Downwash question
Can anybody tell me if there would be any rotor downwash from a pair of stationary Apaches. They were waiting at the threshold, as i came in to land in a PA28, there was a strong wind blowing in the direction from the Apache's towards my landing point, and i experienced turbulence and windshear. I'm not sure if this would be due to the Apaches, or just the strong wind conditions, any thoughts would be greatly appreciated.
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Depends if they’re holding ground taxi power sitting on the brakes. Even then, the symptoms you describe seem a bit severe. |
If they were on the ground, the downwash would be negligible - if they were in the hover then it might have been an issue.
The turbulence and windshear would be due to the strong wind you mention. |
Not necessarily downwash, but turbulence, yes.
Anything upwind, such as a tree or building will give you turbulence. Wind turbines are well known for their turbulence and they are deriving thrust, not imparting it. And don't overlook short finals/ flare/ float is the most vulnerable phase of flight. |
Many thanks, they are big machines, and I think you are all correct, it was turbulence, ATC maybe should have held them further back the taxiway with those wind conditions.
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A 200' wind turbine side on isn't the same as a 60' rotor edge on and a helicopter that is designed to fly through the air with a minimum of drag is unlikely to generate a great deal of turbulence when at flat pitch on the ground.
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Well,
even if the collective is flat pitch - if one of the pilots is lazy on the pedals, the tail rotor can produce quite a bit of wind. I blew a (rotten) wooden fence with the power of a fenestron ;-) |
Originally Posted by Flying Bull
(Post 10623459)
Well,
even if the collective is flat pitch - if one of the pilots is lazy on the pedals, the tail rotor can produce quite a bit of wind. I blew a (rotten) wooden fence with the power of a fenestron ;-) |
Originally Posted by Flying Bull
(Post 10623459)
Well,
even if the collective is flat pitch - if one of the pilots is lazy on the pedals, the tail rotor can produce quite a bit of wind. I blew a (rotten) wooden fence with the power of a fenestron ;-) |
Originally Posted by Davey Emcee
(Post 10624015)
Presumably you were "lazy on the pedals" !!
@ rottenjohn - if someone stands on the brakes its a little bit different then normal - depending on the pedal design and your seating position, you need to stretch the leg/toes to get proper braking action. Assume it is at the holing point of a runway, you´re normally turning a little bit to reach that position - hence uneven braking/pedal position is a possibility |
But again, that is a rotor side on, doing what is designed for - producing thrust - not one edge on at flat pitch.
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Originally Posted by [email protected]
(Post 10624175)
But again, that is a rotor side on, doing what is designed for - producing thrust - not one edge on at flat pitch.
Have seen someone blown away passing to close to the tail - lucky for him, he was on the right side. Was an ground accident to happen.... |
Originally Posted by Flying Bull
(Post 10624206)
The tail rotor produces thrust if you put pedal in, flat pitch on the collective or not.
Have seen someone blown away passing to close to the tail - lucky for him, he was on the right side. Was an ground accident to happen.... in a Super Puma you can roll the aircraft on its side with too much right pedal! |
Quite. You blew away a fence because your TR was producing thrust - the OP was about turbulence from a MR at flat pitch:ok:
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Originally Posted by [email protected]
(Post 10624277)
Quite. You blew away a fence because your TR was producing thrust - the OP was about turbulence from a MR at flat pitch:ok:
Not understanding all the factors - he assumes, it must have been downwash. I just added another possibility - which might not spring into mind helicopter pilots operating smaler helicopters - but heavy "birds" ;-) ahh helicopters need a lot of anti torque - which is produced by the tail rotor. Even a slight foot forward, which won´t move or turn the helicopter will produce quite a lot of wind from the big fan at the back. Understandable now? |
Even a slight foot forward, which won´t move or turn the helicopter will produce quite a lot of wind from the big fan at the back. Understandable now? Yes, a TR will produce thrust on the ground but in the scenario posted by the FW pilot - the turbulence he experienced would not have been due to the helicopters. |
Would you bet your life on that? May be they were already light on the Wheels, ready to line up immediately after the landing aircraft? Thus making „a little bit of wind“? |
I refer to my earlier answer but even then it would only be about 10% Tq above MPOG. Symptoms still seem too severe for the AH to have a demonstrable effect. |
May be they were already light on the Wheels, ready to line up immediately after the landing aircraft? |
I call bull**** on the helicopter turbulence |
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