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  • Dave Smith
    replied
    Cold Starts & Carb Icing

    Dean,

    Taxying over wet grass seems to exacerbate carb icing in certain conditions. It's the only time we seem to experience any evidence of carb icing on our, normally well-behaved, Continental C90 powered Minicab (!).

    On doing hold power checks, revs drop markedly on operating the carb heat, then it coughs and the revs come back up to above where they were before the exercise. Of course, we're talking about an air filter about 6" behind the prop and low down, so it's picking up thoroughly saturated air from the ground.

    Dave

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    Steven Owen wrote: Peter what aircraft was that you were flying, I am glad to see your copy and paste slills are good, . Read below for some facts.

    You have much more chance of getting carb icing in the summer, once the dew point and air temperature are sitting on top of one another then you have perfect conditions for carb iceing, and remember when you check the ATIS you need to calculate minus two degrees for every thousand feet, so flying at two thousand feet you would compensate your calculation by four degrees, to get the correct figure for checking where the dew point and air temps sit on top of each other or come very close, in the winter on these crisp days you have hardly any chance of carb icing.even when very cold Dry air poses little risk of carb icing.

    I do however wish I could jazz up my post with colour but it does not seem to work with firfox browser.

    Regards Steve
    [4]The Clue might have been in the date of the post !!! Posted 28/Oct/2006 3:48 PM (GMT 0) [/4]

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    Peter what aircraft was that you were flying, I am glad to see your copy and paste slills are good, . Read below for some facts.

    You have much more chance of getting carb icing in the summer, once the dew point and air temperature are sitting on top of one another then you have perfect conditions for carb iceing, and remember when you check the ATIS you need to calculate minus two degrees for every thousand feet, so flying at two thousand feet you would compensate your calculation by four degrees, to get the correct figure for checking where the dew point and air temps sit on top of each other or come very close, in the winter on these crisp days you have hardly any chance of carb icing.even when very cold Dry air poses little risk of carb icing.

    I do however wish I could jazz up my post with colour but it does not seem to work with firfox browser.

    Regards Steve

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    [black] Well being an avid reader of the AAIB reports I was reminded that Jabiru engines don't like operational Power Stations !!!! G-TYKE suffered an engine failure and it was attributed to in increase of humidity caused by the cooling towers of a power station nearby to it's flightpath, now G-CEKM [/black]http://www.aaib.gov.uk/cms_resources...KM%2011-09.pdf has the same facts in the AAIB report.

    Now I would not have given much thought to a Power Station causing such a change in humidity levels, but I suppose it stands to reason....guess who will not be flying near Power Stations anymore ?

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    Peter

    I oversee the Grob Vigilant gliders used by the RAF. Carb icing has, and continues to be, a problem. Icing whilst taxying was an issue, but it was during the hold that we had most problems. My advice to anyone is to let the engine warm thoroughly and if at all possible do not delay your departure! To counter this we have recently sanctioned taxying with carb icing on. This has a certain risk in that the filter is bypassed and susceptible to debris etc, however, the benefits certainly outweigh the risk. To support this we carry out stringent engine checks. The frequency of Incident Signals in respect of engine power problems has vastly reduced so it looks like this is working...

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    :idea: are they 3amp or 5amp :yeah:



    Heard a rumour that Wizardboy is looking to buy a new Foxbat Sport, so I assume we will go just for him to use up his loose change :shocked:

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    Yeah, I should be there, slapping a few more bits on the Escapade. Fuse is nearly ready to cover.

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    [/b]

    Are you kicking about Wing Farm next Saturday 4th Nov I have a punter going down there to see G-BMMV with a view to buying it, he is also looking at some Grobs that Tim has down there for sale. He has shown an immense interest in the Brasov and has Brasov money as opposed to Grob money, so it's looking good. The Brasov is still wingless in the hangar at Tim's so you can relax I will not be down there to fly it, anyway I believe Tim is being asked to show him the Brasov as well as the Grobs. So if you see a guy at Wing Farm looking for it, you will know who he is now.

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  • Guest's Avatar
    Guest replied
    Cold Starts & Carb Icing

    Nice article Peter but could you do it in one colour and not the blue ?

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  • Guest's Avatar
    Guest started a topic Cold Starts & Carb Icing

    Cold Starts & Carb Icing

    Now we are well into the Winter months I guess we should pay extra attention to Cold Starts and Carb Icing.

    [/b]

    [color=red>Carb] In the absence of a heat source, an evaporating liquid (avgas or mogas) cools its immediate surroundings. Carb icing becomes possible when the intake air temperature is reduced to below the freezing point of water. The air temperature is reduced both by evaporative cooling of the avgas or mogas and also expansion cooling as air passes through the carb venturi. 4C and 15C (25F and 60F) and high humidity, ice can form in the venturi and on the throttle plate. Icing does not occur when the air temperature is too low, below about 7C to 12C (20F to 10F), because then the air is too dry. [/b]



    Rotax have now retrospectively got a system that uses the coolant to heat the Carb inlet neck between the Air filter and the Venturi, this system brings the inlet temperature up to a point where ice formation shouldn't occur.s, chances are Carb Icing will occur. Carb heat by means of air being drawn from around the exhaust is also commonly used in GA aircraft and is operated by a lever to open the heat exchanger to allow warm air into the Carb intakes.[/b]

    and I knew you could get Carb Icing on the ground, but I had never experienced it.

    [color=red>The weather at the time was



    [color=red>994mb



    [color=red>Dewpoint 11c

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