Approaching Deep Stall

On Sep 6, 12:37 am, wrote:
On Wed, 05 Sep 2007 12:06:01 -0700, cjcampbell

wrote:
On Sep 5, 11:29 am, Fred the Red Shirt
wrote:
For a while I have been wondering why there seem to be no
airplanes with a low wing and a high tail.

Duchess and Seminole come to mind.

doesn't have to be a "high tail". ever heard of the Cheyenne II's
stability augmentation system? didn't really do a whole lot for
controllability, primarily made it feel like there was airflow over
the elevator when there wasn't much...

one has to be exploring the edges of the envelope, but other PA31's
are able to place the tail into "bad" air also.


This is the sort of Zodiac-like high tail I was thinking of:

http://www.icfn.net/bluesky/air1/N70...I%20(OFEK).jpg

and this is not:

http://www.dc3d.co.nz/tutorials/OFP/...enne.lllSm.GIF

Both are what I's call a "high" tail in the sense that the horizontal
stabilizer flies at a higher altitude than does the main wing, and
hence both would seem to have the same vulnerability to
deep stall.

--

FF

Fred the Red Shirt wrote:
On Sep 6, 12:37 am, wrote:
On Wed, 05 Sep 2007 12:06:01 -0700, cjcampbell

wrote:
On Sep 5, 11:29 am, Fred the Red Shirt
wrote:
For a while I have been wondering why there seem to be no
airplanes with a low wing and a high tail.

Duchess and Seminole come to mind.

doesn't have to be a "high tail". ever heard of the Cheyenne II's
stability augmentation system? didn't really do a whole lot for
controllability, primarily made it feel like there was airflow over
the elevator when there wasn't much...

one has to be exploring the edges of the envelope, but other PA31's
are able to place the tail into "bad" air also.


This is the sort of Zodiac-like high tail I was thinking of:

http://www.icfn.net/bluesky/air1/N70...%20PIPER%20PA-
31T%20CHEYENNE%20II%20(OFEK).jpg

and this is not:

http://www.dc3d.co.nz/tutorials/OFP/...enne.lllSm.GIF

Both are what I's call a "high" tail in the sense that the horizontal
stabilizer flies at a higher altitude than does the main wing, and
hence both would seem to have the same vulnerability to
deep stall.

FF

If that is your definition of "high" tail you don't have to leave the Zenith
line to find a low wing that fits that description take a close look at the
601XL. Not as high as the 701 but the bottom of the horz. stabilizer is
higher than the top of the wing.

On Sep 5, 11:29 am, Fred the Red Shirt
wrote:
For a while I have been wondering why there seem to be no
airplanes with a low wing and a high tail.

Tomahawk.

"Fred the Red Shirt" wrote:

For a while I have been wondering why there seem to be no
airplanes with a low wing and a high tail.

http://tinyurl.com/2oefh6

In article .com,
says...
For a while I have been wondering why there seem to be no
airplanes with a low wing and a high tail. Say for instance
with a fuselage and epenage like the Zodiac 701, but with
a low wing instead of the high wing. Then I read about deep
stall, as illustrated he

http://www.answers.com/topic/deep-stall-png

Here deep stall is defined as a condition in which the
main wing is stalled and the stabilizer is enveloped
in the turbulent wake of the stalled wing so that
the pilot has lost pitch control and thus cannot lower
the nose to recover. For certain airframe geometries,
(such as the illustration above) that condition can
occur even if the aircraft is within the proper CG limits.

My question regards the orientation that immediately
precedes the deep stall. If the angle of attack at stall
is exactly the same as the angle that puts the stabilizer
in the shadow of the wing, that will precipitate a deep
stall, right?

What if the wing stalls at a lower AOA? Would the
stabilizer then drop into the wake?

ISTM that if the AOA that stalls the wing is higher than
the AOA that puts the stabilizer in the wake of the wing
then that aircraft is immune to this sort of deep stall,
so long as it is flying within the CG limits, right?

Only Robert's mentioned the Traumahawk - which surely remains one of the
most popular/common training aircraft today.

I did all my ab-initio training in a Tomahawk, it's a great plane to
learn stalls and spins in, with it's sharp wing drop characteristics.

I went out one day and learnt to recover from spins under the hood - my
instructor told me my recovery atitudes were fairly radicle (pointing
almost straight up), but that I had read enough into the lag to nose
over and recover to straight and level (before stalling and possibly
spinning again). I had a lot of fun and my instructor got some laughs
out of it.

He tried some very dissorientating manuevoures that I was to recover
from, the worst was using a partial panel (no AH) going into a half
roll, and letting me recover from upside down (I had no sensation of the
attitude I was in). I am pleased to report that my intructor never had
to take control of the a/c - eg. I never wound the airspeed to redline.

Anyway, back on topic, I've never noted any significant blanketing
effect in the Tomahawk in any flight condition.

Maybe I'm re-opening a can of worms, but I've also never noted any
blanketing effect (again of significance, which is important I think) in
a C-172 on the elevator when sideslipping. My instructor(s) have never
let me sideslip the C-172, but I've done it myself to see the effect
above 4,000' AGL - and I can't make it happen at any airspeed.

--
Duncan

On Sep 5, 6:42 pm, Dave Doe wrote:
In article .com,
says...





