OPEN
FUEL HEATER
PT6A-27/34
1003C PT6A 27-34
TRAINING USE ONLY
FUEL SYSTEM 10.7
FUEL PUMP
Purpose: Provide clean high pressure fuel to the fuel
control unit, that in excess of engine burn fuel flow at all
speeds.
Description: Single stage, positive displacement gear
The gears are supported with brass
type pump.
bushings and sealed with carbon face seals.
Pump
apaci
(PT8A-34, typical)
Wf,
Pressure
Ng
75
140 pph
psig
12%
850 psig
1180 pph
101.6%
Wf at Take Off Power,, approx. 470 pph
Maintenance / Inspection:
Inlet filter: 74-micron wire mesh screen, with integral
bypass feature opening at 1.5 PSID, inspect and clean.
Outlet filter: 10-micron non-cleanable fiber type filter,
protected by a bypass valve (20 PSID), inspect and
replace.
In situ fuel pump coupling inspection: Inspect fuel
pump drain port for traces of corrosion (rust).
Also inspect for traces of dark blue stains. lf found,
replace both the fuel pump and FCU.
Refer to the Maintenance Manual for details.
Operation: Fuel coming from the fuel heater enters the
pump housing and passes through the inlet filter, then
through the pump gears. Fuel is filtered a second time
through the outlet filter before being delivered to the fuel
control unit via an external flexible hose.
The majority of fuel delivered by the fuel pump towards
the FCU is returned back to pump inlet via an internal
cord bypass passage.
CAUTION: Maximum pum .: :heyn¡ng limits
boost pressure = 10.bours. Repláce pump.j..exoeed
PT6A-27/34
UUOUUVUU000090040040 ,,_
TRAINING USE ONLY
9110U
FUEL SYSTEM 10.8
JUUU )4J40
iVUOU
HIGH PRESSURE FUEL
TO FCU
OUTLET
FILTER
FILTER BYPASS
VALVE
CARBON
SEAL
CARBON
SEAL
LIIIIIIH
BRASS
BUSHINGS
COUPLING TO
ACCESSORY
GEARBOX
FCU BYPAS
RETURN
INLET FILTER
(SELF RELIEVING)
I
I
FUEL INLET PRESSURE
I BYPASS FUEL
1 PUMP DELIVERY PRESSURE
PT6A-27/34
1004C PT6A 27-34
BYPASS PRESSURE
REGULATING VALVE
LOW PRESSURE FUEL
FROM FUEL HEATER
TRAINING USE ONLY
FUEL PUMP
FUEL SYSTEM 10.9
FUEL CONTROL UNIT
Hydraulic Section:
High Pressure Relief Valve: The high-pressure relief
valve protects the system from overpressure by dumping
excess fuel pressure to the pump inlet. it is a springloaded plunger, which set to open at 1000 psid (not
adjustable).
Bypass Valve: The bypass valve reguiates the pressure
differential (delta P) between pump delivery fuel (P1) and
metered fuel (P2) across the ports of the metering valve
by returning excess fuel (PO) back to the pump inlet.
it consists of a steel plunger moving within a ported steel
Actuated and supported by means of a
sleeve.
diaphragm and spring, it maintains a constant delta P (P1
- P2 = 20 psid).
Engíne acceleration is adjusted by changing the bypass
valve spring tension (via the accel adjustment dome).
Changing the spring tension modifies the P1-P2
The spring tension varies the pressure
differential.
difference from: 17 18 19 20 21 22 23 psid.
PT6A-27/34
UUQuovuVUU41009414#00;
During acceleration, more fuel is required. To supply that
sudden need, less fuel is returned to the pump inlet by
the bypass valve.
During deceleration, the opposite
situation happens. The bypass valve moves by reacting
to the fuel pressure variations across the metering valve
as it moves. Fuel flow is a function of metering valve
position only, as delta P is always kept constant by the
bypass valve.
A stack of bi-metallic washers is mounted between the
bypass valve seat and the adjuster. Depending on the
fuel temperature, a different volume of that fuel is
required to maintain acceleration constant.
Metering Valve: The fuel flow-metering valve regulates
engine burn fuel flow over a wide range of settings. it
travels between a minimum and a maximum flow stop.
Total travel is .080". It consists of a steel needle moving
within a ported steel sleeve. Position is controlled by
pneumatic bellows via a torque tube. The metering valve
minimum flow setting (90pph) is adjustable (refer MM).
TRAINING USE ONLY
940
FUEL SYSTEM 10.10
)(,)01.)
UUL) 410 )000
ACCELARATION
ADJUSTMENT
MINIMUM FUEL
,- FLOW STOP
METERING VALVE
GOVERNOR
BELLOWS
I P1 PUMP DELIVERY FUEL
I P2 METERED FUEL
PO BYPASS FUEL
I
Fl P3 COMPRESSOR DISCHARGE AIR
I I Px ACCELARATION AIR PRESSURE
Py GOVERNING AIR PRESSURE
I
BYPASS VALVE
NG SCHEDULING
CAM
IDLE SPEED
ADJUSTMENT
[5 RETURN TO TANK
1-)\ RETURN
v TO PUMP
_iii
L-.1 rid
TO PROP.
GOVERN.
MAXIMUM FUEL
FLOW STOP
HIGH PRESSURE
RELIEF VALVE
P1 FROM
FUEL PUMP
ACCELARATION
BELLOWS (EVACUATION)
Px METERING
ORIFICE
FUEL CONTROL UNIT
PT6A-27/34
1005C PT6A 27-34
P3 AIR <
TRAINING USE ONLY
Py METERING
ORIFICE
FUEL SYSTEM 10.11
FUEL CONTROL UNIT: Pneumatic Section
(Governing Section)
FCU pneumatic system: Controls compressor speed (Ng)
acceleration, deceleration and steady state at all power
settings and altitudes. lt govems Ng to a steady state at all
power settings and altitudes. lt governs Ng to a specific Power
Lever Angle (PLA). lt governs the hydraulic section.
Governor bellows: Initiates acceleration, deceleration and
controls Ng steady state. They are moved by modified P3 air
pressure, called Px and Py. To increase Ng, Py is increased.
To reduce Ng, Py is reduced.
Acceleration (evacuated) bellows: They are moved by
modified P3 air pressure (Px). They are attached to the FCU
housing while the rest of the bellows assembly is allowed to
move up and down depending on Px and Py pressure and
torque tube spring loading. The acceleration bellows control
accel & decel rates in response to Px air variations following
changes in Ng.
When only atmospheric pressure acts on the acceleration
bellows, (engine stopped or starting), the torque tube loads the
metering valve to min fuel flow position. Py and Px pressures
are generated and controlled by the Ng governor section of the
FCU.
Governor lever: Controls Py bleed off to actuate the governor
bellows.
PTSA-27/34
U 410
Ng governor: Controls Ng as a function of PLA. Driven by the
accessory gearbox via the fuel pump, the Ng governor
flyweights rotate at a speed proportional to compressor speed.
The cockpit power lever is linked to the speed-scheduling cam
located inside the governor section of the FCU. Movement of
the power lever from ground idle to higher power position
increases the tension on the spring and closes the governor
bleed to prevent Py from venting to atmosphere. The
centrifugal govemor flyweights apply a force in the opposite
direction to re-open the Py bleed.
Interconnecting coupling: Plastic-coupling connecting the
fuel pump drives to the FCU. It drives the Ng governor.
Speed scheduling cam: Connected to the PLA, it moves the
cam follower lever.
Cam follower lever: Contacted by either the idle screw or the
Ng scheduling cam, it applies a spring tension to close the
govemor lever Py bleed.
Torque tube: Transmits the movement of the bellows to the
metering valve. The torque tube is torsion loaded towards
minimum flow. The bellows are spring loaded towards
maximum flow. These tensions will cancel each other;
theref ore, a very small change in air pressure (2 to 5 psia) is
able to move the metering valve to the proper setting. it
consists of 2 arms connected together by a coaxial shaft. The
inner part of the shaft transmits movements from the bellows
to the metering valve and the outer hollow shaft exerts a
torsion force.
TRAINING USE ONLY
lb U 4i)
O
) U U 41 t)
FUEL SYSTEM 10.12
) 4)
) U Cs1
TO FLOW DIVIDER
MIN.
PRES.
VALVE
ACCELARATION
ADJUSTMENT
MINIMUM FUELrEh
FLOW STOP
NG SCHEDULING
BYPASS VALVE CAM
METERING VALVE
GOVERNOR
BELLOWS
1DLE SPEED
ADJUSTMENT
0. RETURN TOTANK
F\ RETURN
TO PUMP
TORQUE
TUBE
MAXIMUM FUEL
FLOW STOP
HIGH PRESSURE
RELIEF VALVE
P1 FROM
FUEL PUMP
ACCELARATION
BELLOWS (EVACUATION)
ri
Py ORIFICE
(WITH FLOW DIVIDER)
10060 PT6A 27-34
DRAIN
PyTO PROP.1
GOVERN. \rj
FUEL CONTROL UNIT
PT6A-27/34
P1 PUMP DELIVERY FUEL
P2 METERED FUEL
1 PO BYPASS FUEL
P3 COMPRESSOR DISCHARGE AIR
Px ACCELARATION AIR PRESSURE
Py GOVERNING AIR PRESSURE
TRAINING USE ONLY
Px ORIFICE
FUEL SYSTEM 10.13
FUEL CONTROL UNIT OPEARTION
Starting: At start, the fuel flow is determined by the pump
Governing: Once the acceleration cycle has been completed,
RPM and minimum position of the metering valve. The
compressor is rotated by the starter until a minimum Ng of
12`)/0 is obtained for introducing fuel. The pilot's power lever
remains at "Idle" position, and the fuel condition lever is moved
to "on" position to start fuel flow. As the engine accelerates
towards idle, compressor delivery pressure begins to move the
metering valve away from the minimum stop. As Ng
approaches idle, the govemor spring forces and opens the
governor orifice. This creates a Py-Px differential, which
causes the metering valve to move to a floating position to
maintain the required Ng idle speed.
any variation in engine speed from the selected speed will be
sensed by the governor flyweights and will result in increased
or decreased centrifugal force. This change in force will cause
the govemor valve to either open or close, which will then be
reflected by the change in fuel flow necessary to re-establish
the proper speed. When the fuel control is governing, the valve
will be maintained in regulating or "floating" position.
