Airworthiness Directives; Lockheed Model L-1011 Series Airplanes

This amendment revises an existing airworthiness directive (AD), applicable to all Lockheed Model L-1011-385 series airplanes, that 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 monitoring system for the engine turbine air temperature. That AD was 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. The actions specified by that 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. This action removes certain airplanes from the applicability of the existing AD.