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Tail Stall


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#1 sflower

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Posted 05 February 2008 - 08:41 PM

Can anyone please explain what exactly "tail stall" or "tail bump" is and how serious is it? Thanks in advance. In case you're wondering what type of aircraft, Lear 36.
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Scott Flower
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#2 Jwade

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Posted 05 February 2008 - 10:32 PM

Can anyone please explain what exactly "tail stall" or "tail bump" is and how serious is it? Thanks in advance. In case you're wondering what type of aircraft, Lear 36.



Scott,

Here you go..

What Is a Tail Stall?

The horizontal stabilizer balances the tendency of the
nose to pitch down by generating downward lift on the
tail of the aircraft. When the tail stalls, this downward
force is lessened or removed, and the nose of the air-
plane can severely pitch down. Because the tail has a
smaller leading edge radius and chord length than the
wings, it can collect proportionately two to three times
more ice than the wings and, often, the ice accumula-
tion is not seen by the pilot!

You are likely experiencing a tail stall if:

When flaps are extended to any setting, the pitch
control forces become abnormal or erratic.

There is buffet in the control column (not the
airframe).

Recovery from a tail stall is exactly opposite the tradi-
tionally taught wing stall recovery. Remember, in a tail
stall recovery air flow must be restored to the tail's
the shortest route through the front instead of flying
the length of the front.

Structural Ice
How quickly a surface collects ice depends in part
on its shape. Thin, modern wings will be more criti-
cal with ice on them than thick, older wing sections.
The tail surfaces of an airplane will normally ice up
much faster than the wing. If the tail stalls due to ice
and the airflow disruption it causes, recovery is
unlikely at low altitudes. Several air carrier aircraft
have been lost due to tail stalls. It also happens to
light aircraft but usually isn't well documented.
Since tail stall is less familiar to many pilots, it is
emphasized in this advisor, but wing stall is the
much more common threat, and it is very important
to correctly distinguish between the two, since the
required actions are roughly opposite.

Wing Stall

The wing will ordinarily stall at a lower angle of
attack, and thus a higher airspeed, when contaminat-
ed with ice. Even small amounts of ice will have an
effect, and if the ice is rough, it can be a large effect.
Thus an increase in approach speed is advisable if
ice remains on the wings. How much of an increase
depends on both the aircraft type and amount of ice.
Consult your AFM or POH.
Stall characteristics of an aircraft with ice-contami-
nated wings will be degraded, and serious roll con-
trol problems are not unusual. The ice accretion
may be asymmetric between the two wings. Also,
the outer part of a wing, which is ordinarily thinner
and thus a better collector of ice, may stall first
rather than last.

Effects of Icing on Roll Control

Ice on the wings forward of the ailerons can affect roll
control. Wings on GA aircraft are designed so that
stall starts near the root of the wing and progresses
outward, so the stall does not interfere with roll con-
trol of the ailerons. However, the tips are usually thin-
ner than the rest of the wing, so they are the part of
the wing that most efficiently collects ice. This can
lead to a partial stall of the wings at the tips, which
can affect the ailerons and thus roll control.

Tail stalls loss of lift from horizontal tail
Icing
Normal forces no ice
lower airfoil surface, and in a wing stall recovery air
flow must be restored to the wing's upper airfoil
surface.

Here is how to recover from a tail stall:

Immediately raise flaps to the previous setting.
Pull aft on the yoke. Copilot assistance may be
required.
Reduce power if altitude permits; otherwise
maintain power.
Do not increase airspeed unless it is necessary to
avoid a wing stall.


TRANSLATION = Potentially VERY BAD ( Read : DEATH ) if corrective action is not taken immediately to exit icing conditions........You can find quite a few NTSB reports on this condition....

Hope this helps...

JW
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John Wade MBA, CCEMT-P, FP-C, RN

"Have the courage to follow your heart and intuition, they somehow already know what you truly want to become" Steve Jobs

#3 Macgyver

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Posted 06 February 2008 - 05:05 AM

TRANSLATION = Potentially VERY BAD ( Read : DEATH ) if corrective action is not taken immediately to exit icing conditions........You can find quite a few NTSB reports on this condition....

Hope this helps...

JW


Yampa Valley at about this time the year before last comes to mind,

http://www.ntsb.gov/...2...00064&key=1 Probable Cause (non PDF format)
http://www.ntsb.gov/...N05FA051&rpt=fi Probable Cause (PDF)
http://www.ntsb.gov/...N05FA051&rpt=fa Final Report
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Ken BHSc, RN, REMT-P

#4 skysix

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Posted 06 February 2008 - 05:24 AM

Yampa Valley at about this time the year before last comes to mind,

http://www.ntsb.gov/...2...00064&key=1 Probable Cause (non PDF format)
http://www.ntsb.gov/...N05FA051&rpt=fi Probable Cause (PDF)
http://www.ntsb.gov/...N05FA051&rpt=fa Final Report


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#5 skysix

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Posted 06 February 2008 - 05:26 AM

oops

Also check out the BCAS near miss from 2005,
http://www.tsb.gc.ca...18/a05p0018.pdf
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