nikeson13 From United States of America, joined Dec 2011, 34 posts, RR: 0 Posted (2 years 1 month 3 weeks 4 days 23 hours ago) and read 4476 times:
Back in 2011, I was flying YUL - SFO on June 10 and halfway through the flight over Minnesota, we drop and then level out and the pilots tell us that the windshield cracked in the cockpit. We then diverted slowly and safely to YWG.
How often do windows crack due to pressure/faults or a mix of both? Can it ever become dangerous?
horstroad From Germany, joined Apr 2010, 307 posts, RR: 0
Reply 1, posted (2 years 1 month 3 weeks 4 days 23 hours ago) and read 4293 times:
windshields are fail safe designed. they consist of several layers. even if the outer ones failed due to FOD or wrong bolt torque/sequence or whatever, the remaining layers will hold the window together safely usually with no pressure loss.
it does happen, but not that often. when it happens you want to get to the ground. though it's completely safe with one layer cracked you don't want to risk the other layer being damaged. see British Airways Flight 5390 to know what happens if the windshield fails totally
oly720man From United Kingdom, joined May 2004, 6980 posts, RR: 11
Reply 2, posted (2 years 1 month 3 weeks 4 days 5 hours ago) and read 3866 times:
The windows are most often going to fracture because of impact (birds/hail) or the window heating system causing problems. Pressure in itself won't cause problems. They don't break as such because they are multi-layered.
As far as the heating goes, the outside temperature can be below -60C and the windshield outer temperature can be raised to around 50C. Because of the nature of glass it can suffer thermal shocks and fracture if heated too quickly so the temperature control is important.
To see what a fractured front windscreen looks like
Tristarsteve From Sweden, joined Nov 2005, 4167 posts, RR: 33
Reply 4, posted (2 years 1 month 3 weeks 2 days 19 hours ago) and read 3600 times:
Quoting oly720man (Reply 2): To see what a fractured front windscreen looks like
Depending on the window construction, some airliners can even operate safely with a cracked window.
On the B767, I had an aircraft arrive with a crazed window similar to the picture. The pilots greeted me by asking which hotel we used nowadays, and I got out the MEL and raised an ADD for the return flight. There were some checks to do, but the cracked glass stayed in.
On the Tristar, we used to completely remove the cracked outer layer, and then the aircraft continued in service.
This is not possible on many aircraft.
tb727 From United States of America, joined Jun 2005, 1794 posts, RR: 11
Reply 6, posted (2 years 1 month 3 weeks 2 days 8 hours ago) and read 3474 times:
Quoting FighterPilot (Reply 5): The seatbelt probably wasn't the only thing clinched when the window originally cracked.
Haha, yeah pretty much. It's always been on the opposite side from me and I still lean away. The time before this last one happened at night and the window heat was malfunctioning causing sparks and little lightning bolt looking arcs on the layer between the glass, it will get your attention. I've heard of a layer shattering all at once and it apparently makes a loud bang but I haven't had that happen.
Per our MEL we can go with the outer pane cracked unless it is in the line of site of the pilot for flying, which it was in the most recent case, so it was no go for me. It continued cracking little by little for a couple hours after we landed until we had a bunch of cracks all over the window instead of the original one.