Yesterday's IFR flight with questions

Peter R. wrote:
" wrote:

a big post-it note on your flap switch or handle saying
"DON'T TOUCH" (flaps can cause a tail stall if you've encountered ice),

Is that true in a low wing?

I don't remember the NASA icing video making a distinction. Are you
thinking of the Cessna slips-with-flaps permathread? I think that's
unrelated.


All the best,


David

" wrote:

A Lieberman wrote:

I'm going to answer these before I read the other replies, to avoid
prejudicing my own answers. Apologies for any duplication.

Question 1 on Sleet. In my case, it was 43 on the ground, and on my climb
to my altitude, the temperature remained well above 32 while I was in IMC.
I climbed to 6000 which was my designated altitude. I broke out at 5,500.
How far up can sleet be created and not melt before hitting the ground?
There was a layer of clouds above me. Seems that from the ground to 6000
feet, I came across some hardy sleet pellets to survive that long in above
freezing temperatures?

I fly some IMC in winter here in central Canada and the NE US in my
Warrior, and do occasionally encounter ice at altitude. Still, I would
not take off if I saw sleet or ice pellets, period. I probably
wouldn't even try it in a twin with boots, due to the risk of severe
clear.

Question 2 on icing. Had I not climbed up like I did, I would have never
seen the ice on the wings or stabilator. I now know to look on that
temperature probe for first signs of icing as I did today, but will it
readily show up in IMC without reflections of the sun?

Clear icing will show up easily on the probe, even at night, because it
changes the shape of the tip. Rime icing, maybe less so.

Figuring on 500 feet per minute
descent, for me, 1500 feet is rather thick for 3 minutes.

You might not want to descend that slowly through an icing layer. I
don't think there's any reliable measure for how slowly or fast you can
ice up -- I haven't had this happen to me, but I know people who've had
the windscreen ice over almost instantly, as if someone threw a bucket
of paint on it. You have to be prepared to land in a slip, looking out
the storm window, if your defrost cannot clear it.

If you're going to have to descend through a possible icing layer, set
up everything in your favour beforehand: carb heat on, pitot heat on,
defroster on, a big post-it note on your flap switch or handle saying
"DON'T TOUCH" (flaps can cause a tail stall if you've encountered ice),
and a fairly steep approach slope. Try to keep the throttle as far
open as you can and don't slow down too much. Oh, did I mention?
Don't touch the flaps.

All the best,

David

I wonder, if you had enough altitude after breaking out below, would it be
advisable to perform a gentle power-off stall to find out what your new stall
speed is with the ice? Or would the new stall characteristics be so
unpredictable as to make the aircraft unstable?

-Nick

Nick Kliewer wrote:
I wonder, if you had enough altitude after breaking out below, would it be
advisable to perform a gentle power-off stall to find out what your new stall
speed is with the ice? Or would the new stall characteristics be so
unpredictable as to make the aircraft unstable?


There's no way in hell I'd do that. Take a lesson from the last time I flew in
such heavy rain that the airspeed indicator became grossly inaccurate: slow
down to your usual speed paying particular attention as it decelerates. If it
starts feeling sloppy, you need more power. If you don't have enough power, you
were going to crash anyway.

Think of the last time you did slow flight... you remember how it just slopped
along? That's bad. Tight controls; that's good. Feel for the ground after
arriving with normally tight controls... perfect.



--
Mortimer Schnerd, RN

VE

" wrote:

I don't remember the NASA icing video making a distinction. Are you
thinking of the Cessna slips-with-flaps permathread?
snip

No. I can visualize how flaps will disturb airflow over the horizontal
stabilizer of high wing aircraft, but I am having difficulty visualizing
how airflow over the horizontal stabilizer of a low wing is disturbed by
the lowering of flaps.

I should point out that I went from a high wing to a V-tail Bonanza after
my instrument rating, so I have no straight-tail low wing time.

--
Peter

"Peter R." wrote

No. I can visualize how flaps will disturb airflow over the horizontal
stabilizer of high wing aircraft, but I am having difficulty visualizing
how airflow over the horizontal stabilizer of a low wing is disturbed by
the lowering of flaps.

It isn't about disturbing the airflow over the stabilizer.

