What, legally, are "Known Icing Conditions"?

[Jim_R]

I'm an IR PPl with 300 hrs. I fly a non-FIKI plane. I live in the south, so icing is only rarely a concern; even in the winter, it's pretty typical to not have to worry about icing when planning a short flight.

I have a growing familiarity with the weather products that are useful in predicting icing potential, and of course I am very interested in avoiding icing conditions because I don't want to die in my plane.

But what I don't understand exactly, is what defines "known icing conditions". I.e., it's not legal for me to fly my plane into known icing conditions. What, exactly, are those conditions?

At the simplest, any time there's visible moisture at or below freezing temps there is the potential for icing.

Does that mean I can't legally shoot an approach from a VFR-on-top enroute leg through a 1000' overcast layer at my destination airport that's below freezing?

Does it become "known icing" if it's snowing instead of just overcast?

Does it become "known icing" if it's raining on the ground, but the clouds are above the freezing level? (Etc.)

Thanks in advance for the education.

 

[rbridges]

Your situation is almost identical to mine. I'd like to know the answer to the question, too.

 

[write-stuff]

Here's a link to the 2009 FAA General Counsel letter on the subject from the Gold Seal Library:
http://www.faa-ground-school.com/library/known-icing-letter.pdf

 

[bbchien]

Looking around for the opinion that followed "bell"....

Late add: the Jan 16, 2009 letter IS THE DEFINITION.

 

[PilotAlan]

What all that means is that the FAA will define known icing conditions after the flight has occurred, notifying via an enforcement action.

 

[koehn]

Thanks for posting this. I was pretty sure the 2009 letter was canonical, but it's good to see others share that opinion.

Basically the letter says that if you make a habit of flying into icing conditions without proper equipment and planning, you should be prepared for some negative consequences.

In my humble opinion the consequences that the FAA might hand out are the ones you should hope for.

 

[poadeleted20]

Looking around for the opinion that followed "bell"....

Late add: the Jan 16, 2009 letter IS THE DEFINITION.

Just so it's clear, the "Bell withdrawal letter" (second on Bruce's list) is the letter the FAA wrote to AOPA in 2008 withdrawing an earlier letter from a Regional Counsel, and saying the FAA would research the issue and come up with something better. The "Bell letter" (first on Bruce's list) is the 2009 letter the FAA wrote to AOPA which is that "something better" and remains the current legal interpretation of what constitutes "known icing conditions."

 

[taters]

here is the key phrase

"If the composite information indicates to take reasonable and prudent pilot that he or she will be operating the aircraft under conditions that will cause ice to adhere to the aircraft along the proposed route and altitude of flight , then known icing conditions exist."

 

[Palmpilot]

To further confuse matters, AIM Table 7-1-8 defines "known icing conditions" as follows:

Atmospheric conditions in which the formation of ice is observed or detected in flight.
Note−
Because of the variability in space and time of atmospheric conditions, the existence of a report of observed icing does not assure the presence or intensity of icing conditions at a later time, nor can a report of no icing assure the absence of icing conditions at a later time.

That would seem to imply that it doesn't become known until it actually shows up on your or someone else's airframe. I wouldn't recommend disregarding the Chief Counsel's opinion though!

 

[Ted]

In a practical sense, when was the last time anyone heard of a Part 91 operator receiving enforcement action for flying into known icing? 135 being a different story.

 

[Fearless Tower]

here is the key phrase

"If the composite information indicates to take reasonable and prudent pilot that he or she will be operating the aircraft under conditions that will cause ice to adhere to the aircraft along the proposed route and altitude of flight , then known icing conditions exist."

Maybe a silly question, but does 'adhering to the aircraft' take the effectiveness of boots into consideration?

IOW, if the boots are doing their job and preventing the ice from accumulating, then is it not 'known icing conditions'?

I am referring to full-de-ice quipped planes, not those specifically certified for FIKI.

 

[poadeleted20]

To further confuse matters, AIM Table 7-1-8 defines "known icing conditions" as follows:



That would seem to imply that it doesn't become known until it actually shows up on your or someone else's airframe. I wouldn't recommend disregarding the Chief Counsel's opinion though!

