Rotorblade Trailing Edge Flap Failure Modes and Effects Analysis

摘要

As part of the Rotor Embedded Active Control Technology project, this paper reports on the impact of trailing edge flap failures on aircraft Handling Qualities. The primary means of assessing the effects of failure transients in this study is through the ADS-33E-PRF failure transient criteria, where flight path deviations resulting from flight control system failures are classified in terms of Handling Qualities Levels. The rotor blades of the FLIGHTLAB REACT Generic Rotorcraft model used in this study feature NACA0012 aerofoil sections with two flaps, each with an operational range of ±3°. Two mean settings were considered - the first at 0° and the second at 4° to simulate a cambered aerofoil. This short study focused on two modes of failures: hardover and oscillatory malfunctions, where the flaps oscillate once per revolution. The worst failure case was found to be in the hover-and-low-speed regime for advance ratio 0.1 with a mean setting of 0°, when all flaps suffer phased 1/rev failures, where the resulting rotor hub loads and aircraft response are similar to the effect of a one degree lateral cyclic pitch input. This failure case takes the transient response into the Level 3 Handling Qualities region. In forward flight, all failure transients were found to remain within the Level 1 region. In addition to determining the 'divided attention' failure transients three seconds after a failure occurs, a test pilot performed 'fully attended' Mission Task Elements to assess the effect of the failure on closed-loop HQs, flying the University of Liverpool's HELIFLIGHT-R simulation facility. Results showed that the worst case failures had little effect on the 'fully attended' handling qualities.