The following article considers issues which should be considered as the aircraft utilisation decreases. Maintenance does not diminish but changes in nature to reflect the changing conditions.
If neglected the cost of not performing maintenance can become significant.
Low utilisation of Aircraft Engines and Components can have an extremely detrimental affect on the operation of the aircraft.
An early change concerns the maintenance program which should be transitioned from the “largely” flying hours based management process to one which is controlled by mostly calendar time.
Particularly important are the lubrication activities. Breakdown in the chemical composition of Oils and greases possibly due to environmental conditions, however may contribute to internal and external corrosion.
Amongst the many negative consideration are the following:
Aircraft structure which is subject to excessive corrosion may as a result be more susceptible to fatigue.
Insulation blankets can retain moisture and can be a source of corrosion if not kept dry.
Low utilisation in general is not good for engines, and can lead to significant costs if not managed correctly, engines not operating may accumulate fluid in areas within the engine without internal drains. Engines are typically not designed with Corrosion Protection features built in due to the expectation that the engine will be running on a regular basis.
Issues of Managing Low Utilisation Aircraft Maintenance Programs include the lack of operation of the aircraft drains. Without aircraft positive pressure to maintain the effectiveness of the aircraft drainage system, the effective functioning of the drains may be impaired.
Accumulation of moisture, is a primary reason why the dry deserts are favoured for the medium to long term storage of aircraft
Control Cables and mechanical systems in general can suffer from corrosion, (but note the comments reflecting humidity)
Existing CPCP Corrosion Prevention and Control Program may prove to be inadequate for low utilisation operations
Seals in systems and components may deteriorate leading to increases in internal / external fluid / gaseous leakage
Packing’s and seals may be heavily dependent on the passage of fluid for continued well being and may exhibit poor performance leading to accelerated wear and increased leakage.
Fuel System contamination is a major consideration with the possibility of microbiological contamination which can have serious consequence including the possibility of corrosion.
Typically when the aircraft spends longer on the ground there is evident deterioration of the undercarriage assemblies including wheels, tyres and brake units. (the latter can deteriorate quite substantially).
Black boxes (electronic components) require low – no moisture, so this can have a detrimental effect, electronic equipment is designed to run not to remain dormant and inactive.
Batteries can deteriorate quickly if not charged/ discharged on a regular basis.
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