Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to supersede two existing airworthiness directives (AD) that apply to certain The Boeing Company Model 737-100, -200, - 200C, -300, -400, and -500 series airplanes. The existing AD, for certain Model 737-100, -200, and -200C series airplanes currently requires repetitive inspections of the aft end of each inboard flap track of the wing outboard flap, and corrective actions, if necessary. The existing AD, for certain Model 737-100, -200, -200C, -300, -400, and -500 series airplanes requires repetitive inspections for cracks in the upper flange of the inboard track at the rear spar attachments of each outboard flap, and corrective action, if necessary. That AD also requires, for certain airplanes, repetitive inspections for discrepancies of the rear spar attachments and cracks in the upper flange of the inboard track at the rear spar attachment of each outboard flap, and eventual rework of the flap track assembly and rear spar attachments, including replacement of the flap track with a new track, if necessary. Since we issued those ADs, we have received reports that the work sequence and procedures used during track installation could also cause loose or cracked tracks. This proposed AD would require an inspection for damage and stop-drill repairs along the flap track; an inspection for damage, cracking, and stop-drill repairs along the track webs; and an inspection for damage of the flap track web and flanges, and corrective actions if necessary. This proposed AD would also require, for certain airplanes, an inspection for signs of movement between the tapered shim and anti-fret strip, installation of the anti-fret strip, and corrosion of the tapered shim and anti-fret strip; an inspection for signs of movement, cracks and corrosion where the track is attached to the wing rear spar; an inspection for cracking of the outboard edge of the track; an inspection for cracking of the inner edge of the track; and related investigative and corrective actions if necessary. This proposed AD would also require repetitive overhauls of the flap track and repetitive post-overhaul inspections and corrective actions if necessary; an inspection to determine the part number of the flap track assembly, and replacement of affected parts if necessary; and would also add airplanes to the applicability. We are proposing this AD to detect and correct cracking and damage in the flap track, which could cause loss of the outboard trailing edge flap and consequent reduced controllability of the airplane.