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Door blows off Boeing 777X during stress test

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Re: Door blows off Boeing 777X during stress test

#61

Post by dmix »

cyberferret wrote: post #21
kbenson wrote: post #19

Earlier quoted context omitted.

> Here is another video of a 777 wing test where it broke at 154% of the normal load I really hope you mean 154% of the max load, and I hope that max load is engineered to be far above what should be seen in actual service. 50% over the normal service load is not what I would consider extreme, and not something I would expect to be acceptable in an aircraft.

Sorry, I mistyped. It is indeed the maximum theoretical load as calculated by the engineering team.

Specifically from the video description:

> This Boeing 777 wing was tested to destruction, finally breaking at one fifty four percent of the designed limit load.

Re: Door blows off Boeing 777X during stress test

#62

Post by ajross »

cyberferret wrote: post #16

It's a stress test. You would expect things to break during a stress test. > "They loaded it up well beyond capacity and bent its wings in an extreme manner, in a way almost certain to never happen in the real world." Here is another video of a 777 wing test where it broke at 154% of the [s/normal/maximum theoretical/] load - a bit beyond what was expected by the engineering team. https://www.youtube.com/watch?v=Ai2H…

You expect things stressed beyond limits to break where you expect them to, and the point of the test is to show that the failure modes are the expected ones. Having a door pressure seal fail explosively during an airframe stress test sounds to me very much like an UNexpected failure mode. That's bad.

Re: Door blows off Boeing 777X during stress test

#63

Post by jethro_tell »

fastball wrote: post #53
bob1029 wrote: post #39

Earlier quoted context omitted.

"It's unlikely this will speed up certification." I assume "this" in the above is equivalent to "the door blowing off the airplane". I think we have a solid conclusion here, despite the previously stated desire to avoid racing towards them.

What is the solid conclusion?

That it is unlikely to speed certification

Re: Door blows off Boeing 777X during stress test

#64

Post by karthikb »

frankharv wrote: post #24
erikig wrote: post #15

..."The test is meant to push the plane beyond its limits. Engineers had the plane pressurized and on the ground. They loaded it up well beyond capacity and bent its wings in an extreme manner, in a way almost certain to never happen in the real world."

I almost didn't shit my pants when the door blew off. I almost didn't didn't make it out of the burning building. 'Almost Certain' to never happen in the real world. Not very scientific to me. Sounds like PR talk.

Per the FAA (https://www.faa.gov/regulations_policies/advisory_circulars/...), the actual number for "Almost Certain to never happen" is no more than 1 loss of life per 10^9 flight hours. There's a real number behind that term, but not necessarily a stat that's accessible to the average news reader.

Re: Door blows off Boeing 777X during stress test

#65

Post by [deleted] »

rolph wrote: post #52
rolph wrote: post #25

ok 1: the wings were bent in an extreme manner. so you have a cylinder to a close approximation, with a hole in the side of it. Then you have two levers [wings] affixed to said cylinder, then you apply force to the levers, and distort the cylinder thus distorting the hole in the cylinder.... at this point i would invoke a toplogical parlour trick of making a quarter fall through a dime sized hole as an analogy. https…

If you dont think this is the case then lets hear your critique, please tell me why you think this is not the case. then if there is time left i can change my most recent actions in this thread ..."The test is meant to push the plane beyond its limits. Engineers had the plane pressurized and on the ground. They loaded it up well beyond capacity and BENT ITS WINGS in an extreme manner, in a way almost certain to never…

[deleted]

Re: Door blows off Boeing 777X during stress test

#66

Post by chiph »

yial wrote: post #6
walrus01 wrote: post #3

Thankfully we seem to have standardized on plug type doors, not outward opening ones, since the dc10 disaster. I wonder what happened. Considering emergency exit doors, cargo doors and primary boarding doors are all plug design it must have been a serious failure. https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-10#Cargo_...

This is pure ignorance on my part, but do plug type doors seal as strongly when on the ground ?

There is a mechanical latch, but they seal much better once the aircraft is pressurized and the door is being pressed into the frame.

If you look at the windows on a research submersible, the Plexiglas windows are cone-shaped and placed facing the opposite direction from those on a plane, as the pressure there is coming from the outside. Same reason - the cone shape means the pressure differential creates a tighter seal as it becomes greater.

Story time: I was once on a Northwest flight, and a passenger in the exit row behind me called a flight attendant back while we were still loading. It seems she could put her arm out of the aircraft through a gap in the over-wing door opening. Sure enough, I look out my window and there's her hand waving back at me. They call a mechanic who reseals the exit (applying a new safety-wire seal) and off we go to our destination.

It almost certainly would have sealed shut once we got to altitude. And probably did for some unknown number of flights before she discovered the problem. But I definitely felt better once it had been repaired.

Re: Door blows off Boeing 777X during stress test

#67

Post by rtomanek »

dmix wrote: post #61
cyberferret wrote: post #21

Earlier quoted context omitted.

Sorry, I mistyped. It is indeed the maximum theoretical load as calculated by the engineering team.

Specifically from the video description: > This Boeing 777 wing was tested to destruction, finally breaking at one fifty four percent of the designed limit load.

I would still expect the `maximum theoretical load` to be well above the `designed limit load`.

Re: Door blows off Boeing 777X during stress test

#68

Post by inferiorhuman »

i_am_proteus wrote: post #56
kbenson wrote: post #31

Earlier quoted context omitted.

> Except, the whole point of the test is stress the plane and to have nothing break. That depends on the type of stress test. Some stress tests are to confirm it acts as expected. Other stress tests are used to determine modes of failure. Good engineering isn't just building stuff to spec and assuming it works, just as good programming isn't just writing code and assuming it works as expected because the compiler doe…

Very importantly, this hasn't been described as a "test failure." No indication of what the test criteria were, if any. Some tests, especially those past design limits, are just for informational data.

Very importantly, this hasn't been described as a "test failure."

That was heavily implied:

Sources tell KOMO there was a stunned silence after it happened.

…

an event occurred that forced the test team to halt testing. … The team is currently working to understand what happened and ensure the area is safe for work to continue.

Edit: You're not going to silence the crowd with a successful test and you don't temporarily halt testing because of a successful test.

Edit 2: Seattle Times says this explicitly: This ground test failure is another blow.

Re: Door blows off Boeing 777X during stress test

#70

Post by ChuckMcM »

rtomanek wrote: post #67
dmix wrote: post #61

Earlier quoted context omitted.

Specifically from the video description: > This Boeing 777 wing was tested to destruction, finally breaking at one fifty four percent of the designed limit load.

I would still expect the `maximum theoretical load` to be well above the `designed limit load`.

And it is, it is 154% or slightly more than 2.5x the 'design limit load'.
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