The tail provides "downward lift" to offset the fact that the center of lift
of the wing is behind the cg. When you lower the flaps you move the center
of lift of the wing even further aft, and this means the tail must work even
harder. If the tail is near stall due to icing, lowering the flaps may
cause a full tail stall which will result in the nose pitching down quite
severely. You probably won't be able to recover because the technique is
totally different compared to recovering from a normal wing stall and the
altitude loss can be dramatic even when proper technique is used.

The NASA video is highly recommended viewing.

BDS wrote:

It isn't about disturbing the airflow over the stabilizer.
snip

Thanks for the clarification. I am not sure where I accumulated that bit
of faulty knowledge.


--
Peter

I wonder, if you had enough altitude after breaking out below, would it be
advisable to perform a gentle power-off stall to find out what your new stall
speed is with the ice? Or would the new stall characteristics be so
unpredictable as to make the aircraft unstable?

The new stall charactaristics may be asymmetric, and recovering from
such a stall iced up may be a problem. If there's precip, even after
you break out you may continue to ice up, so the new stalling
charactaristics will be transitory, replaced by even worse ones.

I'd stay the hell away from stalling while iced up.

Jos
--
He who laughs, lasts.
for Email, make the obvious change in the address.

Jose wrote:
I wonder, if you had enough altitude after breaking out below, would
it be
advisable to perform a gentle power-off stall to find out what your
new stall
speed is with the ice? Or would the new stall characteristics be so
unpredictable as to make the aircraft unstable?


The new stall charactaristics may be asymmetric, and recovering from
such a stall iced up may be a problem. If there's precip, even after
you break out you may continue to ice up, so the new stalling
charactaristics will be transitory, replaced by even worse ones.

I'd stay the hell away from stalling while iced up.

Well, I'd at least stay away from stalling until I was less than 6"
above the runway!

Matt

When I apply flaps in my Archer, I trim down some. This would indicate
to my that I am reducing the "down lift" of the tail and reduce the
posibility of tail stall. Yes/No?

Chuck

BDS wrote:
"Peter R." wrote

No. I can visualize how flaps will disturb airflow over the horizontal
stabilizer of high wing aircraft, but I am having difficulty visualizing
how airflow over the horizontal stabilizer of a low wing is disturbed by
the lowering of flaps.

It isn't about disturbing the airflow over the stabilizer.

The tail provides "downward lift" to offset the fact that the center of lift
of the wing is behind the cg. When you lower the flaps you move the center
of lift of the wing even further aft, and this means the tail must work even
harder. If the tail is near stall due to icing, lowering the flaps may
cause a full tail stall which will result in the nose pitching down quite
severely. You probably won't be able to recover because the technique is
totally different compared to recovering from a normal wing stall and the
altitude loss can be dramatic even when proper technique is used.

The NASA video is highly recommended viewing.

I really don't know about the Archer, but consider a different possibility...
If the need for down-trim with flaps arises from a deflection of airflow
*away* from the horizontal stabilizer (i.e. below it), then I would worry
flaps deployment might move *closer* to a tail-stall, rather than away.

I repeat: I don't know if that's plausible for the Archer.
Can someone who does know Archer aerodynamics, help out here?
In the meantime, Chuck, remain very careful with iced tailplanes.

"Chuck" wrote in message oups.com...
When I apply flaps in my Archer, I trim down some. This would indicate
to my that I am reducing the "down lift" of the tail and reduce the
posibility of tail stall. Yes/No?

Chuck

BDS wrote:
"Peter R." wrote

No. I can visualize how flaps will disturb airflow over the horizontal
stabilizer of high wing aircraft, but I am having difficulty visualizing
how airflow over the horizontal stabilizer of a low wing is disturbed by
the lowering of flaps.

It isn't about disturbing the airflow over the stabilizer.

The tail provides "downward lift" to offset the fact that the center of lift
of the wing is behind the cg. When you lower the flaps you move the center
of lift of the wing even further aft, and this means the tail must work even
harder. If the tail is near stall due to icing, lowering the flaps may
cause a full tail stall which will result in the nose pitching down quite
severely. You probably won't be able to recover because the technique is
totally different compared to recovering from a normal wing stall and the
altitude loss can be dramatic even when proper technique is used.

The NASA video is highly recommended viewing.