Initial flight tests of an automatic slung load control system for the ACT/FHS

Abstract

An automatic slung load control system for the research helicopter ACT/FHS (Active Control Technology / Flying Helicopter Simulator) of the German Aerospace Center (DLR) has been developed and initially tested in flight. The external load is suspended from a rescue hoist which was mounted at the ACT/FHS for flight test purposes. For the load motion detection an optical-inertial sensor system was developed. The sensor system provides estimations of the cable length and cable angle as well as cable angle rates for the slung load control system. Flight testing of the sensor system proved that the optical marker is detected consistently and accurately for cable length up to 50 m. Furthermore, the estimated load motion signals can be used for the control system. To demonstrate the overall system’s functionality, an initial control system for damping of the pendulum load motion was designed and flight tested. The automatic function of the control system was effective in damping the load pendulum motion for a fixed cable length. Under piloted control the slung load damping system showed deficiencies. When actively controlling the helicopter, the pilot acted against the control system resulting in an adverse effect in load damping. Overall, for the first time, a slung load control system for a load suspended from a rescue hoist could be demonstrated successfully.