At 07:54 AM 30/03/06, you wrote:
Mike Borgelt wrote:
Anyway, read the article. It is made quite clear that fore and aft
stick position is all there is to it.
I've often been a bit surprised at the reactions I get from onlookers
when I tell trainees that the stick is essentially an angle-of-attack
control, and that fixed stick positions result in fixed angles of attack.
I'd have thought it was obvious, but perhaps the necessary connections
haven't been made in the minds of all pilots.
- mark
[ yes, I'm dredging up old threads - haven't read aus-soaring for
a while :-) ]
Mark,
You must be one of the few who do this. Ask around "what does the
elevator do?" and you will likely get "controls the pitch". I got
this from two very experienced contest pilots recently You will even
get it from aero engineers who are pilots until they think about it
and then they say "controls the angle of attack". Aero engineers all
know this but most seem to forget it when they learn to fly.
The necessary connections aren't made in the minds of most pilots
because they are not taught this.
The logical corollary is this: Aircraft stall because the pilot
commands an angle of attack greater than the stalling angle by
pulling the stick back to that position.
This is slightly complicated by that position varying with center of
gravity position. As the Cof G is moved aft due to loading of the
aircraft the stick position required to stall moves forward because
a) the reduced static stability means you need less stick movement
for a given angle of attack change and b) the more rearward C of G
means the horizontal stabiliser needs to provide less nose up pitching moment.
So lets get it straght for once and all - aircraft stall because the
pilots make them stall.
Gusts, entering thermals etc may cause momentary stalls but unless
the pilot commands an increased angle of attack by pulling the stick
back the aircraft will recover.
Anyone who has ever owned a free flight model glider will know that
even when grossly upset by entering a thermal the aircraft recovers
on its own. I've never seen one spin.
I think it is possible that most flight training for nearly 100 years
has been sadly incomplete.
Much of flight training emphasises trimming the elevator and stick
*forces*. When it comes to stalling it is stick *position* that matters.
Unless you know the above all the spin/spin recovery training is
essentially worthless.
If you know it you can avoid unintentionally stalling and even if you
do, recover instantly. I suspect even if pilots don't know the above
that there are two classes - those who are subconciously aware of
stick position and those who rely on stick force(which varies
depending on the trim position).
The only exceptions I can think of involve launch cases where
external forces are applied to the glider by the cable.
Off topic sort of :
For those who still think spinning/recovery is entirely predictable
read Bob Grimstead's story in the latest "Australian Aviation"
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
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