Acceleration: As the power iever is advanced above idle, the
speed-scheduling cam is repositioned, moving the cam
follower lever to increase the governor spring force. The
governor spring then overcomes the flyweights and moves the
levers, closing the governor valve. Py increases and causes
the governor bellows to compress, moving the metering valve
towards an increasing fuel flow position.
As Ng and P3 increases, the acceleration bellows
progressively compress and move the metering valve to a
more open position.
Acceleration is then a function of increasing Px (P3). It is
completed when the centrifugal force of the flyweights
overcomes the spring tension and opens the governor valve.
41,
Engine shutdown: the engine is stopped by moving the fuel
condition lever from "Idle" to "Cutoff". This equalizes pressure
on both sides of the minimum pressuring valve and its spring
causes it to close, cutting flow to the flow divider and nozzles.
Altitude compensation: The compressor surge (stall) margin
reduces as altitude increases. Therefore, the acceleration fuel
flow must be reduced at altitude to prevent surging.
This is achieved by the acceleration bellows. As Px (P3) s a
function of engine speed and air density, its pressure will then
react by expanding more, reducing fuel flow during
acceleration. The compressor stall margin reduces as altitude
increases.
TRAINING USE ONLY
PT6A-27/34
U L.‘
Deceleration: When the power lever is pulled back, the speed
scheduling lever is rotated to a lower point on the cam. This
reduces the govemor spring force and causes the govemor
valve to open. The resulting drop in Py moves the metering
valve in closing direction. As Ng and P3 decreases, the
acceleration bellows now expands and progressively move the
metering valve to a more closed position until it contacts the
minimum flow stop. The engine will continue to decelerate until
the governor weight force decreases to balance at the new
governing position.
41 tio
41 44
41 th
J 01#
FUEL SYSTEM 10.14
Notes:
Tle 0 1\(G" -ZE-¿,1`7_s FEN1 c 11°A
0 /n1A
gr2u
po y
•
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"De 14-4 ucl. S.49 (-)
0.4 Q1.44ople.o.
Á
"l
•
,
PT6A-27/34
TRAINING USE ONLY
FUEL SYSTEM 10.15
STARTING FLOW CONTROL
(PT6A-27, 28, 34, 15AG, 135)
Purpose:
Provide fuel "on" and "cutoff" functions.
Divide the flow between primary and secondary manifolds at
start.
Dumps fuel from the manifolds after engine shutdown
Provide a minimum pressure valve to maintain a sufficient
pressure in the system.
A telescopic interconnecting rod linking the starting flow control
to the FCU provides the High Idle option.
Construction:
Minimum pressurizing valve: Spring loaded plunger, opens at 75 80 PSID. Maintains a sufficient pressure in the system. The valve
also assists the sliding piston during engine shutdown.
Sliding piston: A geared plunger actuated by the input lever via a
rack and pinion arrangement. Provides a positive mean of stopping
fuel flow to the engine. Routes fuel to a dump port in "cutoff"
position.
Transfer valve: Spring loaded plunger which opens at a fuel
pressure of 18 - 21 PSIG allowing fuel to flow through secondary
manifold.
Operation: When the cockpit fuel lever is moved to the "fuel on"
position, the sliding piston is moved rearwards by the input lever via
a rack and pinion arrangement. As the piston moves, a passage that
supplied inlet fuel pressure to the back of the min pressure valve will
close. The min pressure valve then opens and fuel will flow through
the piston's center and exit via the primary fuel outlet.
PT6A-27/34
000 0
)QuOQU U UQUO 40
As Ng speed approaches 35%, fuel pressure increases and at 18 21 PSIG. the transfer valve moves to contact a stop and allows fuel
to flow in the secondary manifold. At that point, fuel flows through all
14 nozzles.
When the fuel condition lever is moved to "off" position. the piston is
moved forward (rightward on the view) by the input lever. The piston
now blocks fuel from flowing, at its end. Fuel from the manifolds is
then routed to the piston, and sent outboard to a dump port. This
allows fuel to drain by gravity into a collector can. This prevents
deposit formation in the manifolds and fuel nozzles.
Inlet fuel
pressure is also routed to the backside of the minimum pressurizing
valve, this will cause the fuel pressures to equalize on both sides and
the valve will close. This valve assists the piston to achieve fuel
cutoff during engine shutdown.
Maintenance / Inspection:
Inspect for cracks and leaks
Confirm positive fuel cut off when fitting a replacement unit and
every time a replacement engine is fitted
Replace unit if defe-ctive
TROUBLESHOOTING
.
~01.11:. ' «
-bleiil
:.. ,.
t
-------
e:.:
.....
'.............
Engine is slow to accelerate or
limited in power range.
Secondary valve stuck closed.
Hotter start temperature.
Secondary valve stuck open.
Min pressuring valve stuck open.
TRAINING USE ONLY
FUEL SYSTEM 10.16
ov uuu uu ovuu
ou
BYPASS
NO.1
MANIFOLD
RIGGING SLOTS
(72° , 45° REF.)
TRANSFER
VALVE
FUEL
INLET
TO COCKPIT ----\
-4-
NO.2
MANIFOLD
MIN. PRESSURE
VALVE
.
A CUTOFF & DUMP POSITION
FUEL
INLET
NO.1
MANIFOLD
MAX. STOP
CUTOFF & DUMP
STOP (0° REF.)
OUTLETTO NO.2 MANIFOLD
FUEL
INLET
á NO.2
wr MANIFOLD
B RUN POSTION
PT6A-27/34
OUTLET TO
NO.1 MANIFOLD
10070 PT6A 27-34
NOTE 1
NO.1 MANIFOLD BOSS ROTATED 90° FOR
PURPOSES OF ILLUSTRATION IN VIEW A & B
STARTING FLOW CONTROL
TRAINING USE ONLY
FUEL SYSTEM 10.17
FLOW DIVIDER AND DUMP VALVE:
PT6A-10, A-11, A-21 A-110, A-112, A-114, A-114A, A-135A
Purpose: Divide the fuel flow between primary and
secondary fuel manifolds at startup. Dumps fuel from the
manifolds when the engine is shutdown.
Primary fuel position: Primary valve opens at fuel
pressure of 9 - 13 psid allowing fuel to flow through
primary manif old only.
Secondary flow position: Secondary valve opens at
Description: Two concentric valves spring loaded to the
closed position, operated by fuel pressure.
Operation: When the condition lever is moved to "on"
position, fuel enters the flow divider and pushes against
the spring loaded primary valve piston (9 to 13 PS(G),
and allows fuel to flow in the primary manifold only, to
lightup
atomization
and
optimum fuel
provide
characteristics.
As Ng speed approaches 35°/0, fuel pressure increases
(17 to 22 PSIG) and the secondary valve also moves
Fuel will then flow through all 14
against its stop.
nozzles.
When the fuel condition lever is moved to "off" position,
fuel pressure ends and the two springs push the primary
and the secondary valves toward the closed position,
allowing fuel to drain by gravity into a collector can. This
prevents deposit formation in the manifolds and fuel
nozzles.
PT6A-27/34
fuel pressure of 17 - 22 psid allowing fuel to flow through
secondary manifold.
Dump position: Primary and secondary springs close
the valves, allowing fuel to dump overboard.
Maintenance / Inspection:
Inspect for cracks and leaks
Conf irm positive fuel cut off when fitting a replacement
unit and every time a replacement engine is fitted
Replace unit if defective
TROUBLESHOOTING
0 s . etl róblem
PoSsibiti.iise
Engine is slow to accelerate or
limited in power range.
Secondary valve stuck closed
Hotter start temperature
Secondary valve stuck open
Hung start
Primary valve partly stuck
White smoke on shut down from
exhaust duct
Verify for proper operation of
flow divider and dump / purge
valve.
TRAINING USE ONLY
,t.“JuUti41414#11UUQUO 9 VUVUUV4
FUEL SYSTEM 10.18
VJUVUUVIO
1>
L__I
DUMP POSITION
TO PRIMARY MANIFOLD
PRIMARY
VALVE
SECONDARY
VALVE
,
_r
IEFT
ww:
1
J!íTlL
DUMp
PRIMARY FLOW POSITION VALVE
TO PRIMARY MANIFOLD TO SECONDARY MANIFOLD
PRIMARY AND SECONDARY FLOW POSITION
PT6A-27/34
1008C PT6A 27-34
TRAINING USE ONLY
FLOW DIVIDER & DUMP VALVE
FUEL SYSTEM 10.19
FUEL NOZZLES
Purpose: Deliver and atomize metered fuel into the
Maintenance: Regular fuel nozzle maintenance is important
combustion chamber. The type of fuel nozzles currently used
on the PT6A is single orifice type.
for hot section durability. It cannot be over emphasized.
