Containment Structures for Rotor Failure in Auxiliary Power Units

A small engine in the tail of most commercial airliners, called an auxiliary power unit, satisfies the aircraft’s power needs during boarding and refueling, such as air conditioning, lighting, pilot controls and in some cases engine startup. After passenger safety, reducing aircraft weight is a major aviation concern. If one of the rotors in the auxiliary power unit fails, it could exit the engine and cut through the aircraft cabin. The goal of this project is a design that will contain rotors in the event of a failure, and that weighs a little as possible without compromising passenger safety. This is achieved by placing containment rings outside the turbine and compressor rotors. The nickel-based alloy rings can stretch and absorb the impact of pieces from a fractured rotor. The design was tested using proven mathematical models and analysis. Cost precluded a real-world test, but the team developed a test plan should Honeywell decide to continue with the design.