Extension of HUMS Data for Estimating Flight Severity for Helicopter Airframe Structures

This paper details the development of a flight severity factor (FSF) calculation algorithm for airframe components by leveraging flight parameter data from a Health and Usage Monitoring System (HUMS). The United States Air Force (USAF) has added to the value of its HH-60G Pave Hawk HUMS data by using it to estimate theoretical fatigue crack growth, which is leveraged to update inspection intervals per MIL-STD-1530C. The results yield increased safety, improved component inspection and replacement scheduling, reduced unscheduled maintenance, decision support for service life extension programs (SLEP), and increased aircraft availability. In addition, the FSF is being used in the implementation of an individual aircraft tracking program (IATP) for the HH-60G, using HUMS data to predict theoretical crack growth on a flight-by-flight basis for two structural tracking locations, with an additional six planned for the near future. The paper describes background for the program, including a flight strain survey, a global finite element model, and a durability and damage tolerance analysis used for the damage model.