For a while I have been wondering why there seem to be no
airplanes with a low wing and a high tail. Say for instance
with a fuselage and epenage like the Zodiac 701, but with
a low wing instead of the high wing. Then I read about deep
stall, as illustrated he

http://www.answers.com/topic/deep-stall-png

Here deep stall is defined as a condition in which the
main wing is stalled and the stabilizer is enveloped
in the turbulent wake of the stalled wing so that
the pilot has lost pitch control and thus cannot lower
the nose to recover. For certain airframe geometries,
(such as the illustration above) that condition can
occur even if the aircraft is within the proper CG limits.

My question regards the orientation that immediately
precedes the deep stall. If the angle of attack at stall
is exactly the same as the angle that puts the stabilizer
in the shadow of the wing, that will precipitate a deep
stall, right?

What if the wing stalls at a lower AOA? Would the
stabilizer then drop into the wake?

ISTM that if the AOA that stalls the wing is higher than
the AOA that puts the stabilizer in the wake of the wing
then that aircraft is immune to this sort of deep stall,
so long as it is flying within the CG limits, right?

Only Robert's mentioned the Traumahawk - which surely remains one of the
most popular/common training aircraft today.

I did all my ab-initio training in a Tomahawk, it's a great plane to
learn stalls and spins in, with it's sharp wing drop characteristics.

I've provided primary training in the Tomahawk and never found any
disturbing charactersitics. Stalls were nice and straight ahead thanks
to an AD that mandated stall strips be added. Sadly I could never spin
it because the owner wouldn't allow it but I have a friend who owns
one and he spins it all the time. However, we're both a bit "gurthy"
so I can't ride along while he does the spins.

-Robert, CFII

Fred the Red Shirt wrote:


Here deep stall is defined as a condition in which the
main wing is stalled and the stabilizer is enveloped
in the turbulent wake of the stalled wing so that
the pilot has lost pitch control and thus cannot lower
the nose to recover. For certain airframe geometries,
(such as the illustration above) that condition can
occur even if the aircraft is within the proper CG limits.



Err, that's not how I see it,

The aircraft can/will still pitch down after stall for 2 reasons: First,
the center of wing lift moves aft once the wing is stalled which will
drop the nose. Second, the tail is pushing the nose up to increase angle
of attack so that once blanketed the nose drops.

As far as I understand it, all certificated aircraft must be able to
recover from a basic stall.

My 2c

Cheers

DR wrote:
Fred the Red Shirt wrote:


Here deep stall is defined as a condition in which the
main wing is stalled and the stabilizer is enveloped
in the turbulent wake of the stalled wing so that
the pilot has lost pitch control and thus cannot lower
the nose to recover. For certain airframe geometries,
(such as the illustration above) that condition can
occur even if the aircraft is within the proper CG limits.



Err, that's not how I see it,

The aircraft can/will still pitch down after stall for 2 reasons: First,
the center of wing lift moves aft once the wing is stalled which will
drop the nose. Second, the tail is pushing the nose up to increase angle
of attack so that once blanketed the nose drops.

As far as I understand it, all certificated aircraft must be able to
recover from a basic stall.

My 2c

Cheers
Not so for the F16. Deep stall is an issue for the Viper at specific
angles of attack and cg configurations, especially if the airplane is
out of fuel balance. The result of deep stall in the Viper is a flat
extremely fast ROD either with occiliation or without.
The ONLY way to break deep stall in the Viper is to INCREASE the aoa,
then quickly input forward stick to induce a high nose rate down through
the deep stall region into a recovery.
Make no mistake, if the aoa is not increased before this fast nose down
pitch rate, the Viper will stay in deep stall and can be completely
unrecoverable.
There is no "automatic" nose down pitch rate in deep stall in the F16.


--
Dudley Henriques

Not so for the F16. Deep stall is an issue for the Viper at specific
angles of attack and cg configurations, especially if the airplane is
out of fuel balance. The result of deep stall in the Viper is a flat
extremely fast ROD either with occiliation or without.
The ONLY way to break deep stall in the Viper is to INCREASE the aoa,
then quickly input forward stick to induce a high nose rate down through
the deep stall region into a recovery.
Make no mistake, if the aoa is not increased before this fast nose down
pitch rate, the Viper will stay in deep stall and can be completely
unrecoverable.
There is no "automatic" nose down pitch rate in deep stall in the F16.

Your Aeronautical point is valid, but for most of us flying spam cans,
wing loadings alone dictate that the Aerodynamic forces on the
aircraft will overpower the aircrafts momentum to eventually break
free of a deep stall, as long as the aircraft is designed such that
the cL always remains behind the cG.

EridanMan wrote:
Not so for the F16. Deep stall is an issue for the Viper at specific
angles of attack and cg configurations, especially if the airplane is
out of fuel balance. The result of deep stall in the Viper is a flat
extremely fast ROD either with occiliation or without.
The ONLY way to break deep stall in the Viper is to INCREASE the aoa,
then quickly input forward stick to induce a high nose rate down through
the deep stall region into a recovery.
Make no mistake, if the aoa is not increased before this fast nose down
pitch rate, the Viper will stay in deep stall and can be completely
unrecoverable.
There is no "automatic" nose down pitch rate in deep stall in the F16.

Your Aeronautical point is valid, but for most of us flying spam cans,
wing loadings alone dictate that the Aerodynamic forces on the
aircraft will overpower the aircrafts momentum to eventually break
free of a deep stall, as long as the aircraft is designed such that
the cL always remains behind the cG.

My comment was in response to a general statement that deep stall
results in a nose down pitch moment. This is not always the case.
Notice as well that the Viper is NOT a T tail aircraft.

--
Dudley Henriques