How does maintenance affect the age of an aircraft?
As an aircraft ages the intervals of the maintenance checks known as "C Checks" merge to create even heavier maintenance visits. These visits end up costing more money than initial checks and more non-routines are generated due to the age of the aircraft. Here is an example of a maintenance program and how the age produces a heavier check.
Note: This is a made up example based on the standard 18 month interval mentioned in the Aviation Maintenance Management book written by Kinnick and is by no means meant to reflect any specific airline maintenance program.
Notice how the third interval of the 4C Check/HMV Check matches with the 3C, 2C, and 1C Checks. At 216 months the aircraft would be 18 years old. By now an operator may start thinking about replacing their aircraft before this maintenance visit happens because of how much it costs to actually conduct this maintenance.
No matter how good the maintenance being conducted is the fact is the aircraft is still aging and certain other tasks start populating because of that. The aircraft bins may need to be painted, the light covers yellow, seat cushions have to be replaced, and this doesn't cover the standard hard time components that life span may be coming due. Some hard time components such as slides have to be sent out for overhaul at about 5 to 7 years and depending on the age of the slide will have to be sent out every year to two years for overhaul. At this point it may be more cost effective to just purchase all new slides instead of overhaul this is no different then determining if continued use of an aging aircraft is worth the cost of the maintenance.
Performing continued maintenance is very important for actually reaching the expected economic life of an aircraft as well. When maintenance isn't performed and the aircraft sits on a ramp or in a storage area then the parts tend to start to corrode a little easier because lubricant may not be applied as often as it would normally. Airplanes that rest too long can become home to animals which can damage wiring and insulation in order to make their nests causing additional maintenance tasks in the future should the aircraft ever be attempted to be reactivated.
Proper maintenance during C Checks is also important. Human factors is a huge issue when it comes to maintenance and many times when an aircraft ends up having an issue the maintenance task performed was done so incorrectly. This was part of the reason why the Aloha flight had the issue. Aloha had been operating the aircraft past its economic life which was one of the reasons why the top part of the fuselage separated from the bottom half. Another reasons was due to improper maintenance procedures. When the airline was under investigation it was determined multiple other airplanes were showing the same cracks and issues as the accident aircraft. This is why proper maintenance and an ultimate life are important when dealing with aircraft.
Conclusion
Over the course of this brief blog post the author has spoken about the importance of continued maintenance on the aircraft. By doing continued maintenance there is a reduced chance of animals nesting or corrosion happening on the aircraft. When performing correct maintenance the life of the aircraft can be expected to meet the ultimate life as what is suggested by the maintenance manufacturer. Overall though it is the responsibility of the airline operating the aircraft to ensure that a replacement plan is in place once the aircraft starts nearing its end of life and to make sure that maintenance is performed in a timely manner to keep the aircraft airworthy.
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