Yesterday's IFR flight with questions

The standard lapse rate is 3.5F per 1000'. So it you are going to fly
at 5000' above the ground, the temp up there will be 17.5 degrees
colder. Giving 5 degrees for variation, that is 22 degrees colder. So
in this case it would have to be 44 degrees or higher on the ground to
not have ice 5000' higher. (I've done some rounding). Of course you
COULD have inversion. But inversion means it is warmer above. You could
also have a non-standard lapse rate. But this is a calculation worth
doing.

Usually people have a place on the airplane where ice forms first. It
will usually be something thin, like an antennae or strut. You can use
that as a guage. Thin frontal surfaces ice up first and worse. Some
sort of physics thing about the air in front deflecting the moisture.
More deflection with fatter curves. But usually my first indication of
ice has been decreased aircraft performance (if I am in level flight).
Descending or climbing is a little harder to tell.

As for decending. if it is rime, I think 1500' of undercast is usually
fairly safe. If it is freezing rain then no-go. Someone mentioned 1500'
per minute. But the most important thing is keeping the airplane
upright and not overspeed. You may want to use your standard decent
rate and not go around doing something different. The word is that
horizontal stablizer icing is the worst thing on decent. Don't use
flaps for landing if you have ice when you land and land a little
faster. Do everything at higher airspeed if you have ice. This will
keep you above stall speed (hopefully). See that is the problem. Due to
different shape of the wing due to ice the plane will stall at a higher
airspeed.

Another item. We all know to stay out of thunderstorms, but you should
stay out of towering cumulus too, even if they aren't thundering and
lighting. It is icy in there. I think the abreviation for these is CB.
Don't fly in CB's.

A lot of times there is just a thin layer of clouds, like 1000' thick
that you have to climb and decend through. And there is ice in them.
That one is a close call. If you have a PIREP or other good info and
know it is clear on top, it is tempting to try and climb on up. The
lower the ceiling is below, the riskier this is. You will have to
evaluate and make your own judgement. Talking to a pilot who has just
landed is very valuable. Hang out at the fuel desk. Maybe someone will
come in who just flew through it. Sometimes airmets are wrong. Ice
tends to be worse at the initial part of the front, and an old icing
airmet MAY be invalid, just hasn't been cancelled yet. All depends. But
if someone comes down through it and he says he didn't pick up any ice
and he doesnt think anyone would, that can be helpful information.

Like someone else mentioned. you can venture fairly safely into icy
clouds if you have warm VFR conditions under you, above the MEA, no
mountains and flat terrain. If you ice up, just descend.

If you tell ATC you have ice, be prepared to answer their questions
about it. Rime or clean? What is the temperature etc. They usually want
a full report. After all, if you have ice, YOU'RE the expert.

Having a turbocharged and high power to weight ratio is a godsend in
ice. Just climb up through it to clear above. Thats what the airlines
do. Sometimes they dont even turn on their deice cause it takes away
power. They'd just rather climb like a homesick angel and get out of
it. All depends. But the point is, being able to CLIMB is a godsend.
They need their deice mostly on decent. If you cant outclimb it, and
you have low ceilings below you, my suggestion would be TURN AROUND,
unless you know that you have VMC in front of you SOON. Presumbably,
you didn't get ice back there and if you go back there you wont
accumulate it. Whatever you do , don't just try and hold altitude while
you go slower and slower. That's how you stall and spin. Even a decent
below the MEA is safer than that strategy. And ATC will be telling you
he cant give you any lower. Just declare an emergency if you have to.
MEA's have at least 1000' cushion, usually more. It would be a
desperate crap shoot to be accumulating ice, unable to hold altitude,
and have to decend below the MEA. Good way to run into something. This
is the reason why I don't do this kind of stuff.

Like I said, we all get ice now and then if we fly in the clouds below
freezing. But don't get yourself boxed in. If you don't have an out,
fly to where you do have an out. And don't fly into a trap where you
can't outclimb the ice, and you can't decend because of low ceilings.
That is where the icing accidents occur. That and on landing with a
load of ice.

I hope that helps. Bottom line, you can't really do much about ice
except stay out of it, or get out of it if you are in it.

