CANADIAN FORCES
FLIGHT SAFETY INVESTIGATION REPORT (FSIR)
FINAL REPORT
FILE NUMBER:
FSOMS NUMBER:
DATE OF REPORT:
AIRCRAFT TYPE:
DATE/TIME:
LOCATION:
CATEGORY:
1010-CH147204 (DFS 2-4-2)
136988
13 July 10
CH147D Chinook
18 0730Z Jan 09
Kandahar Airfield, Afghanistan
"B" Category Accident
This report was produced under authority of the Minister of National Defence pursuant
to section 4.2 of the Aeronautics Act, and in accordance with the A-GA-135-001/AA001, Flight Safety for the Canadian Forces.
With the exception of Part 1, the contents of this report shall only be used for the
purpose of accident prevention. This report was released to the public under the
authority of the Director of Flight Safety, National Defence Headquarters, pursuant to
powers delegated to him by the Minister of National Defence as the Airworthiness
Investigative Authority for the Canadian Forces.
SYNOPSIS
Aircraft CH147204 was on a training mission out of Kandahar Airfield (KAF). The
aircraft departed KAF and no anomalies were noted by the crew. Later in the
morning, while the aircraft was still on its mission, maintenance personnel found
an aircraft component on the ramp near where aircraft CH147204 had been
parked. The component was an aft rotor fixed droop stop, which supports the
weight of the blade at low rotor RPM during start-up and shutdown. The
maintenance personnel immediately checked all other aircraft on the ramp and
found that none was missing a fixed droop stop. The crew of the Chinook was
notified of the situation and were directed to return to KAF and to land on the
Dangerous Area Cargo (DAC) ramp. An emergency shut down procedure,
involving the use of a maintenance ladder covered with wooden boards placed
over the fuselage, was used in an attempt to minimize aircraft damage. The
aircraft parking brakes were set and the crew abandoned the aircraft, leaving the
engines running. Once the fuel supply was exhausted, the rotors slowed and the
affected blade ultimately impacted the ramp, resulting in damage to five main
rotor blades, the aft pylon and the fuselage skin. There were no injuries.
i
TABLE OF CONTENTS
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
1.11
1.12
1.13
1.14
1.15
1.16
1.17
1.18
1.19
2
2.1
2.2
2.3
3
3.1
3.2
4
4.1
4.2
4.3
4.4
FACTUAL INFORMATION .........................................................................1
History of the Flight ............................................................................................ 1
Injuries to Personnel........................................................................................... 1
Damage to Aircraft .............................................................................................. 1
Collateral Damage ............................................................................................... 2
Personnel Information ........................................................................................ 2
Aircraft Information............................................................................................. 2
Meteorological Information ................................................................................ 7
Aids to Navigation............................................................................................... 7
Communications ................................................................................................. 7
Aerodrome Information ...................................................................................... 7
Flight Recorders.................................................................................................. 7
Wreckage and Impact Information..................................................................... 8
Medical ................................................................................................................. 8
Fire, Explosives Devices, and Munitions .......................................................... 8
Survival Aspects ................................................................................................. 8
Test and Research Activities ............................................................................. 8
Organizational and Management Information .................................................. 9
Additional Information ........................................................................................ 9
Useful or Effective Investigation Techniques................................................. 11
ANALYSIS ................................................................................................12
Technical Analysis ............................................................................................ 12
Lack of a Rotor Brake System ......................................................................... 16
Summary ............................................................................................................ 17
CONCLUSIONS ........................................................................................18
Findings ............................................................................................................. 18
Cause Factors.................................................................................................... 21
PREVENTIVE MEASURES ......................................................................22
Preventive Measures Taken ............................................................................. 22
Preventive Measures Recommended.............................................................. 22
Other Safety Concerns ..................................................................................... 23
DFS Remarks ..................................................................................................... 23
Annex A - Photographs ................................................................................... A1
Annex B - Schematic of Droop Stop Installation .......................................... B1
Annex C - Before Taxi Check as per Operator’s Manual .............................. C1
Annex D - Before Taxi Check as per Operator’s Checklist .......................... D1
Annex E - Emergency Shutdown Procedure - Droop Stop Failure.............. E1
Annex F - Chinook Blade Deflector Ramp - Preparation ...............................F1
Annex G - References...................................................................................... G1
Annex H - Abbreviations ................................................................................. H1
ii
1
1.1
FACTUAL INFORMATION
History of the Flight
1.1.1
The pre-flight inspection of Canadian Chinook CH147204 was
conducted by the flight engineers (FE) prior to the pilots’ arrival. The FE walkaround is more detailed and more in-depth than the pilots’ walk-around. Upon
arrival at the aircraft, the pilots conducted their own walk-around and the crew
then proceeded with the mission with no anomalies noted.
1.1.2
While the aircraft was on its mission, maintenance personnel found an
aircraft component on the ramp where CH147204 had been previously parked.
The component was identified as an aft rotor fixed droop stop (part number
114R2087-3). Maintenance personnel conducted a quick survey of all other
aircraft in KAF and determined that all aircraft had their fixed droop stops
installed. The Unit’s Chain of Command and operations were advised, who then
notified the crew of the situation and recalled the aircraft. The tower controller
declared an emergency for the crew and operations informed the crew that the
aircraft was to land on the Dangerous Area Cargo (DAC) ramp; a remote location
in KAF. The aircraft landed, and with engines running and rotor blades turning,
non-essential crew disembarked, and ammunition was unloaded. Some
personnel boarded the aircraft to advise the remaining aircrew on the situation
and to discuss the droop stop failure procedure, which was acquired from a
coalition partner. As the CH147D is not equipped with a rotor brake, the crew
considered the option of remaining on board to shutdown, or abandoning the
aircraft and standing-off at a safe distance until the aircraft ran out of fuel.
Meanwhile, the no. 1 engine was shutdown to reduce fuel consumption and
provide more time for an option analysis. CF personnel, with assistance from
coalition personnel, set up a rigged ladder beside the aircraft to shield the
fuselage from possible rotor blade impact during rotor deceleration. After the
preparations were completed, the pilots evacuated the aircraft and approximately
one hour and thirty minutes later, the engine flamed out due to fuel starvation.
As the rotors decelerated, the aft rotor blades contacted the rigged ladder,
eventually causing the rotor blades to come to an abrupt stop and damaging the
left side of the fuselage.
1.2
Injuries to Personnel
Nil.
1.3
Damage to Aircraft
1.3.1
The aircraft sustained very serious damage. Both rotor heads (forward
and aft) and the drive train were subjected to a “sudden stoppage”. Five of the
six rotor blades were damaged during the occurrence. The top of the aft pylon
was damaged at station 570 where the rotor head struck the top surface of the
pylon. Skin deformation was observed at two locations on the aft pylon (port side
1 / 23
at waterline/station 120/600 and, starboard side at waterline/station 70/630). The
top of the Satellite Communication (SATCOM) antennae had contact marks and
the High Frequency (HF) antenna was broken in two locations. The fuselage
skin was punctured at station 260 when the rigged ladder came into contact with
the fuselage.
1.3.2
The aft blades are color coded yellow, red and green. The failed droop
stop that was found on the ramp after the helicopter departure was identified to
be from the yellow blade. The other two droop stops, which failed during the
shutdown, were labelled according to where they were found during the field
inspection post-incident (i.e. “Found 20ft Left of Aircraft” and “Found 147ft Left of
Aircraft”).
