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I'm afraid that the IRS-approved depreciation schedules do not take into account actual expected life, but only expected life for the class of materials.
Airplanes are in asset class 00.21, which is considered 5-year property, with an actual life and alternative depreciation schedule (ADS) of 6 years. It seems unlikely that aircraft parts would have a shorter depreciation schedule.
In fact, I don't see a justification for treating them other than as 7-year property (12 years ADS), but a creative accountant might be able to find a justification.
Repair of a damaged part is a current expense, and, if a part is no longer usable, the remaining unrecovered cost can be written off, regardless of the depreciation schedule.
IRS Publication 946 has most of the information you can use on class life and depreciation.