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Cracked Windshield  
User currently offlineBOAC707 From United Kingdom, joined Nov 2003, 278 posts, RR: 3
Posted (9 years 4 months 1 week 4 hours ago) and read 4354 times:

I saw a news rocker this morning about an Air Canada flight from Calgary to Toronto on March 26 that had to make an emergency landing in Winnipeg due a cracked windshield. I can't find anything in the forum, and I was wondering if anyone had more info...also, beyond a bird strike what makes a windshield crack in cruise?


smokey classics to the end of time
12 replies: All unread, jump to last
 
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 1, posted (9 years 4 months 1 week 4 hours ago) and read 4334 times:

.....a runaway heater will do it. Also, just like any glass, it can develop stress cracks, especially if chipped.


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineKC135TopBoom From United States of America, joined Jan 2005, 12128 posts, RR: 51
Reply 2, posted (9 years 4 months 1 week 4 hours ago) and read 4318 times:

Each window in the cockpit has it's own electric heat, to prevent fogging and icing inflight. Sometimes the heater for a window fails, or it overheats. The rapid temperature change can crack a windshield. Since these windows are very thick multiple layers of glass, where the crack is is very important. If I remember correctly, from my KC-135 days, when you see a crack, you draw a grease pencil mark on the crack, then lean over to one side or the other to determine weather the crack is on the inner or outer paine of glass. If the crack is on the inner paine, you must reduce the cabin pressures and land, If on the outer paine, you could reduce the cabin pressure and continue the mission. But, once on the ground, the aircraft is grounded the windshield is replaced, then another 24 hours to allow the sealant to cure.

But, things that can crack a window include bird strikes, rapid temperature changes, hail, and bullets.


User currently offline777ER From New Zealand, joined Dec 2003, 12082 posts, RR: 18
Reply 3, posted (9 years 4 months 1 week 3 hours ago) and read 4289 times:
AIRLINERS.NET CREW
FORUM MODERATOR

A few thunder storms have cracked some windscreens and I think one even partly smashed throu one

User currently offlineKhenleyDIA From Sweden, joined Feb 2005, 425 posts, RR: 0
Reply 4, posted (9 years 4 months 1 week 2 hours ago) and read 4194 times:

Quoting KC135TopBoom (Reply 2):
But, things that can crack a window include bird strikes, rapid temperature changes, hail, and "bullets".

You forgot sledge hammers and explosives.  scratchchin 

Back to being serious, they can crack from a number of things, but considering all the possibilities and the number of flights, it is rather rare. Of course, don't take that as a fact, I don't know the ratio of cracked windscreens / uncracked windscreens.

KhenleyDIA



Why sit at home and do nothing when you can travel the world.
User currently offlineKC135TopBoom From United States of America, joined Jan 2005, 12128 posts, RR: 51
Reply 5, posted (9 years 4 months 1 week 2 hours ago) and read 4158 times:

It is about 1 cracked windshield for every 10,000,000 window flight hours!

LOL


User currently offlineWhiteHatter From , joined Dec 1969, posts, RR:
Reply 6, posted (9 years 4 months 1 week 2 hours ago) and read 4150 times:

Windscreens will delaminate more often than form traditional cracks. Both mean that the aircrfat needs to be landed quickly.

User currently offline320tech From Turks and Caicos Islands, joined May 2004, 491 posts, RR: 5
Reply 7, posted (9 years 4 months 6 days 21 hours ago) and read 4001 times:

Windscreens will delaminate more often than form traditional cracks. Both mean that the aircrfat needs to be landed quickly.

Not necessarily. It depends on which layer the crack is in. It's common - relatively speaking - for the outer ply to crack. The outer ply is not structural, so other than that the pilot can't see through that windscreen, it's not a major emergency. Obviously, they'll still land as soon as they can.

If the inner structural ply cracks, that's a whole different situation. I'm not aware of it happening with the airplanes I've worked on - mostly Dash-8's and A320's.

Delamination is much more common. Depending on the degree of damage, the window might not be replaced at all. Delamination usually happens along the edges of the windscreen, and so doesn't interfere with pilot vision much.

A common cause of windscreen cracking on the Dash-8's was a water build-up in the window frame. At altitude the water would freeze, and put enough pressure on the windscreen to crack it. The problem was solved by opening a drain in the frame.



The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
User currently offlineBOAC707 From United Kingdom, joined Nov 2003, 278 posts, RR: 3
Reply 8, posted (9 years 4 months 6 days 5 hours ago) and read 3723 times:

thank you all for the info...you learn something new everyday....


smokey classics to the end of time
User currently offline777WT From United States of America, joined Jan 2005, 875 posts, RR: 1
Reply 9, posted (9 years 4 months 6 days 5 hours ago) and read 3698 times:

A long time ago here on A.net, there was a story of a 777 starting to descent to Milan, the window heater malfunctioned and the pilots shut it off. When they did, the glass cracked!

User currently offlineJeb94 From United States of America, joined Oct 2004, 598 posts, RR: 5
Reply 10, posted (9 years 4 months 6 days 5 hours ago) and read 3658 times:

If it was a CRJ its possible the curvature of the windshield wasn't exactly right for the aircraft. Its a known problem, especially on CRJ 700s and 900s.

User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 11, posted (9 years 4 months 5 days 17 hours ago) and read 3422 times:

What was the Aircraft model.Probably Faulty Heat element/Controller.
regds
MEL



Think of the brighter side!
User currently offlineBUFJets From United States of America, joined Jan 2001, 231 posts, RR: 0
Reply 12, posted (9 years 4 months 5 days 15 hours ago) and read 3369 times:

I once had a flight cancelled due to a cracked windshield. We were leaving the first flight out of BUF on a cold February morning. They turned on the heaters (I assume window heaters) and one window cracked. It was a US flight. They flew the 737 out of BUF empty to BOS for repair.

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