The AIM language was discussed by the Chief Counsel. In any event, a Chief Counsel interpretation takes precedence over the AIM in any legal proceeding.

 

[poadeleted20]

Maybe a silly question, but does 'adhering to the aircraft' take the effectiveness of boots into consideration?

IOW, if the boots are doing their job and preventing the ice from accumulating, then is it not 'known icing conditions'?

I am referring to full-de-ice quipped planes, not those specifically certified for FIKI.

I think the FAA would tell you that the presence of some de-icing equipment which may remove some ice does not change the fact that some ice would likely adhere to that non-FIKI aircraft even if that gear might get some of it off.

 

[Palmpilot]

Maybe a silly question, but does 'adhering to the aircraft' take the effectiveness of boots into consideration?

IOW, if the boots are doing their job and preventing the ice from accumulating, then is it not 'known icing conditions'?

I am referring to full-de-ice quipped planes, not those specifically certified for FIKI.

I've never seen a definition of known icing conditions that made it dependent on how the aircraft was equipped. Besides, even de-ice equipped aircraft have parts that are not de-iced, and I think that applies to FIKI-certified aircraft as well.

 

[Palmpilot]

The AIM language was discussed by the Chief Counsel...

Good point. I see that they wrote this about the definition I quoted:

"That definition is not sufficiently broad to reflect the agency's position as set forth in this interpretation. The FAA will initiate action to revise the definition to reflect the interpretation articulated in this letter."​

 

[taters]

In a practical sense, when was the last time anyone heard of a Part 91 operator receiving enforcement action for flying into known icing? 135 being a different story.

Anyone in a non FIKI GA plane that makes a scene in the ATC system over ice is \could have some splaining to do

 

[comanchepilot]

Who the F^&k knows . . . .

honestly, thats the answer. The answer is whatever the FAA believes in that situation it is. . . . it is then up to you to prove it is not.

 

[Ted]

Anyone in a non FIKI GA plane that makes a scene in the ATC system over ice is \could have some splaining to do

That wasn't my question. My question was when was the last time someone actually knew of a Part 91 pilot who got an enforcement action for flying a non-FIKI plane into known icing conditions.

Follow-up question, since I've heard rumors that the LNK FSDO can be a bit anal and overly critical and if your answer was "Yes" I'd expect it to be related to a plane that landed or took off from LNK. How about for airports without a FSDO based there?

 

[taters]

That wasn't my question. My question was when was the last time someone actually knew of a Part 91 pilot who got an enforcement action for flying a non-FIKI plane into known icing conditions.

Follow-up question, since I've heard rumors that the LNK FSDO can be a bit anal and overly critical and if your answer was "Yes" I'd expect it to be related to a plane that landed or took off from LNK. How about for airports without a FSDO based there?

Heres one..and note the scene they made..thats what will get you caught....not the presence of a FSDO..Unless you pull onto their ramp with ice hanging all over your 172 etc...

http://www.aerolegalservices.com/Articles/Known Icing Conditions.shtml

 

[Ted]

Ok, so that's one on a law firm website after an accident occurred. If an crash occurs, then yeah, I'd expect an investigation and enforcement.

How about someone who has a safe landing, and you knew personally? I'm guessing none.

 

[taters]

Ok, so that's one on a law firm website after an accident occurred. If an crash occurs, then yeah, I'd expect an investigation and enforcement.

How about someone who has a safe landing, and you knew personally? I'm guessing none.

That's really my point. You have to make some kind of scene to get in trouble

 

[Ted]

That's really my point. You have to make some kind of scene to get in trouble

Ok then, we agree. And I'd also expect you'd have to crash, or else the controller would have to be in a really bad mood.

 

[azure]

A friend of mine must have been flying with the most paranoid pilots who ever took to the skies. One was even an aviation attorney. She tells the story that she was flying with these guys as a passenger, in IMC (somewhat turbulent IMC at that), when they started picking up ice. She asked the PF why he didn't just call up ATC and tell the controller they were picking up ice and needed a change of altitude. Both pilots quickly answered, no no no, we can't do that, if we do that it's an admission that we were flying in "known icing conditions" and we'll get busted. So they kept flying along, not a peep, all the while accreting ice all over the airframe. I forget whether they eventually got out of the clouds and lost the ice, or whether they landed with it.

