Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747-200B, 747-200C, 747-200F, 747-300, 747-400, and 747SP series airplanes. The existing AD currently requires doing a detailed inspection of the left and right longeron extension fittings, and corrective action if necessary. This proposed AD would add airplanes to the applicability of the existing AD. This proposed AD results from reports that accidental drilling damage to the longeron extension fittings was found on airplanes not subject to the existing AD. We are proposing this AD to detect and correct accidental drilling damage of the longeron extension fittings, which could lead to cracking of the longeron extension fittings and result in rapid decompression of the airplane.