Testing: Ensures the combustion chamber receives properly
atomized and non-streaking fuel.
Construction:
14 fuel nozzle adapters, 10 primary, 4 secondary
(Some engines have 7p - 7s configuration).
14 sheaths.
28 transfer tubes.
14 fuel nozzle tips consisting of: A swirler, a spring, a
strainer, a retaining ring and a plate.
Operation: During operation, the 14 fuel nozzles receive fuel
from the flow divider (or the start flow control) and deliver it to
the combustion chamber.
On start, fuel flows through the ten primary fuel nozzles. The
position of the primary fuel nozzles is such that fuel is sprayed
circumferentially towards the spark igniters in order to facilitate
ignition.
At a specific Ng, the secondary manifold receives fuei and the
secondary fuel nozzles will spray. At this point, all the 14
nozzles will deliver fuel
Test fuel nozzles as per maintenance manual every 200 hours
(for new operators) up to 400 hours (for experienced
operators). The nozzles are tested for operating defects like
leakage, spitting, drooling or streakiness.
Cleaning: Ultrasonically clean in carbon remover solvent.
(Flush with hot water)
"In Situ" fuel nozzle cleaning:
In situ nozzle wash is a method, which permits cleaning of
fuel nozzles without having to remove them from the
engine. Clean every 200 hours. A special rig and cleaning
solution must be used. Refer to the Maintenance Manual
For new operators or if the fuel quality is questionable,
inspect and test fuel nozzles every 400 hours initially, with
extensions of 200 hours, based on inspection results.
For other operators, inspect and test fuel nozzles every
600 hours initially, with extensions of 200 hours, based on
inspection results.
Note: it is recórnmended that this method ciflánkig should
only be ínitiáted on new ol; newty overhauled nozzles, as the .1
procedure will not:::Olear previous bkáticages.
PT6A-27/34
QQC. UUUUU4UU
TRAINING USE ONLY
,P ABOU
FUEL SYSTEM 10.20
U0414114041 UUVUt.,4 )1hOULPIJ
FUEL NOZZLE SHEATH
FUEL NOZZLE
COMBUSTION
CHAMBER LINER
ASSEMBLY
PRIMARY FUEL
MANIFOLD ADAPTER
ASSEMBLY
GAS GENERATOR
CASE ASSEMBLY
SECONDARY FUEL
MANIFOLD ADAPTER
ASSEMBLY
FLOW MANIFOLD
INLET ADAPTER
L>
PRIMARY ADAPTER
SECONDARY ADAPTER
FUEL MANIFOLD ASSY & NOZZLES
PT6A-27/34
1009C PT6A 27-34
TRAINING USE ONLY
FUEL SYSTEM 10.21
FUEL CONTROL UNIT MANUAL OVERRIDE
Purpose: Found on some single engine PT6A powered
aircraft, it is integral with the FCU. Allows the pilot to
directly control the FCU pneumatic system, in the event
of a pneumatic failure.
Test:
Start engine and let it warm up.
Power lever and condition lever at IDLE position.
Slowly advance override control lever toward Max
until target performance parameter is attained.
Description: ln the event of a P3/Py air loss or FCU
pneumatic section malfunction, the pilot can manually
control the bellows to simulate P3 air pressure. A special
lever is provided in the cockpit to that effect.
Note:
Aircraft control linkage must allow the override lever
stop to travel from OFF to MAX
Operation: Movement of the manual override lever in the
cockpit will rotate the manual override control lever on
the FCU. This will act directly on top of the governor
bellows. The rate of acceleration is established by the
speed at which the pilot moves the lever. Any abrupt
setting changes can cause compressor stalls or
overheating the engine.
PT6A-27/34
uuo
No adjustments are permitted.
TRAINING USE ONLY
tá V 11 U 40 4.1 ti 9 0 f t 410
Wohé 4•1
FUEL SYSTEM 10.22
41 41 41 4#4J U1# II 410 1)
POWER RECOVERY LEVER
r:a
METERING VALVE
ACTUATING CAM
BELLOWS
TORQUE TUBE
MANUAL OVERRIDE
PT6A-27/34
1010C PT6A 27-34
TRAINING USE ONLY
FUEL SYSTEM 10.23
FCU ADJUSTMENTS
3. Maximum Ng: (101 .5%)
1. Ground idle: (Speed adjustment)
Start engine and stabilize at ground idle.
Ensure speed is: 52.5% Ng
If adjustment is required, stop engine, tum min goveming
screw CW to increase Ng, CCW to decrease Ng (1/16 tum
approx. 2% Ng).
Note: Idle speed can only be checked or adjusted at Pressure
Altitudes below 3500 ft (25.2"Hg). Above 3500 feet the FCU
ground idle is limited by the min flow adjustment (i.e. ground
idle screw has no effect on Wf).
2. High Idle (PT6A-27, 28, 34, 15Ag): (Make adj. per MM)
Start engine and stabilize at ground idle.
Push condition lever to "Hi Idle"
c) Ensure Ng is 70%
Deploy the Part Power Trim Stop. *
Start engine and bring power lever against the trim
stop
c) Record actual Ng speed and ensure it is within limits:
(PT6A-34 = 97.1%).
If adjustment is required, tum max Ng stop screw CCW to
increase and CW to decrease Ng speed (1 turn approx.
1% N g).
Stow trim stop after check and adjustments are completed.
Part Power Trim Stop: Retractable spacer that allows to
adjust max Ng without exceeding max torque on a cold day, or
max T5 on a hot day.
lf adjustment is required:
14(4: All adjustrnents are done with the engine not
Stop engine.
Set condition lever to RUN (low idle, 72°).
C) With the FCU lever at "Pickup Point", ensure there is a
minimum gap of .030" at lower end of telescoping rod,
when the starting flow control lever is at 72°. With the
rod adjusted as above, movement of the start control
lever from 72° to 900 will give approx. 70°/0 Ng. Final
adjustments are made with the starting flow control
max stop.
..149nning.
NOTE: Ah values are for reference anly Always: : .référ to the
Note: Most installations use the 72° position for their rigging,
however, for installations using the 45° RUN position,
movement of the lever from 45° to 90° will give a mch higher
flight idle Ng. This can be corrected by increasing the rod end
gap.
PTSA-27/34
TRAINING USE ONLY
FUEL SYSTEM 10.24
UOU 004~~041~WWWWWWwwVUVUUVUWWWwwwWW4IUU
MAX. GOVERNING SPEED ADJUSTMENT
IDLE SPEED ADJUSTMENT
ACCELERATION
ADJUSTMENT
PART POWER TRIM STOP
F.C.U. ADJUSTMENTS (WITH STARTING FLOW CONTROL)
PT6A-27/34
1011 PT6A 27-34
TRAINING USE ONLY
FUEL SYSTEM 10.25
FCU ADJUSTMENTS (continued)
6. Minimum fuel flow:
4. Acceleration:
Disconnect Py tube from FCU or Nf governor.
Start engine, stabilize for 3 minutes. No bleed
extraction or auxiliary power extraction.
Record actual Ng, pressure altitude and OAT.
Compare with chart in maintenance manual to
ensure Ng is within the limits.
Start engine and stabilize at idle and let it warm
up.
Increase power from idle to 64% with power lever.
Perform slam acceleration from 64% to 97.5% Ng.
Ensure acceleration is within 2.5 to 4.0 seconds.
If adjustment is required, turn accel dome CW to
decrease accel time (quicker accel) or CCW to
increase accel time (slower accel).
Note:
One click changes accel time by 0.2 to 0.3 seconds
(approx.).
No bleed or power extraction during test. lf adjustment
is required, turn min flow screw CW to increase
minimum flow Ng speed and CCW to decrease.
Range of adjustments = Plus or Minus three clicks
from neutral.
Due to the sensitivity of the min flow adjustment, turn
the screw with 1/16 of a turn at a time.
Ng at min fuel flow, 15° c (PT6A-34)
P. ALT
Ng 62-c-,01
46.7
3000'
50.7
4250'
52.6
6000'
55.2
9000'
60.0
Ground Idle = 52.6% Ng
5. High Idle: (PT6A-21, 36, 112, 114, 114A, 135A):
Start engine and stabilize at ground idle.
Push condition lever to "Hi Idle"
c) Ensure Ng is 70%
If adjustment is required, turn flight idle adjustment
stop screw CW to increase and CCW to decrease.
NOTE: All values are for reference only. Always refer to
the appropriate Maintenance Manual for proper settings.
