Airworthiness Directives; Learjet Model 31A and 60 Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Learjet Model 31A and 60 airplanes. This action requires an inspection to identify the serial numbers of the engine fire pull switch assemblies, and replacement of the assembly with a serviceable assembly, if necessary. This amendment is prompted by a report indicating that certain engine fire pull switch assemblies may contain microswitches that were manufactured with internal defects. Such defects could result in electrical failure of the switch in the open or closed position. The actions specified in this AD are intended to prevent failure of the switch, which could result in the inability of the flight crew to shut down certain systems or to arm the fire extinguishers due to inoperation of the fire tee handle, or inadvertent shutdown of one or both engines due to fuel starvation.