All of EM Aviation’s AOA systems operate using a vane, like most military and airliners. The Vane flies in the relative wind. The angle between the vane and the chord line of the airfoil is called the Angle of Attack (AOA). The critical angle of attack, also known as the stalling angle remains constant, regardless of weight, bank angle, load factor or many of the others where the airspeed indicator is known to have errors.
The RiteAngle systems measure this angle, convert it to a series of LED’s. Green LED’s always means you are at a Safe AOA, Amber LED/s indicate caution, above a safe angle and Red Led/s indicate Danger and is set at 5 kts above the stall per FAA requirements. All display’s except the “BASIC +” are arranged in the form of a arrow showing which way to move the nose for a precision approach at current weights, bank angle, “G” loading and flap position. A Green Diamond indicates “On Speed.”
If the aircraft has flaps, the flaps change the Angle of Attack of the airfoil at which it reaches the critical angle. As on the aircraft with no flaps, this angle is constant for each flap position.
As the stall angle will remain constant, the speed indicated by that angle times 1.3 equals “normal approach speed” when that angle is flown, regardless of weight, load factor etc. The correction for flap position is automatic and “seamless” for the pilot, put the flaps in any position and the RiteAngle Elite+ or RiteAngle Integrity display automatically shows the correct angle to fly!
Smooth air & precise aircraft control during set-up determine the accuracy of your system. All RiteAngle systems are accurate within less than one degree. The atmosphere and most pilots aren’t.
Examples of displays, all systems very similar except Basic.
Vref is 1.3 X stall speed in each configuration. Elite (RA-5) and Integrity (RA5a) automatically correct for flap position.