USAFHummer
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Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 12:41 am

http://www.9news.com/news/article.aspx?storyid=64966

I was at Denver yesterday flying on a CO flight DEN-IAH, and my flight had a lot of pax from a Skywest flight DEN-IAH that had been canceled on account of the story above...I was sitting next to two pax from the Skywest flight, and the story they told was that they were on the takeoff roll, very close to rotation speed, when the windscreens shattered and the takeoff was aborted...when they returned to the gate, the captain said they had been hit by a microburst and that was hat caused the shattering...(don't shoot the messenger, Im just reporting what was told to me!)

I checked with a friend who is a CRJ f/o about the plausibility of this explanation for a windscreen shatter and he argued that there was no way that a windscreen could be destroyed like that...are there any other alternative explanations?? WInds at Denver were pretty strong yesterday...I checked the METAR while I was at the airport and the wind reading was something like 33G40...but obviously it seems that windscreens should be able to withstand the wind...any ideas?

Thanks,
Greg
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FredT
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 1:12 am

A microburst can be full of rather large hail, so it is not implausible.

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Fred
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A342
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 1:41 am

Maybe there was a crack in the windscreen already before it broke ?

Birdstrike ? (I know, the pilot should have seen it.)
Exceptions confirm the rule.
 
USAFHummer
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 1:58 am

Quoting FredT (Reply 1):
A microburst can be full of rather large hail, so it is not implausible.

No hail yesterday in Denver, just light flurrying...

Quoting A342 (Reply 2):
Maybe there was a crack in the windscreen already before it broke ?

Birdstrike ? (I know, the pilot should have seen it.)

13 planes being struck by a bird in the same timeframe??? 13 planes with pre-cracked windscreens all going at the same time? Seems unlikely, oddswise...
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fr8mech
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 1:58 am

Rapid temperature changes have been known to crack windshields. Faulty controllers. Hail. Improper procedures (rare on newer aircraft).

But 8 winshields?

http://news.yahoo.com/s/ap/20070217/ap_on_re_us/winter_weather_86

I have no explanation.

We did have 2 windshields crack a couple of weeks ago, 1 night apart. It was pretty darned cold, but they both cracked at top of descent. A lot colder there, than at ground level.

FYI, some MELs allow an aircrfat to fly with a cracked windshield if certain conditions are met.
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JayDub
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 2:32 am

Possibly a combination of rapid temperature change and a rapid change in pressure?

Maybe New World Order living underneath DEN were testing some new weapons?

It's quite the mystery.
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Scooter01
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 7:08 am

Quoting JayDub (Reply 5):
It's quite the mystery.



Quoting Fr8Mech (Reply 4):

Maybe the same gremlins that that cracks the dashboards in my cars?

2 in Toronto(BMW) and 1 in Oslo(Volvo)

Scooter
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Ralgha
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 7:26 am

Bullets can damage windows.
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airfoilsguy
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 7:45 am

A comedian once said this about hurricanes but I think it applies here too. "It is not that the wind is blowing that is dangerous but what the wind is blowing. A reference to dirt stones and other assorted crap that the wind picks up.
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JayDub
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 8:25 am

The more I hear about it...the more I keep hearing about large chunks of ice being blown off of the terminal buildings.
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1011
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 8:50 am

Did Denver have thunderstorms? It is kinda hard to have a microburst without a thunderstorm. Maybe it was a mountain wave?
 
Goldenshield
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 12:32 pm

Quoting 1011 (Reply 10):
Did Denver have thunderstorms? It is kinda hard to have a microburst without a thunderstorm. Maybe it was a mountain wave?

Denver has them all of the time, storms or clear skies.
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USAFHummer
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 1:14 pm

Quoting 1011 (Reply 10):
Did Denver have thunderstorms? It is kinda hard to have a microburst without a thunderstorm. Maybe it was a mountain wave?



Quoting JayDub (Reply 9):
The more I hear about it...the more I keep hearing about large chunks of ice being blown off of the terminal buildings.

That seems to make a ton of sense...ice blown off roofs, hits cockpit while aircraft is still at gate...aircraft gets up to speed on the runway, windscreen fails on account of that...good thinking JayDub!
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memphis
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 5:55 pm

What about the massive windows lining the terminal? I bet they are not rated to withstand some of the forces that a windshield on a jet could take. Big grin Why weren't they busted?
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David L
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 10:25 pm

Quoting Memphis (Reply 13):
What about the massive windows lining the terminal? I bet they are not rated to withstand some of the forces that a windshield on a jet could take.

On the other hand, they tend not to be rattled along a runway at over 100 kts.  Smile
 
2H4
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 10:59 pm



Stupid question, perhaps, but might the broken windshields have been caused by deicing? For example, if the fluid had been too hot, or sprayed in the wrong places? I know very little about deicing ops, so I'm really just thinking out loud...


2H4


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FredT
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 11:04 pm

Quoting 1011 (Reply 10):
Did Denver have thunderstorms? It is kinda hard to have a microburst without a thunderstorm. Maybe it was a mountain wave?

Naw, microbursts come out of CBs. CBs can be associated with thunderstorms. But there is nothing saying you can't have a microburst without a thunderstorm.

My bet is still on hail. Windshields are either cracked or they are not. If ice blown off a terminal roof could imperceptibly damage windshiels in such a way that they'd later break... and not on one occasion but on several... I'd go by train. The hail from a microburst can be VERY local. And very destructive, if it happens to go across a couple of parked aircraft. Even more destructive if an aircraft happens to fly through the hail storm.

