Fred Scott, Jr.
(434) 295-4188

Angle of Attack Instrumentation
(Here's a complete list of all our AoA pages)

Review the general Plan for the AoA Test Flights then downoad the FINAL REPORTS on the Flight Tests:
S35 Bonanza Angle of Attack - "Legacy AoA" Test Flight Final Report

King Air 90 Blackhawk Angle of Attack - "Dual Legacy AoA" Test Flight Final Report

Human Factors - A Prototype Version - Enhanced Audio & Cascading Lights

King Air 90 Blackhawk - "Dual Eagle AoA" Test Flight Final Report

"Flap Biasing" AOA in the King Air C90 Blackhawk


The Alpha Systems Angle of Attack (AoA) Stall Warning System offers an accurate, repeatable, and very early warning of impending aerodynamic stall. Such clear stall proximity information mounted prominently on the glareshield in full view of the pilot offers enhanced safety in the operation of general aviation aircraft.

A display of AoA as a cross-check to the primary Airspeed Indicator is particularly useful when operating in steeply banked and/or G-loaded flight conditions because the angle of attack at aerodynamic stall is independent of aircraft weight and/or wing loading.

Specifically, within the scope of these test flights, the following germane conclusions were reached:

• The “Optimum Alpha Angle (OAA) Calibration” technique recommended by the Alpha Systems AoA Stall Warning System Installation Manual is an accurate and repeatable method that can be used to reliably set an AoA target that will be adequately before the aerodynamic stall AoA.

• The target AoA, once calibrated, presents data to the pilot so as to provide early warning of an impending stall, prior to the aircraft stall warning audible system, thereby ensuring a safe margin above stall throughout the entire gross weight envelope.

• The instrumentation provides clear, un-ambiguous, and easy-to-comprehend stall proximity information.

NOTE: Some readers have asked why we suggested flap-biasing of AoA data for future products when we didn't observe much--if any--flap effect on AoA in the Bonanza and King Air. Plain flaps, split flaps, and slotted flaps at high AoA do not incur significant Coefficient of Lift (CLmax) shifts from the basic wing section, but Fowler-type flaps can and often do. Accordingly, for wide-span Fowler flap-equipped light aircraft---but there aren't many---flap bias may well be a good idea. The Bonanza and King Air have "de facto" slotted flaps, of course, with only a small initial Fowler action.
NOTE: The flight test team WITHDREW THIS RECOMMENDATION in the Test Flight Reports Revision 1 of 4/10/2011.
See also a later test flight : "Flap Biasing" AOA in the King Air C90 Blackhawk


I have NO financial interest in this company or its products...but I will say---having lost a few too many pals in low-level stall/spins, that I will do everything I can to help them succeed. So will my friend Tom Rosen in California. He recently lost two 30,000-hour (each) airline captains. Close friends gone. Together, Tom and I are trying to prevent these steep-turn crashes from happening again..

Disclaimer: The information provided in this website and AoA/Aircraft portion is provided free of charge. All information provided on this web site is provided 'AS IS'. No guarantee is provided for the accuracy of the information or the application of the information provided herein. I accept no responsibility or liability with regards to the accuracy or currency of the information provided. By using, reading or accessing this web site, you agree to be the user of the information provided. The user accepts full responsibility for all information provided. Although I try to keep the information on this site as accurate as possible, there is no guarantee that the reference materials or the material on this site is correct. This information is provided entirely in the spirit of helpful cooperation.

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