Ice Season!

bbchien

bbchien

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Bruce C
Well got my first ice last night running up to KJOT to get my younger daughter. Skew T appended; ran down at 2,400 in VMC (Min. Vectoring altitude) and just ran VFR at 2,000 on the way back.

It was MODERATE ice, at the freezing line. LOTS of moisture in the system now moving across the mid country!
 

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Hi Bruce:
What alerted you to the ice? This is my first winter as ppl and wonder how you see the ice?
I pull the carb heat about every 30 minutes.

:dunno:
 
I can usually see it growing on the wind screen first, then on the leading edges. It starts in the lower center of the wind screen. Go higher or lower, or turn around, but do something. The tail is collecting ice twice as fast at the wing.
 
That krinkling sound on my windscreen, rapidly followd by the tank comannder's view of the planet. Just got the propellor heat turned on just in time before the crunching of thrown ice takes the paint off the nose bay.

I had the pitot heat on, but my brain was just not engaged in "ICE flying" yet. Sigh.
 
What are some good resources to learn about the Skew T plots?
 
bbchien said:
Well got my first ice last night running up to KJOT to get my younger daughter. Skew T appended; ran down at 2,400 in VMC (Min. Vectoring altitude) and just ran VFR at 2,000 on the way back.

It was MODERATE ice, at the freezing line. LOTS of moisture in the system now moving across the mid country!
Click to expand...

Lots of moisture there and our 3rd snow storm of the season in the Denver metro area. Which means, just as the previous two, the snow will be gone by tomorrow afternoon.

However, the weather on Tuesday afternoon included the comment "Relative Humidity 1%". That's right. Almost no humidity. I've never seen it lower than 10% and that's usually in the summer.
 
Can you pick up ice in seemingly clear air or are you fling into clouds when you pick up this ice? Fairly new PP so please forgive my lack of experience.
 
acluffpoa said:
Can you pick up ice in seemingly clear air or are you fling into clouds when you pick up this ice? Fairly new PP so please forgive my lack of experience.
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On a nice sunny day in VMC, you won't pick up ice. And to be clear, we're talking about *airframe* ice, not carb ice.

Ice is generally regarded as an IMC phenomenon, but if visibility is lowered (ie it's a little misty) it is possible to pick up ice in VMC - I iced up a Super Cub going around the patch in Michigan one morning. That's the only time I've encountered such a phenomenon, though, and accretion won't be very fast if you're in legal VMC.
 
This is a NASA video talking about turbo prop aircraft, but it is interesting to watch. The point being ice accumulation on the tail ( very difficult to see from the pilot's seat ) happens much faster that on the wing leading edges.

https://www.youtube.com/watch?v=w1c4-aDB4k8&feature=youtube_gdata_player

There are 3 videos, be sure to watch all 3. Good stuff.
 
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I use the following to be on the look out for ice:

A: TAT below 10C and SAT above -40 C or F....dealers choice, and

B: Visible moisture (rain or snow), or
Visibility below 1 mile.
 
Snow by itself doesn't seem to cause problems for me, unless the show is mixed with rain. Just plain snow doesn't stick because it is frozen. I've flown in snow for hours. You can see it when the strobes flash.
 
It takes condensed moisture to pick up ice. The two common ways to get it are:
1. Flying into a cloud
2. Freezing rain.

The latter you can very much encounter in good VMC conditions and is perhaps one of the more scary icing scenarios.
 
Worst part about this episode is that I tried it. To my view the SkewT predicted ice- but for some reason I felt compelled to file, and climb into it to see (Ice accrued pretty quick, look at the slope of the congruent fed and blue segment).

I should have asked for the MVA or just gone VFR BEFORE I climbed into it....the alternative was 8,000 (for a 96 mile trip)!
 
bbchien said:
Worst part about this episode is that I tried it. To my view the SkewT predicted ice- but for some reason I felt compelled to file, and climb into it to see (Ice accrued pretty quick, look at the slope of the congruent fed and blue segment).

I should have asked for the MVA or just gone VFR BEFORE I climbed into it....the alternative was 8,000 (for a 96 mile trip)!
Click to expand...

Curiosity killed the cat! Although cats in de-iced twins have a little margin for error
 
As a VFR pilot, ice isn't really a concern. I've never gotten it without IMC. It's one of these things that you'll know when you see it.

I got my first ice of the year yesterday. Had the props and pitot heat on. Got a block altitude and just skimmed the cloud tops for fun.

Bruce, I fully agree with the brain calibration needed for ice season. I find in the spring I have to calibrate my brain for thunderstorms, and in the fall recalibrate for ice. Although because of my typical wild changes in latitude throught the year, I've gotten ice in July and thunderstorms in January.
 
DaytonaLynn said:
Hi Bruce:
What alerted you to the ice? This is my first winter as ppl and wonder how you see the ice?
I pull the carb heat about every 30 minutes.

