Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 777 airplanes. This proposed AD was prompted by reports of failure of wire support clamps in the forward section of the aft pressure bulkhead. This proposed AD would require a detailed inspection of the clamps on the power feeder cable auxiliary power unit (APU) to determine if certain clamps are installed, and related investigative and corrective actions if necessary. We are proposing this AD to prevent failure of the clamp, which could result in wire chafing and potential arcing and consequent fire in section 48 (a flammable fluid leakage zone) or heat damage to the APU power feeder cable, insulation blankets, or pressure bulkhead.