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x1234
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Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 12:13 am

I read somewhere that when the cabin is pressurized while flying there is enough air pressure in that the cabin door won't open. Is this true? I read the case of another person attempting to open the cabin door inflight.
 
jetwet1
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 12:18 am

She short answer is, it is true, the pressure differential would keep the door firmly in place.
 
guy739
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 12:29 am

From my understanding as the aircraft pressurizes, it causes the frame to expand. As it expands it essentially secures the door within the locking mechanisms.
 
Flow2706
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 12:30 am

Doors on pressurized airplanes can't be opened in flight due to the differential pressure. During cruise flight the differential pressure between the cabin and the atmosphere is around 8-9PSI (depending on the aircraft type and altitude). The doors move slightly inwards before opening outwards so you would have to move the door against this pressure and this is not possible. However there is a possibility that the aircraft doors could be opened during takeoff/landing when there is no or only a minor differential pressure (sometimes the air conditioning packs are switched off for takeoff, as this will reduce the wear on the engines and thereby reduce maintenance costs - in this case there is no differential pressure until the packs are switched back on, typically at around 1000-2000ft).
 
777luver
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 12:43 am

Flow2706 wrote:
Doors on pressurized airplanes can't be opened in flight due to the differential pressure. During cruise flight the differential pressure between the cabin and the atmosphere is around 8-9PSI (depending on the aircraft type and altitude). The doors move slightly inwards before opening outwards so you would have to move the door against this pressure and this is not possible. However there is a possibility that the aircraft doors could be opened during takeoff/landing when there is no or only a minor differential pressure (sometimes the air conditioning packs are switched off for takeoff, as this will reduce the wear on the engines and thereby reduce maintenance costs - in this case there is no differential pressure until the packs are switched back on, typically at around 1000-2000ft).


To add to that, using the 8 psi number, that equates to 1100 pounds per square foot. Depending on a/c type of course. So thousands of pounds of force

https://www.google.com/url?sa=t&source= ... h115ogCTdb
 
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Starlionblue
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 2:32 am

guy739 wrote:
From my understanding as the aircraft pressurizes, it causes the frame to expand. As it expands it essentially secures the door within the locking mechanisms.


The frame does not expand. Doors are designed so that they can't be opened straight out. A bit like a sink stopper.

Look at this 737 door operation video. You can see how the door needs to go inwards and be twisted before fitting through the frame.

https://youtu.be/cxzLNBlDVbE

The A320 door has a similar mechanism. You can see that as the handle is pulled up, the door moves up and in, while the upper part folds down. Only then is the door small enough to fit through the frame and be pushed out.

https://youtu.be/1rOI-4oGj7c
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
e38
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Wed Feb 17, 2021 3:39 am

the doors referenced above are called "plug" doors; occasionally I have heard them referenced as "plug-type" doors.

e38
 
n92r03
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 12:47 am

On the L-1011, I seem to remember the door sliding vertical, up into the ceiling. Am I way off base here or was that the case? Last flight on one was ~1995, DL, LAX-SAN.
 
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fr8mech
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 1:56 am

n92r03 wrote:
On the L-1011, I seem to remember the door sliding vertical, up into the ceiling. Am I way off base here or was that the case? Last flight on one was ~1995, DL, LAX-SAN.


Yes, as they do on the DC10/MD11 & the B767. The doors still move in before they move up.
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Starlionblue
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 3:00 am

There are some non-plug passengers doors on airlines, for example, the tail door on the MD-80. But that's for emergencies only.

Cargo doors are a mix. Larger ones on widebodies tend to be outward opening, non-plug type, bulk cargo doors are typically plug, and main cargo doors on narrowbodies are a mix.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Tristarsteve
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 4:00 pm

A little anecdote about door pressure.
Our overnight parked A320 is left on a jetty for the morning departure and has heating /cooling hose connected. It delivers air from the terminal at 22degC at low pressure.
It often happened that the morning departure flight crew arrived at the airport, with the ramp agent, to find the door closed, and the aircraft on ground service. They then opened the door themselves (the ramp agent was not trained in this)
The day in question was very cold, and the crew the previous evening had closed the outflow valve manually before leaving the aircraft to keep it warm.
When the captain tried to open the door in the morning, the handle stopped half way up. Rubbish he said, the packs are not running there is a fault here. He heaved on the handle and the door opened. The first officer caught him as he flew across the airbridge.
I tried this myself the next night, and found that I could not open the door. The air conditioning hose provided enough pressure to keep the door closed.
To stop it happening again, the loading supervisor goes out to the aircraft earlier and cracks open the fwd freight hold door to relieve any pressure.
 