High winds the cause? Not likely, unless the area was struck by winds in excess of 250 knots...

One factor is the fact that airliner windshields are more brittle when the aircraft is parked on the grund than in flight. The reason is the windshield heating.

Speculation, speculation and speculation is all we will be able to achieve without more facts.
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fr8mech
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Feb 18, 2007 11:12 pm

If it was flying debris, why are only the windshields affected? They are hardly the most vulnerable parts of the aircraft. In fact, I would say they are one of the most durable and capable of withstanding a hit.
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Scooter01
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RE: Cockpit Windscreens Getting Damaged By Winds?

Mon Feb 19, 2007 12:46 am

Quoting Scooter01 (Reply 6):
Maybe the same gremlins that that cracks the dashboards in my cars?



Quoting 2H4 (Reply 15):
Stupid question, perhaps, but might the broken windshields have been caused by deicing? For example, if the fluid had been too hot, or sprayed in the wrong places? I know very little about deicing ops, so I'm really just thinking out loud...

Well, they are both made from oil-based chemicals. Maybe some kind of chemical used in the cleaning/maintenance or deicing fluids works over longer time to change some of the properties in the finished product. I was told once by a car cleaning MASTER that use of "Armor-all" was the cause for the cracked dashboards, and the cracking happened during freezing temperatures all 3 times.

Scooter

[Edited 2007-02-18 16:49:17]
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A342
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RE: Cockpit Windscreens Getting Damaged By Winds?

Mon Feb 19, 2007 4:46 am

Quoting USAFHummer (Reply 3):
13 planes being struck by a bird in the same timeframe??? 13 planes with pre-cracked windscreens all going at the same time? Seems unlikely, oddswise...

Sorry, as I didn't read the link, I didn't know 13 aircraft were affected. Very strange indeed.
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HAWK21M
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RE: Cockpit Windscreens Getting Damaged By Winds?

Mon Feb 19, 2007 11:53 am

Difficult to believe only Winds could have affected all those Aircraft Windshield.I believe The Wind was def carrying some Hail or similiar FOD.
regds
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memphis
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RE: Cockpit Windscreens Getting Damaged By Winds?

Mon Feb 19, 2007 1:14 pm

We were taught in never to spray de-ice fluid directly on the cock-pit windows. The intense heat added with the cold window could cause the window to crack. Instead, we were instructed to spray de-ice on the fusalage above the windows and let the hot fluid run down on top of the windows, wipers, etc in order to remove contamination.
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2H4
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RE: Cockpit Windscreens Getting Damaged By Winds?

Mon Feb 19, 2007 1:20 pm




Quoting Memphis (Reply 21):
We were taught in never to spray de-ice fluid directly on the cock-pit windows. The intense heat added with the cold window could cause the window to crack.

Well, that's what I was thinking. Perhaps the individual deicing the aircraft that day was new, forgetful, or uncaring.


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ouboy79
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RE: Cockpit Windscreens Getting Damaged By Winds?

Tue Feb 20, 2007 11:23 am

Quoting FredT (Reply 16):
Naw, microbursts come out of CBs. CBs can be associated with thunderstorms. But there is nothing saying you can't have a microburst without a thunderstorm.

My bet is still on hail. Windshields are either cracked or they are not. If ice blown off a terminal roof could imperceptibly damage windshiels in such a way that they'd later break... and not on one occasion but on several... I'd go by train. The hail from a microburst can be VERY local. And very destructive, if it happens to go across a couple of parked aircraft. Even more destructive if an aircraft happens to fly through the hail storm.

Umm, I bet if you review the observations at the airport at the time you would note no weather close to what you are suggesting. Severe weather season isnt really here yet...though it will get a kicker here in the Southern Plains on Friday (woot woot). Anything that day would have been good ol sleet if there was any precip. Nothing reported in the US even approaching severe criteria that day.

Also any wind that day would not have been from any sort of convection.
 
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RE: Cockpit Windscreens Getting Damaged By Winds?

Tue Feb 20, 2007 12:44 pm

I've seen the landing light lens covers on our fleet crack on numerous occasions due to the hot glycol being applied to a cold soaked aircraft. Granted, the lens cover is nowhere near as beefy as a windscreen, but it's the same principle. For what it's worth, you can fly one leg with the damaged landing light lens cover removed to get to a MX base to have it replaced.
 
FredT
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RE: Cockpit Windscreens Getting Damaged By Winds?

Wed Feb 21, 2007 3:32 am

Quoting Ouboy79 (Reply 23):
Also any wind that day would not have been from any sort of convection.

Now that is a good point.
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Airgypsy
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RE: Cockpit Windscreens Getting Damaged By Winds?

Sun Mar 04, 2007 12:00 pm

Years of maintenance control experience alerts me that this is a procedural problem. The outter Anti-ice pane is very thin and is usually very hot. It is something that is very time restricted for ground operations. The inner (thick) panes are heated for defog and can be operated continuously. I have never seen or heard of an inner pane cracking unless hit by a bird (or other BIG object).
There are temp sensors in the panes with associated controllers. Airflow over the outter pane is important to eliminate hot spots or overheating (which leads to cracking). I imagine there have been some changes to operating procedures.
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