DYNAMIC CALIBRATION OF THE NOSEBOOM SENSORS OF THE FLYING HELICOPTER SIMULATOR

Abstract

For modern highly or fully automated helicopters, both the airspeed and the airflow angles have to be determined as accurately as possible. Research projects dealing with enhancements of in-flight simulation, model following or automatic trajectory control - among them the current DLR ALLFlight (Assisted Low Level Flight and Landing on Unprepared Landing Site) project – need accurate knowledge of the actual helicopter state. Due to rotor downwash, helicopter airspeed measurement in the low speed range via fuselage mounted pitot tubes is inherently prone to errors. The EC-135 Flying Helicopter Simulator (FHS) of DLR is therefore equipped with noseboom mounted sensors to enable measurements relatively unperturbed by rotor downwash effects. This paper describes the calibration of the pitot system and the airflow angle measurement vanes of this noseboom. A variant of the Simultaneous Calibration of Aircraft Data System (SCADS) technique is applied which uses wind box maneuvers to reduce wind influence during the calibration process. Similar to the flight tests performed at the National Research Council (NRC), Canada, position error correction (PEC) tower flyby maneuvers are used to verify the results obtained via the SCADS wind box technique. The calculated velocity independent correction factors obtained from the SCADS technique are compared to those from classical flight path reconstruction technique.