PT6A-27/34
TRAINING USE ONLY
FUEL SYSTEM 10.26
UW..) (JUVU(104k4i#V0t1U(Ith/VOUVUUUUUVOUIOUVU4JUU41404JUUV
IN-USE
POSITION
HIGH IDLE
ADJUSTMENT
CUT-OFF STOP
STOWED
POSITION
IDLE
ADJUSTMENT
VIEW A
ACCELERATION
ADJUSTMENT
CUT-OFF
ADJUSTMENT
PART POWER
TRIM STOP
FUEL BYPASS
MINIMUM FLOW
F.C.U. ADJUSTMENTS (WITH FLOW DIVIDER)
PT6A-27/34
1012 PT6A 27-34
TRAINING USE ONLY
FUEL SYSTEM 10.27
FCU TROUBLESHOOTING
POSSIBLE CAU
SERVED PR
Engine does ‘not lightup.
flotter starting tefl jE rature than normal.
Hung start.
ngine is slow to accelerate or limited in power range.
Engine remains at minimum fuel flow Ng speed and
diles not aCceferate.
PT6A-27/34
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Aircraft fuel supply problem.
Improper starting procedures.
Starting Flow Control or Flow Divider problem.
Internal FCU Lroblem.
Improper starting procedures.
Starting Flow Control or Flow Divider problem.
Internal FCU problems
Improper starting procedures.
Starting Flow Control or Flow Divider problem.
Fuel Pump Filter blockage.
Internal Fuel Pump Problem.
Internal FCU problem.
Aircraft Fuel supply problem.
Faulty rigging, lever not reaching maximum stop.
Restricted P3 line to the FCU or P3 filter.
Small leakage at P3 line to FCU.
Small leakage from Py line or propeller Nf governor.
Fuel Pump filters blocked.
Starting Flow Control or Flow Divider problem.
Internal FCU problem.
Aircraft Fuel supply problem.
Heavy leakage at Py line or propeller governor.
Blocked P3 line to the FCU or P3 filter.
Internal FCU oroblem.
TRAINING USE ONLY
UOU UVUOUI#UVUUQUU0
FUEL SYSTEM 10.28
UUUUUQUUUUUQUQUUUUUti
FCU TROUBLESHOOTING (continued)
POSSIBLE CAUSE
OBSERVED PROBLEM
•
•
Engine surges during acceleration.
•
•
Fluctuations of Ng, Tq, ITT, Wf and Np.
•
Uncontrolled Ng acceleration.
•
White smoke at shutdown from exhaust.
Rust out of Fuel Pump splines and drain.
•
Blue stains between FCU and Fuel Pump or out of Fuel
Pump drain.
•
PT6A-27/34
Bleed Valve problem.
"Pa" bleed blocked (Px bleed to atmosphere). Call help
desk for assistance.
"Px" resistrictor at the left side of the FCU (it should be
at the right side).
Air leakage from Py line or Propeller Nf governor.
FCU Ng Governor bearing problem.
Absence of FCU to Pump coupling.
FCU Ng Governor bearing seized.
Improper function of Fuel cutoff.
Replace Fuel Pump; ensure that the lubricating hole in
the AGB fuel pump drive is free from contamination.
Replace FCU and Fuel Pump.
TRAINING USE ONLY
FUEL SYSTEM 10.29
onnonnnonnonno"nnonnoneloonnonononnonno( N,nonn
PROPELLER SYSTEM
TRAINING USE ONLY
PROPELLER SYSTEM 11.1
PROPELLER SYSTEM
Purpose
Description
Change the power produced by the engine into thrust in
order to propel the aircraft through the air.
The propeller consists of a hollow spider hub that
supports the blades and also houses an internal oil pilot
tube and a feather return spring.
Description
The propellers used on small PT6A engines vary from
three or four bladed propellers made of metal or
composite materials.
Centrifugal counterweights on each blade cuff and the
feathering spring in the servo piston load the propeller
blade angle toward feather position. In opposition, oil
from the propeller governor, tends to drive the propeller
in the fine pitch or low blade angle position.
The propeller system used on all PT6A is of the variable
pitch, single acting type. A propeller governor adjusts the
blade angle automatically to maintain the propeller speed
as selected by the pilot.
Operation
When more power is applied, the angle of attack of the
blade is increased automatically to allow the propeller to
absorb the additional energy without increase in propeller
speed.
Oil from the governor is fed into the propeller shaft and to
the servo piston via the oil transfer sleeve mounted on
the propeller shaft.
As oil pressure increases, the servo piston is pushed
forward and the feather return spring is compressed.
Servo piston movement is transmitted to the propeller
blade collars via a system of levers.
When oil pressure is decreased, the return spring forces
the oil out of the servo piston and changes the blade
pitch to a coarser position.
An increase in oil pressure, controlled by the propeller
governor, drives the blade towards a finer pitch.
PT6A-27/34
TRAINING USE ONLY
PROPELLER SYSTEM 11.2
QUU ik..)UtIllUOUUVOUOUOVV ,QUOUUAJOUtJUOUVVVUOUUlblik
COARSE PITCH
HIGH SPEED
CRUISE
HYDRAULIC
LOW PITCH
IDLE
REVERSE
REVERSE
PITCH
COCKPIT LEVER TO PROPELLER BLADE ANGLE RELATION
PT6A-27/34
1101 PT6A 27-34
TRAINING USE ONLY
PROPELLER 11.3
GOVERNING MODE
Description
The governing mode corresponds to a range of
operations where engine power is sufficient to maintain
the selected propeller speed by varying the blade angle
(pitch). The propeller speed (governing range) is
selected by the pilot and is between 75% and 100% Np.
The system is governing when (on speed)
Indicated propeller speed matches selected propeller
speed.
Change in Ng speed causes no change in propeller
speed (changes in Tq only).
Moving the propeller lever results in a change in
propeller speed.
MAIN COMPONENTS FUNCTIONS
Pressure Relief Valve: Returns oil to the governor pump
inlet when maximum pressure is reached. (380 PSID
approx.)
Pump Gears: Supply a flow of oil at a pressure
necessary to control the propeller pitch.
Flyweights: Sense the speed of the propeller and act
against variable spring pressure to move the pilot valve
up or down.
Speeder Spring: Opposes a mechanical force against
the centrifugal force of the flyweights and determines
propeller speed at which the flyweights will be "on
speed". The pilot controls spring tension through the
propeller lever.
Operation: Oil from the engine main oil pump is supplied
to the governor. A set of gear pumps, mounted at the
base of the governor, increases the flow of oil going to
the propeller governor relief valve.
When the oil pressure reaches the desired level, the
relief valve opens to maintain the pressure. Through
internal passages, the oil is routed to the pilot valve and
then to the propeller transfer sleeve.
The flyweights and the pump gears are driven by a bevel
gear arrangement mounted on the propeller shaft. Once
the speed selected by the pilot is reached, the flyweight's
centrifugal force equals the spring tension of the speeder
spring. The governor flyweights are then on speed.
When more power is applied to the engine, the flyweights
turns faster and go into an overspeed condition, causing
the pilot valve to move up and restrict oil flow to the
propeller dome. The feathering spring increases the
propeller pitch to maintain the selected speed. Reducing
power causes an underspeed of the flyweights,
downward movement of the pilot valve, more oil in
propeller dome, resulting in a finer pitch to control
propeller speed.
Pilot Valve: Moves up or down to control the oil pressure
going to the propeller dome.
PT6A-27/34
TRAINING USE ONLY
PROPELLER SYSTEM 11.4
OUL itJUUUUU4144k4J414)4/ 41404ki#UUVU4itMOULIUUUUUVUVUOU4,/
REVERSING CAM
PUSH-PULL CONTROL
RESET POST
SUPPLY PRESSURE
RETURN TO PUMP
PROPELLER SERVO PRESSURE
li
PROPELLER SPEED
CONTROL LEVER
Py
PRESSURE
RELIEF
VALVE
RESET
ARM
MIN. GOV.
ADJ.
VNN PILOT VALVE
TO SUMP CSU PUMP
TEST SOLENOID
PROPELLER
OVERSPEED
GOVERNOR
FEATHER
SOLENOID
SUMP
PT6A-27/34
1102C PT6A 27-34
ENGINE
OIL
PROPELLER SYSTEM (GOVERNING)
TRAINING USE ONLY
PROPELLER SYSTEM 11.5
FORWARD BETA MODE
Beta Valve: Prevents the blade angie from going below the
specified Primary Blade Angle (PBA) in flight and allows the
pilot to manually control the blade angle on the ground for
taxiing and reverse operation.
Beta Mode: Corresponds to a range of operation where the
blade angle is between PBA and reverse. Control of the
propeller pitch is a direct function of the position of the beta
valve.
Primary Blade Angle (PBA): Minimum blade angle allowed
for flight operation for the aircraft.
The System ls In Beta Mode When: (Underspeed)
Operation: At low power operation, with the propeller lever at
max RPM, the propeller does not turn fast enough to satisfy
the demand. In this condition, the pilot valve moves down and
high-pressure oil goes to the propeller dome, moving the
blades towards a fine pitch.
When the preset PBA is reached, the servo piston, in it's
forward movement contacts the beta nuts.
Any further
movement pulls the beta rod and the slip ring forward. The
forward motion of the slip ring is transmitted to the beta valve
via the beta lever. Forward movement of the beta valve
causes servo pressure to drop, which prevents any further
blade angle change. At this point, blade angle control is no
longer a function of the propeller governor, the beta system is
now in control.
in flight, the beta valve maintains a constant oil voiume in the
propeller dome to ensure blade angle remains at PBA.
Propeller speed indicated is below propeller speed
selected
Ng speed change causes propeller speed change
Propeller lever movement does not change propeller
speed
On the ground, the pilot is able, with the power lever, to
actuate the beta valve and change the blade angle as desired
for taxiing and reverse operation.