1.4
Collateral Damage
The rigged ladder borrowed from a coalition partner was damaged due to the
impact of the rotor blades. No other collateral damage was reported.
1.5
Personnel Information
Pilot
Co-pilot
FE 1
FE 2
Total Flying Hrs
1372.6
1000.1
2461.8
176.2
Total Hrs on type
126.6
69.9
97.5
140.6
Hrs last 24 Hrs
3.5
3.5
3.5
3.5
Hrs last 48 Hrs
6.5
3.5
6.5
6.5
Hrs last 72 Hrs
9.0
3.5
9.0
8.1
Duty Time –
Day of Occurrence
11
11
8
7
Duty Time – 48 Hrs
23
21
18
15
Duty Time – 72 Hrs
35
32
28
23
Table 1: Personnel Information
1.6
Aircraft Information
1.6.1
Aircraft Description: The Boeing CH147D Chinook is a twin-engine,
tandem rotor heavy-lift helicopter. Its primary roles include troop movement,
artillery emplacement and battlefield resupply. There is a wide loading ramp at
the rear of the fuselage and three external-cargo hooks.
2 / 23
1.6.2
Droop Stop System: The Chinook helicopter is equipped with a fixed
droop restraint system on both the forward and aft rotor heads as shown below in
Figure 1a. The aft rotor head also has a centrifugal droop restraint system in
addition to the fixed droop restraint system as shown below in Figure 1b. Unlike
the fixed droop stop system, the centrifugal droop stop system is composed of
mobile components, which move in and out as the rotor RPM decreases or
increases. The purpose of the droop restraint system is to support the weight of
the rotor blades at low rotor RPM, such as during start-up and shutdown, and to
therefore prevent damage to the rotor head, rotor mast and/or airframe. The
droop restraint system has no function while the aircraft is in flight and failure of
the system in flight does not impede safe flying operations. The system is only
effective when the engines are secured and the rotor RPM decreases below
56%.
Forward Fixed Droop Stop
Required Safety Lock-wire
Figure 1a - Forward and aft droop stop assemblies
1.6.3
Within the droop restraint system of the aft rotor head, the aft fixed droop
stops are installed on the bottom of the pitch-varying shaft below the horizontal
pin on each of the three rotor blades. At rest, the droop stops contact the
interposer blocks restricting the droop from 1.25 to 1.75 degrees in the vertical
plane. Additionally, at low rotor RPM, springs hold the arms close to the hub,
keeping the interposer blocks between the hub and the pitch-varying shafts to
limit blade droop angle. However, when the rotor speed increases above 67%
RPM, centrifugal force causes the arms to move out against the spring tension.
As the arms are connected to the interposer block, this moves the interposer
block out from between the hub and the shaft to allow more freedom for the
blades to flap during flight. As rotor RPM increases, the centrifugal droop stop
assembly allows a droop angle of 5.5 to 6 degrees for the aft blades.
3 / 23
Weight
Limiters
Mounting Plate
Springs
Balancing Arm
Interposer Block
Figure 1b - Aft centrifugal droop stop assembly
1.6.4
The aft rotor head has three fixed droop stops, which consist of steel
blocks that are nearly six inches long and have a 0.7-inch square cross section.
Two opposing long edges are sharp or square whilst the other opposite edges,
the other two diametrically opposed edges, are chamfered, with one of the
chamfers being larger than the other. The droop stop is fastened by two bolts
that thread into the block in two slightly angled blind holes located on one side.
One side of the droop stop is painted with a black label “AFT ROTOR BOTTOM”
on a yellow background (Photo1 in Annex A or Figure 3 in section 2). From
Annex G, reference A, the Vertol Division Boeing, Drawing number 114R2087,
Stop, Droop-Centrifugal Droop Stop Aft Rotary Wing Head, Rev B, 24 August
1972, this painted marking is to be located on the side of the block with the larger
chamfer.
1.6.5
The correct installation of the droop stop is critical to give adequate
clearances during operation, as shown in Annex B. From Annex G, reference B,
the Technical Manual for CH-47D Helicopter (TM 55-1520-240-234), section 548, two factors are important to ensure proper orientation and placement during
installation. The first and most important factor is the placement of the droop
stop based on the side of the block with the larger chamfer. The second is the
orientation of the droop stop with the side that is painted “AFT ROTOR
BOTTOM”. The technical manual instructions for droop stop installation,
including the two warning statements, are as follows:
4 / 23
WARNING
The droop stops are to be installed with “BOTTOM” marking down. The
marking may or may not be legible. However, correct installation is
determined by proper positioning of chamfers.
Ensure forward droop stop is installed on fwd head, and aft droop stop is
installed on aft head. Forward and aft droop stops are not
interchangeable.
WARNING
Incorrectly installed droop stops, or droop stops installed on the wrong
head, can cause damage to the helicopter and injury to personnel.
8. Position droop stop on lugs with BOTTOM marking down. Ensure
droop stop chamfer is upward in the radius of the pitch shaft droop stop
boss.
1.6.6
Aircraft Acquisition: The CH147D Provisional Technical Airworthiness
Clearance (PTAC) was issued by the DND Technical Airworthiness Authority
(TAA) on 28 Nov 08. This provided the TAA’s recommendations to the DND
Airworthiness Authority (AA), the Chief of the Air Staff (CAS), for the
Airworthiness Clearance for the CH147D Weapon System. No technical
limitations or restrictions were imposed by the TAA. The PTAC was then used
by the Operational Airworthiness Authority (OAA) as the basis from which the
Operational Airworthiness Clearance (OAC) was prepared and approved. The
CH147D Provisional Operational Airworthiness Clearance (POAC) was issued by
the OAA on 03 Dec 08. This POAC is the authority to operate the CH147D in its
intended roles with the required equipment. This report also provided the OAA's
recommendations to the AA regarding the Airworthiness Clearance for the
CH147D Weapon System and the subsequent Release to Service (RTS). The
RTS, dated 04 Dec 08, followed the DND/CF RTS process and was approved by
CAS on 16 Dec 09. Aircraft CH147204 was transferred to the CF on 30 Dec 08 a
few weeks prior to the occurrence with a total of 8,379.9 airframe (AF) hours.
The transfer took place in the Afghanistan Theatre of Operation. A small team of
CF personnel was sent to KAF to conduct the aircraft transfer and acceptance
process. This team included experienced and qualified aircrew that were
designated by the Commanding Officer of the Aerospace Engineering Test
Establishment (AETE) to provide test and evaluation oversight during the
acceptance and transfer. Similarly, maintenance and engineering personnel
from the Director General Aerospace Equipment Program Management
(DGAEPM) division provided technical and airworthiness oversight. The aircraft
were accepted through an acceptance and transfer process that was deemed
acceptable by all concerned. The acceptance process put in place was a formal
process called a “Unit-to-Unit Transfer”. The acceptance team followed an
Acceptance Checklist that was provided by DGAEPM and added a functional
5 / 23
check, that was conducted during the ferry flights to KAF. The helicopters had
just undergone a maintenance inspection cycle and were deemed operational,
serviceable and airworthy. The CF acceptance team responsible for the transfer
and acceptance of all Chinooks was satisfied that all reasonable and practicable
steps had been taken to ensure that all CH147D aircraft were operational,
serviceable and airworthy and met the conditions of the RTS.
