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Passive flow control methods are widely deployed on aircraft and active control methods are now being considered for application as well. However, there is currently no practical method of detecting incipient or fully developed flow separation, requiring manual activation of an active control system. This study proposes the use of low-cost, durable electret microphones to detect trailing edge flow separation. An × . stall regulated wind turbine blade airfoil is mounted in the UC Davis AWT subsonic wind tunnel with microphones at pressure taps near the trailing edge of the suction surface. Tests are run over a Reynolds number range of × to × with fixed and natural transition. Separation indicators including time domain and several spectral domain RMS calculations from fluctuating pressure signals are studied. Each is assessed for sensitivity to installation location, flight condition, premature boundary layer transition, and minimal calibration requirements. The results show a normalized backwards difference first derivative of provides a robust condition independent separation indicator over the range of conditions tested.

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