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keeping an eye on the vacuum and pneumatic gauges. You want to see those gauges drop and then come back up. The deice switch (auto cycle) opens the pneumatic deice valve and allows air into the boot, causing the gauges to drop. Once the boot is inflated and the air is trapped, the pressure goes back up and so do the gauges. You are looking for 16-18 psi after the drop. If you don’t get it, you should be worried about leaks in the boots. Take a closer look for cracks or weather checking and alert your shop accordingly.
Obviously if a boot doesn’t inflate properly, it can’t bust the ice off the leading edge. In the case of most cracks, your shop can patch them with no problem. The sooner you catch a crack in a boot, the easier it is to patch. A properly installed patch should last a long time; but if it starts to come loose, it usually can be redone. Multiple patches on a boot are not uncommon. Eventually, however, boots need replacement. They are not cheap and it is a labor-intensive job, so paying attention to your boots on a regular basis is good preventative maintenance.
A stern warning about boot dressing: Never use anything but the manufacturer’s recommended product to dress the boots on any aircraft. If you want your King Air to gleam in the sun with shiny black boots, you must rethink this obsession. Any product not specifically designed for your aircraft deice boots will surely hasten their demise, if not utterly destroy them.
I have seen people use car wax and even floor wax on their deice boots. Such products dry out boots faster than no product at all. Likewise, tire dressing products are designed for automobile tires, not aircraft pneumatic boots. Make sure whoever cleans your King Air understands implicitly which product they may use on the deice boots and that no substitutes are allowed. I cannot emphasize this point strongly enough.
External Heat Items
Windshield Heat: To test windshield heat, start with the battery on and select windshield heat. The different King Air models have a variety of windshield heat switches; the point is to cycle the switch through its various positions with a hesitation between each selection. While doing this, look at your magnetic compass – you’ll want to see it swing a couple of degrees with each change of position. The compass won’t swing if the OAT is too hot. It needs to be 75oF or below for this to work properly. If it’s cool outside and the compass doesn’t swing, then your windshield heat is not coming on. Have your shop look into it.
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FEBRUARY 2024
KING AIR MAGAZINE • 25