:dunno:
Click to expand...
If you are IFR, you just look out the window and see if there is anything accumulating on the the leading edges, struts, window etc.... Chances are you will know when you need to start looking, about that time the OAT gets around 0 and you are in visible moisture. Its quite a bit different than carb ice, which as you know will make you engine run rough.
 
flyingcheesehead said:
On a nice sunny day in VMC, you won't pick up ice. And to be clear, we're talking about *airframe* ice, not carb ice.

Ice is generally regarded as an IMC phenomenon, but if visibility is lowered (ie it's a little misty) it is possible to pick up ice in VMC - I iced up a Super Cub going around the patch in Michigan one morning. That's the only time I've encountered such a phenomenon, though, and accretion won't be very fast if you're in legal VMC.
Click to expand...
One MAJOR exception though, is that you can still pick up huge amounts of ice in VFR conditions in a heartbeat if temps are below freezing at your altitude and it's raining, or even drizzling. Freezing rain is probably the single scariest weather event I can think of running into in the air, short of a thunderstorm developing over me out of the blue.
 
azure said:
One MAJOR exception though, is that you can still pick up huge amounts of ice in VFR conditions in a heartbeat if temps are below freezing at your altitude and it's raining, or even drizzling. Freezing rain is probably the single scariest weather event I can think of running into in the air, short of a thunderstorm developing over me out of the blue.
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True Liz...SLD would scare the beejezuz outta me!
 
flyingmoose said:
Its quite a bit different than carb ice, which as you know will make you engine run rough.
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Thought the classic example of carb ice was a steady decline in power, followed by the engine running rough for a minute after you figure out what is going on and turn on carb heat.

The one time I had carb ice in the air, that's exactly how it went. A warm day skimming the tops of a cloud layer at a low power setting in a cessna
 
As pointed out by Azure (and me) freezing rain is a real threat to VFR pilots. I remember wisely cancelling a flight up to JST when although tjhe ceilings were up at 5000, the forecast was for freezing rain.

And ice isn't just a winter thing. I got my first ice this year in early october. The first time I ever experienced ice was on the way back from Oshkosh (in August) the first time I went. I was in the left seat of Paul Bertorelli's Mooney. It was both the first time I think I had been at the controls in actual and shortly it was the first time I experienced ice.
 
DutchessFlier said:
True Liz...SLD would scare the beejezuz outta me!
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Well yeah, but SLD, to my understanding, doesn't necessary imply freezing rain since the droplets can still be small, in the 10s or 100s of microns. SLD is scary too -- personally once I'm rated I couldn't see taking off into freezing or subfreezing clouds unless they were VERY thin or very cold, -20C or preferably even colder, even without any forecast of icing conditions much less SLD -- but freezing rain is the absolute worst. Depending on temps aloft, it might not even be forecast as freezing rain at ground level, just plain old rain. But if your airframe is below freezing, watch out.

On a related topic, a big question mark in my mind is just how significant aerodynamic cooling is. How much above freezing does it need to be in a typical spam can to not worry about ice in the clouds? My current CFII didn't give me a hard number, he just said "a few degrees". Is 5C safe? 4C? 3C? I think I would give any indicated number a +- 2 degree margin of error, so I'm asking about actual temps here, not indicated.
 
azure said:
On a related topic, a big question mark in my mind is just how significant aerodynamic cooling is. How much above freezing does it need to be in a typical spam can to not worry about ice in the clouds? My current CFII didn't give me a hard number, he just said "a few degrees". Is 5C safe? 4C? 3C? I think I would give any indicated number a +- 2 degree margin of error, so I'm asking about actual temps here, not indicated.
Click to expand...

I've never gotten ice when the OAT is saying 1C or above. I realize you're asking actual, but all I have to go on is indicated. :)
 
azure said:
On a related topic, a big question mark in my mind is just how significant aerodynamic cooling is. How much above freezing does it need to be in a typical spam can to not worry about ice in the clouds? My current CFII didn't give me a hard number, he just said "a few degrees". Is 5C safe? 4C? 3C? I think I would give any indicated number a +- 2 degree margin of error, so I'm asking about actual temps here, not indicated.
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Like Ted said. It has to be freezing or below. But with that said, you are assuming that your OAT gauge is calibrated exactly with not mounting error. SO I would be comfortable with +1 +2, if things change then you gotta go.

Aerodynamic cooling makes no difference in the collecting of ice.
 
flyingmoose said:
Like Ted said. It has to be freezing or below. But with that said, you are assuming that your OAT gauge is calibrated exactly with not mounting error. SO I would be comfortable with +1 +2, if things change then you gotta go.
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Yup, I know that, and it's why I included that disclaimer.
Aerodynamic cooling makes no difference in the collecting of ice.
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It's not the "collecting" part that I'm talking about but the actual temperature on the airfoil surface. I would have thought that with constant exposure to the moving airstream, the airfoil would be at ambient temperature, but apparently that's not always true, and my current CFII pointed this out. The FAA certainly thinks it's an issue. From AC 00-6A:
Two conditions are necessary for structural icing in flight: (1) the aircraft must be flying through visible water such as rain or cloud droplets, and (2) the temperature at the point where the moisture strikes the aircraft must be 0° C or colder. Aerodynamic cooling can lower temperature of anairfoil to 0° C even though the ambient temperature is a few degrees warmer.
Click to expand...
 
