Cleaning behind a windshield anti-ice heater panel

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    Hiya all,

    When we bought our T303 in 2008 the windshield anti-ice heater was virtually opaque with crazing from being parked outside in the sun for too long. We bought and had a new one installed, and it works fine.

    However one problem we have is that it fills with water when flying in the rain, and when it dries out it leaves a thin chalky white deposit (scale) where the drops were. Like what you get on wine glasses if you don’t dry them up after washing up. Over the years our anti-icing panel has got more and more dirty, and now I find myself leaning left to look past it when we’re on final. Not ideal.

    I talked to our maintenance guys about getting it cleaned, but it seems the panel is glued to the windshield with silicon. To clean behind it we would have to rip it loose, clean the silicon glue and chalk scale off the windscreen and the panel, and then re-install the panel on the windscreen, again with silicon glue. That’s a lot of work, and risks damaging the panel.

    Have you guys ever had this problem? How did you fix it? Have you ever heard of a way to clean the scale off between the panel and the windscreen without removing it?

    I’m thinking of a procedure something like this:
    – Make a small service hole in the side of the silicon panel mount, near the top
    – Fill the gap between the panel and the windscreen with a weakish vinegar solution. (Vinegar is used in Switzerland to get the chalk scale off the inside of kettles).
    – Over a couple of hours, the vinegar should dissolve the scale
    – Make another small hole in the side of the silicon panel mount at the bottom, and drain the liquid
    – Use lots of distilled water to wash the dregs of the vinegar out. (distilled water doesn’t leave marks)
    – When the distilled water has dried out, fill the service holes with silicon glue

    Has anyone tried or heard of a procedure like that? Maybe vinegar isn’t the right stuff to use – I’m worried that it might damage the perspex windshield and/or panel. What would you use?

    Any other suggestions?





    My brother also has this problem on his 310 and it drives him nuts. When we bought our 340, our hot plate was not sealed on the sides with silicone. I thought it was incorrectly installed and discussed with my mechanic. We reviewed a lot of other airplanes and found that the sealing of the hot plate was not required.

    Though skeptical, I encountered some pretty serious icing while descending from the mountains a few months ago. The minute I hit the hot plate switch, it instantly cleared and I could see perfectly. It seems the hot plate really is designed to shed icing that impacts the plate on our bird.

    If you have the heater elements (small lines in the plate), you can pull the plate, clean the windshield and re-install without the sealing. Then when your window gets dirty, just remove the three top screws, carefully clean underneath and replace the screws with some locktite.

    Hope this helps.



    Thanks for the reply Mike, that’s interesting to know. If we do get the hot plate removed and cleaned I will definitely not let them stick it back on with Silicone.


    Looking at the service manual, it is not clear if the silicon goes around the plate, or just top and bottom. I am not a mechanic.


    Definately have to check your service manual, but ours has silicone at the bottom where the wiring goes into the top of the nose and a bit at the transition between the mounting plate and the plastic plate at both the bottom and top. Other than that, ours floats free.

    You do get some water underneath it in a heavy rain while parked, but I have had no issues while flying so far.


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