Section 3
Concept of Aircraft
Maintenance
Apr-15
1
Aerospace
Engineering
Types of Aircraft Maintenance
Maintenance
Scheduled
Unscheduled
 Routine maintenance Plannable
check
 Replacement of life
limited items
 Performance of
 Cleaning
modification originated
work
 Rectification of
deferred defects
Apr-15
Unplannable
Activities originated from:
 Cabin log book
 Technical log book
 Ground findings
2
Aerospace
Engineering
General
MAINTENANCE DEFINITION
Those actions required for
restoring or maintaining an item
in serviceable condition
TYPES
• Unscheduled
LEVELS
• Scheduled
( Line ( Ramp )
• Servicing
( Hangar or Main base
( Workshop
Apr-15
Mainly
unscheduled
maintenance
limited to the
replacement of
faulty components
that will have
immediate or short
term influence on
aircraft operations
(MMEL).
3
Aerospace
Engineering
General
TYPES OF MAINTENANCE
Unscheduled (or corrective):
Maintenance performed to restore
an item to a satisfactory condition
by providing correction of a known
or suspected malfunction and/or
defect.
Unscheduled maintenance action is
performed if there is a pilot report
or a complaint from the scheduled
maintenance.
Scheduled:
Maintenance performed at defined
intervals to retain an item in a
serviceable condition (availability,
safety and reliability to their inherent
levels)
Scheduled maintenance action is
performed according to the
Maintenance Program requirements
Servicing:
Any act of replenishment for the
purpose of maintaining the inherent
design operating capabilities of an
item.
Apr-15
4
General
Aerospace
Engineering
DIRECT OPERATING COST
BREAKDOWN
Unscheduled
(8.5%)
Scheduled
(3.5%)
Maintenance (12%)
Depreciation
/ Finance
(41%)
Fuel
(25%)
Insurance
(2%)
Landing /
Navigation
taxes (9%)
50
Material
50
Labour
50
40
10
Powerplant Systems Structure
Crew (11%)
DMC = 700 $/FH
Apr-15
5
Aerospace
Engineering
Types of Scheduled Maintenance
► Light or Line Maintenance:
 Preflight Check
 Daily Check
 Weekly Checks
 A (Multiple A) and B Checks
► Base or Heavy Maintenance:
 C (Multiple C) and D Checks
► Shop or Component Maintenance:
 Maintenance on components when
removed from aircraft
Apr-15
6
Aerospace
Engineering
Introduction
Operational Aspects
Operational interruption or disturbances have
repercussions on the following areas:
◦ Passengers Comfort
◦ Corporate Image Of The Operator
◦ Operating Cost
WHAT KIND OF SCHEDULED MAINTENANCE ARE WE
PREPARED TO TOLERATE IN ORDER TO OPTIMISE THE
ABOVE CRITERIA ?
COST OF SCHEDULED MAINTENANCE
<
COST OF FAILURE CONSEQUENCES
Apr-15
7
Aerospace
Engineering
Introduction
Typical inspection interval
Check type
Interval
Content
Pre-Flight
Pre-Flight
General visual from ground for signs of obvious
discrepancies or damage such as fluid leaks,
FOD, lightning strike.
Check logbook .
Check engine oil levels and replenish if
necessary
Terminal Check
(Ramp)
Each terminal
stop
Pre-flight plus tires, tire pressure, wheels and
brakes.
Cabin check.
Apr-15
8
Aerospace
Engineering
Introduction
Typical inspection interval
Check type
Interval
Content
Service Check
8 Cal. days
Hydraulic qty, escape slide gas pressure, oxygen
pressure, brake wear, IDG oil, APU oil, oleo
pressures. Visual check of engine inlet and
exhaust. Optional check of CMS for degraded
fault tolerance (to avoid potential No Go
situation)
1A-Check
500 FH
Exterior general visual from ground. Interior
general visual cockpit, cabin, cargo
compartment, avionics, electrical, hydraulic and
ECS equipment bays, landing gear, landing gear
bays ad doors. IDG oil.
Apr-15
9
Aerospace
Engineering
Introduction
Typical inspection interval
Check type
Interval
Content
2A-Check
1000 FH
Simple operational checks (failure finding tasks)
from cockpit which cannot be accomplished at
4A and above.