On 18 Nov 2005 11:39:06 -0800, Doug wrote:

Hey Doug

The standard lapse rate is 3.5F per 1000'. So it you are going to fly
at 5000' above the ground, the temp up there will be 17.5 degrees
colder. Giving 5 degrees for variation, that is 22 degrees colder. So
in this case it would have to be 44 degrees or higher on the ground to
not have ice 5000' higher. (I've done some rounding). Of course you
COULD have inversion. But inversion means it is warmer above. You could
also have a non-standard lapse rate. But this is a calculation worth
doing.

My thoughts b4 launching was that most of the flight was going to be
between 3500 and 4500 AGL on the first portion of the flight. Since sleet
was falling, I honestly expected the temperature to remain or rise a
little.

More deflection with fatter curves. But usually my first indication of
ice has been decreased aircraft performance (if I am in level flight).
Descending or climbing is a little harder to tell.

Yep, exactly right, I had to add power, and I knew that was not normal,
thus no longer depending on the wings for icing but looking at the
temperature probe. No wing strut for my Sundowner *smile*.

As for decending. if it is rime, I think 1500' of undercast is usually
fairly safe. If it is freezing rain then no-go. Someone mentioned 1500'
per minute. But the most important thing is keeping the airplane
upright and not overspeed. You may want to use your standard decent
rate and not go around doing something different.

Which was my initial thought, to maintain as "normal" as possible. I don't
want to stick around in the clouds any longer then necessary, but I don't
want do something reckless either by descending too quickly.. I wasn't
even going to think about deploying flaps. Figured the less metal hanging
out, the less that ice could collect.

A lot of times there is just a thin layer of clouds, like 1000' thick
that you have to climb and decend through. And there is ice in them.
That one is a close call.

For me, won't take a chance if there is known icing. Not worth it. Just
like anything else we do, there is a risk of the unknown, but for me, if
there is ice reported I simply won't go.

If you tell ATC you have ice, be prepared to answer their questions
about it. Rime or clean? What is the temperature etc. They usually want
a full report. After all, if you have ice, YOU'RE the expert.

Which I did when asked by Center. I was surprised that they gave me a
block altitude. Maybe I was a little more pro-active and insuring I get
out of the situation. Just glad it did not become an event.

it. All depends. But the point is, being able to CLIMB is a godsend.
They need their deice mostly on decent. If you cant outclimb it, and
you have low ceilings below you, my suggestion would be TURN AROUND,

Good advice, and in my case, I was right at the tops, so climbing was my
only option.

unless you know that you have VMC in front of you SOON.

And this was my quandry. I was on top, BWG was VMC but from my view, it
was solid overcast, yet ASOS reported broken 4300. So, I knew that the
clouds were about 1700 feet thick based on my current conditions I was
experiencing.

Like I said, we all get ice now and then if we fly in the clouds below
freezing.

I truly hope I never get myself in this situation. Thankfully, I am down
south where icing is an unusual event. I have been flying in the winter
for two seasons, and only once did I come close to freezing temperatures in
the clouds. It was a local flight, doing IFR training, and I had plenty of
outs since it was local.

But don't get yourself boxed in. If you don't have an out,
fly to where you do have an out. And don't fly into a trap where you
can't outclimb the ice, and you can't decend because of low ceilings.
That is where the icing accidents occur. That and on landing with a
load of ice.

Bottom line, good advice above and well appreciated.

Allen

On 18 Nov 2005 11:39:06 -0800, "Doug"
wrote:

As for decending. if it is rime, I think 1500' of undercast is usually
fairly safe. If it is freezing rain then no-go. Someone mentioned 1500'
per minute. But the most important thing is keeping the airplane
upright and not overspeed. You may want to use your standard decent
rate and not go around doing something different. The word is that
horizontal stablizer icing is the worst thing on decent. Don't use
flaps for landing if you have ice when you land and land a little
faster. Do everything at higher airspeed if you have ice. This will
keep you above stall speed (hopefully). See that is the problem. Due to
different shape of the wing due to ice the plane will stall at a higher
airspeed.

It is my understanding that ice forms less quickly when a propellor
turns faster. If you want to descend quickly (low RPM) would the prop
icing up and be a problem?

As fo noticing ice, in the PA28 I fly, the first hint was on the left
corner of the windshield (can't remember if it was top or bottom).
There was also slight frosting on the temp probe.

: For me, won't take a chance if there is known icing. Not worth it. Just
: like anything else we do, there is a risk of the unknown, but for me, if
: there is ice reported I simply won't go.


