SE airplanes in clouds - near freezing level

Stan Prevost wrote
Thanks for that little story, Bob. You are the only person I have
ever heard report the same kind of occurence. I have been accused of
lying, even though it seems obvious that it will occur.

In the B-707, after an ocean crossing, we always landed with 1/4" of
frost on the bottom surface of the wings.

Bob Moore

The
thin skin without any thermal mass beneath it apparently warmed rapidly
enough to accumulate little and shed it, whereas the fuel tanks had enough
thermal mass to keep the ice frozen.

So, suppose the fuel tanks were insulated from the skin by about half an
inch of (vented?) air... that should solve the problem, no? (albeit at
a weight cost)
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody knows
what they are." - (mike).
for Email, make the obvious change in the address.

-----Original Message-----
From: Jose ]
Posted At: Friday, December 22, 2006 4:22 PM
Posted To: rec.aviation.ifr
Conversation: SE airplanes in clouds - near freezing level
Subject: SE airplanes in clouds - near freezing level

The
thin skin without any thermal mass beneath it apparently warmed
rapidly
enough to accumulate little and shed it, whereas the fuel tanks had
enough
thermal mass to keep the ice frozen.

So, suppose the fuel tanks were insulated from the skin by about half
an
inch of (vented?) air... that should solve the problem, no? (albeit
at
a weight cost)
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody
knows
what they are." - (mike).
for Email, make the obvious change in the address.

It might solve some of the problem, but in our case the upslope cumulus
was pretty unstable. The visible moisture had risen well above the
altitude (temp point) where it should have already turned to ice, so
when we stuck our aircraft into the moisture it quickly adhered to the
entire exterior.

I suppose if you were descending into warmer air the ice would not
accumulate anywhere except on pieces that took a while to warm up or in
areas of reduced pressure. On the other hand, if you are descending into
or flying through moisture that is still liquid but cooling rapidly you
are going to encourage cooling with your cold airframe -- and have a
souvenir to show for it.

"Jose" wrote in message
. net...
The thin skin without any thermal mass beneath it apparently warmed
rapidly enough to accumulate little and shed it, whereas the fuel tanks
had enough thermal mass to keep the ice frozen.

So, suppose the fuel tanks were insulated from the skin by about half an
inch of (vented?) air... that should solve the problem, no? (albeit at a
weight cost)

Probably. If it is indeed a problem.

"Jose" wrote in message . net...
The
thin skin without any thermal mass beneath it apparently warmed rapidly
enough to accumulate little and shed it, whereas the fuel tanks had enough
thermal mass to keep the ice frozen.

So, suppose the fuel tanks were insulated from the skin by about half an
inch of (vented?) air... that should solve the problem, no? (albeit at
a weight cost)
--

How would the vented air behave differently from the free air?
Wouldn't the condensation freeze just as readily, inside the vented volume?

How would the vented air behave differently from the free air?
Wouldn't the condensation freeze just as readily, inside the vented volume?

Vented air would be at ambient temperature. Trapped air would probably
be at equilibrium with the fuel tank. If you are descending into warmer
air, it gives you an edge.

Jose
--
"There are 3 secrets to the perfect landing. Unfortunately, nobody knows
what they are." - (mike).
for Email, make the obvious change in the address.

"John R. Copeland" wrote in message
...
"Jose" wrote in message
. net...
The
thin skin without any thermal mass beneath it apparently warmed rapidly
enough to accumulate little and shed it, whereas the fuel tanks had
enough
thermal mass to keep the ice frozen.

So, suppose the fuel tanks were insulated from the skin by about half an
inch of (vented?) air... that should solve the problem, no? (albeit at
a weight cost)
--

How would the vented air behave differently from the free air?
Wouldn't the condensation freeze just as readily, inside the vented volume?


Vented air would probably add ice inside the wing, but would not disturb
the aerodynamics.

Kusi (us-ppl, sep, d.-ir) wrote:
Those of you, who frequently fly SE airplanes without deicing
equipment, without turbo or second engine but use their IR Ticket to
poke around in water loaded clouds at or near freezing level:

What are your strategies to cope with the weather ?

Situation1: You climb through low clouds, but pass the freezing level
on top in clear sky.
After flying at -20°C for a while, you start your descend into the
water loaded clouds.
How quickly does the plane ice up? The airplane skin is relatively
small, so the exposed mass should be quickly warmed.
What are your personal experiences with the type of cloud? A heavy
loaded nimbostratus will have a different effect as a cirrus, for sure.
How do you preplan such a flight?

Situation2: While climbing through subcooled low clouds, what is the
most practical strategy? Climb further to reach real cold layers, which
are almost dry?
Quickly descend to reach warmer layers?
It depends?

Personally, I'll decend through it to lower air but will not climb up
through it unless its an altitude climb (i.e. I'll climb from 8,000 to
12,000 but not on departure where I can't just decend back down). I'll
file enroute near the freezing level if I'm sure MEAs and ATC will be
flexible with altitudes.

Despite the "modern" FAA teaching method of ice avoidance (i.e. just
stay out), anyone who uses their IFR ticket is going to encouter ice at
some point. Just keep your options open, make sure you have warm air
below.

-Robert

-Robert

The situation to avoid is where the only out you have is to descend
into unknown ceilings and a chance of icing. You have ice, can't climb
above it and can barely hold altitude. That is the ultimate nightmare.
You ice up, can't climb and are forced to descend into unknown
terrain/ceilings. Definitely DON'T do that.

The only situation that is deemed to be even slightly "ok" is to
descend from VMC down through a possible icing layer 1000' thick on
approach where you have weather report and know you can land, where
they are saying "light rime". That might be ok. People do it and get
away with it.

My experience with ice is you can't really predict it. If it's below
freezing and you are in a cloud or it's raining or snowing, you will
probably get it. And without a known ice airplane, you will NOT WANT TO
BE THERE!! Now if you have 7000' of VMC below you and the ground is 70
degrees F and you're up at 11,000' and you fly into a dark cloud and
get a LOAD of ice, you'll probably survive and live to fly another day.
From that experience you take the knowledge that you don't want to do
THAT again. Personally I think it's too risky to get any ice in small
non-deiced GA airplanes. They just don't do well.

So don't go if you think there is ice. You will probably get it some
day and probably survive. But don't push your luck, because if you get
it, you are flying on luck, which is not a good idea at all.

Doug wrote:
You ice up, can't climb and are forced to descend into unknown
terrain/ceilings. Definitely DON'T do that.

Given enough ice, you don't really have any other options.

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Hood River, OR