Angle of Attack Indicator, 1950's US Military Jet Fighter
This is a very unusual Angle of Attack Indicator and the first we've ever seen of this design. In our judgement it may have been used during early 1950s, possibly in a prototype aircraft. What makes this unusual is the angle of attack pointer with it's integrated jet fighter graphic.
The Angle of Attack is the angle formed by the chord of the airfoil and the flight path of an aircraft (i.e., nose up or down wrt plane of flight). The increase in AOA increases lift up to a point, called critical angle of attack (CAA), where the AOA exceeds the limit and results in a loss of lift. The aircraft wing is said to be in a stall when it reaches the CAA. The use of AOA system in an aircraft keeps the pilot informed of the AOA related to the aircraft performance; thus, allowing the pilot to reduce the risk of an inadvertent stall resulting in a loss of control. These indicators seem to have first appeared routinely in USAF/USN aircraft in the early 1950's
In our assessment this is from an early, but not the first, models of US military jet fighter, perhaps a one-off or a prototype. The jet fighter graphic on the pointer is very similar to the 'mythical' Lockheed F-96 whose traces are difficult to find, or the Republic F-84F Thunderstreak (see photos). Both aircraft had swept wings and tailplanes positioned high on the rudder as is the pointer graphic, and both flew for the first time in the early 1950's. The other clue is the size of the instrument, at 3.25 inches diameter, which is the first time we've seen an AOA indicator this size. When AOA indicators began to regularly appear in US jet aircraft, they were 2 inch diameter.
This indicator shows AOA as green from -3 to 10 degrees, yellow from 10 to 15 degrees, and red from 15 to 20 degrees. Measures 3.25 inches diameter and ~4 inches deep. It is in exceptional condition given its age.