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propilot83
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How Strong Are Cockpit Windows?

Thu Mar 25, 2010 8:07 pm

I know that cockpit windshields of commercial airliners can withstand bird strikes at certain speeds, how much of an impact can cockpit windshields of airliners withstand from a bird strike at cruising altitude, approach, take-off? Does any engineer know how strong those cockpit windows really are? Thanks!
 
vikkyvik
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How Strong Are Cockpit Windows?

Thu Mar 25, 2010 8:46 pm

I can't answer how large an impact they can withstand, however...

Quoting propilot83 (Thread starter):
Does any engineer know how strong those cockpit windows really are?

I'd be very surprised if some engineer didn't know.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
BoeEngr
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How Strong Are Cockpit Windows?

Thu Mar 25, 2010 9:18 pm

Been a while since I've worked on that stuff but as I recall, the FAA requirement is that it survive the impact of a 4 pound bird. Internally, at Boeing we have our own requirement of being able to withstand the impact of an 8 pound bird.

And that stands for more than just the windows. It's all the structure up front, around the windows, etc.

Hope I recall correctly.
 
b78710
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How Strong Are Cockpit Windows?

Thu Mar 25, 2010 10:23 pm

Quoting propilot83 (Thread starter):
how much of an impact can cockpit windshields of airliners withstand from a bird strike at cruising altitude

don't get too many birds at 37k feet  
 
GST
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How Strong Are Cockpit Windows?

Thu Mar 25, 2010 10:42 pm

Quoting b78710 (Reply 3):

don't get too many birds at 37k feet

But I do recall a yarn about a 744 first officer who had a leg broken by an eagle that punched through the front.
 
soon7x7
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How Strong Are Cockpit Windows?

Thu Mar 25, 2010 10:55 pm

Broken windscreens are more of a threat from birdstrikes on approach than on take off as the airframe is coldsoaked making the screen more brittle. Some aircraft will engage the window heater before descent to "soften" the acrylic in case of a strike. In addition, your nose attitude on descent vs climb out makes windscreen more vulnerable. I have heard of geese at the 25k flight level but never up in the thirties. You'd feel better about windscreens on airliners if you tried to pick one up. A 747 front lens weighs about 100+ pounds. it is also very thick (3") and laminated to resist failure after a strike. i think you would need a Bald Eagle flying at the plane for total penetration.
 
474218
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How Strong Are Cockpit Windows?

Fri Mar 26, 2010 12:43 am

An airliners main windshield has several layers:

A glass face plate, approximately 0.100" thick.
Then a layer of Polyvinyl Butryal (PVB), about 0.125" thick.
Then a layer of Stretched Acrylic approximately 1.00" thick.
Then another layer of PVB about 0.100" thick.
Then another layer of Streched Acrylic approximately 1.00" thick.

The side fight station windows are the same but have no glass face plate.
 
tdscanuck
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How Strong Are Cockpit Windows?

Fri Mar 26, 2010 1:01 am

Quoting propilot83 (Thread starter):
I know that cockpit windshields of commercial airliners can withstand bird strikes at certain speeds, how much of an impact can cockpit windshields of airliners withstand from a bird strike at cruising altitude, approach, take-off?

They have to at least meet the FAR...as BoeEngr said, they may be considerably stronger. The limits go up to a certain altitude...if you're at Mach 0.9 up high, a big bird will go through the window, but the bird shouldn't have been there in the first place (in a regulator's mind, anyway).

Quoting propilot83 (Thread starter):
Does any engineer know how strong those cockpit windows really are? Thanks!

Yes. They're extensively tested.

Tom.
 
Viscount724
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How Strong Are Cockpit Windows?

Fri Mar 26, 2010 1:11 am

Quoting b78710 (Reply 3):
Quoting propilot83 (Thread starter):
how much of an impact can cockpit windshields of airliners withstand from a bird strike at cruising altitude

don't get too many birds at 37k feet

This goose species has been spotted cruising at 29,000 ft. over the Himalayas during it's annual migrations.
http://www.bbc.co.uk/nature/species/Bar-headed_goose
http://www.audubonmagazine.org/birds/birds0011.html
 
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propilot83
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How Strong Are Cockpit Windows?

