Buffalo Q400 crash

In article
,
xyzzy wrote:

The way you recognize a tail stall is that pitch control becomes
abnormal when flaps are extended. Plus knowing that you're in icing
conditions.

This still sounds like a total crapshoot to me. You can lose pitch
control during a regular stall, and icing can precipitate a regular
stall as well. Obviously in this case the signs were interpreted
incorrectly. Surely it's not a case of "heads we live, tails we die"?
There must be some way to tell which kind of stall is happening besides
these indications which clearly weren't correct in this case, isn't
there?

I guess there doesn't *have* to be, but it's kind of scary if there
isn't.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

Mike Ash wrote:

xyzzy wrote:

The way you recognize a tail stall is that pitch control becomes
abnormal when flaps are extended. Plus knowing that you're in icing
conditions.

This still sounds like a total crapshoot to me. You can lose pitch
control during a regular stall, and icing can precipitate a regular
stall as well. Obviously in this case the signs were interpreted
incorrectly. Surely it's not a case of "heads we live, tails we die"?
There must be some way to tell which kind of stall is happening besides
these indications which clearly weren't correct in this case, isn't
there?

I guess there doesn't *have* to be, but it's kind of scary if there
isn't.

When the flaps are extended, and a tailplane stall results, the aircraft
immediately pitches down. There is no stall warning or stick shaker
activation.

In the case of the Buffalo accident, the nose did not drop, but the stick
shaker activated shortly after the flap setting was made. The stick
shaker is fired by low air speed, and is only a warning of impending wing
stall, with some airspeed margin. It is not an indication of tailplane
stall, or of an actual wing stall. Therefore, the correct action when
the stick shaker fired should have been to push the nose down to keep
speed up and reduce AOA. No question.

Further, the Q400 supposedly will never see a tailplane stall in icing,
but the crew may not have known that. The Saabs the captain previously
flew are subject to tailplane stall in icing, and he might have reacted
based on his previous training and apprehension about such stalls.

In article ,
James Robinson wrote:

When the flaps are extended, and a tailplane stall results, the aircraft
immediately pitches down. There is no stall warning or stick shaker
activation.

In the case of the Buffalo accident, the nose did not drop, but the stick
shaker activated shortly after the flap setting was made. The stick
shaker is fired by low air speed, and is only a warning of impending wing
stall, with some airspeed margin. It is not an indication of tailplane
stall, or of an actual wing stall. Therefore, the correct action when
the stick shaker fired should have been to push the nose down to keep
speed up and reduce AOA. No question.

Further, the Q400 supposedly will never see a tailplane stall in icing,
but the crew may not have known that. The Saabs the captain previously
flew are subject to tailplane stall in icing, and he might have reacted
based on his previous training and apprehension about such stalls.

Ah hah, that makes sense. Given that the stick shaker had activated,
they should have known it was a regular stall and performed a regular
recovery. A tail stall would have happened abruptly with no stick
shaker. Is that about right? Makes sense if so.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

Mike Ash wrote:
Ah hah, that makes sense. Given that the stick shaker had activated,
they should have known it was a regular stall and performed a regular
recovery. A tail stall would have happened abruptly with no stick
shaker. Is that about right? Makes sense if so.

The thing though, at least according to the FAA video on tail stall thing
(it's on video.google.com, search for 'Tailplane Icing') it seems that
tail stall also manifests itself by odd pitch feedback on the yoke... I am
really wondering if there is any clear cut way to identify tailplane stall
from main wing stall as easily as you make it sound...

--Sylvain

In article ,
Sylvain wrote:

Mike Ash wrote:
Ah hah, that makes sense. Given that the stick shaker had activated,
they should have known it was a regular stall and performed a regular
recovery. A tail stall would have happened abruptly with no stick
shaker. Is that about right? Makes sense if so.

The thing though, at least according to the FAA video on tail stall thing
(it's on video.google.com, search for 'Tailplane Icing') it seems that
tail stall also manifests itself by odd pitch feedback on the yoke... I am
really wondering if there is any clear cut way to identify tailplane stall
from main wing stall as easily as you make it sound...

Well, I was just summarizing what I was replying to, to see if I had got
it correct.

In any case, it seems that, if there is not a clear-cut way to
distinguish between the two types of stalls, some way needs to be
created or else these aircraft are too dangerous. (Either that or it
needs to be made impossible to stall them at all.)

Maybe this is just my small aircraft experience misinforming me, and
stalls are rare enough that the potential for a screwup when they happen
is not something to be excessively worried about?

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

Mike Ash wrote:

James Robinson wrote:

When the flaps are extended, and a tailplane stall results, the
aircraft immediately pitches down. There is no stall warning or
stick shaker activation.

In the case of the Buffalo accident, the nose did not drop, but the
stick shaker activated shortly after the flap setting was made. The
stick shaker is fired by low air speed, and is only a warning of
impending wing stall, with some airspeed margin. It is not an
indication of tailplane stall, or of an actual wing stall.
Therefore, the correct action when the stick shaker fired should have
been to push the nose down to keep speed up and reduce AOA. No
question.

Further, the Q400 supposedly will never see a tailplane stall in
icing, but the crew may not have known that. The Saabs the captain
previously flew are subject to tailplane stall in icing, and he might
have reacted based on his previous training and apprehension about
such stalls.

Ah hah, that makes sense. Given that the stick shaker had activated,
they should have known it was a regular stall and performed a regular
recovery. A tail stall would have happened abruptly with no stick
shaker. Is that about right? Makes sense if so.

The FDR data shows the following happening in quick sequence:

- Ice warning showing up on display for first time
- Flap handle setting increased
- Stick shaker activated

The flaps had only extended about 1 or 2 degrees when the stick shaker
fired, but was the crew somehow influenced by the ice warning and the
fact that the flaps setting had just been changed? They certainly took
the wrong action in response to the stick shaker. Why?

On May 15, 7:37*am, Mike Ash wrote:
In article
,

*xyzzy wrote:
The way you recognize a tail stall is that pitch control becomes
abnormal when flaps are extended. *Plus knowing that you're in icing
conditions.

This still sounds like a total crapshoot to me. You can lose pitch
control during a regular stall, and icing can precipitate a regular
stall as well. Obviously in this case the signs were interpreted
incorrectly. Surely it's not a case of "heads we live, tails we die"?
There must be some way to tell which kind of stall is happening besides
these indications which clearly weren't correct in this case, isn't
there?

I guess there doesn't *have* to be, but it's kind of scary if there
isn't.

yes, another reason why it's best for guys like you and me to stay out
of icing conditions. You have to be pretty skilled and experienced
and know what you're doing, which is what we expect from ATP pilots.

As others have said, you can distinguish the difference if you really
know what you're doing, but better not to take that chance if you can
avoid it (which us PPL's, without the pressures of airline scheduling,
can do).