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Charlie757
Topic Author
Posts: 16
Joined: Tue Mar 31, 2015 4:59 pm

Cabin Door Locks

Mon May 04, 2020 6:23 pm

As far as I’m aware cabin doors can’t be opened in-flight due to differential pressure on plug-type doors, or locking devices on doors that open outwards.

I know that on the ground some airliner doors show as ‘Locked’ and show ‘unlocked’ when the handle is lifted/rotated. So are these locking mechanisms engaged when the doors are in the fully closed position or are they just something that’s engaged at a certain phase of flight etc? Any info would be appreciated
 
Tristarsteve
Posts: 3691
Joined: Tue Nov 22, 2005 11:04 pm

Re: Cabin Door Locks

Mon May 04, 2020 6:45 pm

All airliner cabin doors that I have met in my life are plug type doors. Even the B737 and A320, which both open outwards, but when closed are plug type doors. With any pressurisation, they cannot be opened.
The B777 and B787 have a door lock . This engages at about 70 kts to avoid the door opening during take off and landing. Older Boeing aircraft like the B737 have pressurised cabins, even during taxy.
The cabin door opening handles in the cabin have break out pins. If you could heave a B747 door handle open, the handle will shear off before the door opens.

On our nightstop A320, we close the doors, and connect a conditioner to warm the aircraft in the winter. One night, the arriving nightstop crew decided to close the outflow valve in manual before they left. In the morning, the Captain could not open the door. He applied maximum force, and the Copilot caught him as he was catapulted across the jetty. It was nearly impossible to open the door with only a ground conditioner running.
 
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Starlionblue
Posts: 20609
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Door Locks

Mon May 04, 2020 11:55 pm

Charlie757 wrote:
As far as I’m aware cabin doors can’t be opened in-flight due to differential pressure on plug-type doors, or locking devices on doors that open outwards.

I know that on the ground some airliner doors show as ‘Locked’ and show ‘unlocked’ when the handle is lifted/rotated. So are these locking mechanisms engaged when the doors are in the fully closed position or are they just something that’s engaged at a certain phase of flight etc? Any info would be appreciated


The door locks when the handle is used to close and lock it. This is a single action. It can still be opened at this point. Once the aircraft is pressurised, differential pressure will ensure you can't open it until pressure has been equalised again.

On Airbus, there are two types of door indication. One is the Unlocked/Locked flags on the door itself. These are mechanically connected to the door mechanism and show "Locked" once the handle has been used to close and lock the door. The other is the locked indication on the DOOR page in the cockpit. This is driven by sensors.

The handle position or Unlocked/Locked flags do not change the cockpit indication directly. Occasionally, a door will not show as locked in the cockpit, even though cabin crew have closed and locked it correctly, and checked the flag is indicating correctly. Sometimes the sensing is just a bit off, or there is some loose item stuck in the sill, like a scrap of paper. In this case, cabin crew can re-open the door, check for any loose items, and close again.

That being said, we can dispatch with the cockpit indication inop as per the MEL so if the flag shows as locked, the door is securely locked for flight.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
DiamondFlyer
Posts: 3488
Joined: Wed Oct 29, 2008 11:50 pm

Re: Cabin Door Locks

Tue May 05, 2020 12:05 am

Tristarsteve wrote:
All airliner cabin doors that I have met in my life are plug type doors. Even the B737 and A320, which both open outwards, but when closed are plug type doors. With any pressurisation, they cannot be opened.
The B777 and B787 have a door lock . This engages at about 70 kts to avoid the door opening during take off and landing. Older Boeing aircraft like the B737 have pressurised cabins, even during taxy.
The cabin door opening handles in the cabin have break out pins. If you could heave a B747 door handle open, the handle will shear off before the door opens.

On our nightstop A320, we close the doors, and connect a conditioner to warm the aircraft in the winter. One night, the arriving nightstop crew decided to close the outflow valve in manual before they left. In the morning, the Captain could not open the door. He applied maximum force, and the Copilot caught him as he was catapulted across the jetty. It was nearly impossible to open the door with only a ground conditioner running.


