Assessment Of Airspeed Calibration Methods On A Utility Helicopter

Abstract

The calibration of airspeed measurement and indicating systems is an important point in the overall aircraft design, flight test and certification processes. Accurate, consistent and reliable airspeed indication is essential for the safety of the helicopter. Therefore, certification authorities dictate that an aircraft has a sufficiently accurate airspeed indicator system for different flight regimes such as level flight, climb, autorotation etc. In this paper, the airspeed calibration methods due to the position error, engaged during the development of T625 helicopter, are discussed. There are several flight test methods to determine the position error. The Horseshoe Heading (GPS) and the ORBIS methods, the methods used for level flight, depend on accurate GPS data and do not need any further instrumentation or device. The calibration results for these methods are compared with the data obtained with the Trailing Bomb method at which a probe is slung from the helicopter is to collect air data in the absent of rotor downwash.