1.6.7
Aircraft Inspections: All CF aircraft undergo scheduled and preventive
maintenance inspections from the maintenance organizations to allow for the
detection and rectification of deficiencies. These are either based on airframe,
engine or rotor hours (in this case rotor hours) or they are conducted on a daily
basis. In addition, flight crews also conduct their own pre-flight inspections to
offer an additional layer of safety.
1.6.8
Prior to the Chinook acquisition into the CF, aircraft CH147204 had
undergone a phased inspection (i.e., 400-HR Cycle Service Program (CSP)) 5.2
AF hrs earlier at 8374.7 AF hrs. The aft rotor head assembly (PN 145R2004-20,
SN A5-1744) had been installed during that inspection. The records show that
the component hours at installation were 405 hrs. At the start of the mission on
the day of occurrence the aircraft had 8387.8 AF hrs (7.9 AF hrs after the transfer
of the aircraft to the CF). The aircraft had flown four flights under Canadian
ownership before the occurrence. The next phase inspection (i.e., 200-HR CSP)
was scheduled to be carried out at 8574.7 AF hrs. The phased inspection,
overhaul and post inspection quality assurance processes did not reveal any
abnormalities nor did they detect the incorrect installation of the three aft droop
stops. The maintenance daily inspections and flight crew walk-around
inspections conducted by the transferring unit after the inspection and prior to
transfer also did not detect this abnormality. The daily inspections conducted by
CF personnel after the transfer and prior to the occurrence also did not detect the
incorrect installation of the aft droop stops. Additionally, all acceptance process
inspections including the acceptance Maintenance Test Flights (MTF) and walkarounds did not detect the incorrect installation.
1.6.9
Droop stop failure is a rare but well-known problem on the Chinook
helicopter. The most common cause for droop stop failures is a phenomenon
referred to as “droop stop pounding”, where the fixed droop stop comes into
contact with the mast if flight control limits are exceeded. Previous events of
droop stop failure led to the publication in 2000 and 2001 of two Special
Inspections (SI): Service Bulletin TB 1-1520-240-20-132 focussed on the proper
length and wear and tear of the bolts, while Service Bulletin TB 1-1520-240-20136 focussed on the proper on-aircraft installation of the droop stop. At that time,
the SI required examination of the length of the bolts, the installation of the droop
stop and wear and tear limits on the bolts.
1.6.10 Post-occurrence maintenance activities included inspections to ensure
that all droop stops on all CF Chinooks were painted and installed as per the
technical manuals. The field investigation found that the three aft droop stops
6 / 23
were installed incorrectly. Maintenance personnel conducted a local SI of all
aircraft in KAF in accordance with the two Service Bulletins, TB 1-1520-240-20132 and TB 1-1520-240-20-136. The SI revealed only normal wear and tear.
1.6.11 Rotor Brake System: A rotor brake system is designed to assist and
expedite a helicopter start or shut down sequence. On start up, a rotor brake will
hold the rotor head in place and allow for the conduct of engine start, blade
spread/fold (if equipped with a folding rotor head) and start up checks. It will also
hold the rotor head during the initial engine acceleration for the engagement of
the rotor. On shut down, a rotor brake will expedite the deceleration of the rotor
blades and hold the rotor head in place during the shut down checks and the fold
sequence, if required. In the event of a droop stop failure, the greatest risk is the
damage incurred by the drooping blade impacting the fuselage during the rotor’s
deceleration. During this emergency, the rapid and full application of the rotor
brake, at a predetermined RPM, is the only way to minimize the risk of a
drooping rotor blade from impacting the fuselage and thus preventing aircraft
damage. The CF model is not equipped with a rotor brake system.
1.7
Meteorological Information
The weather was reported as CAVOK (no cloud below 5 000 feet, no
cumulonimbus, visibility of 6 statute miles or more, and no precipitation, fog or
drifting snow). The winds were reported to be approximately 5 knots from the
north. Weather is not considered a factor in the occurrence.
1.8
Aids to Navigation
Not applicable.
1.9
Communications
Not applicable.
1.10
Aerodrome Information
KAF has a single runway and is surrounded by taxiways, ramp areas and
helicopter movement areas. There is a DAC ramp area that is used mostly for
loading and offloading dangerous cargo onboard resupply aircraft. When the
DAC ramp is utilized for dangerous cargo loading, a perimeter is set-up to secure
the surrounding area. CH147204 was landed at the DAC ramp and a security
perimeter was set-up due to the possibility of flying debris caused by rotor blade
impact.
1.11
Flight Recorders
The occurrence aircraft is not equipped with any flight data recording devices,
cockpit voice recorders or helicopter Health and Usage and Monitoring System
(HUMS). The Aircraft Vibration Analysis (AVA) system, which is a maintenance
7 / 23
tool used for troubleshooting purposes, was not installed at the time of
occurrence.
1.12
Wreckage and Impact Information
As the rotor blades slowed down, the aft rotor blade with the missing fixed droop
stop (yellow blade) began to fly out of plane and slightly lower than the other two
aft rotor blades. With the fixed droop stop missing, as the rotors slowed down
the yellow blade eventually drooped low enough to strike the rigged ladder set-up
on the side of the aircraft. The other two aft rotor blades also contacted the
rigged ladder. This caused damage to the aft rotor blades, the aircraft and the
rigged ladder itself. After the initial first contact, the aft rotor blades impacted the
rigged ladder seven times within five seconds, with all forward and aft blades
coming to an abrupt stop within the deceleration cycle. The blade impacts
caused the ladder to strike the left side of the fuselage, damaging the HF
antennae and puncturing the aircraft fuselage at station 260. Due to the weight
of each rotor blade, combined with the amplitude of travel when they contacted
the rigged ladder and skipped over the fuselage, the other two fixed droop stops
also failed. One was found approximately 147 feet away and the other
approximately 20 feet away; both at the 7-8 o’clock position from the rear of the
aircraft. It was not possible to determine which fixed droop stop came from
which rotor blade (red or green blade). Five of the six rotor blades were
damaged, the aft pylon shifted and the left side of the fuselage was punctured.
Some of the bolt heads from the droop stop fasteners were also recovered.
1.13
Medical
Blood and urine samples were taken from the pilots and sent to the Armed
Forces Institute of Pathology (AFIP) in Washington DC for toxicological analysis.
This analysis did not indicate any presence of foreign substances capable of
causing intoxication or performance impairment of either of the two pilots.
1.14
Fire, Explosives Devices, and Munitions
The occurrence aircraft was equipped with door guns and associated ammunition
which was removed immediately after landing to mitigate the risk during the
aircraft shutdown sequence.
1.15
Survival Aspects
The uncertainty of what would happen during the shutdown procedure and when
the rotor blades would hit the rigged ladder led the aircraft captain to make the
decision to abandon the aircraft before it ran out of fuel.
1.16
Test and Research Activities
The aircraft aft rotor head was sent to the Quality Engineering and Test
Establishment (QETE) for examination.
8 / 23
1.17
Organizational and Management Information
Not applicable.