CanadianNorth
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 7:02 pm

Many pressurized aircraft have, mostly, plug style doors. A plug door is basically in the closed position the door is bigger than the hole, so the cabin pressure will hold it firmly in place.

Not all pressurized aircraft have that though, HS-748, ATR, and others. Usually in these types of doors there is some kind of a pressure lock installed on each door so once the door is locked and the aircraft is pressurized beyond a given psi (usually 0.5 psi or something like that), a mechanism within the door will engage and physically prevent the door handle from being moved away from the locked position. Once the pressure drops below the set psi the mechanism will naturally release itself and the door can then be unlocked and opened.

On the HS-748 the aft baggage door was in the lavatory and the designers were worried that one day an old lady would go to use the facilities and fall out in flight, so that door actually had a pressure lock and a speed lock installed. Moving the handle closed would engage the door locks, and then the handle would spring into a detent that would engage the secondary locks, and then when the cabin pressure reached 0.5 psi the pressure lock would engage and physically prevent the door locks from being moved, and then when the aircraft hit I believe it was 90 knots the speed lock would engage and also physically prevent the door locks from being moved. Once below the 90 knots for the speed lock and 0.5 psi for the pressure lock a set of springs would automatically pull them back to the unlocked position. The pressure locks were fitted to all doors and there was an indicator on each one that you could visually check any time the aircraft was pressurized and see if they were engaging as advertised. The speed lock it was on a scheduled maintenance check that came up from time to time to simulate 90 knots on the pitot tube get a young legged apprentice to run back there and tickle the baggage door handle to see if it was locked.
HS-748, like a 747 but better!
 
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Horstroad
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 7:20 pm

Starlionblue wrote:
Larger ones on widebodies tend to be outward opening, non-plug type, bulk cargo doors are typically plug

Some cargo doors are outward opening plug type. The aft small cargo door (70") on the B777 for example is an outward opening plug type door (and I'm pretty sure it's the same on the B767).
The forward large cargo door (106") and aft large cargo door (106", if installed) are non-plug type doors.
The aft cargo door on the MD11 (what other manufacturers would call the bulk cargo door) is non-plug type. McD always had to do it differently :D
 
GalaxyFlyer
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Fri Feb 19, 2021 10:39 pm

That 75” x 36” entry door has about 21,600 pounds of pressure on it during flight. If you can lift 21,601 pounds, I wish you all luck opening.
 
Max Q
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Sat Feb 20, 2021 2:04 am

Tristarsteve wrote:
A little anecdote about door pressure.
Our overnight parked A320 is left on a jetty for the morning departure and has heating /cooling hose connected. It delivers air from the terminal at 22degC at low pressure.
It often happened that the morning departure flight crew arrived at the airport, with the ramp agent, to find the door closed, and the aircraft on ground service. They then opened the door themselves (the ramp agent was not trained in this)
The day in question was very cold, and the crew the previous evening had closed the outflow valve manually before leaving the aircraft to keep it warm.
When the captain tried to open the door in the morning, the handle stopped half way up. Rubbish he said, the packs are not running there is a fault here. He heaved on the handle and the door opened. The first officer caught him as he flew across the airbridge.
I tried this myself the next night, and found that I could not open the door. The air conditioning hose provided enough pressure to keep the door closed.
To stop it happening again, the loading supervisor goes out to the aircraft earlier and cracks open the fwd freight hold door to relieve any pressure.



There was a similar set of circumstances a few years ago with a business jet, don’t remember the type

Crew started the APU then closed all doors and the outflow valve, inadvertently pressurizing the aircraft while doing the walk around in very cold conditions


When they tried to open the airstair door it wouldn’t budge, the Captain used all the force he had and the door opened explosively outward with so much force it killed him and did extensive damage to the aircraft



Unintended consequences
The best contribution to safety is a competent Pilot.


