PPRuNe Forums - View Single Post - AOA units - Angle of Attack
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Old 25th Apr 2019, 18:41
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Just This Once...
 
Join Date: Apr 2005
Location: UK
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The AoA can vary over different parts of the aircraft structure and the aerodynamic surfaces and are not always linear across the performance envelope. Often what is claimed as AoA in degrees isn't and units may or may not have a direct correlation with true AoA or may use another term entirely that has a rough correlation with actual AoA. The scaling factors have been explained by safetypee and vary by aircraft type.

There is a thread on this page covering an F-15C accident and is a case in point. This aircraft type displays alpha as Cockpit Units (aka CPU) and are presented to the HUD and helmet in degrees. The CPN units are around 10 degrees higher than actual AoA but the offset varies slightly over the performance envelope. The head-down displays / MFT use the alpha symbol and Angle-Of-Attack nomenclature on the Spin Recovery Display, but are also CPU values displaying up to 45 degrees of CPU.

This is just a gross simplification of a rather big subject.
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