1.18
Additional Information
1.18.1 Operator’s Manuals and Checklists - There is no dedicated procedure for
a droop stop failure on the CH147D Chinook. Neither CH-47D Helicopter
technical manuals, Operator’s Manual (TM 1-1520-240-10), Annex G, reference
C, nor Operator’s and Crewmember’s Checklist (TM 1-1520-240-CL), Annex G,
reference D, which are authorized for use by CF personnel, have an emergency
procedure for droop stop failures. There are discrepancies and omissions within
these two main technical manuals that seem to provide conflicting guidance or
direction to crews concerning the droop stop systems in this aircraft. Flight crews
understand the importance of adhering to warning and caution statements and
also normally adhere to and conduct all of the actions detailed in an itemized
checklist. Although crews normally have a detailed knowledge of the operating
manual, their day-to-day operations rely heavily on the use of the operator’s
checklist. A checklist contains the operator’s and crewmember’s checks to be
accomplished during normal and emergency operations. This checklist does not
replace the amplified version of the procedures in the operator’s manual, but
includes a condensed version of each procedure. A warning statement referring
to “personal injury or death” in the operating manual is intended to highlight this
issue and its level of importance. When these warning or caution statements
include specific actions, it is expected that these actions be detailed as
procedures within both the operating manual and the checklist. As an example,
a manual or checklist with a warning statement directing flight crews to conduct
an emergency shutdown should have an Emergency Shutdown procedure listed
within the emergency procedures section of this same manual or checklist. If an
action is highlighted within a warning or caution statement and then not included,
mentioned or referred to as a checklist item, this exclusion can diminish this
action’s level of importance or contribute to its omission in the conduct of daily
operations. A review of several CF aircraft and helicopter operating manuals and
checklists has revealed that several warnings, cautions and notes from the
operating manual or Aircraft Operating Instructions are included or replicated in
the checklists. Within the Chinook publications that are authorized for use by CF
aircrew, warnings, cautions or notes that are present in the operator’s manual,
such as those within the “Before Taxi” procedure, are not replicated or included
in the operator’s checklist.
1.18.2 The operator’s manual details the “Before Taxi” procedure, Annex C.
which starts with the following warning statement:
WARNING
“Personnel injury or death may occur and damage to airframe and rotor
systems will occur if the forward or aft rotor blade droop stop(s) are
9 / 23
missing or interposer(s) on the aft rotor head are not engaged. After
engine run-up and before flight, or shut-down if flight is not conducted, the
flight engineer will scan the ground in the immediate area of the aircraft for
evidence of detached droop stops.”
1.18.3 The operator’s manual also contains ten actions items for the “Before
Taxi” procedure. Despite this warning statement, there is no specific action item
within the procedure to address the requirement for “the FE to scan the ground…
for evidence of detached droop stops” prior to flight as detailed in the warning
statement. The warning statement is repeated in the “Engine Shutdown”
procedure; however, here the action is listed as a checklist item as “F 19.
DROOP STOPS – Engaged”.
1.18.4 Within Chapter 9 - Emergency Procedures of the operator’s manual, the
Section 9-1-31 - Rotor, Transmission and Drive Systems, shows a similar
warning statement. However, this warning only directs crews to contact
maintenance, attempt to engage the interposer blocks or droop stops and then
prepare aircraft for an emergency shutdown that will minimize damage to aircraft
and injury to personnel. The operator’s manual does not include a specific Droop
Stop Failure procedure either in the Normal Procedures chapter or in the
Emergency Procedures chapter directing flight crews or maintenance personnel
on how to effectively deal with this emergency.
1.18.5 The checklist “Before Taxi” procedure, Annex D, does not have the
warning statement from the operator’s manual nor does it include an action item
for the FE to scan the ground for evidence of detached droop stops as found in
the operator’s manual’s warning statement. Within the “Engine Shutdown”
procedure, there is again no warning statement included but a checklist action
item is included as “F 19. Droop Stops – Engaged.” as in the operator’s manual.
Additionally, within the emergency procedures section of the checklist, there is
also no Droop Stop Failure procedure listed. The checklist does not include a
specific Droop Stop Failure procedure either in the Normal Procedures section or
in the Emergency Procedures section directing flight crews or maintenance
personnel on how to effectively deal with this emergency.
1.18.6 Emergency shut down procedure: The emergency shut down procedure
for a droop stop failure was borrowed from a coalition partner and is detailed at
Annex E. It describes both a failure of a forward and an aft rotor fixed droop
stop. This procedure is predicated on the aircraft having a rotor brake system.
While some differences exist between the coalition partner Chinook model and
the CF model, the main issue in this case is that the CF model does not have a
rotor brake system. The Unit’s Chain of Command and the incident crew were
aware that this procedure relied upon a rotor brake system. However, with no
other alternative available to prevent aircraft or personnel injury, the crew elected
to follow this procedure.
10 / 23
1.18.7 This procedure also includes detailed instructions for setting up a rigged
ladder as detailed at Annex F. Note that the procedure refers to the rigged
ladder or ramp as a “giraffe”. The procedure is in place to prevent or minimize
additional aircraft damage in the event of a droop stop failure emergency. This is
not a CF procedure and as mentioned previously, was obtained from a coalition
partner. The CF does not have a dedicated procedure to prevent or minimize
aircraft damage in the event of a droop stop failure.
1.19
Useful or Effective Investigation Techniques
Not applicable.
11 / 23
2
ANALYSIS
This investigation relied heavily on the technical investigation and report provided
by the Quality Engineering Test Establishment (QETE). The QETE investigation
determined the mechanism and cause of failure of the aft droop stop attachment
bolts. The QETE investigation determined how and why attachment bolts failed
and revealed that the aft droop stops were improperly painted and improperly
installed. The following is a summary of the QETE investigation and is provided
as the main piece of analysis for this investigation.
2.1
Technical Analysis
2.1.1
Using the physical evidence collected, QETE was tasked to determine
the mechanism and cause of failure of the aft droop stop, specifically the droop
stop bolts and reported their findings at Annex G, reference E. The incident aft
rotor head (p/n 145R2004-20) was shipped to QETE for analysis. The three
incident aft fixed droop stops (p/n 114R5087-3) were received with four
recovered bolt heads (p/n NAS624H7) with the shank portions of the bolts were
still screwed into the bolt holes.
2.1.2
Attachment Bolts: Sections from each of the six bolts underwent
material analysis. It was concluded that all droop stop mounting bolts met or
exceeded specifications.
Bolt 1
Bolt 2
Figure 2 – Bolts from the yellow blade
2.1.3
The recovered bolt pieces (p/n NAS624H7) from the yellow blade droop
stop are shown in Figure 2. The bolts were measured and the dimensions were
found to be within the tolerances specified at Annex G, reference F. Visual
12 / 23
examination showed that the bolt shanks were bent. Fractographic analysis of
the bolt labelled ‘Bolt 1’ in Figure 2 found that the bolt had failed in fatigue as the
result of repetitive reverse bending. The second bolt, labelled ‘Bolt 2’ in Figure 2,
was found to have failed in bending overload which probably occurred as a result
of the failure of the first bolt.
2.1.4
The fracture surfaces of the four attachment bolts from the other two
droop stops were also examined. The fracture features of all four were similar to
those of the second bolt from the yellow blade droop stop, consisting entirely of
overload features. Failure was attributed to sudden bending overload, which
probably occurred during the aircraft’s emergency shutdown.
