My first freezing rain encounter

Steve,

Bob is correct, never, ever use flaps on landing if you have any ice on
the airplane, it does not matter a bit about the position of the
horizontal stabilizer. Flaps change the airflow in the area of the
tail and also move the center of lift aft, both of which increase the
angle of attack of the tail, moving it closer to the stalling angle of
attack should it have any ice at all.

You might want to go to NASA's website and find the information there
on icing and tailplane stalls; it's eyewatering. They also sell a DVD
of inflight footage of their testing. Also go to AVweb
(www.avweb.com), click on "columns" then on "The Pilot's Lounge" and
scroll down to the column on tailplane stalls. If you get IFR
Magazine, there is an article on dealing with inflight icing in the
November 2004 issue.

If in ice, leave the flaps up. Cessna POHs make this clear, I'm not
sure whether Piper POH's mention it. Touch down fast, and do NOT
reduce power at all until the wheels are rolling as the power reduction
may take you from flying at above the power on stall speed to
descending fast at below the power off stall speed.
All the best,
Rick

Rick,
I just checked my Cardinal POH and it does state leaving wing flaps
retracted.
I have few questions: for this particular case whether icing is
very mimimum (thin layer of clear ice) and the runway is relatively
short (3000') and there appeared no loss of any lift power, do you
think that I still should have used no flaps and no power reduction
until touch down?
Another question is with the cabin heat and defroster knobs? We left
both on full blast and the POH indicated the same thing but if we want
to melt the windshield ice quickly, shouldn't we close off the cabin
heat to divert all the heat to to the windshield area first?
Hai

AC 23.143-1, which deals with tailplane stalls due to icing, mentions tail
configuration as one of the considerations but does not distinguish between
T-tails and conventional tails in its advice to avoid flap extension if
icing is suspected. No free pass for T-tails or cruciform tails.

Bob Gardner

"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.

Thanks for the kind words, Hai. As is the case with all warnings about ice,
it is not the weight of the ice so much as the distortion of the airfoil due
to ice accretion. On final, chances are that the horizontal stab is going to
be tilted forward (leading edge down), improving the chances of ice
collection on the upper surface. Since the horizontal stab develops a
downward force, ice on the upper surface is the equivalent of ice on the
bottom of the wing's leading edge.

The problem with tailplane icing is twofold: First, you can't see it very
well and must assume the 3-to-1 ratio I mentioned before. Second, when the
tailplane stalls and the nose pitches down when flaps are extended, there is
no time to react. We had a commuter twin dive in from 600 feet over in
Eastern Washington a few years ago with no survivors.

The problem with icing, period, is that it is not predictable or repeatable.
Fly two airplanes through the same cloud at the same speed and the ice forms
will be different; fly the same airplane through the same conditions twice
and the ice forms will be different. The drawings of clear, mixed, and rime
ice in FAA publications don't even come close to reality. Scary stuff, to be
avoided at all costs.

Here is part of AS 23.143.1:

e. Ice Contaminated Tailplane Stall (ICTS). ICTS occurs due to airflow
separation on the lower surface of the tailplane that is caused by the
angle-of-attack of the horizontal tailplane being increased above the
reduced stall angle-of-attack that can result when even small quantities of
ice have formed on the tailplane leading edge. The increase in tailplane
angle-of-attack can result from airplane configuration (for example,
increased flap extension increasing the downwash angle or trim required for
the CG position) and/or flight conditions (for example, high approach speed
resulting in an increased flap downwash angle and reduced angle-of-attack,
gusts, maneuvering or engine power changes). ICTS is characterized by a
reduction or loss, sometimes sudden, of pitch control or stability while
operating in, or recently departing from, icing conditions. For airplanes
with longitudinal control systems that are not powered (reversible control
systems), the pressure differential between the upper and lower surfaces of
the stalled tailplane may result in a high elevator hinge moment, forcing
the elevator trailing edge down. This elevator hinge moment reversal can be
of sufficient magnitude to draw the control column forward with a level of
force that is beyond the combined efforts of the flightcrew to overcome. On
some airplanes, ICTS has been caused by a lateral flow component coming from
the vertical stabilizer, as may occur in sideslip conditions or due to a
gust with a lateral component. An evaluation should be made to determine if
this unsafe flight condition is likely to occur. Susceptible airplanes are
those having a near zero or negative stall margin with contamination. Flight
test procedures for determining susceptibility to ICTS are included in AC
23.143-1, "Ice Contaminated Tailplane Stall (ICTS)".


