Summary
The Federal Aviation Administration (FAA) proposes to supersede an existing airworthiness directive (AD) that is applicable to Lockheed Martin L-1011-385 series airplanes. That AD currently requires modifications of the engine turbine cooling air panel at the flight engineer/second officer's console, pilot's caution and warning light panel on the main instrument panel, and installation of an engine turbine air temperature monitoring system. This proposal would require the same modifications. In addition, this proposal would add Lockheed Martin L-1011-385 series airplanes with RB211-22B-02 series engines to the applicability, would require installation of a revised engine front bearing housing assembly, installation of a revised speed probe loom electrical support assembly, and installation of a low pressure (LP) compressor shaft extreme axial movement detector system. Also, this proposal would require additional modifications to the engine turbine cooling air panel at the flight engineer/second officer's console, pilot's caution and warning light panel on the main instrument panel. This proposal is prompted by reports of an undetected fire breaching the high speed gearbox (HSGB) case on certain Rolls-Royce engines installed on in-service airplanes due to lack of an internal fire detection system within the HSGB. In addition, this proposal is prompted by an undetected LP compressor shaft location bearing failure, and the discovery of possible fatigue failure of the speed probe loom electrical support assembly. The actions specified by the proposed AD are intended to prevent undetected fires originating within the HSGB from breaching the HSGB case, which could result in engine damage and increased difficulty in extinguishing a fire, and to prevent undetected LP compressor shaft location bearing failure, which could result in LP compressor and turbine shaft assembly failure, turbine overspeed, and possible uncontained engine failure.