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Discussion in 'Hangar Talk' started by overdrive148, Jun 29, 2020.
Very limited info but what the heck is going on here?
Windshield heat failing. These are all very thick laminated assemblies using multiple plies of plastic/glass/vinyl and are basically on a slow self-destruction process as soon as they are manufactured.
IDK specifics but from what I understand, the Lear 35/36 windshields are some of the most expensive ones ever produced for civil aircraft as the C21 military version required a higher bird strike resistance than regular civil aircraft regulation did. I think they only typically last 8 years or so before delaminating beyond airworthiness.
A lot of them have a glass outer ply that can shatter in service and scare everyone but its just the very thin outer ply that failed in those cases.
Interesting. I would think turning the heat off before something catastrophic happens, but I don't really know nutten about these things.
Had the outer pane on a Challenger fail once. Never even noticed till we landed. Perfectly legal to fly, just have to avoid known icing. $30,000 part
We had two windows crack on a King Air. From the lower left of the left side to the upper right of the right side. It was night and we didn't even notice it until we were on the ground.
If you are lucky, a King Air windshield will last 10 years. Whenever you see a cost analysis of a KA, new windshields $20K apiece (20 years ago) are never mentioned........never.
We’ve had a few crack at Endeavor. It’s mostly a non issue from what I’ve read in the reports and you can continue to your destination as planned.
I think cracking is pretty common on King Airs. It never happened to me, but I did a recovery flight once where I took mechanics out to one that had failed and got a look at it. Would have been a little tough to see through.
I watched a windshield delaminate on a Hawker once. It was slow, but you could see it happening.
The windshield have two structural panes, either one of which can support the full aerodynamic and pressurization loads. Between those panes is a layer of conductive material which, when energized, heats the window. The window heat is on for all phases of flight as the heated window is more flexible and can withstand bird strikes better than an unheated window.
When a pane fails you often have the arcing as shown in the video. The procedure will have you deactivate the window heat for the affected pane and also includes the restrictions for no flight through know icing conditions and to not exceed 250kts below 10,000' due to the reduced bird strike protection of the unheated pane (because there are situations where you can fly faster than 250kts below 10,000').
Usually is a non event, unless of course the pilot makes it one.
I had to cancel a flight one cold Winter morning due to a windshield fire. "A what?"
Yep. 115VAC running through gold layers in a very expensive windshield...