OK, attitude adjustment complied with. I have to live up to my surname that follows me around though.
Main Entry: 1bick·er
Pronunciation: 'bi-k&r
Function: noun
Etymology: Middle English biker
Date: 14th century
1 : petulant quarreling :
It has made this thread longer and brought a few out of the woodwork.
CTD: accept your comment. In your example, you are 100% correct. When SASless said downwind t/o I took it to mean lifting off with tail to wind, and continuing forward with the wind. Not backing up and turning (which makes more sense).
At these speeds (5-10kts), any lift, positive or negative, created by the elevator is negligible. It’s basically hanging there in the way.
If you got it wrong - what would the lurkers have made of it. Probably out there giving it a go right now. At 5-10kts airspeed I agree it would be negligible. You actually need a little more than this to see the benefit.
Nick Lappos: I calculate about 20 pounds of lift from an optimum angle of attack on 20 square feet at 20 mph. Peanuts.
The downwash on the tailcone and horizontal tail is not peanuts, however, and might increase hover performance by 100 to 200 pounds when the downwind hover flow pushes it away from the tail, as opposed to the head wind pushing it onto the tail.
I agree with your statement 20 square feet at 20 knots. This is of course if the elevator is out in clean air not living under the rotor wash. My assumptions are based on the fact that as you use aft cyclic and the aircraft is moving backwards (relatively) the sync elevator is now in a position to produce lift or put another way to have reduced vertical drag. It is now a canard and the more aft cyclic you use the more lift (or reduced drag) you get. As you get faster going backwards the pitch rate can become divergent or negative. Get a Bell 47 going backwards at 40 knots and have a play. This is placarded as "prohibited" by the way.
helmetfire: the synch elevator will provide no such lift at the speeds we are talking about, and when it does produce lift, it produces a pitching moment to the aircraft rather than significantly contribute to the total lift moments
So what is the "speed" of the elevator. Do you think that the wake from the main rotor is now in front of it? No such lift - agreed but what about less drag in the vertical plane? When it does produce lift it produces a pitching moment rather than significantly contribute to the total lift moment. Hmmm is this pitch moment not aligned with the lift vector? Take a look at a "Rutan" style aircraft where both horizontal surfaces produce lift as opposed to a "conventional" aircraft where the rear one doesn't. Maybe this is all a load of bollocks but the question in this post was why, I am just expounding a possibly flawed theory. SASless and CTD assumed that the takeoff was done in the downwind direction which was incorrect.
Nick Lappos: BTW, we call the situation where one hovers with one's ass into the wind as a downwind hover. I will have to tell the old test pilots at Sikorsky how very wrong they have been all these years. Just think, in 7500 hours of flight, the majority in engineering or experimental test, I have not yet got that right. John Bicker,. can you again clarify the situation?
(from Cambridge International Dictionary of English)
downwind
adverb, adjective_
in the direction in which the wind blows; with the wind behind_
A tail wind is a wind blowing from behind a vehicle._
Planes travelling from America to Europe usually have a tail wind rather than a head wind.
Shall we say that the difference is who is meant by we. Geographical? I like the one that refers to the vehicle. I also like to stay away from the downwind term in light of the fact as you have expounded here that the main rotor doesn't know which way the wind is blowing and in English english it refers to movement and here we are in the stationary hover. Remember the surname! For example another term that has a difference is the reference to "hover auto". I know what is mean't buy the term but where I come from it is called a power failure in the hover. Use of this terminology during a flight test with the authorities will result in failure. Geography again.
helmetfire
Will post in the "phase-shift" as to what happened.
Are we having fun yet?