Sat Mar 27, 2010 12:16 am

Thanks for the answers people, very helpful information. Yea I kind of figured that any airliner traveling at speeds of 400+ mph would not stand a severe bird strike at all. At those velocities I dont think any type of window can withstand a devastating blow. I know that one window pane of a 747 costs as much as a BMW  Wow!
 
bohica
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How Strong Are Cockpit Windows?

Sat Mar 27, 2010 2:12 am

Quoting propilot83 (Reply 9):
I kind of figured that any airliner traveling at speeds of 400+ mph would not stand a severe bird strike at all.

Click on the second link in the post before yours and scroll down to the bottom.

Quote:
The highest-flying bird ever recorded was a Ruppell's griffon, a vulture with a wingspan of about 10 feet; on November 29, 1975, a Ruppell's griffon was sucked into a jet engine 37,900 feet above the Ivory Coast--more than a mile and a half higher than the summit of Mount Everest. The plane was damaged, though it landed safely.
 
474218
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How Strong Are Cockpit Windows?

Sat Mar 27, 2010 2:53 am

Quoting propilot83 (Thread starter):
I know that cockpit windshields of commercial airliners can withstand bird strikes at certain speeds, how much of an impact can cockpit windshields of airliners withstand from a bird strike at cruising altitude, approach, take-off? Does any engineer know how strong those cockpit windows really are? Thanks!

Then theres always this story:

http://www.airwaysmag.com/channels.html?_1d=78&channel_id=7
 
AirframeAS
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How Strong Are Cockpit Windows?

Sun Mar 28, 2010 1:12 am

Quoting 474218 (Reply 6):
A glass face plate, approximately 0.100" thick.
Then a layer of Polyvinyl Butryal (PVB), about 0.125" thick.
Then a layer of Stretched Acrylic approximately 1.00" thick.
Then another layer of PVB about 0.100" thick.
Then another layer of Streched Acrylic approximately 1.00" thick.

Also to add, they weigh something like 25-40 lbs, depending on the type of window. Man, those are heavy and a PITA to install!!!
A Safe Flight Begins With Quality Maintenance On The Ground.
 
PWMRamper
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RE: How Strong Are Cockpit Windows?

Sun Mar 28, 2010 4:58 pm

What about hail? I've heard stories of windscreens cracking or even breaking due to hail...any info on that?
 
jetstar
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RE: How Strong Are Cockpit Windows?

Sun Mar 28, 2010 6:03 pm

On the Lockheed JetStar, a Part 25 transport category airplane, each of the 3 main windshields were over 2 inches thick and weighed over 30 pounds.

Primary purpose of windshield heat was for bird impact, if windshield heat was inop, airspeed was limited to 250 knots indicated. Heating of the windshield made the windshield more pliable and able to withstand an impact from a bird strike.

In JetStar school, I saw pictures taken during certification testing, Lockheed put a windshield in a test rig and took the pressure to over 20 psi when the windshield finally cracked and bowed out, but it still held pressure. Maximum JetStar pressurization was 8.9 psi, so the windshield could hold up under more than twice the pressurization requirements.

JetStar
 
Viscount724
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RE: How Strong Are Cockpit Windows?

Mon Mar 29, 2010 3:03 am

Quoting AirframeAS (Reply 12):
Quoting 474218 (Reply 6):
A glass face plate, approximately 0.100" thick.
Then a layer of Polyvinyl Butryal (PVB), about 0.125" thick.
Then a layer of Stretched Acrylic approximately 1.00" thick.
Then another layer of PVB about 0.100" thick.
Then another layer of Streched Acrylic approximately 1.00" thick.

Also to add, they weigh something like 25-40 lbs, depending on the type of window. Man, those are heavy and a PITA to install!!!

Cracked windshields, even without any impact, seem quite common. I glance through the Transport Canada daily incident reports most days, and there are usually a few cracked windshiled reports almost every week. Are temperature changes also a factor?