The Beta Valve ls Operated By Two Means:
Beta feedback system: in low pitch operation, the beta
nuts, beta rods, slip ring, carbon block and the beta lever,
which compose the beta feedback system, actuate the
beta valve.
Power lever: Movement of the power lever in the beta
range causes the reversing cam to actuate the beta valve,
thus causing the blade angle to change.
Lock pitch solenoid valve: Optional device, bolted to the
prop governor, serves as a backup to the beta valve. Consist
of a solenoid (energized by the airframe 28V), an oil cutoff
plunger, and a slip ring position sensor.
lf the blade angle goes below PBA in flight, the sensor
(microswitch or another carbon block) will close the 28V circuit
to the solenoid. The plunger will then block the oil flow to the
prop servo dome, therefore locking the blade angle at a value
slightly lower than the PBA (ref Airf rame manual).
To permit reverse thrust after landing, it is deactivated by a
microswitch in the power lever quadrant.
PT6A- 27/34
())
PROPELLER SYSTEM 11.6
TRAINING USE ONLY
(i) 411 4> 4# V ta4 4$4 41>
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REVERSING CAM
PUSH-PULL CONTROL
_JO
RESET POST
PROPELLER SPEED
CONTROL LEVER
BETA VALVE LEVER
GOVERNOR
SPRING
SHUT-OFF (LOCK PITCH)
SOLENOID VALVE
RESET
ARM
YJ
MIN. GOV.
ADJ.
PILOT VALVE
BETA
VALVE
CSU PUMP
CARBON
BLOCK
ENGINE
OIL
SUPPLY PRESSURE
L] RETURN TO PUMP
PROPELLER SERVO PRESSURE
PROPELLER SYSTEM (BETA)
PT6A-27/34
1103C PT6A 27-34
TRAINING USE ONLY
HYDRAULIC
LOW PITCH ADJ.
PROPELLER SYSTEM 11.7
REVERSE BETA MODE
Purpose:
Operation:
Allow the pilot to control the propeller blade angle in
reverse.
Moving the power lever rearwards causes the reversing
cam and cable to move the beta valve rearward, allowing
more oil to flow into the propeller dome, causing the
blades to go to reverse pitch.
Description:
Reverse operation is obtained by moving the power lever
The
below the Idie detent, into the reverse range.
reversing cam pulls on the reversing cable to move the
beta valve inwards, allowing more oil to flow into the
propeller dome and send the propeller blades in reverse
pitch.
The reset arm on the Nf governor is also moved rearward
by the reversing cable while the blade angle is moving
toward reverse. This causes the reset lever and reset
post to move down.
As Np increases in reverse operation, the governor
flyweights begin to move outwards. Before the flyweights
reach the on-speed position, the speeder spring cup
pushes the reset lever, which pivots and allows Py to
bleed into the propeller governor. This will limit Ng to
control Np to a preset level.
Propeller speed control in reverse is controlled differently
depending on Airframe installation. Some installations
limit Ng with the max reverse stop on the FCU. Other
installations use the Nf governor in reverse as described
above.
PT6A-27/34
L>J 1U
TRAINING USE ONLY
OU(JUULkt>4114.14JUVLIVVVVVUVUU404Jkl
PROPELLER SYSTEM 11.8
lOtitiákilJták, 411./V
Notes:
PT6A-27/34
TRAINING USE ONLY
PROPELLER SYSTEM 11.9
PRIMARY BLADE ANGLE (PBA) CHECK
If:
Purpose
To ensure that the minimum allowed blade angle for
flight is within specified limits and safe for low power
operation.
To ensure that, on twin applications, both engines
propel the aircraft with the same force at low power
operation (PBA).
Indicated torque is lower than target —> PBA is too fine.
Indicated torque is higher than target —> PBA is too coarse.
Adjust beta nuts as per Airframe Manual to rectify:
Move beta nuts forward for a finer PBA
Move beta nuts rearward for a coarser PBA.
Therefore Tq rises.
Adjust nuts one flat at a time (60 0 per flat)
Procedure
Record OAT.
Record field barometric pressure or pressure altitude
(Refer to the Airframe Maintenance Manual).
Ex. Hartzel Propeller > 35 ft. lbs. per flat.
Start engine.
Note (1): Some airframe manufacturers do not allow
adjusting the beta nuts. The only option left is to adjust
the beta valve, inwards only. This will give a finer PBA
on the higher indicating engine.
Allow oil to warm up to operating temperature and
perform two feathering cycles.
Set propeller lever at maximum position.
Increase power until target Np is reached. Target Np
speed is always less than selected speed to ensure
the beta valve is controlling.
Note (2): Never move the beta valve out (forward), as
this will restrict the oil flow to the propeller.
Stabilize engine and record torque.
Compare indicated torque with torque given by chart
in Airframe Maintenance Manual.
Note: Ensure gauges are properly calibrated.
PT6A-27134
UUU
TRAINING USE ONLY
PROPELLER SYSTEM 11.10
OVUOUU4i414JVU414JUUUtIttltdatJUVUULdtd14414Pliii1UOUIMJ4JUU
EXAMPLE: SEA LEVEL , 15°C, TORQUE = 800 Lb -Ft
PRESSURE ALTITUDE (FEET)
60
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900
800
700
600
500
400
300
PROPELLER TORQUE (Lb -Ft) AT 1800 RPM
PRIMARY BLADE ANGLE CHECK CHART (typical)
1104 PT6A 27-34
TRAINING USE ONLY
PROPELLER SYSTEM 11.11
PROPELLER FEATHERING
Purpose:
Maintenance / Inspection:
Minimize drag in flight in the event of an engine
shutdown.
Check feathering operation as per Airframe Maintenance
Manual instruction.
Description:
Retarding the propeller lever to the feather position
causes the Propeller Governor to dump propeller servo
oil into the reduction gearbox sump.
The pressure loss in the propeller hub causes the
feathering spring and the propeller counterweights to
quickly bring the propeller to feather.
PT6A-27/34
TRAINING USE ONLY
PROPELLER SYSTEM 11.12
00U1/4, 4.14JtJUVUVUU40404JUVU IktikUlit0414141UVVIUVUUUQUI,›Utiltil
A
RESET POST
AIR BLEED ORIFICE
SPEEDER SPRING
RELIEF VALVE
Py
MAX. STOP SCREW
Eh
MIN. GOVERNOR ADJUSTMENT
PILOT
VALVE
FROM TO SUMP
PROPELLER SERVO
PUMP
GEARS
,---P0
GOVERNOR PUMP
ENGINE OIL SUPPLY
PT6A-27/34
1105C PT6A 27-34
PROPELLER SYSTEM (GOVERNING)
TRAINING USE ONLY
PROPELLER SYSTEM 11.13
PROPELLER OVERSPEED PROTECTION
Purpose: To provide protection against propeller and power
turbine overspeeds. There are two propellers overspeed
systems on the reduction gearbox:
Overspeed governor (hydraulic)
Nf governor (pneumatic)
2. Nf GOVERNOR
Purpose: In forward propeller operation: Provide a bacbp
to the propeller overspeed govemor. it will limit Np to appx.
10°/0 above selected speed.
In reverse propeller operation: Limit propeller speed to a vue
below the selected propeller speed to ensure propeller ich
remains in reverse. It will limit Np to approx. 5% bow
selected speed.
1. OVERSPEED GOVERNOR
Limits the propeller overspeed to 104`)/0 by hydraulically
adjusting the blade angle,
Description: The propeller overspeed governor has flyweights
connected to a pilot valve. The prop shaft drives the
flyweights. Two solenoid valves are mounted on the unit, one
for testing purposes and the other one to feather the propeller
in the autofeather mode. A speed reset solenoid valve allows
for verification of the unit at speeds below maximum.
On twin installation, a second solenoid valve is mounted on
the overspeed govemor and is used in conjunction with the
aircraft autofeather system. The system is switched on
(armed) for take off and in the event of a loss of power will
energize the solenoid valve to dump propeller servo oil into the
reduction geartoox sump. The feathering spring and propeller
counterweight move the blade quickly to feather.
Description: The Nf govemor consists of a Py bleed, a set
post, a reset arm and a reset lever.
Operation:
In the event of a propeller overspeednot
controlled by the propeller overspeed governor, the flywehts
in the propeller governor will move outwards until the spder
spring seat contacts the reset lever. The movement othe
reset lever around its pivot opens the Py air passage to bed
into the reduction gearbox, iimiting the fuel supply tcthe
engine.
This will prevent the propeller from accelerating beyondhe
preset limit.
Maintenance / Inspection:
Maintenance / Test:
With the reset solenoid energized, verify the speed at
which the overspeed governor reacts (propeller speed
stops increasing).
Turn the speed adjusting screw to increase or decrease
speed as required.(If permitted by the Airframe
Manufacturer).
PT6A-27/34
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Adjust speed limit in reverse using the minimum goveing
adjustment screw.
Overspeed limit adjustment in forward propeller operam
is not permitted.
TRAINING USE ONLY
PROPELLER SYSTEM 1.14
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PT6A-27/34
1106C PT6A 27-34
TRAINING USE ONLY
OVERSPEED PROTECTION
PROPELLER SYSTEM 11.15
PROPELLER GOVERNOR ADJUSTMENT
Reset arm rigging:
Maximum propeller speed (Np): (2200 or 1900 RPM)
Set propeller lever at maximum position in the cockpit.
