bod43 wrote:

James Robinson wrote:

Jessica wrote:

James Robinson wrote:

wrote:

Standard practice is to wait until you have a positive rate of
climb before raising the flaps. *Raising the flaps if the
airplane was on the verge of a stall would be a big mistake.
*Lowering the nose and applying full power would be the best
course of action, and once a positive rate of climb could be
achieved, then the flaps could be raised.

There is some debate about that. *For a wing stall, you are
correct, however, some have pointed out that the PIC's experience
was recently on Saabs, which can see tail stalls in icing
conditions - the Q400 isn't subject to tail stalls. *A tail stall
is most often first seen when the flaps are extended, and the
effect is for the nose to drop. The reaction to a tail stall is to
retract the flaps, and pull the nose up. *Was that what the
captain was reacting to?

Perhaps, but even that doesn't make sense either. *The airplane
stall warning system/ stick shaker was activating. *This would only
indicate a stall condition is imminent for the wing. *The stall
warning system does not indicate anything about the tail, so the
only corrective measure to take for a stick shaker would be a
conventional wing stall recovery, such as full available power,
prop forward, pitch down, don't bring up the flaps until a positive
rate of climb is achieved.

The question is what to do when everything happens at the same time?
That is, after the flap setting is increased, the stick shaker
stall warning fires, and the nose pitches down. What would you do
then? *The stick shaker is only an indication of an impending stall,
and there are probably a few MPH margin left, but the increased flap
setting might have started a tailplane stall, on aircraft that have
that tendency.

Immediately retracting the flaps might be the best course, along with
either level flight with increased power or slightly pushing the nose
down to keep the speed up. Pulling on the control column likely
wouldn't be a good idea, unless the pitch down was extreme. I don't
know.

I'm not familiar with the specific stall recovery for that type,
but you get the idea. *If the pilot pushed the stick over to
recover from a non-existent tail stall, that was a bad move. *I
haven't seen anything to suggest that happened however.

The FDR shows moderate backpressure (20 lb, 40 lbs total) momentarily
applied to the control columns on both sides in response to the stick
shaker.

If memory serves me correctly, from my reading of NTSB material
the two control column force
transducers are *not* representative of the forces on the
two pilots' control columns.

There are two force sensors but I interpreted the explanation
to mean that it cannot be determined how much force each pilot
was applying.

http://www.ntsb.gov/Dockets/Aviation...027/417236.pdf
3.5.4. Control Column Forces
"With the system operating normally (for example,
disconnect not pulled), there is no way to determine
if pilot, copilot or both are flying."

There is more in the original doc. Quite complex and hard to
follow.

Thanks for pointing that out. I hadn't read it before, and it goes a
long way to explaining how the sensors work. It helps to read the
instructions.

You are correct that the system doesn't separate the forces on each
side, and the recorder only shows that somebody (or both) pulled back on
the control column(s) when the stick shaker intially fired. The pull
totaled about 40 lbs. A reasonable assumption is that the PF did the
deed alone.

The force applied by the PF relaxed as the aircraft pitched up, but when
the stick pusher activated, the backpressure on the column was reapplied,
even though the aircraft was pitched up by 30 degrees. The PF more or
less maintained the force against the stick pusher until impact.

Remember that while all of this is going on, the aircraft is wildly
rolling left and right.