Bob Gardner



wrote in message
oups.com...
Bob,

Thank you very much for your tailplane stall explanation. We
attended a Wing Safety Seminar last November on Winter Operations where
it was mentioned but only in term of symptoms and recovery process. I
did not realize that there would be more chance of a tailplane stall
than wing stall due to heavier ice accumulation.

Before landing, I had discussed with my husband, Rick on whether I
should have landed with no flaps or with 10 degree flap. Since the
standard Cardinal takeoff procedure calls for 10 degree flap, we
thought it would provide more lift. We did not think of the possiblity
of tailplane stall. Although I had practiced landings with different
flap configurations every few months, I generally dislike the noflap
approach due to extremely nose high position. I hate not being able to
see a darn thing ahead while landing. The practices did come in handy
late last fall in our long cross country trip from New York to northern
Minnesota. Within an hour of flying, we had complete electrical
failuires due to a bad crimp job on one ot the alternator wires. We
have owned our plane for about 1 1/2 years and put over 200hrs on it.
It was our luck that we landed at Seaman airport and the folks at O&N
aviation (the home of the Silver Eagle) were open on Saturday. They
found the problem right away and get us going within few hours. The
owner did not write up a bill and told us just to give a tip to his
mechanics. Fantastic folks!. (Note to Jay: In our short flying
career, this was our first 'emergency' situation, the icing incidence
was the second. Luckily ;-) , I was the PIC in both cases and Rick
mainly offered assistance and did not insist on taking over. Just
wonder how you and Mary handle your flying responsibilities?).

On an aside note, for our instrument training, I bought at least
half a dozen books on the subject. Rick was ahead of me so he had
reviewed all of them. His main text book was your book, "The Complete
Advanced Pilot". He got 98 on his written and recommend me to start
right away with your book using others as supplemental readings. We
have also made good use of your "Say Again, Please" book. Thank you so
much for imparting your years of aviation skills, experiendce, wisdom
and insight to many next generations of pilots.
Best regards,
Hai Longworth

wrote in message oups.com...
Rick,
I just checked my Cardinal POH and it does state leaving wing flaps
retracted.
snip
Hai



Original Cardinals had problems with horizontal tail stall, thus the slot on the LE. I can only imagine landing one iced
up...

"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,

Geez, it's amazing how things become old wives tales. Only a small
number of the very first model 177s (original 1968 model year
airplanes) left the factory before it was noticed that with full flaps
and when slipping toward a landing the pilot could experience an
intermittent "tug" on the control wheel. It was traced to the airflow
over the stabilator in those conditions and the stabilator nearing the
stall angle of attack. It was decided to put the slots in the
stabilator to allow it to fly at a higher angle of attack. It solved
the problem. The ones in the field that didn't have them were modified
and all subsequent airplanes (rest of the 177s, all of the 177As and
177Bs) left the factory with the slots. It also resulted in removing
the recommendation against slips with full flaps from the Owner's
Manual.

Totally separate issue from tailplane stall in icing.
All the best,
Rick

Hai,

You've just defined the classic icing problem for general aviation
airplanes: the need to come down final fast, with flaps up, toward a
runway that isn't terribly long and may be contaminated. (Get the
November issue of IFR Magazine for a long discussion on it). On top of
things, you need to allow a little altitude over the threshold if there
is any snow in the area because the plow driver may have piled snow at
the end of the runway (which is not appropriate but sometimes happens).


Once you get any ice whatsoever on the airplane you become a test
pilot. At some point you will have enough that if you deploy the flaps
the tail will stall and the airplane will pitch down radically...as has
happened on a number of well-publicized commuter crashes. As a result,
you don't know what the wing and tail are doing, so the only safe
approach is to fly final fast, flaps up, with power (I owned a 117B
Cardinal for a while and would come down final at 90-100 knots, flaps
up, if I had ice). You don't know when the wing will stall, either.
On the times I had to land the airplane with ice, I set up so that I
would be in a position to see whether there is any snow pile at the end
of the runway, and then land as near the threshold as conditions
permit, flare slightly (at that speed with flaps up the airplane is
pitched up anyway, so you don't need to worry about landing on the
nosewheel) and put the wheels on the ground. Close the thottle
immediately on touchdown and gently start applying the brakes to see
what you've got. If the runway is contaminated, it's going to be
challenging to keep the airplane straight and get it stopped. In 3,000
feet you should be able to do so unless it's icy. The reality is that
you may go off the end of the runway. However, you have just been in a
classic emergency: the airplane is iced up and you were at risk of
loss of control while in the air at 90-110 knots; the impact from that
would probably be fatal. If the choice is a loss of control at 100
knots or sliding off the end of a runway at 20 knots, I'll take the low
speed impact every time. That's why we have insurance.

