Pop Goes The Window
During this last trip I had an unusual experience with a windshield on a Boeing 757. There we were minding our own business at Fl 390 when we heard a loud bang, the copilot jumped, and his outside window screen shattered into numerous pieces. This all happened at once and in the blink of an eye. BANG! Then a seriously damaged window. The windows on airliners are sturdy beasts able to withstand great abuse. They are engineered in two separate layers, one on top of the other. They are coated with a material that is similar to tough plastic. The two layers give added strength and a backup window under the exterior layer. The plastic layer keeps the shattered window together in what looks like a cool glass puzzle, keeping the window in place but in many pieces. The exterior layer is also heated to make the window more pliable in the event of impacting an object. What kind of object? I was flying a military cargo jet once low to the ground at about 200 miles and hour, at night. The lights in the cockpit were low, none of us were talking, just concentrating on what we were doing, when out of nowhere a tremendous “BANG!” scared the hell out of us. “What was that!” someone yelled. The jet we were flying was huge, had four engines and more systems than a skyscraper. There were two pilots flying, two more pilots sitting in back, and two flight engineers. Everyone started talking at once, well actually yelling at once. We were all checking the engine instruments, hydraulics, pneumatics, flight controls, and anything else to pinpoint the mechanical disaster we were sure was alluding us. Nothing, not a single abnormality could be found and we were all dumbfounded. The right seat pilot said, “I think there is something on my window.” A flashlight was shone on the window and there appeared to be something clouding up his window, right in the middle and about a foot square. In the dark of night we could not see that well. We continued on and had maintenance personnel meet us when we landed. After about 10 minutes of checking out the jet a maintenance supervisor said to all of us pilots in a thick southern drawl, “Sirs, it appears as though you hit a duck.” Then he held up a feather and said, “Mallard be my guess.” Someone said, “You’re shittin me!” “No sir.” He said. The only thing left of that poor bird was a smear of duck goo and that one feather, but the window was fine, not a scratch on it. I read an accident report about a military cargo plane that took off and ran into a flock of over 200 large birds in thick fog. They lost two engines, sustained damage to numerous flight controls, but had intact widows the entire time. They could barely see through all the guts and feathers on the windows. If I remember correctly the crew received some type of safety award for bringing that bird back in one piece. To test the strength of aircraft windows, engineers have developed a canon that fires a chicken into a jets canopy or window. They can get these dead birds moving at over 500mph. I have seen high speed videos of this modern version of a catapult and it is impressive to see the windows flex and bounce back as the chicken turns to liquid. The Myth Busters did a show on this; the video is at “http://www.youtube.com/watch?v=yHfejwdrMVQ.” There is a story floating around about a canopy prototype for a jet fighter being destroyed when the chicken was fired into it. Another canopy was brought in for testing and once again it failed. The engineers were baffled and could not understand why the canopies were not withstanding the canon firings. A young and inexperienced technician humbly brought it to the attention of the engineers that maybe the chickens they were using should be defrosted and not frozen. The next test was a resounding success.
Our problem on this recent flight had its origins not in hitting an object, but in the electrical components of the window. I have yet to hear about a bird that can fly at 39,000 feet. No, I knew right away that the window was either defective or overheated, with overheated being my first choice. I had witnessed this a few times in the military. The window appears fine one second, and then cracked into a hundred pieces the next. The heating elements at the top of the window were burned and melted. This was most probably an electrical short that started the failure. We ran the checklist for a broken window. The window heat switch for that window was turned off. This isolates the window from the electrical system. With the inner ply intact, we continued on to our destination. The pictures above are the copilot’s window, my window and his window (what a difference), a close up of a burned heating element, a normal looking heating element, and the window heat switches. We sent our maintenance coordination center a message informing them of our situation. The message from the center read, “ recvd your msg. should be ok to continue.” The copilot wrote back, “riiiiiiiigghhtt, then why does the captain refuse to switch seats with me.” To which he received a reply, “because the captain is smart.” I couldn’t have agreed more. Be safe FlyGuy.
posted by FlyGuy @ 7:12 AM
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