Stall is mainly misundertood to be defined by airspeed
Yeah, OK, sloppy wording on my part.
I am well aware that stall is defined by incidence and that the critical value depends on Mach number - not much up to about 0.4 or 0.5 but a steady fall thereafter.
I was however addressing the question of engine behaviour.
Certification stalls are done at idle power, which effectively defines a non-dimensional mass flow demand. Per unit cross sectional area of the entry stream tube this quantity gets bigger as Mach increases, so the intake area required decreases.
The intake is carefully sized to supply cruise thrust requirement.
At altitude, or indeed almost everywhere, at idle the engine demand is far smaller than the potential intake supply, so the principal differences between high and low altitude stalls in this regard is the amount of intake spillage.
Flow distortion due to incidence is another matter, but hey, we aren't talking big numbers here. At 0.65M stall might be about 9 deg
A lot of stall testing is done with high lift devices in use, because this is where you get closest to the margins
Well actually, the g margin retained in cruise is 0.4 incremental ( to buffet onset) whereas in approach (1.3 Vs) it is 0.69.
For me at lesst the emphasis on high lift stall testing is that small margins not cashed can have a large effect on certificated field performance and sales potential
Sorry if this sounds carping - bit liverish today!
OG
Last edited by Owain Glyndwr; 1st Apr 2016 at 11:37.
Reason: typo