A few random examples within the past few months. There are close to 100 similar reports since the beginning of 2009, and that's just Canada.

ACA695, an Air Canada Airbus 320, registration C-GIUE, was en route from St. John's, NL to Toronto when the crew declared a PAN situation due to a cracked left windshield. The crew requested and received a clearance to divert the flight to Halifax where the aircraft landed safely without further incident. The windshield was replaced and the aircraft has been returned to service.

Air Canada Airbus A319 aircraft (operating as flight ACA1814) was on a scheduled IFR flight from Toronto (CYYZ) to Cayo Coco, Cuba (MUCC). The Federal Aviation Administration advised that the aircraft was en-route, operating in Boston ARTCC airspace, when the flight crew elected to return to Toronto due to a cracked windshield. The aircraft subsequently landed without incident at 1309Z.

The crew of the scheduled Westjet Boeing 737-800 enroute from Edmonton (CYEG) to Toronto (CYYZ) advised they had a cracked side windshield . The crew requested descent, no emergency, no assistance required, and landed without incident.

TSB reported that the Province of Saskatchewan Beech King Air B200, registration C-GLLS operating as SGS 9, was departing Regina, SK, when the pilot's outer windscreen cracked. The flight returned to Regina and landed without further incident.

IBE6253, Iberia Airbus A340-300, enroute from Madrid (LEMD) to New York (KJFK), reported a cracked windshield 100 miles east of St. Pierre. The aircraft descended from 34,000 ft. to 28,000 ft., and subsequently to 22,000 ft. No emergency was declared and no assistance was required. The flight exited Canadian airspace at 00:20Z. Nil TSB.

Alaska Airlines Boeing 737-400 aircraft, N764AS, operating as ASA61, was en route from Seattle to Juneau, Alaska, cruising at FL340 in the vicinity of Comox when a cockpit outer windscreen panel cracked. The crew requested, and were cleared for, a descent to 10,000 feet and a return to Seattle. The aircraft landed at Seattle without further event. Maintenance changed the windshield and returned the aircraft to service.
 
411A
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RE: How Strong Are Cockpit Windows?

Mon Mar 29, 2010 4:39 am

Quoting jetstar (Reply 14):
In JetStar school, I saw pictures taken during certification testing, Lockheed put a windshield in a test rig and took the pressure to over 20 psi when the windshield finally cracked and bowed out, but it still held pressure. Maximum JetStar pressurization was 8.9 psi, so the windshield could hold up under more than twice the pressurization requirements.

20psi was also applied to Mobil Oil's first JetStar during final assembly, and the fuselage was so deformed, that the wings had to be removed, and a new fuselage fitted.
Charlie Morris, Mobil's chief pilot at the time, was not exspecially pleased.

TriStar windshield adhoc test.
Standard .45 automatic bullet fired from about ten feet away...will penetrate, but not completly go through.
I have seen it personally.
Twice.
 
kiwiandrew

RE: How Strong Are Cockpit Windows?

Mon Mar 29, 2010 7:12 am

Quoting b78710 (Reply 3):
don't get too many birds at 37k feet

For what it is worth , I am sure that I remember a few years ago reading about a very high altitude bird strike in India involving a vulture . The details are a bit hazy but I am fairly certain that it was above FL300 and that it not only broke a cockpit window but also caused serious injury to one of the flight crew . Does anyone else know the incident I am referring to ? I think the carrier was IC ?
 
jetstar
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RE: How Strong Are Cockpit Windows?

Mon Mar 29, 2010 4:08 pm

Quoting 411A (Reply 16):
20psi was also applied to Mobil Oil's first JetStar during final assembly, and the fuselage was so deformed, that the wings had to be removed, and a new fuselage fitted.
Charlie Morris, Mobil's chief pilot at the time, was not exspecially pleased.