The CRJ main cabin door isn't a plug door, only thing I can think of off hand that isn't a plug door of some kind.
From my cold, dead hands
 
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Starlionblue
Posts: 20609
Joined: Fri Feb 27, 2004 9:54 pm

Re: Cabin Door Locks

Tue May 05, 2020 12:09 am

DiamondFlyer wrote:
Tristarsteve wrote:
All airliner cabin doors that I have met in my life are plug type doors. Even the B737 and A320, which both open outwards, but when closed are plug type doors. With any pressurisation, they cannot be opened.
The B777 and B787 have a door lock . This engages at about 70 kts to avoid the door opening during take off and landing. Older Boeing aircraft like the B737 have pressurised cabins, even during taxy.
The cabin door opening handles in the cabin have break out pins. If you could heave a B747 door handle open, the handle will shear off before the door opens.

On our nightstop A320, we close the doors, and connect a conditioner to warm the aircraft in the winter. One night, the arriving nightstop crew decided to close the outflow valve in manual before they left. In the morning, the Captain could not open the door. He applied maximum force, and the Copilot caught him as he was catapulted across the jetty. It was nearly impossible to open the door with only a ground conditioner running.


The CRJ main cabin door isn't a plug door, only thing I can think of off hand that isn't a plug door of some kind.


IIRC the MD-80 emergency aft door is non-plug.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
vc10
Posts: 1436
Joined: Thu Nov 15, 2001 4:13 am

Re: Cabin Door Locks

Tue May 05, 2020 12:31 pm

On the old VC-10 airliner [and I think it is similar on the Airbus aeroplanes ] the entrance door from shut sequence is for the door to move up and then out .
Now in the early VC-10 days it was found that with no pressurization diff pressure on the door and during certain manoeuvres the door could move upwards without any handle movement and clear the door lugs .
To prevent this a mod was raised to ensure a locking hook was installed to prevent any movement of the door unless initiated by the handle itself. To check whether this hook was in place a clear view window was cut into the trim so the position of the G LOCK [as it became known ] was correct for flight and the cabin crew call was doors shut and locked. I presume that at a later date the G- Lock correct position was shown by a warning light.
Now this might not be relevant to today's aircraft but I will leave that to you younger folk to decide
 
shamrock137
Posts: 403
Joined: Mon Jul 25, 2005 7:10 am

Re: Cabin Door Locks

Tue May 05, 2020 4:16 pm

737 NG's and MAX's have locks on the over wing exits. When the ground/flight sensors sense flight, the throttles are set for takeoff, and three or more other doors are closed, the locks engage. They then disengage when the opposite is sensed, or if power is lost. They are not plug type doors, so technically without the locks, they could be opened in certain conditions. I think I remember reading that the 777 doors lock above 80kts... cant find something to confirm though.
Time to spare? Go by air!
 
Max Q
Posts: 8760
Joined: Wed May 09, 2001 12:40 pm

Re: Cabin Door Locks

Wed May 06, 2020 2:50 pm

Tristarsteve wrote:
All airliner cabin doors that I have met in my life are plug type doors. Even the B737 and A320, which both open outwards, but when closed are plug type doors. With any pressurisation, they cannot be opened.
The B777 and B787 have a door lock . This engages at about 70 kts to avoid the door opening during take off and landing. Older Boeing aircraft like the B737 have pressurised cabins, even during taxy.
The cabin door opening handles in the cabin have break out pins. If you could heave a B747 door handle open, the handle will shear off before the door opens.

On our nightstop A320, we close the doors, and connect a conditioner to warm the aircraft in the winter. One night, the arriving nightstop crew decided to close the outflow valve in manual before they left. In the morning, the Captain could not open the door. He applied maximum force, and the Copilot caught him as he was catapulted across the jetty. It was nearly impossible to open the door with only a ground conditioner running.



There was a similar incident with a corporate jet in Finland ? I think where one of the pilots was killed when the door opened extremely violently
The best contribution to safety is a competent Pilot.


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