What indicates a failure in the flap system?

A failure in the flap system can be indicated by flap twisting or asymmetry because these conditions directly affect the aircraft's aerodynamics and control. When flaps are designed to extend or retract symmetrically to provide balanced lift and drag, any twisting or deviation from this even deployment can lead to significant variations in the aircraft's performance. Asymmetrical flap extension can cause unpredictable handling characteristics, potentially leading to difficult landing scenarios or increased aerodynamic stall risks.

While flaps not extending can indicate a malfunction, it does not provide specific information about the nature of the failure compared to the implications of twisting or asymmetry, which can immediately impact flight safety. Increased noise from the flaps might suggest an operational issue or wear, but it does not necessarily indicate a failure. Flap rusting is a maintenance concern and could indicate corrosion, but it is not a direct indicator of a failure in the flap system during operation. The concern primarily lies in the effective functioning and reliability of the flap system, making twisting or asymmetry a more critical indication of a malfunction.