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StereoTechque
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Sat Feb 20, 2021 3:13 am

Horstroad wrote:
Some cargo doors are outward opening plug type. The aft small cargo door (70") on the B777 for example is an outward opening plug type door (and I'm pretty sure it's the same on the B767).
The forward large cargo door (106") and aft large cargo door (106", if installed) are non-plug type doors.
The aft cargo door on the MD11 (what other manufacturers would call the bulk cargo door) is non-plug type. McD always had to do it differently :D



Any other term for non-plug type doors.? Never come across any apart from conventional.
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GalaxyFlyer
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Sat Feb 20, 2021 4:04 am

Pressure door by Lockheed’s term.

The Gulfstream 150 door that killed the captain in Finland who was opening the door from the outside was caused by using APU to warm the cabin but not checking the outflow valve was fully open. In 2005 a US carrier F/A was injured in similar fashion. All doors were closed and external AC connected partially pressurizing the cabin. Galley door was opened and she was ejected. Third incident was a C-17 Loadmaster who opened the door before fully depressurized. One thing in common, all ground events with relatively low differential applied.
 
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Horstroad
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Sat Feb 20, 2021 1:32 pm

StereoTechque wrote:
Any other term for non-plug type doors.? Never come across any apart from conventional.

That's the official Boeing terminology. McD doesn't say anything about plug type or non-plug type in the description and operation part of the AMM. I don't know how Airbus calls it.
 
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Starlionblue
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Sun Feb 21, 2021 12:05 am

Horstroad wrote:
StereoTechque wrote:
Any other term for non-plug type doors.? Never come across any apart from conventional.

That's the official Boeing terminology. McD doesn't say anything about plug type or non-plug type in the description and operation part of the AMM. I don't know how Airbus calls it.


The bulk cargo door is referred to as "plug-type" in the A330 FCOM. The outward opening cargo doors don't seem to have a specific "type" designation.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
FlyHossD
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Mon Feb 22, 2021 2:43 am

A pressurized airplane on the ground is a tough nut to crack, too. This thread reminded me of this "bad day at the office":

https://app.ntsb.gov/pdfgenerator/Repor ... L&IType=IA
My statements do not represent my former employer or my current employer and are my opinions only.
 
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Starlionblue
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Mon Feb 22, 2021 3:06 am

FlyHossD wrote:
A pressurized airplane on the ground is a tough nut to crack, too. This thread reminded me of this "bad day at the office":

https://app.ntsb.gov/pdfgenerator/Repor ... L&IType=IA


THE CREW FAILED TO MANUALLY DEPRESSURIZE THE ACFT AND THE EVACUATION WAS DELAYED UNTIL A KNOWLEDGEABLE PASSENGER WENT TO THE COCKPIT AND DEPRESSURIZED THE ACFT.

That's awkward. :oops: :oops: :oops:
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Mon Feb 22, 2021 3:12 am

GalaxyFlyer wrote:
Pressure door by Lockheed’s term.

The Gulfstream 150 door that killed the captain in Finland who was opening the door from the outside was caused by using APU to warm the cabin but not checking the outflow valve was fully open. In 2005 a US carrier F/A was injured in similar fashion. All doors were closed and external AC connected partially pressurizing the cabin. Galley door was opened and she was ejected. Third incident was a C-17 Loadmaster who opened the door before fully depressurized. One thing in common, all ground events with relatively low differential applied.



Glad you were able to provide additional details on the biz jet, IIRC the AA incident was on an A300 where the FA was ejected from the aircraft after opening a cabin door with some residual cabin pressure


Not enough to prevent door operation but enough to cause it to open violently, the FA was still holding on to the handle and was thrown out and on to the ramp sustaining fatal injuries


I believe these doors were modified later to show a warning flag or something similar if the aircraft was not completely depressurized
The best contribution to safety is a competent Pilot.


GGg
 
889091
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Re: Is it true that when flying air pressure won't allow the cabin door to open?

Mon Feb 22, 2021 7:09 pm

fr8mech wrote:
n92r03 wrote:
On the L-1011, I seem to remember the door sliding vertical, up into the ceiling. Am I way off base here or was that the case? Last flight on one was ~1995, DL, LAX-SAN.


Yes, as they do on the DC10/MD11 & the B767. The doors still move in before they move up.


Just curious why Boeing went for the electrically operated, upward sliding door on the 767?

The 737, 747, 757, 777 and 787 family of Boeing aircraft have the doors hinged on the side.

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