A “Stand Alone” Instrument
As the RiteAngle series of AOA systems are primarily a safety instrument, it does not depend on anything except electrical power from the aircraft. If the glass display goes out, you now still have the AOA for reference. LED life in the unit is approximately 10,000 hours.
It’s all about measuring lift!
We have all heard the old adage “Lose Not Thy Airspeed Least the Earth Rise up and Smite Thee”. All commercial airliners, military aircraft , even the Space Shuttle required an Angle of Attack (AOA) for safety. The RiteAngle AOA systems all accurately measure the angle of attack by using a vane flying in the “relative wind”. This resultant signal is converted and displayed for the pilot using green, amber, and red LED’s. The display module is designed in accordance with FAA recommendations; green indicating safe, amber caution, and red for danger. For accurate readings at various flap settings, the aerodynamic change in airflow must be corrected by the AOA system for an accurate display.
Airspeed is of less value to the pilot than AOA due to its inherit errors. Short Take-off and Landing operations require the aircraft be able to operate with precision for repeated maximum performance. The indicated airspeed during these maneuvers will vary due to weight, load factor and other factors, however the AOA will be correct, ask any Navy pilot that has flown onto and off of a carrier!!
Angle of Attack (AOA)
The Angle of Attack (AOA) is the angle that is formed by the chord line of the airfoil and the direction of the air that strikes the airfoil, this is known as the relative wind. As the angle of attack changes, the lift and drag also change as the pilot changes the attitude of the aircraft. The increase in AOA increases up to a point. Too high of an angle of attack results in a loss of lift and cause an aircraft to stall, which is known as exceeding the critical AOA. The critical AOA will remain constant for the airfoil, however it will vary with any change in the airfoil, such as lowering the flaps or modifying the airfoil in any way.
The critical angle of attack
The critical Angle of Attack is exceeding the angle of attack which the air will flow sufficiently and smoothly over the upper surface of the airfoil. At this point, the wing will no longer support the aircraft in level flight and is said to be in a stall. A fixed wing aircraft always stalls at the same Critical Angle of Attack, rather than at the same airspeed. The airspeed at which the aircraft stalls is variable, depending upon weight of the aircraft, load factor at the time, and thrust from the engine. As the Flaps are extended, the airfoil has been modified, and the lift changes . The AOA must be corrected for this change in lift. The RiteAngle AOA systems for aircraft with flaps automatically correct for this change in lift, and the lower critical angle of attack with the flaps extended. The critical AOA will vary on every aircraft, depending upon the design of the wing.
I just wanted to tell you how much I enjoyed your presentation on the AOPA website last night. I bought your system ten years ago and installed it on my Glasair IIS-RG. It’s worked great ever since then. My Navy background (F-8 Crusaders on carriers; POW for 8 years) lets me appreciate the value of angle of attack.
Elbie, I flew it to Fairbanks, AK last June. The RiteAngle works great. One thing I haven’t heard mentioned as a benefit of the unit is that it can replace your ASI in the event of an ASI failure.