Transactions of Nanjing University of Aeronautics & Astronautics
Design of a High-Robustness Flap Skew Detection Monitoring Threshold
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Abstract:
Focusing on civil aircraft flap skew detection design， this paper proposes a high-robustness monitoring design methodology to address insufficient monitor robustness that may trigger false alarms and disrupt airline operations. Based on flap skew detection principles and threshold design criteria， the threshold range is defined with upper limit of maximum deformation under aerodynamic load and lower limit of sensor error margin and nominal flight deformation. Since the complex loading conditions of maximum flap differential deformation （max Δλ） during normal flight cannot be theoretically determined， probabilistic methods are employed： Flight test data from hundreds of sorties are analyzed using generalized extreme value distribution. Confidence levels are verified via Kolmogorov-Smirnov （K-S） hypothesis testing. Then probability density function of max Δλ is established. The false alarm rate is calculated through cumulative probability values of max Δλ at varying thresholds. Boundary conditions for false alarm rate are determined by safety assessment and dispatch reliability analysis. The derived monitoring threshold is verified against finite element analysis predictions and iron bird rig test. The results confirm the methodology’s validity， meeting all design objectives.
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TN925
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