As someone else mentioned, icing airmets are present for large sections of the
country for large portions of the year. Given the litigious society we're in and the
unknown of icing, SCARE-MET zulu is issued if the conditions are possibly favorable
for icing. It is sometimes possible to fly safely in such conditions if one knows
what they're doing. It's also quite possible to be really stupid and/or ignorant
about it and get into big trouble.

Certainly nobody should fault you for a conservative attitude like that. If
they are, they're an arrogant ass. Icing is nothing to mess around with for real.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Just a side note. "Evaporated on its own" is called sublimation. Defined as
any time a substance goes from solid to vapor without a liquid phase. The
flip side is when water vapor becomes frost without an itermediate liquid
phase.

That's the virtue of getting on top; any ice accumulated on the way up will
sublimate off over time...within reason. A trace of rime, a glaze of
clear...sure. An inch of mixed ice? Don't bet on getting on top.

Bob Gardner


Bob Gardner

"A Lieberman" wrote in message
...
What a flight I experienced yesterday! Got to do more things I never did
which made for such a wonderful learning experiences and also raised
questions in my mind (surprise, surprise!).

Really worked over my decision on to launch or not to launch today to fly
from 2G2 (Steubenville, OH) to BWG (Bowling Green, KY) to MBO (Madison
MS).

Was closely watching the weather in Ohio, winds on the ground, winds
aloft,
clouds and ceilings, freezing level and everything else weather could
throw
a kink. Called FSS yesterday and this morning, no reports of icing, only
airmets for moderate turbulence 10K and below. No TFRs in my route.
Cloud
tops were forecasted to be 6000. The further south I go, the better the
conditions. Headwinds of 40 knots for the first leg, and tail winds of 15
knots for the second leg. The upper winds forecast were just about spot
on.

2G2 is an uncontrolled airport. Weather was suppose to be IFR this
morning, and I have never left an uncontrolled airport in IFR conditions.
This of course required that I call FSS and get an ATC clearance. Every
other time I have left an uncontrolled airport, I got my clearance in the
air, but today, too much scud floating above my head. Temperature on
departure was 43 degrees, with light sleet and rain falling. Figured the
decision to leave was good, as somewhere above my head would be warmer
weather then freezing temperatures due to the sleet falling. Also, based
on
radar trends, I knew I would be out of the precipitation within 10 miles.
Question 1 at the bottom of this post regarding this situation.

Got my ATC clearance from FSS and had to be off the ground in 13 minutes
or
my clearance was void. Not a problem, as I was the only one in the
traffic
pattern *smile*. Off I go, entering IMC at 2000 feet (900 feet AGL). I
turn on my Pitot tube heat. Rain and sleet was falling, temperature held
at 43 degrees entering the clouds. Break out on top at 5500. Final
cruise
altitude was 6000 (so I thought). Air was silk smooth!

The further south I go, the clouds start to slope up hill, and I am more
in
IMC the further I go. Amazingly, the further south I go, the lower the
temperature goes too. About 1 hour into my flight, center calls me and
says, Sundowner 1943L, I have a reroute for you, are you ready to copy. I
had filed direct, but I still am old fashioned by tuning each VOR in my
path to help with my situational awareness. I replied standby, and grab
my
pen and erasable paper. Center says, you are now cleared direct to York
VOR then direct to BWG due to MOA activities. Look on my maps, could not
find YRK. Punched NRST on Garmin 296, and York was not listed.
Sheepishly, I key up the mike and ask center for the frequency of York
VOR.
Center graciously gave me the frequency, and I dial it in and start
tracking toward the VOR.

Since I was in IMC, didn't want to mess around with the GPS, since it did
not show on the list of nearest. What concerned me even more, was my DME
was not reading a distance. I then called back into center and asked for
the distance to the York VOR. They said I had 90 miles to go! Well crap,
no wonder I couldn't locate it on the maps, I wasn't looking far enough
down the road! This made me feel a little better, as I started wondering
if I had lost situational awareness. I was then able to quickly find the
YRK VOR on the en route map, and then decided to program my 2 GPS's for
the
YRK VOR for distance until my DME picked up the signal. I used my NAV1
and
NAV2 for tracking, which really was fun to do, since I have not really
tracked a VOR en route for some time .

