Airworthiness Directives; Boeing Model 727 Airplanes

The FAA is superseding an existing airworthiness directive (AD) that applies to all Boeing Model 727 airplanes. The existing AD requires a boost pump dry bay inspection to detect leakage of fuel through an arced-through conduit, and corrective action as necessary. The existing AD also requires repetitive inspections of the in-tank fuel boost pump wiring to detect chafing of the wire insulation, evidence of electrical arcing, or arc-through of the conduit wall, and applicable corrective action; and installation of sleeving over the in- tank fuel boost pump wires as a method to protect the wiring from chafing. This new AD removes certain inspection requirements from the existing AD. This new AD adds new repetitive inspections for damage of the electrical wire and sleeve that run to the fuel boost pump through a conduit in the fuel tank, and arcing damage of the conduit and signs of fuel leakage into the conduit; applicable investigative and corrective actions; and a new repetitive engine fuel suction feed operational test. Initiation of the new inspections terminates the requirements of the existing AD. This AD results from reports of a fuel tank explosion on a Model 727-200F airplane on the ground; and of chafed wires and a damaged power cable sleeve of a fuel boost pump that were discovered during an inspection required by an existing AD on a Model 737-300 airplane. We are issuing this AD to detect and correct chafing of the fuel boost pump electrical wiring and leakage of fuel into the conduit, and to prevent electrical arcing between the wiring and the surrounding conduit, which could result in arc-through of the conduit, and consequent fire or explosion of the fuel tank.