Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to AlliedSignal Inc. 36-300(A), 36- 280(B), and 36-280(D) series Auxiliary Power Units (APUs). This proposal would require installation of an external load compressor containment shield, or installation of a load compressor impeller with lower stress concentrations. This proposal is prompted by reports of load compressor impeller failures. The actions specified by the proposed AD are intended to prevent an uncontained APU failure and damage to the airplane.