Get to the YRK VOR, turn direct to BWG. At this point, I am skimming the
tops of the clouds more in then out. In a matter of 10 miles the
temperature went from 35 to 25 degrees around this VOR. Watching my
wings,
see no ice, watching my windscreen, no beads of water or ice so I figured
all was well (so I thought). I am still skimming the tops of the clouds,
in visible moisture, but not your typical "hard" IMC.

A few minutes later, I noticed that I had to sneak in a little more power
then normal, which I thought was odd, so I decided lean a little forward
to
take a peek at the temperature probe. Sure enough there is a small
coating
of rime ice! I call into center and request to climb to 6,500 due to ice,
and center quickly approved giving me a block altitude from 6000 to 7000.
Center asked me to report when I climbed out of the clouds and to report
when the icing has shedded. Cool I thought, I would stay 500 feet above
the clouds and climb when needed. Turned out the clouds were reasonably
level, so I was able to maintain level flight at 6,500. When the sun hit
the wings, I could clearly see the ice on the leading edges as well as the
leading edge of the stabilator. This really alarmed me as I could not see
it while in "semi" IMC. I also was shocked how much accumulated in "semi
IMC" as it was like wisps of clouds zinging by with some hard IMC
interjected.

I never really did shed the ice, it kinda evaporated on it's own, as the
outside temperature was now down to 18 degrees. I reported to Center that
I was out of the clouds and the ice was slowly disappearing.

So now here I am on top, solid overcast and wondering just how safe will
it
be to descend through the cloud deck! (Question 3) Luckily, this never had
to be answered as within 10 miles of BWG, the clouds broke up and I was
cleared for a visual approach into BWG. I was monitoring any AWOS, ASOS
and ATIS en route and found the closer to BWG I got the thinner the clouds
got.

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?

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? Especially clear
icing? Where else should I look besides the temperature probem? I have a
white plane with blue strips in the wing tips, but I never saw the ice!
It
truly scared the bejeebers out of me to see the ice on the leading edges,
and luckily, I am intimately aware of my plane and it's idiosycrosies that
I knew that adding power was not a normal thing for straight and level
flight.

Question 3 on icing. knowing that flying into known icing is a big no no,
(no kidding!). So, here I am on top, evaluating the cloud thickness, and
finding that the clouds were generally 1,500 feet thick. Temperatures
were
dropping, which made me even more nervous about descending. Obviously
every situation is different, but what would be a reasonable amount of
time
for descending into clouds that the temperature appears to be below
freezing when the cloud deck is NOT thick. Figuring on 500 feet per
minute
descent, for me, 1500 feet is rather thick for 3 minutes. I would
naturally descend quickly and as safely as possible, but is there a
reasonable gauge for getting below a potentially THIN icy cloud deck?
Clouds today were widespread all the way down to BWG. When I left,
ceilings at BWG were 4200 which would have been a 1800 thick layer of
clouds. As forecasted, the clouds broke up, but what if the forecast had
busted? It's not like I could dip my wings to see if I get ice or not.

Thanks for answering my questions!

Allen

wrote:

It is my understanding that ice forms less quickly when a propellor
turns faster. If you want to descend quickly (low RPM) would the prop
icing up and be a problem?

Don't know the answer to the icing question, but if I want to descend faster
(vertical speed) I go to *high* RPM. More drag and you can point the nose down
more steeply without picking up as much speed.

On Mon, 21 Nov 2005 11:11:04 -0500, Dave Butler wrote:

wrote:

It is my understanding that ice forms less quickly when a propellor
turns faster. If you want to descend quickly (low RPM) would the prop
icing up and be a problem?

Don't know the answer to the icing question, but if I want to descend faster
(vertical speed) I go to *high* RPM. More drag and you can point the nose down
more steeply without picking up as much speed.

Thanks.
I guess you have variable prop - I don't (PA28) :-)

wrote:
On Mon, 21 Nov 2005 11:11:04 -0500, Dave Butler wrote:


wrote:


It is my understanding that ice forms less quickly when a propellor
turns faster. If you want to descend quickly (low RPM) would the prop
icing up and be a problem?

Don't know the answer to the icing question, but if I want to descend faster
(vertical speed) I go to *high* RPM. More drag and you can point the nose down
more steeply without picking up as much speed.


Thanks.
I guess you have variable prop - I don't (PA28) :-)

Righto. That occurred to me right after I clicked 'send'.

DGB

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

" 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?


--
Peter