With ice, avoid setting up high on final; when you have an emergency
try to make everything else as normal as possible, so that you see a
sight picture that is consistent with what you are used to. The
problems I've seen include pilots who are high on final and don't touch
down in the first part of the runway and then try to go around with a
load of ice. It doesn't work. Set up for a normal approach, just
fast. In fact, practice some no flap landings so it's not a new
experience when you have to do it for real.

Yes, get the defroster going full blast. You may even want to block
off the copilot's defroster to put more on your side of the windshield.
Divert all cabin heat to the defroster if you can. In the Cardinal
you can also open the little window on your side at approach speed and
use it to help you see forward. Yes, the cold air and snow or rain
coming in won't be fun, but the idea is to see the runway.
All the best,
Rick

(Note to Jay: In our short flying
career, this was our first 'emergency' situation, the icing incidence
was the second. Luckily ;-) , I was the PIC in both cases and Rick
mainly offered assistance and did not insist on taking over. Just
wonder how you and Mary handle your flying responsibilities?).

We have discussed this issue at length, and we handle cockpit resource
management in the same way you do. Whoever is in the left seat is
pilot-in-command, and has absolute authority to make decisions. (This, of
course, doesn't stop us from offering advice or making snide remarks about
certain landings... :-)

The right seater is only allowed to take the controls in the event of an
emergency that threatens imminent danger. In Mary's 500 or so hours, I've
taken the controls just once from the right seat, and that was when a NORDO
Stinson tried to trade paint with us in the pattern. The plane was coming
in from behind Mary's left shoulder, in her blind spot, and breaking hard
right seemed the wise thing to do.

It was sheer luck that I spotted it at all. As the Stinson flew through the
spot we had just occupied, moments before, Mary didn't argue!

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Rick,
I was quite lucky to have a safe landing inspite of my complacency
and naivety. Since my windshield had became clear and there was no
apparent loss of lift, I assumed that I could almost land 'normally'.
I did have some concerns about not being to perform a go-around hence
the decision to drop 20 degree flap and reduced power after crossing
over the fence to make sure that I would not have landed long.

If I had realized the potential for tailplane stall and the
unpredictability of icing condition, I would have been more cautious
and woud have seeked out better options. I could have asked the tower
for a longer runway (rwy 24 with 5000'). The crosswind was quite mild
(only 6 or 7 knots! The Cardinal has no trouble handling 15-20 knots
xwinds). The other option is to fly to KSWF just across the river but
with 9600' runway.

The valuable advices that I received here from you, Bob and others
along with an email that I received today from FAA RON on Ice
contamination (quoted below) gave me a healthy respect for ice!

"Greetings, This is important info. NTSB Issues Warning on Wing Ice
As a result of its ongoing investigation of the Nov. 28, 2004 fatal
takeoff accident involving a Challenger 604 in Montrose, Colo., the
NTSB
on December 29 issued a special alert involving the detection and
effects of ice accumulation on the wing. "It has become apparent that
many
pilots do not recognize that minute amounts of ice adhering to a wing
can
result in severe control penalties," the Safety Board said. "Some
pilots believe that if they cannot see ice or frost on the wing from a
distance, or maybe through a cockpit or cabin window, it must not be
there-or if it is there and they cannot see it under those
circumstances, then
the accumulation must be too minute to be of any consequence."
Despite
evidence to the contrary, the NTSB emphasized, "These beliefs may
still
exist because many pilots have seen their aircraft operate with large
amounts of ice adhering to the leading edges and consider a thin layer
of ice or frost on the wing upper surface to be more benign."
However,
the Safety Board noted, "Research has shown that small amounts
of ice accumulation on the upper surface of a wing can result in
aerodynamic degradation as severe as that caused by much larger (and
more
visible) ice accumulations." Fine particles of frost or ice, the size
of a
grain of table salt and distributed as sparsely as one per square
centimeter over a wing's upper surface, can destroy enough lift to
prevent
an airplane from taking off, according to the agency. "The bottom
line
is that pilots should be aware that no amount of snow, ice or frost
accumulation on the wing upper surface can be considered safe for
takeoff."
..