"B S D Chapman" mail-at-benchapman-dot-co-dot-uk wrote in message
news
On Thu, 12 May 2005 23:39:29 +0100, Dudley Henriques .net
dhenriques@noware wrote:

Any airplane built in the normal/utility category will need pro spin
controls applied at stall to enter a spin.


I think "WILL NEED" is a very misleading and bland statement!

If you have a fuel imbalance, are flying out of balance, or have ailerons
(reasonably) displaced, one wing WILL stall before the other, you will get
undemanded roll, and that is a sign of the incipient spin. Do nothing
about it, and the full spin may develop before the other wing gets round
to stalling.

I've never seen a 150 or 152 or the Bat even come close to the scenario you
are describing. The 150 for example has 13 gals of gas in each tank feeding
through gravity and a simple on/off selector. Even with a fuel imbalance,
with two gravity feeding tanks and an on /off selector working a maxium of
13gals of gas in each tank, you would need one hell of a lot more fuel
imbalance than a 150 is capable of producing to cause a yaw/roll couple at
stall :-)
Secondly, as you have correctly said, aileron held in at stall will indeed
drop a wing, and the low descending wing will develop a higher angle of
attack than the outside wing. this is a nose low condition, but unless FULL
BACK ELEVATOR is held through this process, the stall will break and the
airplane will recover nose low without spinning.
All this amounts to is that, if at stall you have a wing low break caused by
any of the conditions you have mentioned , unless pro spin controls are
applied while this process is taking place, these airplanes will recover
nose low. Also naturally, if pro spin controls are applied at stall, by the
pilot, or by any combination of out of rig conditions, an incipient spin can
easily be introduced.
Basically what I said stands. Unless pro spin controls are applied at stall,
the Cessna 150 and 152 series including the Bat won't spin. You can make
them break wing down by the factors you have mentioned, but without that
needed coupling in roll and yaw , (autorotation) all you will get is a nose
low recovery as that back elevator (pro spin) is released. Notice I haven't
stressed elevator here. Without full elevator you break the stall as the
angle of attack decreases below Climax regardless of a wing drop. No
stall......no spin......no back elevator....no stall!
You can stretch the out of rig thing and the fuel imbalance thing into a pro
spin environment of course, but in a Cessna 150, these factors won't
override the lack of pro spin controls being needed as present to produce
spin.
One of the exercises we used to teach our primary aerobatic students in the
Aerobat was a max deflect cross controlled accelerated stall below Va. The
recovery was simply to release the back pressure and nutralize the ailerons.
Nose low recovery every time. Normal recovery with power to level flight
with NO SPIN!!
We never even came close to spinning the airplane in these conditions.

Dudley Henriques