Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747 airplanes. The existing AD currently requires repetitive inspections to detect evidence of wear damage in the area at the interface between the vertical stabilizer seal and fuselage skin, and corrective actions, if necessary. The existing AD also provides for an optional terminating action for the repetitive inspections. For all airplanes, this proposed AD would require doing repetitive inspections for wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin, doing a detailed inspection for wear damage and cracks of the surface of any skin repair doubler in the area, and doing corrective actions. For airplanes on which the fuselage skin has been blended to remove wear damage, this proposed AD would require doing repetitive external detailed inspections or high frequency eddy current inspections for cracks ofthe blended area of the fuselage skin, and corrective actions if necessary. This proposed AD results from reports of wear damage on airplanes with fewer than 8,000 total flight cycles. In addition, there have been three reports of skin wear damage on airplanes that applied BMS 10-86 Teflon-filled coating (terminating action per AD 2002-26-15). We are issuing this AD to detect and correct wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin in sections 46 and 48, which could cause in-flight depressurization of the airplane.