Rotorcraft Active Crash Protection Systems

This paper presents the results of an ongoing Advanced Aircrew Protection Program jointly funded with U.S. Army Aviation Applied Technology Directorate (AATD) to develop a prototype Active Crash Protection System (ACPS) for improving the crash survivability of rotorcraft. The prototype ACPS under development is an integrated system that includes sensors, electronic control unit, crash activation algorithm software, and active crashworthy subsystems. The architecture for the ACPS has been established and prototype electronic hardware and crash activation algorithm software was developed. A prototype external airbag crash protection subsystem was also developed as the first active crash protection system to demonstrate the ACPS. During the ongoing program, prototype active landing gears using magneto-rheological (MR) fluids are being developed and integrated with ACPS. An MD-500 airframe is being used as the test-bed for demonstrating the ACPS technology. The prototype external airbag configuration includes four airbags attached to the landing gear cross tubes. The airbags also incorporate burst disks that are used to vent the airbags following the initial crash impact. The airbags are inflated using hybrid gas generators that use both solid propellant and CO2 for gas generation. The prototype active landing gears include dampers that use MR fluid technology to increase their energy absorption capability and also adapt to changes in aircraft gross weight and impact velocity. The aircraft state data (altitude, velocity, acceleration, etc.) from various sensors are processed by the ACPS control unit to determine if a hard landing or crash event is eminent. Based on the predicted time-to-impact and impact conditions, active crash protection subsystems are activated and controlled during the crash impact. The prototype ACPS is being demonstrated by modeling and simulation as well as by full-scale drop tests.