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ATPL systems stalling EAS

Old 11th Mar 2013, 03:41
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ATPL systems stalling EAS

Reading ATC and AFT notes

AFT says stall EAS increases due to stall occurring at lower AoA at altitude as compressibility causes airflow disruption.

ATC says stall EAS remains the same as stall AoA is constant.

So I guess the question is according to casa does stall AoA always remain constant?

Does anyone have a good online reference for getting my head around the constant Mach what's happens to tas or ias type questions.
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Old 11th Mar 2013, 05:27
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Since a wing always stalls at the same incidence, and the aeroplane is only interested in EAS, the stall will occur at a fairly constant EAS. However at the very high altitudes of which a jet is capable, the indicated stall speed increases. This is due to two things. Firstly, the compressibility correction, which forms part of the difference between ASIR (airspeed indicator reading; the uncorrected reading on an airspeed indicator) and EAS (the other parts being instrument error and position error), is larger in the EAS to ASIR direction due to the effect of Mach number. Secondly, the actual stall EAS speed increases due to Mach number effect on the wing. At very high altitude the EAS stall speed occurs at a significant Mach number (180 knots = 0.61 Mach number, for example); the pressure pattern is disturbed and a higher stall speed results. Courtesy D. P. Davies

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Old 11th Mar 2013, 11:15
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Read Hurt's Naval Aviators - still the best reference - not only explains everything you need without much you don't, but CASA's answers always seem to agree with Hurt

Just ignore the obviously unnecessary bits - supersonic flight etc.

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