Alaska Airlines flight forced to make an emergency landing... 82

[LittleInch]

The Boeing guy before ems to say it was removed a second time to fix an issue with the seal.[highlight #FCE94F][/highlight]

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

The door flying open is another undocumented safety feature which apparently Boeing decided the pilots didn't need to know about.

Normally they have blowout vent panels but 1960's design... Bullet proof door retrofitted.

But now the door is none compliant because everyone knows if you want to get into the cockpit you just take a window out and it will bang open.

Quite how that one will play out is anyone's guess. It will likely be all the NG series of aircraft which have the same feature.

If they deem it none compliant for Flight deck security and needing fixed that's billions.

Modern designs the outflow valve isn't in the tail, the air has multiple routes to escape the cockpit, ours it gets directed through the footwell into the forward cargo hold which is heated. And there is ducting from the toilets taking it to the same place. There are blow out panels on the door and in the hold as well.

 

[LittleInch]

Does the passenger floor have panels that work in both directions to stop the floor breaking?

Taking a window out to get onto the flight deck is a bit OTT...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

My guess is that the cockpit door only failed due to the HUGE hole in the airframe in this case compared to a slower depressurisation caused by a much smalller area window failure?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

No it didn't fail it was meant to let loose and open as a safety feature. More than likely due structural load on that section.

I would post the fcom from the a220 but suspect it would breach some rule.

Yes there are blow out panels for both airflow directions and a few other things before they ultimately release.

Survivable Explosive decompression is pretty rare.

 

[dik]

That opens another can of worms, maybe. Because of the large surface area of a door, like the panel, it would be subject to quite a force.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Alistair_Heaton]

It certainly does and I think someone has decided to drop them in it for it.

Now it's public....

I suspect it was a none public certification waver.

I am sure the USA pilots unions will have something to say about it.

Some of those retro fitted cockpit doors caused some major headaches structurally. But those in the forum will know more about it than me.

It wouldn't suprise me though if it's exactly the same as the retro fit compliance setup...

 

[dik]

I think this is a real problem of extending certification of new models, based on earlier models where significant changes have been made.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Ng2020]

Dik et al, there is no problem with the way certification authoritiesdeal with change. The process is addressed in part 21.101 - called the 'changed product rule', and provides pragmatic criteria for the identification of the appropriate cert basis for modifications to existing designs, i.e. work to the latest amendment for 'major' design changes.
If you look at the 737 tcds you will see the cert basis becomes incrrasingly complex with each generation, as various new amendments become applicable to the incrementally changed systems/structures.
Furthermore the regulator & applicant can agree upon special conditions where the basic regulations are deemed inadequate for specific novel design features, which is the case for just about every contemporary aircraft type.
It's a misconception that 737ng/max are designed entirely to 1960s design standards.

 

[ctopher]

I thought this was funny.

Chris, CSWP
SolidWorks
ctophers home

 

[JohnRBaker]

Thanks for reposting the above image ;-)

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[3DDave]

Better than the previous Alaska Airlines disaster, eh? Also a repeat of the FAA failed oversight which in turn is the US Congress failing to apportion sufficient funds to the agency to do the job correctly.

 

[ctopher]

Oops, sorry John. Completely missed that.


Chris, CSWP
SolidWorks
ctophers home

 

[Alistair_Heaton]

Wouldn't worry its made me laugh twice

Much like the off road memes about the off road in Vilnius last week. Black humour

 

[Murph 9000]

Latest from the 737 tech channel, summary and analysis of the NTSB preliminary report:

AS1282 NTSB Preliminary Report

 

[debodine]

I have been trying to keep up with the sequence of events. I would appreciate correction if I missed something.

As I understand it, the four missing bolts are there only to keep the door plug from moving upwards. It is the 12 pads surrounding the door plug that transfer load from the door plug into the corresponding frame pads and thus into the airframe. So the aircraft flew some flights with the pads still making enough contact and this would continue as long as the door plug did not move upwards too far.

Here is my opinion of the sequence of events:

Aircraft leaves Boeing with 4 bolts missing.
Aircraft flies several flights, door plug is slowly moving upwards from vibration and pressure differential.
On the incident flight door plug eventually moves far enough upwards for the 12 pads to disengage.
Door plug departs.

 

[SWComposites]

debodine - yep, you got it. what many of us suspected from the start.

 

[Sym P. le]

The four ""missing" "bolts"" are essentially retaining pins. They are not loaded axially. The "bolts" themselves are kept in place with castle nuts and cotter pins, if they were ever there in the first place.

 

[dik]

It may have hit a 'bump' to dislodge the door initially from the restraints.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Sym P. le]

Landing?