Inspection of engine fan blades. Check engine
chip detectors. Engine starter oil change.
Landing gear lubrication.
4A – Check
2000 FH
Lubrication of some flight control items in
accordance with past service experience.
Simple operational checks (failure finding tasks)
which cannot be accomplished at C and above.
8A – Check
4000 FH
Check fuselage drainage system
Apr-15
10
Aerospace
Engineering
Introduction
Typical inspection interval
Check type
Interval
1C-Check
15 months
Content
External general visual inspection of areas with
moderate sensitivity to damage or deterioration
such as lower and mid fuselage, windows,
doors, wing lower surfaces, flight control
surfaces, horizontal and vertical stabiliser
leading edges and pylons. General visual
inspection of power plant and engine with cowls
open, landing gear and landing gear bays, wing
fixed leading edge, rear fuselage and tail cone.
Cleaning or replacement of air conditioning
filters. Systems operational checks (failure
finding tasks). Flight control general lubrication
and gearbox oil replenishment. Hydraulic
system internal leakage. Cabin check.
Check drainage systems.
Apr-15
11
Aerospace
Engineering
Introduction
Typical inspection interval
Check type
Interval
Content
2C-Check
30 months
External general visual inspection of areas with
low sensitivity to damage or deterioration such
as upper fuselage, horizontal and vertical
stabilisers and wing top surface. Internal general
visual inspection installations in equipment bays
and pylons.
Intermediate
Layover (4C)
60 months
Internal general visual inspection of structure
and installations in areas of moderate to high
sensitivity to damage or deterioration such as
cargo compartments, area below cargo and
cockpit floors and below toilets and galleys.
Internal general visual inspection of wing in
sump areas. Systems operational and functional
checks. Detailed cabin check including floors in
high traffic areas, galleys and toilets.
Apr-15
12
Aerospace
Engineering
Introduction
Typical inspection interval
Check type
Interval
Major Layover
(8C)
120 Months
Content
General and detailed external and internal
structural (sampling or 100%) inspection for
corrosion and fatigue damage. Systems
operational and functional checks.
Remarks:
Aircraft on jacks
Note:
some operators may wish to integrate items into
C- Check packages.
Apr-15
13
Introduction
Aerospace
Engineering
Boeing Typical Inspection Interval
Letter
check
Aircraft
757
737-100
737-200
737-300
737-400
737-500
727
Recommended initial interval (FH)
A
B
750
200
80
D
(Structural
Inspection)
3,000
3,200
400
20,000
20,000
B
D
(Structural
Inspection)
2,840
21,000
220
3,300
21,500
5,000 18,500
500 or
70 days
747-400
650
Cathay Pacific
450
C
170 700
16,000
777
(Cathay Pacific)
MD-80
A
6,000 FH
(Sys.)
3,000 FC
(Struc.)
500 FH (Sys.)
300 FC (Stru.)
125
C
World weighted fleet interval (FH)
3,500
150 365 Days
days or 3000 hrs
6,750
?
30,000
15,000
Apr-15
14
Introduction
Aerospace
Engineering
Airbus Typical Inspection Interval
Letter
check
Aircraft
Recommended interval
A
C
D
=
4C
A310
400 FH
15 Months
A300-600 Initial: 250 FH Initial: 12 months
Structural inspection
FD threshold: 18,000 FC
ED threshold: 10/7.5/5/2.5 years
5 Years
A319
A320
A321
500 FH
15 Months
A330
A340
700 FH

500 FH
18 months

15 months
A380
Objective:
750 FH
Objective:
24 months
Cathay
Pacific
5 Years
Cathay
Pacific
Apr-15
FD threshold: 24,000 FC
ED threshold: 9/5/2.5 years
FD threshold: 20,000/8,000 FC
ED threshold: 10/5/2.5 years
15
Introduction
Aerospace
Engineering
Economics aspects of scheduled maintenance
C
MH
A
2
A
A
3
A
A
4
A
2
A
A
1
2
3
4
MH
4
A
2
A
A
1 year
2
3
4
C
4
A
2
A
A
2 year
Semi
equalise
d plan
A + x% of 2A + y% of 4A
1
Block
check
plan
1year
2year
Apr-15
16