How strong are airliner cabin windows?

[B757-200]

Whilst on a 757-200 last month i was resting my head against the cabin window beside me and i was stunned to find that the inside covering was just flimsy, thin plastic which some-one could of easily hit out with their hands or even just a pen! The inside frame is also fragile, not hard to pull off. My guess is that some weirdo could break the inside glass and then smash through the outer layer which is not good when an airliner is at say 39,000ft? when there is literally a gaping hole in the side of the aircraft. This was not just one flight where the window was dodgy. On the return flight to Luton the window was just as flimsy. This raised the question: if you can break the inside layer just how hard is it to break the outer glass? This really does worry me into how well airliners are really built!

[sir.pratt]

the whole aeroplane is built like that. the real strength is in the plastic interior - lots of kevlar and carbon fibre. once you're through that though a simple pair of nail clippers could open the side of the fuselage like it's made out of tinfoil! have you ever seen the control surfaces on a DC3 or similar? they are only made out of bed sheets! a brand new 777 isn't much better, with only the thinnest aluminium covering it.

[sir.pratt]

and another thing - did you know that a 747 engine is only held on by 3 bolts? how the don't just fall off i'll never know.

[Dr Illitout]

THREE bolts!???? Because of cost cutting we use Velcro. We can do an engine change in about an hour. If we are down the line it will take us about a week mind you:)

Rgds Dr I

[11Fan]

Hey B757-200,

They're just having a little fun with you. Sort of a welcome to PPRuNe if you will.

The window "glass" is in the neighborhood of 5 millimeters thick and quite safe. That inner plastic that you leaned you head against serves no other real purpose than to, well, lean your head against. The thickness of the skin is around 2 to 3 millimeters, but it is pretty strong stuff and secured to the "frame/structure" quite adequately with rivets.

Modern aircraft last quite a long time. It's really more dependant on the amount of times it takes off and lands, or more accurately, the amount of times that the aircraft is pressurized. These are called "cycles".

There a many aircraft that have lasted much longer than they were expected because of this strength. DC-8's for example were built in the 50's and 60's and still going strong. There's even still a lot of DC-3's that were built during World War 2 that are flying today.

There are people on this forum who are quite more knowledgeable than I in this matter and may lend more insight.

Until then, consider yourself welcomed. :ok:

Regards,

11Fan

[Seloco]

Not long ago I was in a window seat in an A320. After a less than "greaseful" landing in rather difficult conditions, the inside plastic window pane, and its plastic retaining frame, fell into my lap. During the taxi I tried to replace it, since it was apparent that the frame simply clipped into place within the surrounding trim panel. Unfortunately I was unsuccessful as some of the frame tabs had broken, so I handed pane and frame to the captain who had emerged from the flightdeck as we deplaned. He accepted it gratefully and pointed out that it had been the FO flying the landing.......

[Paracab]

Have also had a the inner pane fall into my lap on landing, the aircraft was a 747-200. I didn't mind, I was grateful to fly on a 747 for the first time, and a 200 for that matter. Then once on the ground the APU failed. The aircraft was having a bad day!

[vapilot2004]

The innermost layer is part of the plastic cabin fascia commonly referred to as a scratch panel or pane. It serves no structural purpose.

The load bearing portion of the window is a dual pane assembly firmly attached to the fuselage with several dozen rivets around an aluminium frame. Either piece of this acrylic sandwich consisting of inner and outer panes would be strong enough to carry the full load alone. :ok:

[Flying Torquewrench]

VAPILOT2004,

You are right regarding your description of the windowpane itself. However the window is not secured to the structure by rivets but by bolts. (12 on a 737NG). If they were really rivited than it would take a long time to replace one. In the current situation you can replace a pane in 15 to 30 minutes.

Cheers, FT

[The SSK]

and another thing - did you know that a 747 engine is only held on by 3 bolts? how the don't just fall off i'll never know.

Before the 747 had even flown, they used to tell the same story about the Trident middle engine.

[vs69]

I think if you were to peek under the cowlings and look at the (two) pylon mounts you would be relieved to find 8 bolts in total on a B744

[enicalyth]

Well dun Sir Pratt and thy fellow knights... thou art goed and faithful servants... enter in and feast on the repast that is prepared in thine honour for thou see-est the twonk and the troll. Verily I say unto thee, blessed are the pith takers. Meanwhile...
Actually its only two bolts and a fork lift truck that hold engines on and they do fall off. If you can't get the last bolt in then because there is a factor of safety of two don't worry. Bag the unused bolts up and leave a note for the engineers that Engine No 2 seems to be missing and the plane is flying funny. And...
As for window "panes", if they fall on your lap, that's okay. It's if they fall outwards at great speed that there is a potential problem.
As for DC3s flying forty years and more. Rubbish. They'd have run out of fuel by now.
Oh Smudger. You have been B757-200'd.
Nice try B757. But after mid-day on April the First jokes don't count.