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4 Answers

Encounter icing conditions…climb to a higher altitude?

Asked by: 8150 views
General Aviation

I am currently studying for my FAA Private Pilot Oral Exam.  I just read a question in my exam guide that states:

What action is recommended if you inadvertently encounter icing conditions? The answer: Change course and/or altitude; usually, climb to a higher altitude, if possible.  Temperature is always wamer than freezing at some higher altitude.

The latter sentence seems counterintuitive.  If temperature decreases with altitude, how can temperature be warmer than freezing a higher altitude?  I would think that if one continues to climb, icing conditions would only worsen due to standard temperature lapse rate (2 degrees C per 1000 feet).

 

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4 Answers



  1. Kent Shook on Jan 04, 2011

    Wow.
     
    First of all, I don’t think you need to worry about icing questions on your *Private* oral exam – That’s more of an instrument question. While it is possible to ice up an airplane while being legal VFR if you fly into some light precip, you sure don’t want to *climb* and get into clouds as well! While freezing precip does imply warmer air at a higher altitude, I think that suggesting you should climb into clouds as a VFR pilot is a TERRIBLE idea! If you start to ice up VFR, you should execute a 180º turn (or anything else that will get you out of the freezing precip) and land ASAP. Do not use flaps until you stop accumulating ice, and maintain a higher speed prior to landing. Turn on your pitot heat, windscreen defrost, and any other anti-ice systems you have. If your air filter ices up, you may need to use carb heat and/or alternate air as well. Be aware that use of carb heat in cold conditions can actually *cause* carb ice – See “land ASAP.”
     
    For an instrument pilot, the answer makes a little more sense in a freezing precip encounter (the precip had to be liquid at some higher altitude to become freezing precip in the first place), but there are other reasons why you can ice up as an instrument pilot too, since you can be flying in the clouds. That should be part of your instrument training and your instrument oral, but not for your private.
     
    Finally, remember that temperature doesn’t always decrease with altitude. When temperature increases with altitude, you have a temperature inversion. This sort of thing is common with a warm front.
     

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  2. Wesley Beard on Jan 05, 2011

    I agree with Kent that if you are VFR and are picking up ice the best bet is to get on the ground immediately.  You will not be able to get above the clouds to warmer air.
     
    I think it is important to remember that you must have some sort of visible moisture to pick up ice.  This visible moisture can be freezing rain, sleet, slush, snowflakes, clouds, fog, etc…   If you can climb above the clouds then you can effectively climb above the icing conditions.  I have flown down into a cloud layer where above the clouds my outside air temperature was +18 deg C and as soon as I entered the cloud layer, the temperature decreased to +6deg C.  You could definitely say it was a temperature inversion. 
     
     The most important thing to think about when flying IFR in the winter time is where the warmer air is and your exit strategy for each section of the flight should you get yourself into icing conditions.  The other thing to remember is that small GA aircraft usually cannot get high enough to climb above the clouds (apart from marine layers) to get out of icing conditions.

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  3. Matthew Waugh on Jan 05, 2011

    So I agree with the other answers about VFR – it’s certainly possible for you to be flying in visible precipitation, in VFR and at a temperature such that you encounter icing. I suppose there are a set of conditions in which you could remain VFR, climb, and exit icing conditions. But those conditions are so rare I wouldn’t bet on them.
     
    So VFR – turn, descend, land, whatever it takes, but don’t climb.
     
    As for IFR/IMC and encountering icing. There are a very small set of conditions that will lead to airframe icing. It can be too cold to ice as well as too warm. I believe the general rule of thumb is “change altitude by 4,000 feet and you will exit icing conditions”. The other idea is climbing to get on top of the visible moisture and hence out of icing. So climbing is an option. But not in many GA planes. If you’re climbing to get on top it’s true that the worse icing are in the top of the clouds. Ask any jet pilot and they’ll tell you of the numerous times they’re climbing happily in clouds, ping they get the ice detection warning, and moments later they climb into bright sunshine.
     
    But it’s an option, and if you know enough about the performance of your plane, probably with more ice on it than you currently have, and you have a good idea of flight conditions and temperatures aloft – by all means give climbing a shot.
     
    But to re-iterate – not VFR and not as a Private Pilot. 

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  4. MaggotCFII on Jan 16, 2011

    Here is another source for you: An AOPA Safety Advisor on Aircraft Icing.
    http://www.aopa.org/asf/publications/sa11.pdf
    Note page 11, Approach and Landing which discusses use of flaps, airspeeds and perhaps choosing a different airport at which to land.
    Good luck with the ground portion and flight portion of your practical test!

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