On Feb 20, 9:15*am, jcarlyle wrote:
Bumper, Toad - thanks. Sorry for my confusion about pitch direction -
you're right, it would pitch down. The recovery with a tail stall,
though, is to pull back on the stick, not push forward. That's why I'm
worried about differentiating a tail stall from a wing stall.

Bill, please see comments embedded in your reply.

Why would the recovery be different? *The tail is an inverted wing
producing a down force. *You stall it by pulling back on the stick
increasing its AOA until it stalls. *Releasing the back pressure
initiates a recovery - same as a wing stall.

According to the videos, if the tail stalls you need to recover by
pulling back on the stick, not pushing forward on the stick as we
usually do.

It doesn't really matter. *With many trainers, the buffet students are
taught to recognize as wing stall is, in fact, tail stall with a
little bit of turbulence from wing root flow separation thrown in.
Allowing the tail to stall limits up elevator authority so the wing
can never get into a full stall. *Cessna 152's and SGS 2-33's are
examples.

What? I would love to see you provide evidence to back this up. The
buffet is primarily caused by the wing stalling (i.e. causing airflow
separation) near the root of the wing, and the ugly airflow from this
striking the aft fuselage and tail as it goes by.

A tail is an upside-down wing in a conventional aircraft (canard
aircraft are the exception) - therefore raising the angle of attack of
the wing *decreases* the angle of attack of the tail.

NOTE: There is a difference between a tail stall and an aircraft who's
tail is sized and limited in elevator travel to prevent the pilot from
really getting a good full stall with a break. My DG-300 is an
example of this - I can get a stall break if I perform an accelerated
stall; but if I start in slow flight and gradually increase the stick
pressure, the aircraft doesn't exhibit a true "stall break" - it just
buffets a lot and develops a good rate of descent.

There's a simple test for this. *With the stick full back and the
glider exhibiting pre-stall buffet, apply aileron and if the glider
responds normally in roll, the wing wasn't stalled. *If the wing was
stalled, the glider would probably try to spin with the application of
aileron.

Uhhh, no not necessarily. You are ignoring the effects of wing taper,
twist, and span-wise distribution of lift. Wings can (and ARE)
designed to stall near the wing root first, and then progress outward
along the span. So you can get "stall buffet" and still have aileron
control because the outboard parts ofthe wings are not stalled (they
are flying at a lower effective angle of attack and therefore still
have clean airflow over part or all of the wing chord). It has
nothing to do with the tail stalling!

Oh, and before you do that test, please remember that applying aileron
input will make one of the ailerons move _down_ - thus increasing the
angle of attack on that part of the wing. If you've got a partially-
stalled wing and you increase the angle of attack on the outboard
(unstalled) part of it, you may stall the whole wing. Meanwhile, you
are _decreasing_ the angle of attack on the wing that has the aileron
deployed upwards. Thus that wing will likely _not_ completely stall.
Everyone knows what happens when one wing stalls and the other doesn't
completely stall, right? Spin time! This is why we teach people not
to use much (or any) aileron input when feeling the pre-stall buffet.
Again, this has nothing to do with the tail stalling.

--Noel