737 max loses window
Discussion
In "risk" industries there is a recognition that everything is a careful balancing act between what is theoretically possible and what can actually be achieved on a sensible basis. Safety in cars, trains and planes is taken incredibly seriously but it's impossible to rule out every avenue of possible failure.
I was hoping you might be able to draw attention to your own field of experience where things are handled better.
I was hoping you might be able to draw attention to your own field of experience where things are handled better.
hidetheelephants said:
It does look that way; 3 of the 4 could be missing and the plug would still be held in place as there's no force on the bolts.
As long as the roller pins are present all 4 locking bolts could be missing and the door wouldn’t fail so long as the roller pins remain in the latch. The bolts have to resist very little force just holding the roller pin in the latch. I would expect that the pressure differential in service would hold the pins in the latch by design.In theory no bolts could be safe for years if the door doesn’t become partially dislodged from the latch.
I suspect it will turn out these where missing at final assembly and due to being behind a panel are not a line inspection item. Then some sort of ground handling issue in service has knocked the door partially off said latches before failing later.
b0rk said:
As long as the roller pins are present all 4 locking bolts could be missing and the door wouldn’t fail so long as the roller pins remain in the latch. The bolts have to resist very little force just holding the roller pin in the latch. I would expect that the pressure differential in service would hold the pins in the latch by design.
In theory no bolts could be safe for years if the door doesn’t become partially dislodged from the latch.
I suspect it will turn out these where missing at final assembly and due to being behind a panel are not a line inspection item. Then some sort of ground handling issue in service has knocked the door partially off said latches before failing later.
Is there a wedging or overcentre action in the pin/socket arrangement? If there isn't, between impulse from rough landings, turbulence etc and the springs in the hinge mechanism the door could release itself with no bolts restraining it.In theory no bolts could be safe for years if the door doesn’t become partially dislodged from the latch.
I suspect it will turn out these where missing at final assembly and due to being behind a panel are not a line inspection item. Then some sort of ground handling issue in service has knocked the door partially off said latches before failing later.
hidetheelephants said:
tim0409 said:
The more I read about this, the more I come to the conclusion that the four bolts were left off during assembly. I think Boeing already know this having looked at the lack of damage to the fixings, which would explain why they were able to roll out an inspection so quickly (otherwise how could they determine what they were looking for in the inspection).
It does look that way; 3 of the 4 could be missing and the plug would still be held in place as there's no force on the bolts.hidetheelephants said:
Is there a wedging or overcentre action in the pin/socket arrangement? If there isn't, between impulse from rough landings, turbulence etc and the springs in the hinge mechanism the door could release itself with no bolts restraining it.
https://twitter.com/fl360aero/status/1743934719987...Based on the picture of a door plug being inspected on Twitter I think with no bolts the plug relies on the base hinge? spring providing enough force to overcome any downward loads applied to the plug. So the latch doesn’t appear to have any designed effective overcentre action.
A rough landing could I’d suspect dislodge the plug from the latches if the bolts where missing.
I don’t know how rigid the base point is, maybe one of plane experts could explain the designed mechanism more. As this is never supposed to be opened in service I’d have hoped the plug base / aperture base was designed as a rigid connection.
valiant said:
WyrleyD said:
Also found a still working iPhone after falling 16,000 feet that had a baggage check on it for that flight.
Wonder what phone case and screen protector it has?16000ft drop and it survives intact.
Marketing dream.
I imagine soft undergrowth though!
airbusA346 said:
In different circumstances that would have been gut retchingly poinant..craig1912 said:
United Airlines has found at least 5 plug doors with loose bolts during the inspection of a Boeing 737 Max 9 plane
Unbelievable. Presumably it is someone’s job to torque the bolts correctly, and someone else’s job to check that the bolts have been torqued correctly before the thing leaves the factory. Cue a frantic rush by airlines across the world to check every bolt on every aircraft in their fleet asap. Overtime bonanza for the engineers this month. There was a really good article about Boeing’s problems. Long story short, they decided having an engineering lead approach wasn’t generating enough shareholder returns, so went for a bean counter first approach. 737 Max is one of the fruits of that. They ditched the bean counter CEO, because of all the problems and the new guy is going for a blended approach.
Edited by wyson on Monday 8th January 21:35
Bradgate said:
Unbelievable. Presumably it is someone’s job to torque the bolts correctly, and someone else’s job to check that the bolts have been torqued correctly before the thing leaves the factory. Cue a frantic rush by airlines across the world to check every bolt on every aircraft in their fleet asap. Overtime bonanza for the engineers this month.
There's also the issue of the loose nuts in the tail.I believe they got rid of a load of the people doing QC, and now rely on digital torque wrenches etc that log when bolts/nuts are tightened.
Yikes!!! Look at the image in this tweet. 
https://twitter.com/ByERussell/status/174446013685...
It'll be interesting to know how many turns that bolt is in.
https://twitter.com/ByERussell/status/174446013685...
It'll be interesting to know how many turns that bolt is in.
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