Idiots.

 

[Jim_R]

Many thanks (especially to Dr. Bruce for the letters). This addresses my "concern". I wasn't sure if there was a clear definition of "known icing conditions" in the regulations somewhere that I couldn't find. I now know there is not, but that there is a Chief Counsel letter that pretty much says, "Do what you've been doing: Check the weather, plan flights to avoid regions of high icing potential (or reported icing), and have a plan for how to get out of icing conditions if you happen to run into them."

I'm okay with that.

 

[Captain]

Okay, there's all the foggy legal interpretations. Here's what I use real world:

Temperature: 5C to -40C (warmer is too warm at piston speeds and below -40C ice is impossible), AND

Visible moisture: That means rain, snow, sleet or clouds with vis less than a mile.

If you have both then you have conditions that a reasonable pilot should expect icing. I know the legal beagles will be after me with letters and whatnot, but it works and is the short answer to your question.

...fircken lawyers. Screw up everything.

 

[Sac Arrow]

FSS brief: "icing above 6,000"

Sac Arrow: Been bitten by that once, fortunately lived to tell about it.

FSS brief: "icing............"

Sac Arrow now: "Thanks, the car has a full tank of gas...."

You guys back East can deal with your icing. I'll deal with my terrain. No trades.

 

[gprellwitz]

Okay, there's all the foggy legal interpretations. Here's what I use real world:

Temperature: 5C to -40C (warmer is too warm at piston speeds and below -40C ice is impossible), AND

Visible moisture: That means rain, snow, sleet or clouds with vis less than a mile.

If you have both then you have conditions that a reasonable pilot should expect icing. I know the legal beagles will be after me with letters and whatnot, but it works and is the short answer to your question.

...fircken lawyers. Screw up everything.

That's not known icing, that is possible icing, not even probable icing. That will keep you grounded much of the winter in the northern latitudes, though it will certainly keep you legal and safe, in respect to icing, at least. I certainly don't find fault with you choosing this conservative approach, but personally I find it a little too restrictive.

 

[azure]

Okay, there's all the foggy legal interpretations. Here's what I use real world:

Temperature: 5C to -40C (warmer is too warm at piston speeds and below -40C ice is impossible), AND

Visible moisture: That means rain, snow, sleet or clouds with vis less than a mile.

If you have both then you have conditions that a reasonable pilot should expect icing. I know the legal beagles will be after me with letters and whatnot, but it works and is the short answer to your question.

...fircken lawyers. Screw up everything.

What are you flying that you consider 5C even POSSIBLE (much less known) icing? (assuming we're talking about structural icing here, not carb ice) Granted, 5C in clear air might be colder in the clouds, but I've seen my wings soaking wet at 3C in solid IMC (as indicated on my JPI), no sign of freezing.

 

[ArtPileggi]

That's not known icing, that is possible icing, not even probable icing.

Everything thing I have read prohibits flight into "known icing conditions". That is not "known icing" but conditions which could lead to icing. You as PIC can certainly choose to ignore that regulation, or any other one for that matter, but you should not be suprised if you get bitten. Complaining that obeying the rules would ground more than you would like is not a defense.

 

[ja_user]

Everything thing I have read prohibits flight into "known icing conditions". That is not "known icing" but conditions which could lead to icing. You as PIC can certainly choose to ignore that regulation, or any other one for that matter, but you should not be suprised if you get bitten. Complaining that obeying the rules would ground more than you would like is not a defense.

People fly into those conditions all the time and don't produce any ice, anywhere.

 

[Captain]

That's not known icing, that is possible icing, not even probable icing. That will keep you grounded much of the winter in the northern latitudes, though it will certainly keep you legal and safe, in respect to icing, at least. I certainly don't find fault with you choosing this conservative approach, but personally I find it a little too restrictive.

Not conservative. It used to be 10C to -40C with vis moisture until the latest FAA interpretation.

I figure a plane doing 250+ has more heating so I can use 10C. A piston had better stick with 5C. Regardless, that's what the airlines use. Do what you like.

