What exactly is KNOWN icing?

viper548

Well-Known Member
Here's the question, what exactly is known icing? Obviously if you look out the window and see ice, that's known icing. A pirep would also be "Known." What if the cloud layer starts at 4000 feet and you want to fly at 6000 with the freezing level at 5000? I've heard different answers to this, and heard the FAA won an enforcement case where the pilot got caught in ice and said that the pilot should have known there was icing becuase he planned to fly above the Freezing Level in clouds.
 

xdashdriver

Well-Known Member
I believe the current interpretation that the FAA is enforcing is forecast icing....mainly through Airmet/Sigmet issuance. In other words, if it is forecast, then it is "known icing"

Cloud above freezing level does not necessarily indicate icing conditions, just a potential for icing. Now, flying in clouds or precip above the freezing level in an area where an Airmet or Sigmet has been issued for icing would consitute a violation unless you are operating an aircraft that is certified for flight into known icing conditions, AND all of the equipment necessary for said certification is operational.

These issues are what was discussed at our winter flying FAA safety meeting last week.

Ray
 

NJA_Capt

Well-Known Member
[ QUOTE ]
what exactly is known icing?...What if the cloud layer starts at 4000 feet and you want to fly at 6000 with the freezing level at 5000?

[/ QUOTE ]

Excellent question. Unfortunately most of the people flying "non-certified" aircraft have no idea.

Anything less than +10 degrees C and visible moisture is considered known icing.

In your example above, you could not fly in the clouds above the freezing level without expecting to get ice. If you can avoid clouds and/or remain VMC you are fine. You may or may not get any ice, but the expectation of ice is always there. I have heard people in Cherokees over the radio asking ATC for help because they are IMC over the mountains and getting ice. It's scary to listen to, but you always wonder what the heck they were thinking. The freezing level is at ground level, and they decided to go for a ride in the clouds
 

SEAN

New Member
are super cooled ice crytals in clouds susceptible to airframe icing? meaning, if the air is 10 or 20 degrees below freezing at altitude and you are in clouds are you likely to pick up ice?
 

DE727UPS

Well-Known Member
NJA Capt

"Anything less than +10 degrees C and visible moisture is considered known icing."

Is this your opinion or something you can back up as an official FAA policy? Please cite your source.
 

stuckingfk

Well-Known Member
Re: NJA Capt

I found this in the AOPA archives:

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In the NTSB's eyes, "known icing" exists if the forecast predicts temperatures below freezing and visible moisture.

[/ QUOTE ]
 

DE727UPS

Well-Known Member
Re: NJA Capt

Okay...the NTSB can't violate you or suspent your license. I'd like to see something considered the official stance of the FAA or a legal opinion from the FAA general counsel. I have a feeling that, the way the FAA works, it would boil down to one inspectors opinion.

Every instrument student I've ever had I've tried to get into icing in a controlled and safe situation....just so they can see what happens when you get a little ice in a 172. I find some obscure VOR to hold over and negoitate a block altitude that allows me to get some ice...when you've had enough you just descend back down to a lower altitude and get out of the clouds.

You fly around enough in actual condiditons and you're gonna see ice sooner or later, so you should know what it's about. I don't see the federalies running around trying to enforce the fact that sigments and airments all winter long mean known icing....or that if your in a cloud and it's colder than plus ten C...it's known icing. Now....if you crash a 172 that's loaded up with ice....they are gonna throw the book at you. I just want to know where in the FAR's or FAA legal opinion, known icing is defined.
 

stuckingfk

Well-Known Member
Re: NJA Capt

DE727UPS,

I glanced at the AC91-74 for a few minutes and what is condsidered "Known Icing" doesn't seem to be in there.

I found this article very informative on the effects of icing. But it to also dances around what is "Known Icing."

AOPA
 

pilot602

If specified, this will replace the title that
Re: NJA Capt

End result = no one knows.

(as with most things CFR/FAA related)
 

NJA_Capt

Well-Known Member
Re: NJA Capt

[ QUOTE ]
Is this your opinion or something you can back up as an official FAA policy? Please cite your source.


[/ QUOTE ]
The FAA is regulator, they tell the manufacturers that they must withstand the icing certification. They do not place the temp limits on the airframe. Every AFM in a "known ice" aircraft will have the limits set forth for that type aircraft. Of all the planes I have flown, they have all said 10 degrees C and visible moisture.

The FAA website spells out the effects etc of supercooled water, "Aviation Weather" gives temperature ranges to expect supercooled water, visible moister, and so on.

