Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 727 series airplanes. This proposal would require a one-time visual inspection of the manual extension gearbox assembly of the main landing gear (MLG) to detect whether certain gearbox housings have been installed; repetitive dye penetrant inspections of these housings to determine whether cracking has occurred; and ultimately, replacement of these housings with correct housings. This proposal is prompted by a report indicating that a manual gearbox assembly which contained an incorrect housing was installed on a Model 727 series airplane. The actions specified by the proposed AD are intended to prevent the installation of manual extension gearbox assemblies with incorrect housings. This condition, if not corrected, could reduce the structural integrity of the manual extension gearbox assembly, and ultimately result in an inability to lock the MLG in a down position during landing.