SE airplanes in clouds - near freezing level

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?

Sep,,

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.

If you fly a plane that will bring you to an altitude with -20 C after
flying through low clouds, you'll likely have de-icing equipment.

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?


Well, your first strategy really depends on whether you can climb high
enough while you airplane will still climb. Often, that will not work.
Turbocharging helps, of course. So yes, the freezing level absolutely
needs to be above the MEA/MORA or whatever it is called where you fly. Or
it needs to be in the clear below the cloud base, with enough room to the
ground to fly safely.


--
Thomas Borchert (EDDH)

-----Original Message-----

From: Kusi (us-ppl, sep, d.-ir) ]

Posted At: Friday, December 22, 2006 7:52 AM

Posted To: rec.aviation.ifr

Conversation: SE airplanes in clouds - near freezing level

Subject: SE airplanes in clouds - near freezing level



....

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?





Having enjoyed this ride in a Commander 112 back in November '75 I can
relate that after flying in -15C at 12K on top of a solid deck from
Seattle to Bozeman we entered the side of an upslope cumulous there at
the ridge between Bozeman and Livingstone. The aircraft RAPIDLY built
enough ice to completely clog the engine air intake screen, take down
the long-wire ADF antenna and generally turn our world very bad, very
quickly. We switched to alternate intake but slung the ice off the prop
unevenly and induced some serious vibration. The instrument student in
the left seat executed a nice standard rate 180 but we lost enough
altitude that we never flew back out of the side of the buildup. We came
out of the bottom of the overcast in a little snow storm and were VERY
lucky to break out in a valley with a paved road in the bottom. Not much
damage to the aircraft except outboard of the fuel tanks where we hit
the bridge railing - the pastures were wet and snow covered.



We still had over 1 1/2" on the airframe after we came to a stop. Based
on the size of the airframe, I figure we picked up close to 1600# of ice
in less than 2 minutes.



After the aircraft was repaired, when we flew it back to Seattle we had
to let down again with a cold airframe through about 8000' of visible
moisture, but we had about a 1000' ceiling underneath. It seemed the
best way was to execute a modified ILS into BFI, so we hit the IAF
outbound at around 10K and flew the teardrop. Rolled out of the
procedure turn and hit the FAF almost perfect. Didn't pick up much ice
on the way down so what we did accumulate was gone before we touched
down.



How do you preplan such a flight?



If you don't have known ice equipment or don't know how to use it, and
you can't get over or around the highest tops enroute then I'd plan on
taking the bus or driving. But that's just my personal minimums now. If
all you have to do is penetrate a small layer during an approach then
depending on the probability of having to do a missed, and the aircraft
capability to execute the missed with a load of ice, and how big that
load of ice might be, and lots of other considerations, you might still
try it. The problem with this approach is that once you start you're
committed -- no pulling over to rethink the options. Personally, 30
years later, I have to admit that I like my ice in a glass and not stuck
to aluminum or plexi.

Jim Carter's experience is telling. When a cold-soaked airframe descends
into the clouds it is going to collect a lot of ice in a hurry. Where does
the "quickly warmed" idea come from?

Bob Gardner

"Kusi (us-ppl, sep, d.-ir)" wrote in message
ups.com...
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?

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

"Bob Gardner" wrote:
Jim Carter's experience is telling. When a cold-soaked airframe descends
into the clouds it is going to collect a lot of ice in a hurry. Where does
the "quickly warmed" idea come from?

The thin sheet metal skin on the plane warms up fast. It's the fuel in the
tanks that hold the cold. So, obviously, the answer is to make sure you
don't have any fuel left when you start your descent :-)

"Bob Gardner" wrote in message
. ..
Jim Carter's experience is telling. When a cold-soaked airframe descends
into the clouds it is going to collect a lot of ice in a hurry. Where does
the "quickly warmed" idea come from?


It doesn't even have to get into the clouds. A cold soaked airplane
descending into humid air can accumulate a layer of frost, thickness of
which depends on time of exposure, humidity, and how cold the airplane was.
This is an exception to the common theory that visible moisture is required
for accumulation of airframe icing. It has happened to me in a Saratoga, I
landed with still 1/4 inch or so of ice under the wings, where the inboard
fuel tanks are located, and a little elsewhere. Never passed through a
cloud or any kind of visible moisture, had been flying a couple of hours at
16,500 or so, saw ice accumulating during descent through warmer air. 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.

The recent FAA regional counsel letter about icing conditions included areas
of high humidity with near freezing temperature as known icing conditions.
It has widely been hooted down, but is not entirely wrong.

BTDT, in a Lear descending into Baton Rouge after a flight in the high 30
flight levels. Mucho ice on the bottoms of the wings.

Bob

"Stan Prevost" wrote in message
...

"Bob Gardner" wrote in message
. ..
Jim Carter's experience is telling. When a cold-soaked airframe descends
into the clouds it is going to collect a lot of ice in a hurry. Where
does the "quickly warmed" idea come from?


It doesn't even have to get into the clouds. A cold soaked airplane
descending into humid air can accumulate a layer of frost, thickness of
which depends on time of exposure, humidity, and how cold the airplane
was. This is an exception to the common theory that visible moisture is
required for accumulation of airframe icing. It has happened to me in a
Saratoga, I landed with still 1/4 inch or so of ice under the wings, where
the inboard fuel tanks are located, and a little elsewhere. Never passed
through a cloud or any kind of visible moisture, had been flying a couple
of hours at 16,500 or so, saw ice accumulating during descent through
warmer air. 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.

The recent FAA regional counsel letter about icing conditions included
areas of high humidity with near freezing temperature as known icing
conditions. It has widely been hooted down, but is not entirely wrong.

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.

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).
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