Brendan Moran wrote:
>
> > As my areobatics instructor stresses, pull the stick back to position
> > 'X' at any speed and the wings will stall, so you may be better
> > monitoring the back pressure on the "stick" to detect when a stall is
> > imminent.
>
> I think that there may be two separate discussions in progress here.  When
> you mention stalling, Tony, you are speaking specifically of a wing stall,
> rather than not having lift at all.  They are two different things.

I understand that.

zero speed  = zero lift, no stall
some speed + zero attack = zero lift, no stall
any speed + overly high attack (>16') = zero lift, stall
some speed + good attack = no stall, lift (up)
speed + straight up + good attack = no stall, lift (horizontal)
speed + straight down + good attack = no stall, lift (horizontal)
speed + upside down + good attack = no stall, lift (down)

Just because a wing is not producing lift doesn't mean it is stalled.
When the wing loses the 'abillity' to produce lift, then it is stalled.

Wings will generate lift in any forward aircraft direction with a good
angle of attack, because all they act on is the parcel of air that
surrounds them at the time. In a straight up climp, forward stick
pressure may be needed to stop the plane looping over backwards. ie.
less lift force needed from the wing, because of engine thrust, so you
have to counteract it somehow.

> I know of one Russian prop stunt plane that had so much prop force that it
> could literally hover using its prop.  Not to mention that many fighter jets
> will not stall going straight up unless the throttle is low (for going
> straight up, less than 90% counts as low) but by that point, the wings are
> no longer causing any lift, and therefore are stalled, while the aircraft
> clearly continues to have lift, and is therefore not stalled.

I've seen Pip Borman do that at Tyabb airfield. Very very impressive,
but the planes weight is being conteracted by the propellor/jet thrust.
The wings are not stalled because they are in a static position and
obviously producing no lift. Can you consider a wing stalled while just
sitting on the tarmac.

My instructor has actually seen a plane lift off the ground purely from
wind gusts. Scared the bejeezes out of the pilot.

> The other guy (sorry forget the name and it's waaayyyy back in my PIC box)
> who was talking about all the different factors was, I think, talking more
> about when the aircraft would cease to gain lift at all.

> What I'm trying to say is that a wing can stall and the aircraft can
> continue on un-stalled (though if the aircraft is stalled, I think you're
> almost guaranteed to have all wings stalled).  It depends on all the factors
> originally mentioned.

Of course an aircraft can continue on if the wings are stalled, but
probably not where you want it to go, and will require a pilot with some
knowledge to recover lest he/she finds themself in an inadvertant spin.
A stalled wing is a departure or loss of control whether intentional or
not.

> If you've built a model jet fighter, and it can climb
> straight up, chances are that if you punch the throttle, you'll never stall
> the little beggar, though the wings may only be serving as fins at that
> point.

It will stop when it reaches full throttle height :-)

As I mentioned, in this case weight is counterbalanced by the engine
thrust. The wings are producing no vertical component of lift at all,
but they could be producing horizontal components of lift and as such
are still subject to stalling.

Interestingly, as you can see, more lift is required by a wing in
straight and level than in any climb.

I could be misunderstanding your reasoning, but you seem to be confusing
aircraft speed with stalling. Speed has nothing to do with stalling, and
I don't think you can say an aircraft has stalled just because the wings
are producing no lift or it has stopped mid air.


--
Best regards

Tony

mICros
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