I remember that incident quite well, it happened at Airesearch at ISP when their JetStar was in for service, not during final assembly at Lockheed. Airesearch or actually their insurance company wound up buying Mobil a new JetStar. Mobil’s original JetStar went back to Lockheed and had a new fuselage built for it. If I remember correctly, the fuselage failed in the wheel wheels and the loud cracking sound was the first indication to the technician that something was wrong. They eventually did temporary repairs and ferried the JetStar back to Lockheed.

From what I heard from one of Mobil’s mechanics, Charlie Morris was more than just not pleased, Mobil at the time was one of the largest operator of corporate airplanes, I am sure Aireaserch, who at that time was one of the largest corporate maintenance and completion centers lost some business from other corporate operators because of this screw up

At one time Lockheed was going to take the fuselage from another JetStar that had the wrong sealant used in the fuel tanks and the wings developed extensive corrosion, so Lockheed had initially planned to use the fuselage from this JetStar and the wings from Mobil’s JetStar to make one good airplane, but instead built another set of wings for this other JetStar and sold that one as well.

In the interim while Mobil was waiting for their replacement JetStar to be built they leased another JetStar, a trade in from another company who bought a later model from Lockheed who then used it as a demo, After Mobil returned it back to Lockheed, another company bought it and I was hired by this company and this was the first of the 2 JetStars that I was Chief of Maintenance/First officer on.

In my early A&P days working for an FBO at HPN around 1968, at times I was farmed out to Mobil to polish their airplanes, Mobil did not believe in washing their airplanes, so on the JetStar we used Prestone auto polish, and on their Hawker DH-125 we used glass wax. At times 2 of us would spend the whole week there hand cleaning their airplanes, needless to say this was a very boring job and not very popular with our mechanics.

JetStar
 
soon7x7
Posts: 2267
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RE: How Strong Are Cockpit Windows?

Wed Mar 31, 2010 12:03 pm

Quoting kiwiandrew (Reply 17):

If we are talking about the same incident it was the highest recorded bird strike at 37,000 ft. On November 29, 1973, a Ruppelis Griffon Vulture had the encounter with the aircraft over the Ivory coast. The aircraft was a USAF T-37...Vultures are sizable birds...would love to see the pix...g
 
PolymerPlane
Posts: 832
Joined: Thu May 11, 2006 1:12 am

RE: How Strong Are Cockpit Windows?

Wed Mar 31, 2010 6:35 pm

Quoting 474218 (Reply 6):
An airliners main windshield has several layers:

A glass face plate, approximately 0.100" thick.
Then a layer of Polyvinyl Butryal (PVB), about 0.125" thick.
Then a layer of Stretched Acrylic approximately 1.00" thick.
Then another layer of PVB about 0.100" thick.
Then another layer of Streched Acrylic approximately 1.00" thick.

I am curious why they don't use polycarbonate as the windshield.
One day there will be 100% polymer plane
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: How Strong Are Cockpit Windows?

Wed Mar 31, 2010 6:47 pm

Windshield heat malfunction is the most common cause of cracked windshields.

Quoting PolymerPlane (Reply 20):
I am curious why they don't use polycarbonate as the windshield.

The following should provide the information requested:

http://www.saint-gobain-sully.com/GB/aviation/technical/index.asp
 
kiwiandrew

RE: How Strong Are Cockpit Windows?

Wed Mar 31, 2010 7:24 pm

Quoting soon7x7 (Reply 19):
If we are talking about the same incident it was the highest recorded bird strike at 37,000 ft. On November 29, 1973, a Ruppelis Griffon Vulture had the encounter with the aircraft over the Ivory coast.

I think it must be a different incident , the one I am thinking of was definitely a civilian aircraft and over India . I have been googling like mad and so far have not found it , but I know that I did not dream it up , I am sure that eventually I will find it .
 
soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: How Strong Are Cockpit Windows?

Thu Apr 01, 2010 6:13 am

Quoting kiwiandrew (Reply 22):

I was googling to death the other day about a DC-8 years ago over upstate New York that slammed into Ducks, knocking out the Captains windscreen injuring him fairly severly, the aircraft If I recall put down at Stewart Airport safely, but this was like 20 years ago...couldn't find anything...but I distinctly remember the event happening.

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