Section 3 Concept of Aircraft Maintenance Feb21 1

Section 3 Concept of Aircraft Maintenance Feb-21 1

Aerospace Engineering Types of Aircraft Maintenance Scheduled Unscheduled Routine maintenance Plannable check Replacement of life limited items Performance of Cleaning modification originated work Rectification of deferred defects Feb-21 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 • Servicing LEVELS ( Line ( Ramp ) ( Hangar or Main base ( Workshop Feb-21 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. Feb-21 4

General Aerospace Engineering Unscheduled (8. 5%) DIRECT OPERATING COST BREAKDOWN 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 Feb-21 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 Feb-21 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 Feb-21 7

Aerospace Engineering Introduction Typical inspection interval Check type Interval Content 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. Feb-21 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) 1 A-Check 500 FH Exterior general visual from ground. Interior general visual cockpit, cabin, cargo compartment, avionics, electrical, hydraulic and ECS equipment bays, landing gear bays ad doors. IDG oil. Feb-21 9

Aerospace Engineering Introduction Typical inspection interval Check type Interval Content 2 A-Check 1000 FH Simple operational checks (failure finding tasks) from cockpit which cannot be accomplished at 4 A and above. Inspection of engine fan blades. Check engine chip detectors. Engine starter oil change. Landing gear lubrication. 4 A – 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. 8 A – Check 4000 FH Check fuselage drainage system Feb-21 10

Aerospace Engineering Introduction Typical inspection interval Check type Interval 1 C-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. Feb-21 11

Aerospace Engineering Introduction Typical inspection interval Check type Interval Content 2 C-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 (4 C) 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. Feb-21 12

Aerospace Engineering Introduction Typical inspection interval Check type Interval Major Layover (8 C) 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. Feb-21 13

Introduction Boeing Typical Inspection Interval Aerospace Engineering 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 B D (Structural Inspection) 2, 840 21, 000 220 3, 300 21, 500 5, 000 18, 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 Feb-21 14

Introduction Airbus Typical Inspection Interval Aerospace Engineering Letter check Aircraft Recommended interval A C D = 4 C A 310 400 FH 15 Months A 300 -600 Initial: 250 FH Initial: 12 months FD threshold: 18, 000 FC ED threshold: 10/7. 5/5/2. 5 years 5 Years A 319 A 320 A 321 500 FH 15 Months A 330 A 340 700 FH 500 FH 18 months 15 months A 380 Objective: 750 FH Objective: 24 months Structural inspection Cathay Pacific 5 Years Cathay Pacific Feb-21 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 Economics aspects of scheduled maintenance Aerospace Engineering 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 2 A + y% of 4 A 1 Block check plan 1 year 2 year Feb-21 16