Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-300, 747-400, 747-400D, and 747SR Series Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747- 300, 747-400, 747-400D, and 747SR series airplanes. This AD requires a one-time inspection to determine whether any steel doubler (small or large) is installed at the lower forward and upper aft corners of the fuselage cutout at main entry doors (MEDs) number 3. Depending on the results of this inspection, this AD also requires repetitive inspections for cracks of the skin, bearstrap, and small steel doubler (if installed) at the applicable corner or corners of the fuselage cutouts, and related investigative/corrective actions if necessary. This AD also provides the optional terminating action for the repetitive inspections of installing a large steel doubler at the affected corners. This AD results from reports of cracks in the skin and bearstrap at the upper aft corner and at the lower forward corner of the fuselage cutout at MEDs number 3. We are issuing this AD to detect and correct cracks in the skin, bearstrap, and small steel doubler (if installed), which could propagate and result in rapid decompression of the airplane.