A letter I sent to the Wings Channel

"Steve House"
wrote:

According to my textbooks that's not true. Maximum lift is just before the
stall. Once in the stalled condition itself, at or beyond the separation
point of the flow of air over the airfoil, lift is lost and "the airplane
ceases to fly." (From The Ground Up, Aviation Publishers, Ottawa, page 35
and Flight Training Manual, Transport Canada, page 75)

You completely misunderstand stall and your misunderstanding
is perpetuated by the complained-about programming. Maximum
lift is just before stall and just after stall the lift is
just about equal to that maximum. Understanding that lift
is produced during stall is essential to a proper
understanding of spins and aerobatic flight.

Of course not all
lift is gone - if you want to get picky about it, even a dropped brick has
SOME lift -

The lift remaining just after stall is almost the same as
the lift just prior to stall, and is still supporting almost
all of the aircraft's weight.

but what does remain is insufficient to support the weight of
the airplane

The one difference is that as AOA increases, lift decreases,
and since the aircraft is designed to increase AOA when the
wings are not producing enough lift, after stall, the plane
automatically produces less and less lift if the pilot
allows the pla ne to "do its thing" and increase AOA
further.

It is actually possible in some fully aerobatic high-powered
aircraft to supplement the small amount of missing lift from
a stalled wing with engine thrust. The plane can then be
flown with the wings fully stalled. I saw it demonstrated
last year. Similarly, some spin modes have both wings fully
stalled, and the descent rate is constant. Thus, the wings
are fully supporting the weight of the aircraft with the
lift produced when stalled.

and as you said in another message, the airplane is indeed
falling rather than flying. Thus "at the stall" would be the point at which
the wing stops producing (adequate) lift, just as he said.

Saying it produces less lift after stall is correct. Saying
it stops producing lift is not correct and is highly
misleading.


Todd Pattist
(Remove DONTSPAMME from address to email reply.)
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