Avweb.com has some good articles on icing.
Also:
http://www.tcpilots.org/safety/
Flight Safety Questions and Answers
Q: What is the definition of "known icing?"
A: Although the term is not defined in Part 1 of the Federal Aviation Regulations, the NTSB's administrative law judges have developed a solid definition of known icing in their decisions on icing-related certificate actions over the years. Beginning with a case in 1957, the NTSB has stated that icing conditions exist when temperatures are near or below freezing and visible moisture is present. They have said further that because the flight service station network states the existence of those conditions in reports and forecasts that are available to pilots both before flight and while en route, the icing conditions become "known." In a 1993 case in upholding a certificate action against a pilot who relied on pilot reports in making his go/no-go decision, the board made it clear that official weather reports and forecasts take precedence over "anecdotal" pilot reports.


Your post above is NOT a controlled environment. A controlled environment would be flying in an APPROVED aircraft and allowing it to accumulate, then blow the boots. I have been in a Navajo that picked up 1" of ice in less than 3 seconds. That could kill someone in a C172. You never know if you are going to get a trace or an inch.
That reminds me of the guys that simulate and engine failure, in a single engine, by pulling the mixture. It's not simulating and emergency, that's causing an emergency.

Here are several people violated (91.13) for flying inappropriate aircraft in icing conditions.

http://www.ntsb.gov/alj/o_n_o/docs/aviation/3770.pdf
http://www.ntsb.gov/alj/o_n_o/docs/aviation/4525.pdf
http://www.ntsb.gov/ntsb/brief.asp?ev_id=8222&key=0
http://www.ntsb.gov/ntsb/brief.asp?ev_id=6894&key=0
 

DE727UPS

Well-Known Member
Re: NJA Capt

What you consider controlled and I consider controlled, I guess, is open to opinon...since I disagree with you.

Cessna 172 models from 1969 and earlier do not have a prohibitation from flying in known icing in the aircraft handbook/owners manual. I believe this makes these aircraft perfectly legal to fly in known icing.

Ice certainly is a dangerous thing when encountered and one needs to know how to respond to it....to include a plan B and a plan C. I don't think parking every light aircraft from late fall to late spring with the airmets and sigments for ice, and the chance of possibly getting in the clouds with below freezing temps, is the answer.
 

NJA_Capt

Well-Known Member
Re: NJA Capt

I agree.....to disagree that is. My opinion won't get you violated. The lack of a prohibition is not permission. There are placards/and statements in the POHs of C172 that say "Approved for day/night VFR/IFR." If it is approved for icing it WILL say, "Approved for Flight into known icing conditions."

Anything else is 91.13

Anywho.....
Keeps in mind that just because a plane has a "hot" prop and maybe de-ice boots doesn't automatically mean it is approved for icing. A good example is the Beechcraft Baron. Many of the Barons come with full boots, and a hot windshield and they ARE NOT approved. Always check the POH/AFM.
 

JHines

New Member
Re: NJA Capt

[ QUOTE ]
Every instrument student I've ever had I've tried to get into icing in a controlled and safe situation....just so they can see what happens when you get a little ice in a 172.

[/ QUOTE ]

My instrument instructor did the same for me...would take me into icing (well maybe very light ice/frost) conditions, by finding a layer where he was SURE we could climb or descend a few hundred feet and get to a high-temperature area and/or into direct sunlight...I'm glad I got the experience.

This is a real gray area...if you take the "freezing temps and visible moisture" definition literally, wouldn't you have to park most GA planes a good part of the year???
 

NJA_Capt

Well-Known Member
[ QUOTE ]
This is a real gray area...if you take the "freezing temps and visible moisture" definition literally, wouldn't you have to park most GA planes a good part of the year???

[/ QUOTE ]

Most of us flatlanders have enough room to fly under the freezing levels through winter. Sometimes you have to stay on the ground.

Consider that most CFIs, like the ones giving "icing instruction," have 250-600 hours, and have never even flown a plane with anti-ice equipment, or been in "real" icing conditions. Things that make you go hmmmm.
 

EatSleepFly

Well-Known Member
[ QUOTE ]
Consider that most CFIs, like the ones giving "icing instruction," have 250-600 hours, and have never even flown a plane with anti-ice equipment, or been in "real" icing conditions. Things that make you go hmmmm.


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Personally, I have more hours than that, I've flown airplanes with anti-ice, and I've been in "real" icing conditions- both in equipped, and non-equipped airplanes. And I can honestly say that there is no way that I would intentionally take a 172 into icing just to show a student what it looks like. Not a chance. Ever.
 
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