Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The original NPRM would have required repetitive lubrication of the left and right main landing gear (MLG) forward trunnion pins; and an inspection for discrepancies of the transition radius, lead-in chamfer, and cross bolt bore of the MLG forward trunnion pins, and repair or replacement if necessary. Doing the applicable inspections and repairs/replacements, or overhauling the trunnion pins as proposed in the original NPRM, would end the repetitive lubrication requirements of this proposed AD. The original NPRM resulted from a report that the protective finishes on the forward trunnion pins for the left and right MLG might have been damaged during final assembly. This action revises the original NPRM by changing the inspection of the trunnion pins to allow inspection in-situ. If a certain repair is done, this action would require repetitive inspections for discrepancies of the transition radius. We are proposing this supplemental NPRM to prevent cracking of the forward trunnion pin, which could result in fracture of the pin and consequent collapse of the MLG.