known icing?

Center_Mid

Well-Known Member
So I call the FSS and they say that moderate rime is forecast from 6,000 feet on up. Then, they say that the freezing level is at 4,000 with a broken layer base at 2,100.

Would a flight into the broken layer at 4,000 feet be a flight into "known icing" conditions, or just flying at or above 6,000? I'm not going to try it either way in the 'ol 172, but I was just trying to figure out what known icing is.

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So I call the FSS and they say that moderate rime is forecast from 6,000 feet on up. Then, they say that the freezing level is at 4,000 with a broken layer base at 2,100.

Would a flight into the broken layer at 4,000 feet be a flight into "known icing" conditions, or just flying at or above 6,000? I'm not going to try it either way in the 'ol 172, but I was just trying to figure out what known icing is.

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Nope....wouldn't do it.
You more or less answered your own question. Because, by the forecast, you "know" there is a 99.999999% chance of ice.

The forecast included all the ingredients for ice. Moisture (cloud=water vapor) and freezing temperatures.

The general rule of thumb to expect ice is +5 degrees C or less and visible moisture.

A C172 in that forecast is begging 91.13

From what I've heard, the FAA considers forcasted icing to be "known icing". So if there's a forecast for ice, an airmet for ice, or a pirep reporting ice, it's known icing.

While flying into known icing in a C-172 under Part 91 doesn't have a specific reg violation, the FAA can nail you under 91.13 like NJA Capt said. You're operating outside the limitations of your aircraft.

Two things to consider: is it really illegal to fly into known icing in something like a C-172? And, if there's ice, it may be okay to fly that day if there's an "out".

Part 91.527, which talks about the prohibition of flight into know icing conditions, is in Subpart F which is about Large and Turbine-Powered Multi-engine airplanes. There is no FAR for single engine planes that I know of. Crashing as a result of it, however, could be considered reckless. Also, the POH of a new plane might specifically mention that the aircraft is not certificated to fly into known icing conditions.

The second thing I think about if there's a chance of ice is if there's an out. If you're flying 100NM and the terrain along the route is flat at sea level and the clouds are OVC050 with tops reported at 080, I don't see why you couldn't go if the MEA is something like 2000'. You've got a quick solution if you start to pick up ice at, say, 6000'. As long as you start to get out of the ice as soon as you notice it, you're not likely to lose control of the situation.

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Two things to consider: is it really illegal to fly into known icing in something like a C-172?

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Yes, without a doubt. If you fly a 172 into known icing, you are operating it contrary to the limitations published in the flight manual. 91.13, no question.

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From what I've heard, the FAA considers forcasted icing to be "known icing". So if there's a forecast for ice, an airmet for ice, or a pirep reporting ice, it's known icing.

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Really? I wouldn't think so, because a forecast isn't "known" it is just a likelihood. I'm not saying it would be a good idea to fly it, just saying forecast doesn't constitute "known". That's not gospel though, just my opinion. But then again, they're like buttholes right....everybodies got one.

Surf

172's before 1969 do not have a known ice prohibitation, from 1969 on they do.

172's don't fall out of the sky when they get a little ice. What's important is that you can get out of it. What are the MEA's? If the MEA's are 2,000. Freezing level is 4,000. And ice is forcast at 6,000. I'd have no problem going to 4 with the knowledge that I can get out of it by descending. Also, it would have to be good VFR below the bases all along the route.

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Really? I wouldn't think so, because a forecast isn't "known" it is just a likelihood. I'm not saying it would be a good idea to fly it, just saying forecast doesn't constitute "known". That's not gospel though, just my opinion. But then again, they're like buttholes right....everybodies got one.

[/ QUOTE ]Since 1974 the NTSB (through caselaw) has established that "known icing" can include "forecasted" icing. Specifically, "We do not construe the adjective 'known' to mean that there must be a near certainty that icing will occur, such as might be established by pilot reports. Rather we take the entire phrase to mean that icing conditions are being reported or forecast in reports which are known to a pilot, or of which he should reasonably be aware." Administrator vs. Bowen, EA-585, 2 NTSB 940 (1974).

