Airworthiness Directives; Cessna Model 750 Airplanes

The FAA is superseding an existing airworthiness directive (AD) that applies to certain Cessna Model 750 airplanes. The existing AD currently requires repetitive inspections for clearance and chafing of an auxiliary power unit (APU) fuel tube assembly in the tail cone area of the airplane, and corrective actions if necessary. For certain airplanes, the existing AD also requires replacing the APU fuel line. This new AD adds airplanes to the applicability and allows operators to modify the APU fuel line by installing new fuel lines, fairleads, and clamping configurations, which is an optional terminating action for the repetitive inspections. This AD results from reports of chafed APU fuel tubes leaking into the tail cone area due to interference between the fuel tube assembly and elevator flight control cables, hydraulic lines, and high-temperature bleed air couplings. We are issuing this AD to detect and correct this interference, which could result in chafing, fuel leaking into an area where ignition sources are present, and possible fire in an area without fire detection or extinguishing provisions.