The PA-46 windshield has received lots of justifiable negative press lately. It’s super-expensive to replace ($35k+ installed) and many in the fleet have been failing more than most think they should. Most of the time the damage is slow, over time, with sagging amp draws over the years. But, there is sure-fire way to damage your windshield quickly…just leave the switch in either HIGH or LOW on the ground. Here’s a video that will show what can happen:
In flight the air dissipates the heat, but on the ground the heat build-up can seriously damage the windshield. Care should be taken to follow the checklist and ensure the icing switches are turned OFF after flight. And…when external power is applied, make sure the various cockpit switches are in the correct position BEFORE allowing the electrons to flow.
Additionally, there’s another switch in the PA-46 that needs to be OFF on the ground…the Stall Warning Heat Switch. In fact, I cannot think of a single time that the stall warning heat should be ON. If the wing is loaded with ice, then the stall warning will not give an accurate indication of when the wing is about to stall. In fact, the wing could stall MUCH earlier when loaded with ice. So, Stall Warning Heat is simply not needed. The Stall Warning Heat is supposed to be amp-limited on the ground (hooked up to the Weight-On-Wheels “WOW” Switch), but if that protection fails (for whatever reason), the stall warning heat can burn up the Stall Warning Switch (requiring expensive replacement, at best) or even causing a fire (at worst).
Bottom line…windshield’s are expensive and windshield heat on the ground can damage the windshield. Know your switch position!