Ensure lever contacts maximum Np stop screws.
Start engine .
Allow oil to heat up and do two feathering cycles.
Increase power. Ensure Np stabilizes at quoted speed.
Adjust screw counterclockwise to increase maximum Np,
clockwise to decrease.
Ensure the arm always contacts its forward stop.
Beta valve rigging:
Adjust the barrel so that the beta valve slot face is flush
with the beta valve cap nut.
Maximum propeller reverse speed:
Set propeller lever at maximum Np position.
Disconnect reset arm from interconnect rod and tie
rearwards to the lifting bracket.
Start engine, increase power until Np stabilizes (95% Np).
Check that Np stabilizes within specified limits.
Adjust underspeed eccentric screw if required.
Propeller governor Py leak check:
Disconnect Py line from prop govemor.
Cap Py line at governor.
Start engine and set power lever at ground idle.
Advance PLA sufficiently to bring Np at max speed.
(goveming). Mark position on pedestal. Stop engine.
Reconnect Py line.
Start engine and move PLA to previous Mark.
Verify Ng has not dropped more than 100 rpm
Replace propeller governor if necessary.
PT6A - 27/34
TRAINING USE ONLY
PROPELLER SYSTEM 11.16
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PT6A-27/34
1107 PT6A 27-34
TRAINING USE ONLY
PROPELLER SYSTEM 11.17
REVERSING CAM
Purpose: To operate the propeller reversing cable, to
control the prop blade angle for beta operations.
Description: There are several types of reversing cams.
Three types can be found on the small PT6A's:
Linear beta: Standard cam
Quiet Taxi: Found on the majority of Beech King Airs.
STOL cam: Found on the Short Take Off and Landing
aircraft. Ex: DH Twin Otter
PT6A-27/34
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TRAINING USE ONLY
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PT6A-27/34
1108 PT6A 27-34
TRAINING USE ONLY
PROPELLER SYSTEM 11.19
PROPELLER SYSTEM TROUBLESHOOTING
Bt.
Np and Torque
Fluctuations
o Ng, ITT or Wf
ctuations)
At HIGH
power
Propeller slow to unfeather
p Tq, ITT and Ng fluctuation
Propeller RPM too high
Propeller RPM.too low
PT6A-27/34
Overspeed governor interf eres with propeller governor.
Propeller governor problem. Replace unit if necessary
Reduce Np during hi power operation - See if problem clears
Verify if slip ring is not distorted.
Ensure that the BETA nuts are evenly adjusted.
Verify operation of lock pitch solenoid.
Carbon block worn out or beta valve rigged too far out.
Air in the propeller dome (first start of the day)
Ensure reset arm is positively sitting against forward stop.
Verify Py line for leaks. Replace FCU if problem is still present.
Adjust governor. Replace governor if adjustment is not effective.
Check accuracy of propeller speed indicating system.
Adjust governor. Ensure Ng is not limited by any P3 or Py leak.
Check accuracy of propeller speed indicating system.
Replace governor
TRAINING USE ONLY
PROPELLER SYSTEM 11.20
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MAINTENANCE PRACTICES
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.1
HOT SECTION INSPECTION
Purpose:
HSI Frequency:
To optimize engine performance, fuel economy, safety and
prolong component life. The condition of the hot section parts
has a direct effect on engine performance. Deterioration of the
hot section can be detected by using engine condition trend
monitoring (ECTM) and / or by doing performance checks
(refer to chapter 9).
Deterioration of hot section components may include cracking,
burning, buckling, erosion, fretting wear and corrosion.
Hot section distresses is usually attributed to malfunctioning
fuel nozzles, hot starts, running the engine beyond acceptable
ITT limits, continuous operation at maximum power, doing
rapid accelerations, or abusing reverse thrust or FOD.
Pre HSI Actions:
Do a performance check. The result of the performance
check will be compared with a post HSI check to monitor
performance recovery.
Remove and inspect oil filter, magnetic chip detector and
RGB strainer for metal contamination.
Remove air inlet screen and inspect first stage compressor
blades for F.O.D.
Return engine to an overhaul facility if any of the above checks
are beyond limits.
Goals of the HSI include:
Maintaining CT blade tip clearance close to a minimum
Optimizing lug to slot fits on CT vane
Minimizing P3 air leaks, internal or external
Ensuring that replacement compressor turbine vane ring
and power turbine vane ring classes are kept the same as
installed in engine latest build.
RT6A-27/34
Scheduled (1250 hours, as per SB1003 or SB3003)
On condition (as per ECTM result)
Engine Disassembly:
Remove power section
Measure Compressor Turbine blade tip clearance
Remove Compressor Turbine assembly
Remove fuel nozzles
Remove spark igniters
Remove combustion chamber liner
Remove CT vane assemble
Remove large exit duct
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.2
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Notes:
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.3
4
BORESCOPE INSPECTION
Procedure:
Description:
The borescope inspection allows operators to visually
inspect hot section components without disassembling
the engine.
The following components can be inspected with a
borescope:
Compressor turbine blades
Leading and trailing edges of compressor turbine
vane ring. Inner and outer walls of vane rings.
All CT vanes can be inspected when fuel nozzles are
removed for inspection.
Turbine shroud segments
Cooling rings and dome section of the combustion
chamber.
Use the borescope with care since it is a very fragile
device.
Engine must be cool prior to using the borescope. Cool
down engine for a minimum of 40 minutes.
PT6A-27/34
0000(... )00004)00900041)
Remove one fuel manif old adapter
Insert the guide tube through the open port
Install the holding fixture to the engine "C" flange
Connect the borescope to the light source
Insert the borescope into the guide tube with care
Note: Keep in mind that you are looking 125 degree
away from the point of entry of the tip as shown in the
figure.
All compressor turbine blades can be inspected through
one fuel nozzle adapter port. Using the proper tool in the
starter drive can rotate the compressor.
Ensure
borescope tip does not interfere with compressor turbine
blades.
The guide tube is not required for the inspection of
combustion chamber liner.
A 35-mm camera or a video camera may be mounted on
the viewer to record inspection of hot section areas
(adapters required).
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.4
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FUEL MANIFOLD ADAPTER PORT
RIGID GUIDE TUBE
POINT OF ENTRY (REF.)
FIBERSCOPE TIP
VANE RING
DISTAL POINT
RELATION BETWEEN POINT OF ENTRY AND DISTALTIP
VIEW FROM EXHAUST DUCT
TOWARD AIR INLET CASE
PT6A-27/34
1201 PT6A 27-34
//k.
GUIDE TUBE ORIENTATION
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.5
Hot Section Tools:
Power section sling (with the propeller installed on the
engine).
Compressor turbine holding wrench.
Spacers (4).
Spreader.
Compressor turbine puller.
Protector sleeve.
Puller no. 2 bearing cover.
Dial indicator.
9. Shroud grinder adapter.
10.Grinding wheel.
11.Grinder.
12.Crimper.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.6
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HOT SECTION TOOLS
PT6A-27/34
1202 PT6A 27-34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.7
CT Tip Clearance Measurement
Procedure:
Measure tip clearance using a tapered or a wire feeler
gage, at the trailing edge of the blades.
The tip clearance limits for each individual model is
listed in the Engine Maintenance Manual.
Do not rotate turbine while taking measurements.
For best accuracy, install the rubber blocks between
the small and large exit ducts.
Three limits are shown in the Maintenance Manual:
Average clearance for new segments.
Average clearance for used segment (that ran at
least 5 minutes at take off power).
Hi - low clearance for used segments (performance
permitting).
Amount of readings taken:
Average all readings and compare with limits stated in
Engine Maintenance Manual.
For PT6A-34 & 40 series, take 3 readings per
segments (3 readings x 9 segments = 27 readings)
For PT6A-27 series, take 2 readings per segments (2
readings x 16 segments = 32 readings)
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.8
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PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.9
HOT SECTION INSPECTION (continued)
INSPECTION
Gas generator case
CT vane
inspect case for cracks, distortion, corrosion and
evidence of overheating.
Inspect engine mount threads.
Inspect P3 air supply holes at CT vane flange for
blockage.
Inspect diffuser pipes for cracks and fretting wear.
Inspect shanknuts at CT vane flange for security.
Combustion chamber liner
Visually inspect the liner for evidence of burning,
cracking, buckling or metal to metal fretting wear.
Regap cooling rings if they are distorted.
Stop drilling of cracks and welding may be required
(refer M/M for limits).
Inspect vane ring for evidence of burning, cracking
and coating loss.
Insure proper sliding fit (lugs to slots) with mating
parts
Check air-cooling holes for blockage. (A-34 series only).
Shroud housing
Inspect shroud housing for cracks, blockage of
cooling air holes, fretting wear at sealing ring contact
area
Shroud segments
inspect shroud segments for cracks, burning
distortion and metal buildup
Combustion chamber large and small exit ducts
Compressor turbine
Inspect the small and large exit ducts for evidence of
burning, cracking, buckling, coating loss or metal to
metal fretting wear.
Stop drilling of cracks may be required (refer M/M for
limits)
PT6A-27/34
Inspect CT biades for: tip rub, cracks, sulphidation,
erosion, burning and coating loss.
inspect CT disk for damage.
Wash turbine blades based on past sulphidation
experience.