Ted DuPuis said:
I've never gotten ice when the OAT is saying 1C or above.
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My experiences echo the above. I have discovered that the Flybaby hauls ice pretty damn well though.
 
jesse said:
My experiences echo the above. I have discovered that the Flybaby hauls ice pretty damn well though.
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I'd expect it to. Big, draggy airfoils typically don't care about ice since the thing is so unaerodynamic anyway.
 
Liz, I'm not an aerodynamic person. But typically what I worry about temperature wise is a cold-soaked wing, and OAT being 0C or below. Once it's -20C or so ice is pretty rare.

Ice builds on the leading edge of surfaces. So props, spinners, wing and tail leading edges, windshield, nose. In those areas, you have a local pressure increase where the air is building up and then forced to move around the airfoil. This results in heating (ideal gas law).

Like I said, I'm not an aerodynamic guy, I'm an engine guy. But I've not been a stranger to ice, either.
 
azure said:
Yup, I know that, and it's why I included that disclaimer.

It's not the "collecting" part that I'm talking about but the actual temperature on the airfoil surface. I would have thought that with constant exposure to the moving airstream, the airfoil would be at ambient temperature, but apparently that's not always true, and my current CFII pointed this out. The FAA certainly thinks it's an issue. From AC 00-6A:
Click to expand...
Well if it says it can, then go with it. I like other have never seen it much above +1, but being conservative and leaving a buffer will do you well.
 
Ted DuPuis said:
Liz, I'm not an aerodynamic person. But typically what I worry about temperature wise is a cold-soaked wing, and OAT being 0C or below. Once it's -20C or so ice is pretty rare.

Ice builds on the leading edge of surfaces. So props, spinners, wing and tail leading edges, windshield, nose. In those areas, you have a local pressure increase where the air is building up and then forced to move around the airfoil. This results in heating (ideal gas law).

Like I said, I'm not an aerodynamic guy, I'm an engine guy. But I've not been a stranger to ice, either.
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I'm not a specialist either (far from it!) but my understanding was that aerodynamic cooling would be the exact opposite of what you described, due to expansion of air moving in areas of local pressure DEcrease (upper surface of airfoil mostly, I would expect).

Again, I've never heard of anyone actually encountering structural icing due to aerodynamic cooling "in the wild", and I would have thought the effect was insignificant, or at least smaller than calibration errors anyway, and if I saw ice at 2C I would chalk it up to a faulty reading rather than aerodynamic effects. Which is why I asked whether it was more significant than that -- and apparently the answer is no, but that doesn't mean it's a good idea to neglect it entirely. As Matt says, leaving a buffer for whatever reason is a healthy practice.

Thanks for the replies!
 
Ted DuPuis said:
I've never gotten ice when the OAT is saying 1C or above. I realize you're asking actual, but all I have to go on is indicated. :)
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there are some ways to get in trouble well above freezing, for example coming down from the flight levels in a wet-wing plane with the plane chilled, you can get impressive ice flying through a warm cloud down low.
 
JHW said:
there are some ways to get in trouble well above freezing, for example coming down from the flight levels in a wet-wing plane with the plane chilled, you can get impressive ice flying through a warm cloud down low.
Click to expand...

Correct, the cold-soaked wing is a big concern especially.

My point wasn't that it can't happen, just that I haven't seen it.
 
azure said:
I'm not a specialist either (far from it!) but my understanding was that aerodynamic cooling would be the exact opposite of what you described, due to expansion of air moving in areas of local pressure DEcrease (upper surface of airfoil mostly, I would expect).
Click to expand...

Correct, and that's where ice doesn't form, at least it typically doesn't.

A buffer zone is always a good idea. I'm just reporting my experiences.
 
I've also frequently seen the temperature decrease when entering clouds. I don't think the cloud is causing the temperature decrease, though. I think it's the temperature decrease which is causing the water vapor to condense which forms the cloud. Could be a chicken/egg thing, though. In any case, I've observed this temperature decrease many times so if you are outside a cloud at +2C you could enter a cloud and find that it is -2C.
 
Don't forget about that lowering of air pressure causing a drop in temperature. Airplanes have all sorts of low pressure areas...that's how they fly and move right?

Wings, props, structures... All can lower the pressure enough to make a few degree difference in GA planes.

So 2C indicated could be -1C True could be -4C local. Food for thought...
 
anyone who wants to debate temperatures down the 1 or 2 degrees would be well served to take the OAT out of the plane and check it in a cup of distilled ice water
 
dell30rb said:
Thought the classic example of carb ice was a steady decline in power, followed by the engine running rough for a minute after you figure out what is going on and turn on carb heat.

The one time I had carb ice in the air, that's exactly how it went. A warm day skimming the tops of a cloud layer at a low power setting in a cessna
Click to expand...

Same deal here. A 182 in IMC on an IR lesson. Took a while before enough brain cells lined up to say "Pull the carb heat, dummy!!!".
 
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