Summary
This document proposes to revise an earlier proposed airworthiness directive (AD) that would have required the following on certain British Aerospace Model B.121 Series 1, 2, and 3 airplanes: installing an inspection opening in the area of the main spar web, repetitively inspecting the area at the main spar web for cracks and the area of the wing to fuselage attach bolt holes for corrosion, and repairing or replacing any cracked or corroded part. The proposed AD was the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom. Since issuing the NPRM, British Aerospace has developed additional service information to that referenced in the previous proposal to include the installation of nuts of improved design at the wing to fuselage main- spar attachment fittings and the deletion of the inspection of the area of the wing to fuselage attach bolt holes for corrosion. The improved design nuts provide better torque retention than the nuts originally installed. The Federal Aviation Administration (FAA) has determined that the above-referenced changes in the revised service information should be incorporated into the NPRM, and that the comment period for the proposal should be reopened and the public should have additional time to comment. The actions specified by the proposed AD are intended to prevent structural failure of the main spar web area caused by fatigue cracking or separation of the wing caused by loose nuts at the wing to fuselage main-spar attachment fittings, which could result in loss of control of the airplane.