100-Hour, Annual, and Major Alteration Sign-Offs
A flight school’s Cessna 172 is due for both a 100-hour inspection and an annual inspection. The school’s A&P mechanic, who holds airframe and powerplant ratings but no inspection authorization, replaces a cracked exhaust muffler, performs the 100-hour inspection, and signs the airframe log. The owner then asks the same mechanic to (1) sign the annual inspection, (2) approve and return to service a major alteration installing a new avionics rack, and (3) let the owner perform the next oil change and sign it off as preventive maintenance. The mechanic has current manufacturer’s manuals and the aircraft records. The owner wants all work signed off the same day.
1. Which of the three requests can the A&P mechanic legally accomplish? Explain each.
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The A&P may perform the 100-hour inspection and approve that inspection for return to service, assuming recent experience and proper records. The A&P may not sign the annual inspection; an annual requires an IA (or an appropriately rated repair station or the FAA). The A&P may perform the major alteration work but may not approve the major alteration for return to service; that requires an IA or repair station, approved data, and Form 337. The owner may perform preventive maintenance such as an oil change if it is not complex, uses acceptable methods and tools, and is recorded; the A&P should not sign as though he performed it.
2. What records must be made for the muffler replacement and 100-hour inspection?
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Muffler replacement: make a maintenance record entry under 14 CFR 43.9 with the work description, date, mechanic’s name, certificate number, and approval-for-return-to-service signature. 100-hour inspection: make the inspection entry under 43.11 in the airframe log (and engine and propeller logs as applicable), including date, aircraft total time, signature, certificate number, and approval for return to service. Record any applicable AD compliance. Verify the muffler is an approved part and installed per the manufacturer’s manual.
3. What is required before the avionics rack alteration can be approved and returned to service?
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First determine whether the avionics rack installation is a major alteration (likely if it affects weight and balance, structure, or electrical load). Obtain approved data: STC, DER-approved data, or field approval as applicable. Install per those data, revise weight and balance, complete FAA Form 337, and make the logbook entry. An IA or appropriately rated repair station must approve the major alteration for return to service. The A&P can do the work but cannot self-approve the major alteration or the annual inspection.