Handling Qualities Degradation in Tilt-Rotor Aircraft Following Flight Control System Failures

Handling Qualities are critical in terms of performance and flight safety and will have a strong influence on the design of a future Civil Tilt-Rotor. As with all civil aircraft, the design must comply with civil aviation airworthiness regulations within which safety standards play a major role, thus any handling qualities degradations caused by a flight control system component failure must be quantified through a safety analysis. This paper presents the steps taken to determine failure severity for different types of component failure such as a loss, malfunction or degradation, focusing on the results from a series of piloted simulation trials, with the FLIGHTLAB XV-15 tilt-rotor model, held at the University of Liverpool for the European 5th Framework ACT-TILT project. Degraded failure results are presented for several mission tasks in aeroplane, conversion and helicopter modes and an aircraft maximum tolerable actuation rate limit recommended, followed by a malfunction failure analysis which determines the maximum tolerable hard-over position and ‘passivation ’ time for each function. Work in the ACT-TILT project focuses on the AGUSTA-WESTLAND ERICA tilt-wing/tilt-rotor design concept and as such also considers the affect of a tilt-wing failure and the possibility of using helicopter controls in the event of a control function failure in aeroplane mode