Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 707 airplanes and Model 720 and 720B series airplanes. This proposed AD would require repetitive inspections of the left and right support ribs for the main landing gear (MLG) trunnion, related investigative/corrective actions if necessary, and other specified actions. This proposed AD is prompted by reports of in-service cracking of the support ribs for the MLG trunnion. We are proposing this AD to detect and correct corrosion and cracking of the support ribs for the MLG trunnion, which could result in collapse of the MLG.