2.1.5
On the bolt labelled ‘Bolt 1’ in Figure 2, the fatigue features indicated that
the load on one side was larger than the load on the opposite side. This
asymmetrical loading can be explained by considering the schematic of the
droop stop installation as detailed in Annex B. When the droop stop is installed
incorrectly, the bolt holes in the droop stops, which have an angle of 2°30’ when
turned upside down, cause a bending load on the bolt.
2.1.6
Droop Stop: All three aft droop stops were visually examined. All three
were clearly labelled with black lettering “AFT ROTOR BOTTOM” on a yellow
background; however, on all three fixed droop stops the marking was located on
the side of the droop stop with the small chamfer rather than the side with the
large chamfer, which is contrary to the technical instructions found in Annex G,
reference A (see Figure 3 below). It is important to note that the visual
differences between the large and small chamfer are noticeable but minor and
not obvious; differentiating between the two chamfers can be difficult. The
installation of the droop stop is dependant upon firstly, the correct positioning
with respect to the larger chamfer, and secondly the paint labelling “AFT ROTOR
BOTTOM”. However, it is the paint that is the most obvious of the two.
Additionally, as the technical instructions shown in paragraph 1.6.5 indicate, in
both the warning and the instruction step 8, the reader’s attention is brought to
the paint markings first and then to the positioning of the chamfer. This can be
read and misinterpreted making the positioning of the droop stop markings “AFT
ROTOR BOTTOM” the priority as opposed to the proper positioning of the
chamfers. It is deduced that this combination of improper painting of the aft
droop stops and the ambiguous technical instructions are contributory factors
that led to the improper installation.
13 / 23
The painted surface is on the upper
surface (near small chamfer) versus on
the underside.
Small
chamfer
Square
corner
Bolt hole
Square
corner
Large
chamfer
Figure 3: Fixed droop stop (note the two bevelled edges or chamfers)
2.1.7
Installation: It was noted that there is no built-in feature or engineering
design to prevent droop stops from being installed upside down during assembly.
Annex B shows the difference between the correct and the incorrect installation.
Specifically, when the rotor RPM <67% the interposer block is horizontal, as
compared to when the rotor RPM >67%, the interposer block moves out or down
from between the hub and the shafts. When the droop stop is installed correctly,
the droop stop sits firmly on the two surfaces of the pitch shaft and both chamfers
fulfill their purpose. The large chamfer allows for more clearance with the
interposer block as it moves out of the way and the smaller chamfer clears the
pitch shaft corner radius. When the droop stop is installed incorrectly, various
problems occur. First, as mentioned, the bolt holes are at an angle of 2°30’ and
when turned upside down this causes a bending load on the bolt and the droop
stop no longer sits firmly on the pitch shaft mating surfaces. In addition, because
the hole is not centered width-wise on the droop stop face it causes the droop
stop to sit lower than it should causing an additional 0.090 inch step between the
droop stop and the pitch shaft flange. Also, again due to the location of the hole,
the droop stop is no longer supported by two surfaces, leaving a gap between
the pitch shaft and the droop stop. Finally, in the upside down position, the large
chamfer no longer helps in clearing the interposer block and due to the droop
stop basic angle of 3°15’ on the droop stop/interposer block mating surface the
droop stop corner is even closer to the interposer block. This can allow for
interference between the interposer block and the droop stop when the rotor
RPM is above 67% and the pitch varying shaft moves toward the center of the
hub as a direct impact between the interposer block and the droop stop can
14 / 23
occur. However when the pitch varying shaft returns to its original position (i.e.
rotor RPM <67%) the droop stop may again interfere with the interposer block but
this time the interposer block will be sliding along its surface and the force will be
less.
2.1.8
The yellow paint on all three droop stops showed signs of wear along the
sharp corner and along the adjacent side. As shown below in Figure 4, the paint
along this edge and adjacent side was missing for a length of approximately 4.5
inches, which corresponds to the length of the interposer block. The paint along
the rest of the corner and adjacent side of the droop stop or at both ends of the
droop stop (i.e. the areas outside of the interposer block length) was intact. This
paint wear indicates that there was interference between the two components.
No paint wear
Paint wear
Interposer block width
Pitch shaft width
Figure 4 - Paint wear on aft fixed droop stop matching length of interposer block.
2.1.9
On the mating surface side of the droop stop block where the droop stop
bolts onto the pitch shaft, a horizontal impact mark as shown in Figure 5, was
noted on all three aft droop stops. The length of the mark corresponded to the
length of the mating pitch shaft corner. The vertical location of the impact mark
along the droop stop corresponded to the distance of the edge of the pitch shaft
corner when the droop stop would be installed with the ”AFT ROTOR BOTTOM”
label facing down.
15 / 23
Pitch shaft corner
Impact mark
A material lip was formed as the
result of an impact
Figure 5 – Impact marks on improperly installed droop stop.
2.1.10 Evidence that all three aft droop stops were installed upside down was
provided by the paint wear at the droop stop sharp corner and adjacent side
shown in Figure 4 and the impact mark found on the pitch shaft to droop stop
mating surface shown in Figure 5. The paint was removed from the corner over
the same length as the interposer block length indicating that the interposer block
had been interfering with this corner. In addition, the impact mark could only
have occurred if the droop stop was installed on the wrong side. The mark width
was the same as the pitch shaft flange and the mark height corresponded to the
pitch shaft flange corner. Had the droop stop been installed on the correct side
no edges would have been present to create such a lip. Again, supported by the
paint wear and impact marks, it is deduced that due to the combination of the
ambiguous technical instructions and the improper painting, all three aft droop
stops were improperly installed which eventually caused an attachment bolt to
fail and allowed one droop stop to fall away from the aircraft.
2.2
Lack of a Rotor Brake System
With no other procedure available, and aware that the borrowed procedure
included steps that required the use of a rotor brake system, the incident crew
elected to follow the coalition partner’s procedure even though several steps are
directly related to using a rotor brake. As well, action item 6, c. (1) within the
procedure calls for the aircraft captain to “manually extend the aft LCT”. This tips
16 / 23
the aft rotor disk forward and places the tip path plane closer to the fuselage.
Both the lack of a rotor brake and the position of the disk were cause for concern
to the crew. This procedure was developed to facilitate the identification of the
blade with the failed droop stop in a timelier manner as the blade starts to sail out
of plane. Once the blade is identified, the groundcrew can then advise the
aircrew when this blade crosses over the fuselage for the rapid and complete
application of the rotor brake with the intent to have the rotors stop within one
revolution and before it impacts the fuselage. The use of the ramp is to prevent
additional aircraft damage should the drooping blade complete its revolution and
return to impact the fuselage. In this case, the ramp is positioned to allow the
drooping blade to initially strike and ride up the ramp and then be allowed to sail
or be deflected over and away from the fuselage. With no rotor brake system
and without a proper shut down procedure including the availability and
positioning of a ramp, the drooping blade would have impacted the fuselage with
much greater force and would have caused considerably more damage to the
aircraft.
