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HIGH SPEED STALL

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Old 02-04-2012, 05:26 AM
  #26
apereira
 
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Default RE: HIGH SPEED STALL

There are several types of stalls, probably the term high speed stall is being confused with dynamic stall wich is the one related to 3D flying models for example. High speed stall is related to the Mach critical speed indeed, remember Chuck Yeager flights and how the high speed stall affected the flights of the X1?

Per definition, high speed stall can not happen in the current RC designs, as the air is not compressible at subsonic speeds.

I agree with the fact it is been confused with a "radio hit" .

This thread should probably needs to moved to the Aerodinamics forum.
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Old 02-04-2012, 05:28 AM
  #27
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Default RE: HIGH SPEED STALL

(double post)
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Old 02-04-2012, 05:32 AM
  #28
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Default RE: HIGH SPEED STALL

For me is yes, an aircraft can have a high speed stall effect above from its normal low speed stall when the air velocity produce enough drag and moment to cause the elevator to stall first then followed by the wings. However this effect shouldn't be happening to model aircraft without other factors like weight, CG position, wing camber, size of elevator and its distance. Also at high speed even door and gear extended produce a lot of nose down effect.

Example, a high wing loading sweep wings aircraft with lesser wing camber flies better at higher speed but when camber increased it shifted center of pressure backward producing pitching down moment. Without sufficient distance to the elevator and its size a bigger surface area of deflection is required otherwise it would stall and if too much angle is used it would also stall. When elevator stalls it follows nose down effect then lesser lift on the wings.
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Old 02-04-2012, 08:57 AM
  #29
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Default RE: HIGH SPEED STALL

All your comments have been very helpful thank 's everybody.
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Old 03-05-2012, 07:38 PM
  #30
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Default RE: HIGH SPEED STALL

While Ihave not measured the G my model aircraft are subjected to, Iam quite sure that they are so much stronger than full size aircraft that it would be quite possible to pull 15 and possibly even 20 Gs without breaking them. We don't know what speed our airplanes are flying at and, as their power is greatly in excess of full size aircraft, they can reach these high Gs without stalling. On the other hand, we use, let's call it higher speed stall, in snap rolling manoeuvres all the time in aerobatic schedules so to say that model aircraft don't stall is quite wrong. You can set one up to have insufficient elevator authority such that you would find it difficult to stall by approaching the stall fairly slowly. Pulling the aircraft up to a very steep attitude even with limited elevator travel will usually produce a stall but the recovery, given that small elevator movement, will be almost instantaneous so it will "look" as if it has not stalled. Idon't know how many folks have lost an aircraft on short finals to the dreaded stall/spin situation - Icertainly haveand I've seen quite a few others go that way!
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