Investigation of a General Aviation Differential Pressure Angle of Attack Probe

Le résumé fourni par la source

A wind tunnal calibration of a commerically available general aviation differential pressure angle of attack probe was conducted. Differential pressure varied linearly with pitch angle for each dynamic pressure tested. Beyond ±6 ◦ of yaw angle, differential pressure rolled off rapidly with yaw angle. Normalizing differential pressure with dynamic pressure collapsed the differential pressure to a single curve for pitch. Similarly, normalizing differential pressure with the dynamic pressure collapsed the differential pressure to a single curve for yaw. Normalizing the differential pressure with dynamic pressure removes the effect of speed and density altitude when deriving angle of attack from differential pressure. Normalizing the differential pressure using the pressure from the 45 ◦ probe surface similarly collapsed the differential pressure to single separate curves for both pitch and yaw. Differential pressure varied parabolically with pitch angle when normalized using the pressure from the 45 ◦ probe surface. For pitch angles above six degrees, a linear relation between differential pressure normalized with the pressure from the 45 ◦ probe surface and the square of the pitch angle provided an adequate approximation. The typical two-point linear approximation based on two in-flight calibration points results in significant errors in displayed angle of attack. Moving the low angle of attack in-flight calibration point closer to the stall angle of attack reduces the displayed angle of attack error in the critical stall region. Using a four-point linear approximation significantly reduces the error in displayed angle of attack throughout the angle of attack range. Combined pitch, yaw and roll results in sideslip, which produces significant error in displayed angle of attack based on calibration at zero yaw and roll.

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