2.3
Summary
The QETE investigation determined the mechanism and cause of failure of the
aft droop stop and the respective attachment bolts. It was determined that the
incident aft droop stop fell off due to failure of the attachment bolts. It was
determined that the bending loads placed upon the attachment bolts, which
caused them to fail, were due to the improper (upside down) installation of the
incident droop stop. It was not possible to determine why all three aft droop
stops were installed upside down. The QETE investigation also revealed that all
three aft droop stops were improperly painted. It was not possible to determine
why all three aft droop stops were improperly painted. It is deduced that the
reason the droop stops were installed upside down was due to the improper
painting and the fact that the technical instructions call to have the painted
surface facing down. While proper installation is primarily dependant upon the
placement of the large and small chamfers, the ambiguous technical instructions
and the high visibility of the paint are significant factors that could guide
personnel to only consider the positioning of the paint during the installation of
the droop stop. When considering the emergency procedures dealing with this
incident, it is evident that the available manuals and associated procedures were
lacking. While the availability of a rotor brake system would have prevented or
minimized aircraft damage, it would not have prevented this accident.
17 / 23
3
CONCLUSIONS
3.1
Findings
3.1.1
The CF acceptance team, responsible for transfer and acceptance of the
CH147D Chinooks, was satisfied that all reasonable and practicable steps were
taken to ensure that all aircraft were operational, serviceable and airworthy.
(1.6.6)
3.1.2
The phased inspection, overhaul and post inspection quality assurance
processes did not reveal any abnormalities nor did they detect the incorrect
installation of the three aft droop stops. (1.6.8)
3.1.3
The maintenance daily inspections and flight crew walk-around
inspections conducted by the transferring unit after the inspection and prior to the
transfer or those done by CF personnel after the transfer and prior to the
occurrence also did not detect the incorrect installation of the aft droop stops.
(1.6.8)
3.1.4
The CF model CH147D Chinook is not equipped with a rotor brake
system. (1.6.11)
3.1.5
In the event of a droop stop failure, there is no dedicated CF procedure
to prevent or minimize aircraft damage to the CH147D Chinook. (1.18.7)
3.1.6
The emergency shut down procedure for a droop stop failure was
borrowed from a coalition partner. (1.18.6)
3.1.7
Neither the technical manual, Operator’s Manual for CH-47D Helicopter
(TM 1-1520-240-10), nor the Operator’s and Crewmember’s Checklist for CH47D Helicopter (TM 1-1520-240-CL), which are authorized for use by CF
personnel, have an emergency procedure for droop stop failures. (1.18.1)
3.1.8
Within the Chinook publications authorized for use by CF aircrew,
warnings, cautions or notes that are present in the operator’s manual are not
replicated or included in the operator’s checklist. (1.18.1)
3.1.9
Within the operator’s manual, despite the warning statement contained
in the “Before Taxi” procedure “…the flight engineer will scan the ground in the
immediate area of the aircraft for evidence of detached droop stops.”, there is no
specific action item within this procedure to address this action. (1.18.3)
3.1.10 The operator’s manual does not include a specific Droop Stop Failure
procedure directing flight crews or maintenance personnel on how to effectively
deal with this emergency either in the Normal Procedures chapter or in the
Emergency Procedures chapter. (1.18.4)
18 / 23
3.1.11 Within the checklist, the “Before Taxi” procedure does not have the
warning statement from the operator’s manual nor does it include an action item
for the FE to scan the ground for evidence of detached droop stops as found in
the operator’s manual’s warning statement. (1.18.5)
3.1.12 The checklist does not include a specific Droop Stop Failure procedure
directing flight crews or maintenance personnel on how to effectively deal with
this emergency either in the Normal Procedures section or in the Emergency
Procedures section. (1.18.5)
3.1.13 Forensic examination of the failed bolts revealed that they met or
exceeded the manufacturer’s specifications. (2.1.2)
3.1.14 Analysis of one bolt from the first failed droop stop (yellow blade)
indicated failure in fatigue as the result of repetitive reverse bending. (2.1.3)
3.1.15 The second bolt failed in bending overload, which probably occurred as
a result of the failure of the first bolt. (2.1.3)
3.1.16 The other four attachment bolts from the other two droop stops failed
due to sudden bending overload, which probably occurred during the aircraft’s
shutdown procedure. (2.1.4)
3.1.17 As per the technical instructions, the painted marking with a black label
“AFT ROTOR BOTTOM” on a yellow background is to be located on the side of
the droop stop block with the larger chamfer. (1.6.4)
3.1.18 As per the technical manual, the first most important factor is the
placement of the droop stop based on the side of the block with the larger
chamfer. (1.6.5)
3.1.19 As per the technical manual, the second factor is the orientation of the
droop stop with the side that is painted “AFT ROTOR BOTTOM”. (1.6.5)
3.1.20 Contrary to technical instructions, all three aft droop stops were labelled
with black lettering “AFT ROTOR BOTTOM” on a yellow background located on
the side of the droop stop with the small chamfer (2.1.6)
3.1.21 The visual differences between the large and small chamfer are
noticeable but minor and not obvious and as such, it can be difficult to
differentiate between the two. (2.1.6)
3.1.22 Although the installation of the droop stop is dependant upon firstly, the
correct positioning with respect to the larger chamfer and then the paint labelling
“AFT ROTOR BOTTOM”, it is the paint that is the most obvious of the two.
(2.1.6)
19 / 23
3.1.23 In the technical instructions, in both the warning and the instruction step
8, the reader’s attention is drawn to the paint markings first and then the
positioning of the chamfer. This can be misinterpreted making the positioning of
the droop stop markings “AFT ROTOR BOTTOM” the priority as opposed to the
proper positioning of the chamfers. (2.1.6)
3.1.24 The droop stops were improperly painted in comparison with the
technical manual. (2.1.6)
3.1.25 The combination of improper painting of the droop stops and the
ambiguous technical instructions are contributory factors that led to the improper
installation. (2.1.6)
3.1.26 The paint wear on the three droop stops, along the sharp corner and
along the adjacent side, which corresponds to the length of the interposer block,
indicates that there was interference between the two components. (2.1.8)
3.1.27 On the mating surface side of the droop stop, where the droop stop bolts
onto the pitch shaft, a horizontal impact mark was noted on each of the three
droop stops, which could only have occurred if the droop stop was installed on
the wrong side. (2.1.9, 2.1.10)
3.1.28 Evidence that the droop stops were installed upside down was provided
by the paint wear and the impact marks. (2.1.10)
3.1.29 With no rotor brake system and without a proper shut down procedure
including the availability and positioning of a ramp, the drooping blade would
have impacted the fuselage with much greater force and would have caused
considerably more damage to the aircraft. (2.2)
20 / 23
3.2
Cause Factors
3.2.1
Active Cause Factor
3.2.1.1 The aft fixed droop stops were installed improperly causing metal fatigue
of the attachment bolts that resulted in one of the aft fixed droop stops falling off
and subsequent damage to the aircraft by the rotor blades on shutdown.
3.2.2
Latent cause factors
3.2.2.1 The painted markings “AFT ROTOR BOTTOM” were applied to the
wrong surface of all three aft fixed droop stops contributing to their improper
installation.
3.2.2.2 The visual differences between the large and small chamfer are minor
and not obvious and contributed to the improper installation of all three aft fixed
droop stops.
