Emergency door opened on plane whilst airborne

[LittleInch]

https://www.theguardian.com/world/2...-plane-door-opened-mid-flight-asiana-airlines

Seems the plane, an A321, was only 200ft off the ground so I can only assume the inside air pressure was the same as outside as normally everyone says you can't open the door in flight??

So no one would be "sucked out", but isn't there some way to prevent this?

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[Murph 9000]

This is one of those situations where you have competing engineering risks. The doors are normally a plug type, so greater pressure inside should make them impossible to open. Reportedly, the plane was at low altitude when this happened, so the pressure differential must have been absent or low enough to allow it to be opened.

If you were to try to implement some sort of secondary locking mechanism, you have to ensure that it can never fail to unlock in an emergency on the ground, including after the plane has received crash damage or when there has been total loss of power.

 

[dik]

Don't the doors hinge to the outside? Higher pressure inside would make it easier to open?

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

-Dik

 

[Murph 9000]

The doors have a complicated multi-pivot hinge mechanism, where they first pull in before turning sideways, pushing out and looking like a door that opened outwards on a simple hinge. When fully closed, the internal pressure is pushing them against the frame.

 

[Murph 9000]

737 front door opening and closing:

https://www.youtube.com/watch?v=tO2wkubIsGc

 

[SnTMan]

Because there is not room for the doors to remain inside when opened...

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[dik]

Didn't know that... thanks...

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

-Dik

 

[LittleInch]

I assume the evacuation slide just got ripped off but I'm surprised this hasn't happened before in flight that I can recall.

There are a couple of times people have done it on the ground.

How it doesn't become a "thing"....


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[Alistair_Heaton]

its a plug door

And we land with positive pressure in the tube to stiffen it...

It Requires several tons of force to shift the door on the ground with the engines running and air bleeds on.. At altitude I will admit i have never tried it but it doesn't compute with everything else working.

 

[LittleInch]

So at what point do you equalise pressure?

Surely on the ground even with engines running you can open the doors in the event of a fire etc?

This door looks like one of the powered ones??

Is this s chat on the airline forums?

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

 

[Murph 9000]

Here's the probable explanation of how it was possible on an A321 from a 777 pilot YouTuber who consistently delivers high quality coverage of significant aviation incidents:

https://youtu.be/mf0yT8kN49U

The A321 doors are a different design to the classic plug doors on the 737, which I linked above, which I think also factors into it. In addition to not requiring the door to move inwards significantly, they even have a high pressure nitrogen bottle to blow the door open via an actuator integrated into the main hinge mechanism. In theory, they should be impossible to open with a significant pressure differential, but the small differential at low altitude makes it possible for a determined person to do it.

 

[waross]

During my yondering days in the tropics I often flew out to the Islands on small commercial planes.
It was about a 45 minute flight.
The doors were hinged at the bottom and swung down to form the boarding ramp.
They could easily be tripped open.(That's another story).
I was out on the island and the plane landed to take us back to the mainland.
For the 45 minute flight, the door was held closed by a mechanic sitting on a wooden box on the floor beside the door.
Probably not an acceptable solution in civilization today.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[LittleInch]

So looking at that video it seems that that door slides vertically down about 100mm into four sets of pins on either side to lock. So it's really just the friction between the door and the pins which stops it moving. That's not the same as trying to move the door inside first. I wouldn't call that a semi plug door.

How many other aircraft doors work that way?


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Also: If you get a response it's polite to respond to it.

 

[LittleInch]

Waross.

Non pressurised aircraft.

I've been in lots of planes where we opened doors in flight in order to jump out.

Always helped to be wearing a parachute!

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

 

[Alistair_Heaton]

There is a gradient to get it in and out of the guide rails.

Don't know how the pressurisation system works on the A320 but it's 1980's tech.

Ours it's controlled by a computer.

There are spring drain valves along the bottom of the hull which open at a set delta P the outflow valve gets adjusted to keep a bit of pressure on to blow all the condensation out.

To be honest it's not something I am going to play with.

It's an utter swine if the plane doors are all shut and it heats up and pressurises. The technicians need to override the cargo door interlocks to get one of them open.

I have seen three of them try to do it on the main door by brut force and couldn't

 

[Alistair_Heaton]

found this off an aviation site discussing it.

Its the cabin pressure profile.

The ground phase I believe is mainly done by the hull condensate dump valves. There is sometimes issues if the aircraft operates in sub zero conditions for days because the condensate internally never melts and the dry operating mass can increase quiet dramatically. And when you then go somewhere warmer a lake forms under the aircraft on stand which alarms the ground handlers.

 

[TugboatEng]

That is one confusing way to produce a graph. Turn it upsidedown and it will make much more sense.

 

[Alistair_Heaton]

I am sure there is a graph like that for submarines that you would like.

But if you did upside down it would give a nonlinear pressure on the Y

 

[Murph 9000]

That is one confusing way to produce a graph. Turn it upsidedown and it will make much more sense.

That graph is almost certainly aimed at aircrew, who think of cabin pressure in terms of altitude, rather than kPa / psi. They do use psi for the differential pressure, but altitude is the one they actually set on the pressurisation panel. You can see the relevant panel on a 737 here:

http://www.b737.org.uk/pressurisation.htm

 

[Alistair_Heaton]

It is historic, and regulations.

Everything centers round 10 000ft and oxygen provision.

It would be extremely complicated if it was any other method. Aircrew have a history of mucking pressurisation up as it is with a guage with red yellow white yellow red. Or digital numbers changing colour.

Edit to add the sonic booms recently chasing a citation biz key were likely pressurisation. It eventually crashed 4 people died.

Interpretation of raw number's would be a km diameter hole in the cheese.