TRAINING USE ONLY
O UG )() U G)Q C.)(2 0 0 (.10 0 0
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MAINTENANCE PRACTICES 12.10
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HOT SECTION INSPECTION (continued)
SEALING SURFACE RESTORATION
Interstage Sealing Ring:
Inspect sealing ring(s) for fretting wear on sealing
diameter and face.
Fit ring on sealing diameter for full contact.
Purpose:
To achieve best sealing of P3 in the gas generator case
area and keep leakage to a minimum.
Power Turbine Vane:
Inspect vane ring for evidence of burning, cracking
and coating loss.
Ensure proper sliding fit (lugs to slots) with PT stator
housing.
Damage to the power turbine vane ring is not
common unless bad fuel nozzles caused damage to
CT area.
Power Turbine:
inspect the turbine for: cracks, burning, coating loss,
corrosion, and impact damage and blade shift.
Return the power section to an authorized overhaul
facility if the turbine needs to be replaced.
Description:
There are 2 sealing surface contacts that must be
checked for proper seating:
Lockplate to vane ring inner diameter.
Vane ring outer diameter to small exit duct.
Gas tight contact ,between these surfaces, depends on
surface finish and flatness. Surface finish should be
better than 32 micro-inches and .0005" max waviness.
Lapping can be used to eliminate minor surface
When lapping is impractical, the
imperfections.
assemblies should be machined at an approved overhaul
facility.
Exhaust Case:
Inspect the case for general condition.
Check the case for cracks near the flanges.
inspect inner ski jump area for wear caused by #3
bearing cover.
inspect flange -D- area for cracks around PT shroud.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.11
HOT SECTION INSPECTION (continued)
FITTING OF HOT SECTION PARTS
Step 1:
Purpose:
Install the vane ring on a bench with the inner lugs
uppermost. Install the #2 bearing cover slots around the
vane ring lugs.
To achieve best fitting of the hot section parts for
minimizing side play which can result in CT tip rub.
To allow thermal expansion to take place, without any
binding.
Description:
There are 2 lug to slot fit areas that must be checked for
proper fit:
Vane ring inner lugs to #2 bearing cover slots.
Vane ring outer lugs to shroud housing slots (A34 &
A40 series)
OR
2. Vane ring outer slots to small exit duct lugs (A-27
series).
Rotate the vane in the direction it would want to turn, as
the gas flow through it. Hold the #2 bearing cover still.
This will force the lugs to contact the slots on one side
and to have a loose fit on the other side. Measure
clearance on both sides with a narrow feeler gage, ref.
MM for limits.
Step 2:
Install the shroud housing on a bench with the slots
uppermost. Install the vane ring lugs inside the shroud
housing lugs.
Rotate the vane in the direction it would want to turn, as
the gases flow through it. Hold the shroud housing still.
This will force the lugs to contact the slots on one side
and to have a loose fit on the other side. Measure
clearance on both sides with a narrow feeler gage, ref.
MM for limits.
If clearance cannot be achieved, reindex the parts and
measure. If clearance can still not be obtained, remove
material lightly with a stone until fit is achieved.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.12
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Shroud segment grinding
To achieve optimum Compressor Turbine tip clearance all
around the shroud.
Note: operators who are equipped with the proper tooling and
do their own grinding use this procedure. The preferred
method is to send the hot section kit to an approved P&WC
service center, which can achieve a superior surface finish and
concentricity control. The hot section kit consists of the
following:
CT vane assembly (vane ring, small exit duct, shroud
housing and segments.
#2 bearing cover and / or flange.
Lockplate.
Compressor turbine assembly.
Grinding can be minimized by carefully selecting classes to
compensate for ovality or eccentricity of the shroud housing.
The best fitting class segments is picked after measuring the
CT outside diameter and referring to a table from the Engine
Maintenance Manual. It is recommended to go 1-class higher
(thicker segments) to offset any excessive ovality from the
shroud housing.
The shroud inside dimension (radius) is measured by
comparing reference master tool to the shroud dimension.
The dimension stamped on the master tool is the radius from
the center of the gage to the step on the master tool. Set gage
dial to zero when it is on the master.
Calculate actual tip clearance before grinding as follows:
(the numbers used are for examples only)
Dimension stamped on side of gage (master).
Dial gage reading.
(plus or minus sign is important)
CT largest diameter + 2 (8.532 + 2).
= 4.282"
= -0.009"
= 4.266"
Step 1 Find the radius of the shroud:
(master + dial reading => 4.282" -.009")
= 4.273"
Step 2 = Find actual CT tip clearance:
(shroud radius - disk radius => 4.273" - 4.266") = 0.007"
Step 3 = Determine material to be removed, assuming
required tip clearance is .010".
Preparations
Mask vane ring, #2 bearing and gas generator area
carefully.
Install the 4 rubber spacers with equal tension between the
large and small exit ducts.
Install the grinder adapter on compressor stub shaft.
Install the radius gage on the adapter and calculate the tip
clearance.
PT6A-27/34
Calculating amount of metal removed by grinding
(actual clearance - required clearance : .007" - .010") = -.003"
We need to grind .003" off the segments.
Note: Refer to Maintenance Manual for proper grinding
procedure.
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.13
HOT SECTION INSPECTION (continued)
Fuel nozzle functional check: Ensures the engine
combustion chamber receives properly atomized fuel.
Pressure Test:
Pressure test for leakage between nozzle tip and adapter
at 500 PSI, no leakage allowed.
Inspection interval:
Fuel nozzle cleaning:
200 hours for new operators.
400 hours max interval afterwards, depending of
condition.
Spray pattern check:
Flow test for spray pattern at 20 PSI. Check for
drooling and spitting (none permitted).
There might be an onion or tulip shaped spray
pattern.
Flow test for spray pattern at 60 PSI. Check for spray
pattern streakiness, drooling or spitting.
20% max streakiness is allowed
Note 1:All values are for reference only. Aiways refer to
the appropriate Maintenance Manual for proper settings.
When spraying, brush tip with a non-metallic brush to
loosen any possible carbon debris.
If above method is not effective, ultrasonically clean
nozzles ín carbon remover solvent.
Always hot water rinse nozzles after cleaning, since
carbon solvent is corrosive.
Fuel nozzle sheaths:
inspect sheaths for erosion on the dome top.
Inspect sheaths for wear at combustion chamber
contact area.
Check gap between sheath and adapter flange.
Check concentricity between sheath and adapter
orifice with a .020" drill.
Note 2: If a streaking nozzle is found during testing, a
visual HSI or borescope inspection of the hot section
should be done.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 1 2.1 4
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HOT SECTION INSPECTION (continued)
T5 system functional check:
Heat response test (T5 probe functional check)
T5 system inspection should be performed during hot
section inspection with the engine split at flange "C" or
whenever a T5 indication problem is suspected.
This check is done to verify proper functioning of T5
probes. Ensures T5 probes respond to heat.
Continuity Resistance (loop) check:
With engine split at "C" flange, connect test set to alumel
and chromel lead. Heat each probe individually and
verify response. Replace faulty thermocouple probe.
Ensures continuity and proper resistance in the T5
probes, busbars, wires and terminals.
Note:
Disconnect all leads from T5 terminal block on gas
generator case (use care, while disconnecting leads, to
avoid cracking the insulation material) and measure
resistance between Alumel and Chromel terminals.
Disconnect T5 probes from busbar and measure
resistance between Alumel and Chromel terminals, refer
to Maintenance Manual for resistance limits.
Each T5 probe can be checked for loop and insulation
resistance if a fault is suspected.
Always clean connector carefully to ensure resistance
of the system is not disturbed
Trim thermocouple check
This check is done to ensure proper resistance of the trim
stick.
Insulation (ground) resistance check:
This check is done to ensure system is not grounded
(shorted). Ensures that neither Alumel nor Chromel bus
bars are contacting the casing.
Connect test set between alumel or chromel and ground
(gas generator case) and measure insulation resistance.
Minimum resistance must not be less than specified limit.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.15
BASIC ENGINE RIGGING
Description:
Provide the operator with a basic approach to engine
rigging. This section defines the logical sequence that
should be followed when rigging the engine. lt also
describes the post run-up adjustments necessary to get
an ideal cockpit lever to engine response relationship.
Use the airframe maintenance manual for specific engine
rigging information.
Pre-rigging verification:
Ensure that cockpit levers and cables operate freely
and do not bind before making the connections to the
engine.
Ensure that the engine reversing cable is not
damaged and operates freely when disconnected
from the beta lever.
Remove the rod end clevis at both ends of the
reversing cable and inspect condition of wire rope and
attachment parts. Reinstall clevis and ensure lock
wire cannot be inserted through safety holes at both
ends (refer to the engine maintenance manual).
Verify that the propeller-reversing lever is connected
to the beta valve and make sure the carbon block is in
good condition.
You are now ready to rig the engine.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.16
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POWER
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MAX. POWER
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MIN. RPM
FEATHER
POWER
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CAM ASSY
(POWER CONTROL
LEVER)
PROPELLER SPEED
CONTROL LEVERS
POWER LEVERS
MIN. POWER
MAX. RPM
FUEL CONDITIONS
LEVERS
LEVER LOCKS
PROPELLER
LEVER
PROPELLER GOVERNOR
(PROPELLER LEVER)
LOW IDLE
SHUT-OFF
HIGH IDLE
FUEL
LEVER
PT6A-27/34
BASIC ENGINE RIGGING
1203 PT6A 27-34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.17
REAR LINKAGE RIGGING
With the airframe power lever cable and the engine
reverse cable disconnected from the cambox, move
the cockpit power lever through the full range and
verify motion is free of binding and excessive friction.