3.2.2.3 The technical instructions, in both the warning and the instruction step 8,
bring the reader’s attention to the paint markings first and then to the positioning
of the chamfers, which contributed to the improper installation of all three aft fixed
droop stops.
3.2.2.4 The lack of a rotor brake system on the CH147D Chinook contributed to
the aircraft damage.
21 / 23
4
PREVENTIVE MEASURES
4.1
Preventive Measures Taken
4.1.1
A special inspection of all CF Chinook aircraft was conducted, in
accordance with two service bulletins (Service Bulletins TB 1-1520-240-20-132
and TB 1-1520-240-20-136), and revealed only normal wear and tear.
4.1.2
A local survey coordinated between the deployed unit and the
Directorate of Aerospace Equipment Program Management (Transport and
Helicopters) 3 [DAEPM (TH) 3] was carried out for the inspection of all in-stock
fixed droop stops in the CF inventory to ensure the components are both painted
and installed in accordance with technical publications.
4.1.3
DAEPM (TH) 3 has communicated the initial factual information via a
meeting between the CH147D Weapon System Manager (WSM) and the
coalition partner in February 2009. Liaison between the CH147D WSM staff and
our Foreign Military Sale (FMS) case management staff has occurred but no
formal report was submitted.
4.1.4
DAEPM (TH) 3 has shared the contents of a draft version of this report
contents with Project Management - Cargo Helicopter Safety Section at the
Safety Systems and Environmental Working Group (SSEWG) meeting 3 – 5 Mar
10 and has recommended the issuance of a Service Bulletin for the inspection of
all in-stock fixed droop stops.
4.1.5 1 Canadian Air Division (Cdn Air Div) / Tactical Aviation Standard and
Evaluation Team (TASET) has issued B-GA-002-147/FP-001 CH147D
PUBLICATION SUPPLEMENT to the approved CH-47D Operator’s Manual and
Checklist used for the employment of the CH147D. This is to provide information
specific to operating the CH147D that either are not covered in or supersede the
published CH-47D procedures. Within this Supplement, Section 2 includes a
warning statement and an additional step to the checklist - Operator’s and
Crewmember’s Checklist (TM 1-1520-240-CL). This specific action item within
the BEFORE TAXI checklist requires the FE to scan the ground for departed
droop stops before taxiing as directed in the subject warning statement provided
in the Operator’s Manual (TM 1-1520-240-10).
4.2
Preventive Measures Recommended
It is recommended that;
4.2.1
1 Cdn Air Div / TASET, in conjunction with DAEPM (TH) 3, develop,
validate and publish an emergency procedure for droop stop failures applicable
to the CH147D Chinook.
4.2.2
1 Cdn Air Div / TASET amend Section 2, paragraph 4 of the B-GA-002147/FP-001 CH147D PUBLICATION SUPPLEMENT which directs the inclusion
22 / 23
of a additional step to the checklist (as detailed at 4.1.5), also direct that it apply
to and include the Operator’s Manual (TM 1-1520-240-10).
4.2.3
DAEPM (TH) 3 recommend to the coalition partner to reword the
technical instructions to emphasize the importance of correct positioning and
installation of the droop stop with respect to the small and large chamfers and
consistent with the location of the painted markings “AFT ROTOR BOTTOM”.
4.2.4
DAEPM (TH) 3 recommend to the coalition partner to review the droop
stop painting process and provide solutions to limit the possibility of human error
in the painting process of the droop stop and to ensure that paint is applied to the
proper side of the droop stop.
4.3
Other Safety Concerns
With the impending acquisition of 15 new Chinook F-model helicopters, it is
recommended that ADM(Mat) / PMO MHLH review droop stop systems design,
installation and maintenance procedures and include normal operating,
maintenance and emergency procedures to deal with droop stop failures.
4.4
DFS Remarks
We were fortunate that the outcome of this occurrence resulted in minimizing the
damage to the aircraft and no injuries to personnel. This was in large part due to
the professionalism displayed by the members of the CHF (A) team. The
conduct of all concerned personnel from the moment the droop stop was first
discovered lying on the ramp up to and including the follow-up actions to address
this unique emergency, is indicative of an engrained positive flight safety culture;
particularly noteworthy in a theatre of war.
The investigation focused on the mechanical failure caused by the improper
installation of three droop stops on the aft rotor head assembly. I believe that the
preventive measures that have been implemented as well as those proposed
should prove effective in preventing a recurrence.
// original signed by //
G.R. Doiron
Colonel
Director Flight Safety
23 / 23
Annex A
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex A - Photographs
Photo 1: Fixed droop stop found on the ramp (aft rotor yellow blade)
Photo 2: CH147204 after the rotor blades have stopped
A-1
Annex A
1010-CH147204 (DFS 2-4-2)
13 July 2010
Photo 3: Damage to the aft rotor head and to the rigged ladder or ramp
Photo 4: Damage to the fuselage left side and to the HF antennae
A-2
Annex A
1010-CH147204 (DFS 2-4-2)
13 July 2010
Photo 5: Centrifugal droop stop (held in the extended position)
Photo 6: The rigged ladder (or ramp) borrowed from a coalition partner
A-3
Annex B
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex B - Schematic of Droop Stop Installation
Pitch varying shaft will move toward center of hub to
allow more freedom for the blade to flap.
Small
Chamfer
Pitch Shaft
3º 15’
2º 30’
Large
Chamfer
Clearance
Bolt NAS624H7
When rotor RPM is >67% the interposer block
moves out from between the hub and the shafts.
Interposer block
Hole angle in the droop stop
causes bending in the bolt.
Angle in droop stop
causes horizontal
displacement and
reduces clearance.
B-1
Normal
Step
height
Gap
Vertical displacement and
gap result in 0.090 inch
increase to step height
Possible Interference
Annex C
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex C - Before Taxi Check as per Operator’s Manual
REF C, TM 1-1520-240-10, Pg 8-2-11
8-2-20. Before Taxi
WARNING
Personnel injury or death may occur and damage to airframe and rotor
systems will occur if the forward or aft rotor blade droop stop(s) are
missing or interposer(s) on the aft rotor head are not engaged. After engine
run-up and before flight, or shutdown if flight is not conducted, the flight
engineer will scan the ground in the immediate area of the aircraft for
evidence of detached droop stops.
CAUTION
To prevent damage to the cargo hooks and structure, do not ground taxi
over rough or uneven terrain with the forward and aft cargo hooks
installed.
* 1.
SWIVEL switch — As required.
* 2.
AFCS switches — As required.
* 3.
Cyclic Trim Indicators — CHECK GND position.
O* 4.
M-130 or AN/ALE-47 safety pin — Remove and stow.
F* 5.
Chocks — Removed and secured.
F* 6.
Ramp and cabin door — As required.
F* 7.
Crew, passengers, and mission equipment Check ready for taxi.
O* 8.
HUD — Adjust brightness, mode, barometric altitude, pitch and roll as
necessary.
F* 9.
Taxi director and blade watchers — Position as required (fig. 8-2-1).
* 10.
PARKING BRAKE — As required.
C-1
Annex D
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex D - Before Taxi Check as per Operator’s Checklist
REF D, TM 1-1520-240-CL, Pg N-8
BEFORE TAXI
* 1.
SWIVEL switch — As required.
* 2.
