Airframe Maintenance Economics

Scheduled maintenance tasks need to perform on aircraft to make them fly continuously. Maintenance Planning Document list all scheduled maintenance tasks that has to be performed periodically. Some of these tasks are grouped together so that all can be complied at a same time after certain amount of usage typically called checks. Heavy Maintenance visit is by far more comprehensive and demanding check that occurs approximately every 6 to 12 years. In this visit the entire aircraft is removed from service for more than a month for complete inspection and Overhaul. Even the paint may be removed completely to find out structural damages and corrosion on the metal skin.

Because of the nature of check and number of routine and Non routine tasks, the maintenance cost associated with these type of checks are high. Older aircrafts are being phased out of a particular airline’s fleet are either stored or scrapped upon receiving next D check due to high costs involved.

Maintenance reserves are payments made by the lessee to the lessor to accrue for those schedule major maintenance events that require significant aircraft grounding time and/or turn-around time for certain major component overhauls. Lessor collects maintenance reserves on monthly basis from operator to protect asset value, Reimbursement of amount will be considered once operator perform subject maintenance check.

According to MPD Scheduled maintenance tasks are divided into three groups, such as

1. Systems and powerplant program, developed to perform operational and functional checks on airframe systems and equipment’s.

2. Structural Inspection Program, developed to assess each airframe structures and perform repairs. Detection of corrosion, stress corrosion, minor damage and fatigue cracking by visual and/or NDT procedures are considered

3. Zonal inspection program, is to assess the general condition of attachment of all systems and structures items contained in each zone by use of defined zonal inspection tasks. The zonal inspection tasks include visual checks of electrical wiring, hydraulic tubing, water/waste plumbing, pneumatic ducting, components, fittings, brackets, etc.

Maintenance cost drivers:

Aging of aircraft:

Life span of the aircraft can be categorised into three groups commonly known as First run, Mature-run and Aging-run. The maintenance cost associated with each phase will be different due to increase in non routine items during HMV. First run is the initial operating years mostly first 4-6 years. during this phase cost are related to only routine MPD tasks. Assessment of repairs, Component maintenance, material scrap rate and non routine items are less as structure, system and components are delivered as new. Mature run typically falls between first heavy maintenance check and the second maintenance visit. Aging run begins after the end of 12 year check when the effects of airframe age result in higher non routine maintenance cost. MR reserves will be collected based upon the aircraft usage and utilisation. For new aircraft monthly rent will be high and minimum MR reserve, for old aircraft MR reserve will be high.

Typical Qualifying Work : Man-hours associated with scheduled grouping of MPD routine tasks and all non-routine man-hours generated by routine tasks, material costs related to the above tasks, basic cabin refurbishment, and rotable overhaul for time-controlled items. Some lessors include strip & paint into their standard reserves if these events occur at regularly scheduled heavy structural checks.

Typical Excluded Work : Work related to Service Bulletins (SBs), Service Letters (SLs), Airworthiness Directives (ADs), airline unique tasks, vendor tasks, local regulatory tasks, cabin reconfiguration costs, accidental damage repair. Packaging, duties, and shipping & handling fees are also generally excluded.