![]() ![]() ![]() ![]() The reducing density means you need to speed up to fly at the same dynamic pressure, and.Increasing altitude will raise the flight Mach number in two ways: Let's just say that the local Mach number in the suction peak has a strong influence on the stall angle of attack, and flying at a higher Mach number lowers the stall angle of attack, sometimes dramatically. This suction is equivalent to higher local speed, and if the critical speed (when local flow speed equals the local speed of sound) is exceeded, the flow past the suction peak will no longer behave similarly to the flow at the same angle of attack but a lower flight Mach number. When increasing the angle of attack, the flow around the airfoil's nose will develop a suction peak. An increased pitch rate can push the stall angle of attack 50% higher than what the stall angle of attack is in stationary conditions. The angle of attack dependency is discussed here. It seems to be very basic but when we correctly think about it we can find ourself a little bit confused.įor me, the answer is : The IAS stall speed will increasesĪirplanes do not stall at the same indicated speed or even at the same angle of attack - it all depends on circumstances. I don't need an exact value but I would love to have a logic and smart answer. We can also keep it simple and think about it for a non pressurized single engine aircraft. Maybe that it's a representative value of IAS/CAS calculated by the Air Data Computer from an EAS but still, our IAS stall speed has rised. We agree in saying that the low speed buffet here is not the same as the one at sea level but look, our IAS/CAS stall speed has a higher value now. Let's assume that our IAS stall speed is 100kts at sea level, what will be our IAS stall speed at 30 000 feet with exactly the same aircraft ? (Assume ISA atmosphere)Įveryone would be tempted to answer that it doesn't change, right? but what about the low speed buffet in this picture ? So we also know that our TAS/ Mach number will increase with increasing altitude. First of all, we all know what IAS is and if not for some people you can follow this link to read the basics about stall and the differents speeds. ![]()
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