AFCS switch — As required.
* 3.
Cyclic trim indicators — Check GND position.
FO* 4. M-130 or AN/ALE-47 safety pin — Remove and stow.
F* 5.
Chocks — Removed and secured.
F* 6.
Ramp and cabin door — As required.
F* 7.
Crew, passengers, and mission equipment — Check ready for taxi.
O* 8.
HUD — Adjust as necessary.
F* 9.
Taxi director and blade watchers — Positioned.
* 10.
PARKING BRAKE — As required.
D-1
Annex E
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex E - Emergency Shutdown Procedure - Droop Stop Failure
(Annex B TO RAF ODIHAM AESO BOOK 2 EMERGENCY PROCEDURES
SUPPLEMENT ORDER NO 4)
1.
The area in which the aircraft is to be shut down is to be designated by
the Incident Controller.
2.
Whilst the blade deflector is being prepared, the Incident Controller is to
ensure that the area is cleared of other ac, equipment and personnel.
3.
Position the prepared giraffe so that it can be secured to 2 picketing
points on the Dispersal. The giraffe should be positioned to take account of the
wind direction so that as the blades approach the fuselage they are moving into
wind, i.e., the wind is to be from the right hand side of the ac. Secure the giraffe
to the picketing points using chains and tensioners, and ascertain where the aft
left hand wheel of the ac is required to be and mark this position.
4.
Move the giraffe, chains and tensioners to a safe distance and arrange
for the ac to taxi onto the marked position.
5.
Position the giraffe on the left-hand side of the ac so that the working
platform is between stations 400-440 (for a fwd fixed droop stop failure) or
between stations 195-235 (for aft fixed or centrifugal droop stop failures) with the
rubber tyre abutting the transmission tunnel covers. Adjust the platform height if
necessary to leave clearance of approximately 25mm between the platform and
the top of the fuselage. Lock the giraffe stabilisers firmly down and anchor the
giraffe frame to the picketing points using chains and tensioners.
6.
The Incident Controller is to brief the ac captain and crewman on the
following:
a.
Only the minimum number of crew is to remain in the ac.
b.
The crewman is to position himself where he has a clear view of
the blade disc so that he is able to give instructions to the ac captain.
c.
Aft Droop Stop Failure.
(1)
When the crewman is in position he is to:
Instruct the captain to manually extend the aft LCT.
(2)
Instruct the captain to shut down, allowing the rotors to
coast down initially.
(3)
As the RRPM decays, attempt to identify the drooping
blade. This may not be possible until the blade actually strikes
the ramp of the blade deflector. When the blade strikes the
ramp of the blade deflector or as the affected blade crosses the
E-1
Annex E
1010-CH147204 (DFS 2-4-2)
13 July 2010
fuselage, the crewman is to call for the rapid and complete
application of the rotor brake.
d.
Fwd Droop Stop Failure.
to:
When the crewman is in position he is
(1)
Instruct the captain to shut down, allowing the rotors to
coast down initially.
(2)
As the RRPM decays, attempt to identify the drooping
blade. This may not be possible until the blade actually strikes the
ramp of the blade deflector. When the blade strikes the ramp of
the blade deflector or as the affected blade crosses the fuselage,
the crewman is to call for the rapid and complete application of the
rotor brake.
7.
At a RRPM of 10% or less, rapid and complete application of the rotor
brake will bring the rotors to a standstill in less than one revolution and minimize
damage to the ac.
E-2
Annex F
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex F - Chinook Blade Deflector Ramp - Preparation
(Annex A TO RAF ODIHAM AESO BOOK 2 EMERGENCY PROCEDURES
SUPPLEMENT ORDER NO 4)
1.
Position the giraffe on the left-hand side of an ac such that the working
platform is between stations 195-235 (for an aft droop stop failure) or stations
400-440 (for a fwd droop stop failure). Station locations can be found at Figure
1. Adjust the height of the platform so that it is approximately 25mm above the
fuselage and with the rubber tires abutting the transmission tunnel covers.
Ensure that the working platform is positioned so that the HF and upper UHF
and TACAN aerials are not damaged.
2.
Move the giraffe away from the ac and fit Panel No 2 to overlap Panel No
1 by approximately 15mm. Fit panel No 3 to butt up against Panel No 2 and
secure both panels with nuts, bolts and washers (see Diagram 1).
3.
Apply a thin layer of any general-purpose grease to the panels.
4.
tape.
Pad the giraffe jack with horsehair matting secured with black adhesive
FIGURE 1 – FUSELAGE STATION
F-13
Annex F
1010-CH147204 (DFS 2-4-2)
13 July 2010
DIAGRAMMATIC REPRESENTATION OF THE BUILD-UP OF THE DROOP STOP FAILURE RAMP (Giraffe)
Panel 1
Panel 2
Panel 3
Rubber Tire
Tensioners
F-23
Horse Hair Matting
Annex G
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex G - References
A.
Vertol Division Boeing, Drawing number 114R2087, Stop, DroopCentrifugal Droop Stop Aft Rotary Wing Head, Rev B, 24 August 1972
B.
Department of the Army, Technical Manual for CH-47D Helicopter, TM 551520-240-234, 19 September 2002
C.
Operator’s Manual for Army CH-47D Helicopter (TM 1-1520-240-10)
D.
Operator’s and Crewmember’s Checklist for Army CH-47D Helicopter (TM
1-1520-240-CL)
E.
QETE report 10081-D024808 (Q2-7MB), FINAL REPORT
INVESTIGATION OF FAILED CH147204 AFT FIXED DROOP STOP
BOLTS, 20 May 2009
F.
National Aerospace Standard, Drawing number NAS624, Bolt - Twelve
Point – Steel External Wrenching, 5 February 2001
G-1
Annex H
1010-CH147204 (DFS 2-4-2)
13 July 2010
Annex H - Abbreviations
AA
ADM (Mat)
AETE
AF
AFIP
AVA
CAS
CAVOK
Airworthiness Authority
Assistant Deputy Minister (Materiel)
Aerospace Engineering Test Establishment
Airframe
Armed Forces Institute of Pathology
Aircraft Vibration Analysis
Chief of the Air Staff
Ceiling and Visibility OK (no cloud below 5 000 feet, no
cumulonimbus, visibility of 6 statute miles or more, and no
precipitation, fog or drifting snow)
CSP
Cycle Service Program
DAC
Dangerous Area Cargo
DAEPM (TH) Directorate of Aerospace Equipment Program Management
(Transport and Helicopters)
FE
Flight Engineer
HUMS
Health and Usage and Monitoring System
KAF
Kandahar Airfield
MTF
Maintenance Test Flight
METAR
Meteorological Aviation Report
OAA
Operational Airworthiness Authority
OEM
Original Equipment Manufacturer
PM
Project Management
PMO MHLH Project Management Office Medium-Heavy Lift Helicopter
PN
Part Number
POAC
Provisional Operational Airworthiness Clearance
PTAC
Provisional Technical Airworthiness Clearance
QETE
Quality Engineering and Test Establishment
RTS
Release to Service
SI
Special Inspection
SME
Subject Matter Experts
SN
Serial Number
TAA
Technical Airworthiness Authority
TASET
Tactical Aviation Standard & Evaluation Team
WSM
Weapon System Manager
H-1