Airworthiness Directives; Boeing Model 747 Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 747-200B, 747-200C, 747- 200F, 747-300, 747-400, and 747SP series airplanes. That AD currently requires doing a detailed inspection of the left and right longeron extension fittings, and corrective action if necessary. This new AD adds airplanes to the applicability of the existing AD. This 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 issuing 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.