Ensure the cambox-input lever is installed at the
required angle from engine centerline. (Refer to
airframe manual)
Cycle the cockpit power lever between maximum
forward and reverse position and ensure the power
lever cable terminal travel exceeds the required input
lever displacement. Move the airframe power lever
cable on the airframe-supporting bracket to suit.
Connect the airframe power lever cable to the
cambox-input lever at the "track point". This point
should correspond to the PLA idle detent in the
cockpit. The track point is defined as the position of
the cambox input lever when the reverse cam moves
back 1/32 inch (apply light forward force on reverse
cam while measuring). Make sure this dimension is
the same on both engines.
PT6A-27/34
With the FCU interconnecting rod removed and the
fuel lever in the cut off position, move the FCU control
arm clockwise until the "pick up point" (spring tension
is felt) the angle between engine center line angle
control arm should be 22.5° below centerline. Adjust
with the serrated washer.
Move the FCU control arm 1/8 inch away from the
pick up point and connect the FCU control rod to the
specified holes (airframe manual). (The length of the
rod for this position is specified in the airframe manual
for reference purposes). Measure dimension X and
ensure it is the same on both engines.
Move the power lever through the full range. Ensure
that the lever is not binding and that the maximum
stop on the FCU is contacted. The cam follower pin
should not bottom out at either end of the reverse
cam slot.
Adjust the dead band screw as per airframe
maintenance manual instructions.
TRAINING USE ONLY
000UU0000410UOUUOVOU
MAINTENANCE PRACTICES 1218
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REVERSE CAM
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REVERSING
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DEADBAND ADJUSTMENT
,
FCU INTRECONNECTING ROD
FCU ACTUATING
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FCU ARM
CAM FOLLOWER
PIN
CAMBOX
INPUT
LEVER
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22.5°
CAM BOX
AIRFRAME
POWER LEVER
CABLE
MAX. NG
STOP
REAR LINKAGE RIGGING
PT6A-27/34
1204 PT6A 27-34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.19
FRONT LINKAGE RIGGING
Make sure that the reverse cable is not connected at
the cambox.
Move the cockpit power lever between idle and
maximum power.
With the CSU interconnect rod in place, pull forward
on the beta lever and adjust the front clevis so that
the beta valve clevis slot face is flush with the beta
valve nut.
Connect the reverse cable rear clevis to the reverse
cam required hole. Adjust the clevis so that the cable
is in light compression (pushed forward) when the
clevis pin is installed.
Cycle the cockpit power lever from idle to maximum to
confirm smooth motion. Adjust the reverse cable
preload at the rear clevis connection if excessive
friction is observed.
PT6A-27/34
TRAINING USE ONLY
k.) JUOUUUVUOUUUJUU
MAINTENANCE PRACTICES 12.20
Ut)OQUJUU0
RESET ARM MAX. STOP
DO NOT ADJUST
FRONT CLEVIS
BETA LEVER
-\)yos.
*4
,Ji•-•
1*• n -11
&E'l
$0 de
BETA VALVE
CAP NUT
INTERCONNECT ROD
RIG FLUSH
FRONT LINKAGE RIGGING
PT6A-27/34
1205 PT6A 27-34
BEAT VALVE
TRAIN1NG USE ONLY
MAINTENENCE PRACTICES 12.21
FUEL LEVER RIGGING
PROPELLER SPEED LEVER RIGGING
Rig as per airframe manual instructions then:
Rig as per airframe manual instructions then:
Ensure that there is a positive contact with the cut off
stop, and that the condition lever moves freely
through the entire range.
Ensure high idle stop is contacted when fuel lever is
moved to high idle position.
Prior to starting the engine, disconnect the fuel line
coming out of the flow divider.
Perform a wet motoring run to confirm Positive fuel
cut off
Ensure cut-off happens when the fuel lever position is
halfway through the cut off detent.
Connect the propeller speed cable to the speed
control lever on the CSU.
Move cockpit propeller lever to the maximum Np
position and make sure that the skirt contacts the
CSU maximum Np stop screw.
Move the propeller lever to feather and check that the
feather stop screw is contacted. If the engine is fitted
with a feathering valve, check that valve depresses as
specified in the airframe maintenance manual.
Ensure the propeller feathers when the cockpit
propeller lever is halfway through the feather detent.
Check low and high idle as per aircraft maintenance
manual.
PT6A-27/34
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.22
)UtJUQUQUOUVUVUOU(.0 900 JUt)00(Jtá JUUU0t, 10000
FEATHER STOP SCREW
RESET ARM MAX. STOP
(DO NOT ADJUST)
114_.»
(-1:
...12111
41j1
n_t>!
HIGH IDDLE
CUT-OFF STOP
MAX. SPEED ADJUSTMENT
FCU
CSU
FUEL & PROPELLER SPEED LEVER RIGGING
PT6A-27/34
1206 PT6A 27-34
TRAINING USE ONLY
MAINTENENCE PRACTICES 12.23
POST RUN UP ADJUSTMENTS
Prior to running the engine ensure that
The FCU maximum Ng stop is contacted when the cockpit power lever is advanced to the maximum position.
The cut-off stop is contacted when the condition lever is at the cut-off position.
The speed select lever on the CSU makes firm contact with the maximum speed stop.
.SYMPTOMS
FIX
.
Ensure minimum flow is not too high.
Ensure FCU control rod is not rigged too short.
Idle Nwtoo high
Acrust.
Ensure there are no P3 or Py leaks.
Idle Nattio low
Adjust.
Before adjusting, ensure that:
.
.erlever
Unequa ,
Low and high idles are the same on both engines and Ng pick-up point is the same on
travel MOyement from
both engines.
-Adle to take off between
To shorten the power lever travel, (PLA ahead) lengthen the FCU control rod. This will
the two engffies
.
-displace the Ng pick-up point.
(progl
..- essive staggeriy
Reposition the pick-up point by adjusting the serrated washer (counterclockwise in this
case).
Before adjusting make sure that:
The deadband is the same on the two engines.
Ng pick- up point is
The power lever travel movement from idle to take off is the same on the two engines
different on the two
(stagger is constant).
engitiéáf
To move the pick-up point forward on the quadrant, turn the serrated washer clockwise.
(Do not change the rod length) NB: 2 teeth change on serrated washer -- .040"
movement on the cocksit suadrant.
.
•
—
PT6A-27/34
TRAINING USE ONLY
OUUt.)4)04,› UUUUU U IJ (.1 tJ
MAINTENANCE PRACTICES 12.24
4.1 U VO UV 4,1 V U 411 01.1 WIJUQ U U u v 4)
POST RUN UP ADJUSTMENTS (continued)
sympToms
Primary blede andle
•
cheók shows a difference
between the two engines •
•
Propellerwo pitch
position (Np increase in . ., •
rearward deadband) is
•
staggered on the two
•
engihes.
•
PT6A-27/34
Verify position of the beta valve is identical on the two engines when the cockpit power
lever is advanced halfway between idle and maximum power.
Adjust beta valve position if adjustment required is small, otherwise adjust beta nuts.
Confirm the beta valve position is flush with the beta valve cap nut.
Ensure the reverse cable clevis is connected to the specified reverse cam hole.
Ensure Ng is in deadband zone (no increase yet)
Perform primary blade angle check (Calibrate torque transducer).
Adjust PBA as required.
TRAINING USE ONLY
MAINTENANCE PRACTICES 12.25
SUMMARY OF CONTROLS
•
Safety only ; reduces
fuel flow if Np exceeds
selected RPM by
approx. 6°/0 to 10% in
case
of a malfunction.
Scheduled by
FCU
via power lever
Supplies servo oil to propeller
via beta valve. Pilot valve
open.
Safety only
Schedule by FCU
Ng is at low idle
or high idle
(Via condition
lever)
Supplies servo oil to propeller
via beta valve. Pilot valve
open.
Safety only
Schedule by FCU
Ng remains at idle
Supplies servo oil to propeller
via beta valve. Constant
speed action inoperative.
Progressively reduces
fuel flow to ensure
actual Np is always less
than selected Np.
Scheduled by
FCU and modified
by Nf governor Py
bleed (high power
reverse operation)
Maintains constant prop RPM
by controlling oil supply to
propeller via pilot valve
plunger.
Beta valve fully open.
PT6A-27/34
-1.>o
TRAINING USE ONLY
Tatt.
Provides for
minimum blade
angle only;
normally
inoperative in
this range of
operation.
Beta valve
maintains PBA
by controlling oil
flow to propeller
Beta valve
maintains blade
angle selected
by pilot.
Beta valve
maintains blade
angle selected
by pilot.
Power lever
schedules Ng only.
Propeller reversing
mechanism is
inoperative. Beta
valve is fully open
Cockpit power lever
schedules Ng only.
Beta valve controls oil
to propeller.
Power lever
schedules
blade angle directly.
Ng remains at idle
Cockpit power lever
schedules blade
angle directly,
schedules fuel flow,
and resets Nf
governor down.
MAINTENANCE PRACTICES 12.26
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