Airworthiness Directives; AlliedSignal Inc. TFE731 Series Turbofan Engines

This amendment revises an existing airworthiness directive (AD), applicable to AlliedSignal Inc. TFE731 series turbofan engines, that currently requires installation of an improved flexible (flex) fuel tube. This amendment clarifies that installation of the improved flex fuel tube and that the use of a clamp on the original rigid fuel tube are optional for engines installed on Learjet 35, 36, and 55 series airplanes. This amendment is prompted by confusion from operators regarding the applicability of these Learjet engine installations. The actions specified by this AD are intended to prevent cracking of the fuel tube and the subsequent leakage of fuel on or around electrical components, which can cause an engine fire.