FAA Aviation Mechanic Powerplant (AMP)Engine InspectionEasy
During an inspection, a mechanic notices a hairline crack radiating from one of the attachment screw holes on an aluminum propeller spinner dome. What should the mechanic do?
- AStop-drill the crack and continue to monitor it at each inspection
- BReinforce the area with a doubler riveted over the crack
- CRemove the spinner from service and repair or replace it per the manufacturer's data
- DApply a bead of sealant over the crack to prevent further propagation
Show answer & explanationAnswer & explanation
Correct answer: C. Remove the spinner from service and repair or replace it per the manufacturer's data
Cracks in a spinner dome, especially at attachment points where vibration loads concentrate, are not acceptable to be stop-drilled or patched in the field; the spinner must be removed and repaired or replaced only in accordance with the manufacturer's approved data because a failure in flight can release debris into the propeller/engine.
Why the other options are wrong
- A. Stop-drilling is not an approved repair for spinner cracks.
- B. Field doublers are not an approved repair without manufacturer data.
- D. Sealant does nothing to address structural cracking.
Propeller Spinner Crack Inspection
Spinner domes are inspected for cracking, especially near screw holes and the bulkhead attachment, since they are subject to vibration and centrifugal loading.
- Cracks concentrate at fastener holes due to vibration
- No field stop-drill or patch repairs are approved
- Must follow OEM repair/replacement data
Memory trick: A cracked spinner is a spinning bomb — replace, don't patch