How it Works - Mechanical
The ALPHA SYSTEMS AOA system was primarily designed as a standalone device to improve operational safety of airplanes by increasing pilot awareness during operations at high angles of attack (slow flight). This AOA system meets the stated objective of the FAA’s Advisory Circular, AC23.1309-1C, “to improve the safety of the airplane fleet by fostering the incorporation of both new technologies that address pilot-error and weather related accidents and those technologies that can be certified affordably.”
The mechanical ALPHA SYSTEMS AOA system measures the change of differential pressures from the AOA probe mounted solidly to the aircraft at a location that would allow undisturbed air to be sampled at all angles of attack to convey a reliable, instantaneous and continuously variable angle of attack needle movement that is accurate regardless of aircraft weight, temperature or altitude.
Calibration of the Mechanical Alpha Systems AOA is set in-flight at the aircrafts’ Optimum Alpha Angle (OAA). The calibration is accomplished by the pilot to first fly the aircraft at the OAA (Optimum Alpha Angle), Zero sink, full control, minimum climb, full effectiveness of ailerons, rudder, and elevator. While holding the aircraft at the identified AOA, determine needle orientation in reference to the RED/YELLOW junction. When the needle is directly over the line between the RED/YELLOW junction, the gauge references the identifier (OAA). If the needle is not on the calibrated line, the AOA probe angle must be re-adjusted on the ground, and a second in flight calibration must be preformed. Typically it takes 2 calibration flights to align the probe to give the calibrated needle orientation.
In most installations the AOA Probe’s mounting plate replaces an existing inspection cover. The mechanic simply uses the existing inspection cover as a pattern, cutting the Alpha Systems AOA probe mounting plate to the exact size, shape, drilling mounting holes that matches the same pattern. When complete, the AOA mounting plate replaces the old inspection cover. The AOA probe faces forward at a ~50 degree angle (typical starting angle, final probe angle to wing relationship may need to be changed to bring needle on gauge at the calibration setpoint.
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