Plug doors
 

I've always understood that, at least on large Boeing airliners, the doors in the passenger cabin are designed so that they must be pulled inward in order to open them, which supposedly functions as a built-in way of preventing them from opening when the cabin is pressurized.

Today I read in several places that Airbus doesn't use plug doors, but instead has a different mechanism.

So, two questions: (1) Can someone confirm that Boeing doors really cannot be opened when the aircraft is normally pressurized in flight; and (2) is this also true for Airbus airliners, and if so, do they do it the same way, or in a different what (which way?)?

As SLF I recall that Boeing aircraft seem to have doors that move inward before opening. I recall seeing some aircraft that had doors that seemed to move inward and roll upwards (Boeing, or who?). I don't recall what Airbus doors look like when they open.

In cases where pressure alone does not hold a door shut, what other mechanisms are used to prevent accidental (or deliberate) opening of the door in flight? On some smaller pressurized aircraft, it looks like it's just a mechanical lock that has nothing to do with pressure at all.

I did search for previous discussions but couldn't find anything that seemed to cover the same ground.

I can only speak for the B737 as the Boeing or the MD-80 as to the Douglas side. Yes Boeing doors are of a plug type. You have to pull them in and then there is some articulation in the hinge system that allows the do to go back out through the opening when the door is fully open and outside the aircraft.

The Airbus does not use this system, it is not a plug door and it opens outward. There does not seem to be a problem with the Bus. It is my current assignment and we operate a large fleet and have not had any problems with the door. It is very robust and the lock system seems to work well.

To be honest we have had some problems with the Boeing doors. they have a very safe design philosophy in that they are plug doors but the mechanism and articulation is sensitive. These doors require more maintenance than I have seen so far on the Bus.

Please note our Boeings are old and the Buses are newer which could account for some of the difference.

Sorry, I only answered one of the questions.

The Boeing is almost impossible to open in flight because cabin pressure is holding the door closed. The bus, I believe has pressure switches on the handle which lock it and prevent operating the lever in flight with the cabin pressurized.

Here is all we have in pilot hand book:

7a.2.2 Passenger Doors. The cabin entry/service doors can be opened either from inside or outside. They incorporate a damper actuator which limits door travel; and in an emergency assists opening the door.
Each door is equipped with a single-lane escape slide or dual-lane slide-raft. A slide arming lever connects the slide to the floor brackets when in the ARMED position. If the door is opened from inside while the slide is armed, the
door is pneumatically-assisted and the slide will inflate and deploy automatically. The slide may be inflated manually if automatic inflation fails. Opening the door from outside disarms the door.

7a.2.3 Overwing Emergency Exits (A319/A320). The overwing emergency exits are equipped with a dual-lane escape slide mounted on the fuselage at the trailing edge of each wing. This slide is always armed. If an overwing
emergency exit is opened from inside, the slide will automatically deploy. The slide may be inflated manually if auto mode fails.

7a.2.4 A321 Emergency Exits. Two plug type doors on each side of the cabin are emergency exits. They open outward and forward. Each door has an escape slide stowed in a compartment below the cabin floor. Operation of
these exits is similar to that of passenger doors.

All Airbus and Boeing pax main entry doors are plug type.

Airbus doors are very similar to Boeing 777 doors.

The Airbus doors first move inwards and lift up slightly like the 777 doors do. That way they can get past the tabs that make them plug type doors.

Pre 777 Boeing A/C (except L1011 like doors on the 767) don't lift so they come inwards and articulate as stated to get past the same tabs that all main entry doors have.

If they weren't plug type doors they would require pull in hooks and multiple independent rotary locks like the main cargo doors.

Each of these doors is approximately 6' x 4' around 3,500 square inches, at a differential pressure of 8 psi makes that 28,000 pounds. No one will open that and the handle is not designed to, the mechanism will break long before any door opens.

Smoc said it rightly. If you notice at the interior edge of an Airbus door opening in the airframe, you will notice a number of squarish metal "tabs" sticking out of the door edge. These are the "tabs" that are preventing the door from blowing out in the air. I'll explain clearer if i can find a pic.

I'm not too sure I would describe the 320 entry doors as plug type.

Boeing 737 have the tabs that fold in and with a convoluted mech action allows the door to come into then out of the cabin with the tabs folded down.

767 are internal and plug the opening when set closed.

320 doors push up against the pressure seals and then are locked with thumping big latches. From memory without the latches the door would just be free to blow out.Hence it will not plug the opening.

I think the issue is what defines a plug door.Too me it means a door thats basically larger than the hole it plugs like a plug in a sink and will not push thru the opening.

I was shocked the first time I saw a non-plug door in an airliner - the BAe-146.

Grey beard which door on the 146....they are all plug.....on the main entry doors the action of closing pulls the door in and then down behind the stops, also the door then goes slightly outward....a plug in my book....All the rest on the lower lobe and the flight deck are definite plugs....