There is a very good article relating to such caselaw at Avweb. It's a long read, but worth it:
http://www.avweb.com/news/airman/184265-1.html

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172's before 1969 do not have a known ice prohibitation, from 1969 on they do.

172's don't fall out of the sky when they get a little ice. What's important is that you can get out of it. What are the MEA's? If the MEA's are 2,000. Freezing level is 4,000. And ice is forcast at 6,000. I'd have no problem going to 4 with the knowledge that I can get out of it by descending. Also, it would have to be good VFR below the bases all along the route.

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I'll back this up. 172s actually carry ice pretty well, doesn't mean it's a good idea though. Like DE727UPS, I'm comfortable in a situation such as he outlined. Just keep a close eye on the situation and be prepared to take your "out".

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Since 1974 the NTSB (through caselaw) has established that "known icing" can include "forecasted" icing.

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That's good to know, thanks Jeff

Remember, just because somebody else is flying in ice, doesn't mean you should.
If you don't have much icing experience, then don't do the long flight with an out. Do a local flight with two outs.

Getting experience in ice is good, but you don't want too much too soon.

Known icing... If you know about it, it's known!!!
Seriously, in the situation described, (2000ft ceiling, 4000ft freezing level, forecast icing at 6000ft), in a 172... If I had to do this trip, I would certainly stay at 1500ft in VFR, much easier, don't have to talk to anybody, especially over a flat terrain...
I had a pretty bad experience in ice in an aircraft of 25,000lbs, couldn't get above 8,000ft... Respect ice, avoid it as much as pratical (except in your gin).
I wouldn't knowingly look for ice in a C-172.
An other point to this: the reason why the de-icing equipment on an airplane is black, is because you can see ice accumulating over it, it is not very visible on a white surface (leading edge, struts on a Cessna).

&gt;&gt;Since 1974 the NTSB (through caselaw) has established that "known icing" can include "forecasted" icing. &lt;&lt;

Interesting... I fly in the northeast and I just wonder why ATC and anybody doesn't seem to care when many pilots fly IFR when known icing is forecast. Wouldn't that be illegal if it goes against the regulation, like you say?

If you can avoid the icing situation, you can file. Of course you have to go with your expirience and knowledge of how to get out of it if the white stuff starts to build up.

Lower isn't always the answer either. I recall a flight up to Lake Placid one day where I was picking up ice at 9,000 in a 172. Since the MEA up there is somewhere around 8,000 I got a climb to 11,000 (yep still in a 172) to get out of it. That high, it sublimates off of the surface of the airplane and the stuff up there is so cold it just bounces off of the plane so it doesn't accumulate.

As a benifit too, I got a healthy tail wind that day and was doing 170 KTS across the ground (yep, still in the 172)

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. . .I got a climb to 11,000 (yep still in a 172) . . .

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I do it all the time, bro!!!

That was my one and only time above 10,000. Quite fun and unique for me.

I spent just about all of the rest of my 400 hours from 0-6000. And most of those hours were in a 152... so to see 170 KTS on the DME, it was neat.

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If you can avoid the icing situation, you can file. Of course you have to go with your expirience and knowledge of how to get out of it if the white stuff starts to build up.

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ATC will accept a flight plan through an area of forecast icing, and will not vector you around it either, unless you ask for it (they will though let you know about it). I don't think it is regulatory in nature, it is advisory. Just like a sigmet, if it is not backed up by a pirep, it is only advisory...

Just because the conditions are right for ice, doesn't mean you will get it. But having said that, I wouldn't stray too far from home in a 172. Light singles will carry ice, it is good to get it early on so that when later in your career you do nothing but fly with ice hanging all over the plane it won't be so freaky.

I would try to get out of it as fast as possible in a single engine, a 172, even if it carries ice quite well, it accumulates ice very fast also. Even in a de-iced 172 I would be carefull. But that is just me, of course, I might be over-cautious, but I've read many accident (or incidents) involving single engine in icing conditions... I don't want to see my name in one of those!

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