"steve.t" wrote in message
oups.com...
The tail plane stall that all keep talking about, isn't it caused by
icing over a stablizer that is at or just below the plane of the wing?
Then when the flaps are deployed, the air is disturbed sufficiently
that the tail stalls?

Therefore, if flying a T tail (or similar), deployment of flaps should
not affect the tail. Is this correct?

I'm asking because of flying a Piper wherein the wing is actually below
the stabliator. Deployment of 15 degrees of flaps should not
sufficiently disturb the airflow to cause the tail plane stall in this
case. Is this correct?

Later,
Steve.T
PP ASEL/Instrument

ps. I'm almost at that 350hr mark some one else mentioned. T-storms,
fog and ice conditions are automatic no-go situations for me. Too much
at stake.


The tailplane stall, in the iceing case, is caused by leading edge
contamination by ice.
The scenerio goes something like this:
Leading edge ice causes less tail lift (or tail download ) to be available
at at particular elevator angle. To maintain trim the pilot flies with an
increased elevator angle. When flaps are selected the nose down pitching
moment (NOT TRIM CHANGE) is controlled by more elevator deflection. In the
iceing case this extra elevator deflection may cause the tailplane alpha to
exceed the stalling angle (with ice). Tail download is then much reduced
and the aircraft pitches nose down uncontrollably.
My experience with tailplane stall in a turboprop twin (during flight test)
is that the pitch down is sudden and dramatic - 0g or less, a height loss
of 1500 to 2500 ft, and usually overspeed gear and flaps. In this case the
elevator hinge moments reduced markedly and full aft stick could be easily
applied but with no effect. Recovery was rapid if the airflow re-attached
to the tailplane with full aft stick applied ie very easy to overstress the
aircraft.
Cheers,