I'll defer to your recent experience, Spanner, as I haven't seen a 146 up close in 20 years. But I saw plenty of the 20 flown by PSA beginning in 1984.

GB

The cargo doors are non-plug and have inadvertently opened in flight, with catastrophic and lethal consequences, numerous times.

Some examples would include a Turkish Diesel-10; a United Airlines 747 and probably an Air India 747.

Yeah, looks like a320 doors are not plug-type:
YouTube - Operacion Type C door

A320 FCOM 1.52.10: "The aircraft has four plug-type doors that open outward and forward"

Either way, FAA doesn't define plug doors. The official term is "doors for which the initial opening movement is inwards". The Airbus doors qualify as inwards opening doors, otherwise they need locks and flags like the cargo doors. Part 25.783 is the applicable section.

I heard it's the same design on every Airbus product, including the Concorde.

Concord was built by Airbus?

IMO (not even humble, lol) if a door slaps up against the fuse from outside and is held in position with dirty big C latches, that aint a plug, and I dont care what airbus or BAe choose to call it.
next time I plug a sink from underneath I'll reconsider.
Dont get me wrong I like the bus (and its doors) , spent a long time working the 320 in the early days.

It's not the plug-type pax doors which cause the explosive decompression disasters. It's (almost) invariably the non-plug cargo doors which trigger those disasters, eg Air India 182, United 811 etc etc.

Combine non-plug electrically opened doors with Kapton or Poly-X wiring and you've got the recipe for a catastrophe. Added terrorists not necessary.

You will not open Boeing or Airbus doors in flight!! No matter how strong you are.

At the risk of oversimplification: Concorde was built by Aérospatiale and BAC. Aérospatiale was one of several companies in the original Airbus consortium that merged to form EADS, which now owns the Airbus brand and manufactures aircraft under that brand. I think.

IIRC Airbus held the type cert and provided manufacturer support. My understanding is that it was partly (if not mainly) due to Airbus's unwillingness to continue to provide such support (a commercial decision) which forced the type's retirement.

Plug doors
 

I believe that is very true.....

In a passed life I was closely involved with a smoke evacuation test on a B747-100. This meant I and another were lashed into the aircraft with 1.5" rope and body harness. The aircraft was depressurised at FL100 and the two redundant engineers tried to open door 1L, we managed to just crack the door and no more. I would even go to say it was the upper and lower gates that moved and not the actual door.

The idea being that in the event of cabin smoke the small cabin crew would crack open the forward and a rear door to create the draft and airflow to remove any smoke.....just like that:eek:

The noise from the airflow and roar was something I will always remember.

If a person was 'super human' the door handle would shear off first before any of these plug type doors began to open under pressurisation.

Well that was certainly kicked into touch.
But an idea that was explored, still alive to mention it - good plug!

TW

Actually, remember that Qantas 747-400 that blew an O2 bottle? It hit the door handle on the way up thru the floor and broke the handle shaft and cam. The door handle rotated to the open position, but the door didn't open.

And to add to AnthonyGA, BAC became BAe, who made Airbus wingsets in Filton, where they built the Concorde (the other Concorde line being Toulouse). That plant was sold by BAE Systems to EADS to become Airbus UK.

Checking out a picture (http://websites1st.co.uk/Websites/Co...rde%20door.jpg), it is the same system as the Airbus.

Can't believe somebody has uploaded the training videos on youtube, takes me years back hearing the narration.

When watching the video, the door mechanisim is best seen when the attendent is closing the door. The little tabs at the edges of the door are the structural pressure bearing stops. The door swings in but when the handle is drawn down, the door with its stops move down vertically, aligning with the stops on the airframe aperture. This takes the pressure loads from the door into the structure. The opposite happens when opening.

Hence this is a plug type door.

Any door when in closed position is larger than its cutout is a Plug type door.
The Entry/Gall/Bulk cargo doors on the B737 are examples.
The end gates above & below the cabin doors move to enable the door to move inside the cutout before closing.

Door unlocked
 

Hi,
Thanks for your input on the passenger doors
I am still in the dark as when the doors can open.
The landing altitude is set in the cockpit and the local QNH ,is this related to the doors.

Any reply appreciated.
Atkin

While I agree based on the math of a pressurized airplane I'll throw in a technicality... what if you depressurize first and then open it in flight? :}

On a more serious note I remembered the DB Cooper incident when I was reading through the replies, while the door in the aft bulkhead on a 727 is a plug type door it opens inward only. From my point of view (I go in and out of it often enough) and from a purely functional stanpoint it's near identical to the L-1 door (well duh, it's a door), but I'm wondering how much pressure, if any, DB Cooper was dealing with when he went to do that. I doubt it was 8.6 DPSI, but I bet someone knows the exact figure.

