FAA AMT (Aviation Maintenance Technician) Airframe Practice Exam

When installing transparent plastic enclosures retained by bolts, how should the self-locking nuts be tightened?

1. Tightened to a firm fit then backed off two full turns

2. Tightened to a firm fit then backed off one full turn

3. Tightly screwed without backing off

4. Hand tightened only

The correct answer is: Tightened to a firm fit then backed off one full turn

When installing transparent plastic enclosures retained by bolts, it is crucial to tighten the self-locking nuts to a firm fit and then back them off one full turn. This specific procedure is essential because over-tightening the self-locking nuts could potentially cause stress concentrations and lead to cracking in the plastic material. Backing off the nut by one full turn after achieving a firm fit allows for proper stress distribution and helps prevent damage to the plastic enclosure. Option A is incorrect because backing off two full turns may leave the nut loose, affecting the security of the assembly. Option C is incorrect because tightly screwing the nut without backing off could result in over-tightening, which can cause damage to the plastic enclosure. Option D is incorrect because hand tightening only may not provide enough clamping force to secure the transparent plastic enclosure properly.