 

[Captain]

What are you flying that you consider 5C even POSSIBLE (much less known) icing? (assuming we're talking about structural icing here, not carb ice) Granted, 5C in clear air might be colder in the clouds, but I've seen my wings soaking wet at 3C in solid IMC (as indicated on my JPI), no sign of freezing.

There's a little thing that makes airplanes fly. It's a low pressure over the wing...

Perhaps you've also heard that when you lower an airmass's pressure it gets colder. So, while you are reading a temp of 5C on your thermometer, the low pressure over the wing (and every other curved surface of your plane...look around, there are many) is a bit colder. 5 degrees is a pretty good buffer for this effect. I use 10C personally, but only when over 250 kts TAS.

 

[Captain]

What are you flying that you consider 5C even POSSIBLE (much less known) icing? (assuming we're talking about structural icing here, not carb ice) Granted, 5C in clear air might be colder in the clouds, but I've seen my wings soaking wet at 3C in solid IMC (as indicated on my JPI), no sign of freezing.

BTW, this doesn't mean anything. I've seen icing conditions where we didn't get any ice and I've seen non-icing conditions where we picked it up. Go figure.

Me, I have 10K hours with only 1,000 in pistions. All the rest has been turbine and certified into ice.

 

[azure]

There's a little thing that makes airplanes fly. It's a low pressure over the wing...

Perhaps you've also heard that when you lower an airmass's pressure it gets colder.

Sounds like you are talking about aerodynamic cooling. Actually it is not lowered pressure that causes a decrease in temperature, it's the adiabatic expansion that results when the pressure is lowered too quickly for the gas to exchange heat with its surroundings. Just about everyone I've talked to about this (including here, where I asked a question about this a few months ago) says that at the speeds piston planes fly at, this effect is in the noise and measurement errors due to gauge inaccuracy and mounting errors are MUCH more significant.

I will admit, though that I haven't done the calculation myself.

 

[azure]

BTW, this doesn't mean anything. I've seen icing conditions where we didn't get any ice and I've seen non-icing conditions where we picked it up. Go figure.

Now we're definitely talking about different things. I didn't say anything about "icing conditions". I gave an indicated temperature and a condition (wing literally dripping wet) under which, if the temperature on the wing skin was below freezing, it would most certainly have iced up. I'm not arguing that ice is impossible when the OAT gauge reads a few degrees above freezing, but to my understanding, if you see ice under those conditions, the ambient temperature (and not just the skin temperature) is actually below 0C.

 

[Captain]

Switch 'ambient' with 'local' and we're in complete agreement. The water doesn't know or care. If the plane is going g fast enough to register 8C but the local temp over the wing is -2 C you are in a spot to pick up ice. Go a bit faster is my first thought. Climb out of the layer if possible is my second. Descend? Do we have fuel for that? Turn on the ice protection regardless...

 

[spiderweb]

here is the key phrase

"If the composite information indicates to take reasonable and prudent pilot that he or she will be operating the aircraft under conditions that will cause ice to adhere to the aircraft along the proposed route and altitude of flight , then known icing conditions exist."

Is that the actual quote? What a grammatical mess!

 

[Piloto]

1. How the FAA knows if you are encountering icing conditions, unless you report it.

2. How long after icing conditions are reported in an area should I wait before entering that area?

Can I fly into "unknown icing conditions" rather than "known icing conditions" without de-icing equipment? Then if I don't ask about icing conditions then it is legal for me since I don't know.

What a puzzle

José

 

[bbchien]

Many thanks (especially to Dr. Bruce for the letters). This addresses my "concern". I wasn't sure if there was a clear definition of "known icing conditions" in the regulations somewhere that I couldn't find. I now know there is not, but that there is a Chief Counsel letter that pretty much says, "Do what you've been doing: Check the weather, plan flights to avoid regions of high icing potential (or reported icing), and have a plan for how to get out of icing conditions if you happen to run into them."

I'm okay with that.

But remember they judge you after the fact.

 

[Palmpilot]

Is that the actual quote? What a grammatical mess!

No, the letter at Bruce's link says "a" where the quote says "take"