A little story for those that are worried about doors opening in flight.

A320 nightstop. Aircraft is left on the ground service bus, all the doors are closed and a ground air heater is plugged in.
The temp is around M15, and the arriving crew have read their FCOM and without asking the engineer have pushed the ditching switch.
In the morning the new crew come down the jetty. The door is closed, and the cabin pressure warning light in the door is flashing. The dispatcher, who usually opens the door, says that he can't open it. The Captain says that the flashing light MUST be a false warning and heaves up the lever to open the door. The FO catches him as he is propelled across the jetty by the door opening explosively.
He should have heard the hissing noise as the air escapes past the door seals, obeyed the warning light, and asked the ground crew to turn off the heater.

The little ground heater can pressurise the aircraft enough to nearly seal the door closed.

Opening doors in flight
 

It has been a while, however my recollection is that on the B747 the cabin smoke evacuation procedure called for both No1 and No 5 (L or R) to be cracked open to provide air flow through the cabin. Of course the procedure also called for flight below FL140 (to preclude the rubber jungle) and depressurisation of the aircraft. Never had to do it in operations, but the procedure was there.

aviatorhi states...

aviatorhi asks

The answer aviatorhi's question is 0 PSI Diff. as the aircraft was depressurized. The DB Cooper switch was installed in 1972 after a few incidents to prevent the ventral stairs from being lowered in flight. The DB Cooper Switch is a spring loaded vane that rotates 90 degrees.


http://upload.wikimedia.org/wikipedi...ooper_Vane.JPG

On the ground the plate which is attached to the vane is out of the way of the ventral stairs for normal operation. A preflight item is to ensure that the spring in the vane operates as it should. As airflow hits the vane, it rotates about 90 degrees so that a plate will cover the ventral stairs to prevent operation during flight.

All doors, including cargo doors on the 727 are plug type doors.

Thanks for the info on the DPSI when that occured, but that statement there is incorrect, the right side cargo (pit) doors are hinge type doors which open outward (except on certain 727-200s which had 3 cargo doors in which the aft one is a plug door). The cargo converted 727s I fly all have hinge type main cargo doors which lock into place with 6 big locks on the bottom and (I believe) 5 camlocks along each side.

On the727, starting with the cargo door closed, when you actuate the cargo door handle the door moves up a bit above it's lip before the door actually opens, thus technically the cargo doors are plug type.

Ampclamp - If you can find any "dirty great C latches" on a 'bus door you get a prize. There ain't any. The door is a plug because when it's shut the door drops, and door and frame stops line up, thus holding it against a/c pressure.

A ground heater will also pressurise a 146/RJ. The area of the pax door means it's virtually impossible to raise off it's stops. I can just manage to force the avionics hatch open with my shoulder when it happens.

Myself and the Aircraft Manual respectfully disagree. The upward motion is only necessary for the locks to clear above the locking components on the side of the door.

Quote:

---

2 . Passenger/Crew Doors

A. Forward Entry Door
(1) The forward entry door is on the left side of the airplane. It is
an inward-outward opening plug type of door which can be operated

from inside or outside the airplane.

---

Quote:

---

4 . Cargo Doors

A. ALL EXCEPT 727-200;
There are two cargo compartment doors on the lower right side of the
fuselage, one serving each cargo compartment. Both doors are hinged at
their upper edges and open inward. Access panels are provided in the
external skins of the cargo doors, to enable manual release of the cargo
door latches if the operating mechanisms fail. Except for slight
differences of shape, both doors are identical in design and operation.
Access to the aft cargo door is covered by the trailing edge of the wing
to body fairing. The rear end of this fairing is a separate section
mounted on rails so that it can slide aft to allow access to the cargo
door.
B. 727-200;
There are three cargo compartment doors on the lower right side of the
fuselage. The No. 1 and 2 cargo doors are hinged at their upper edges
and open outward. The No. 3 cargo door is a plug-type, inward opening
door. All three cargo doors have a balance mechanism which
counterbalance the door weight. A portion of the trailing edge of the
wing to body fairing is attached to the No. 2 cargo door. When the door
is locked, the outboard handle is flush with the exterior of the fairing.
The outboard handle is connected to the door latching mechanism by a

control rod.

---

I'm unsure as to the exact nature of the doors in Paragrah A, however Boeing does not describe them as plug doors, as I've never flown a 100, Paragraph B applies to me, but is not true of all 200s just some have the 3 door option, all the ones I've flown only have 2.

I've got lots of hours on the old -100... no greater bird in the sky.

Anyway I don't have the Boeing 727 Mx Ref. Man. on this computer to send you a graphic. But the the initial actuation of the cargo door on the -200 lifts the door out of it's sill about an inch before opening outward. True on the surface the door does not appear to be a plug type door, but per Boeing's descriptin it is.

Next time you fly the jet check it out.