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Semi Plug And Plug Type Door On A/c  
User currently offlineAPwannabe From Hong Kong, joined Oct 2004, 17 posts, RR: 0
Posted (10 years 1 month 4 weeks 1 day 11 hours ago) and read 10382 times:

Grateful if anyone can help me on these 2 types of door... I just knew that one of those are using mechanical parts to secure it and another one the door is simply bigger than the door frame and using the pressure to secure it while inflight.....

[Edited 2004-10-02 07:12:47]


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16 replies: All unread, jump to last
 
User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 1, posted (10 years 1 month 4 weeks 1 day 4 hours ago) and read 9937 times:

Not quite sure what you are asking.

A plug door is a door that is bigger than the opening. It fits into the door frame and the aircraft pressurization keeps the door sealed.

A non-plug door (never heard of semi-plug) is held closed by latches, rollers and/or hooks. They mechanically lock the door in place.

This is not to say that a plug door is not locked mechanically. There are mechanical locks, usually rollers, cams and over-center links, that keep the door closed. The plug function allows the pressurization system to assist in sealing the door. On a non-plug door, you are relying on the rig of the locking mechanisms to keep the door in place to form a good seal.

Rig is important with the plug doors also. The door needs to get close enough to the frame so that it will seal under pressure. Seen plenty of plug doors that didn't even come close after installation.


User currently offlineMiamiair From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 1 month 4 weeks 1 day 4 hours ago) and read 9922 times:

A good example of a plug door is the Main Entry Door of a 707/727/737; the door pivots inward at the forward end, and the aft end rotates outward, providing clearance with the fuselage structure. In a cross section, the door also looks like a plug; it is beveled, the outer skin is smaller than the inner skin. The upper and lower ends(gates) fold inward to provide clearance. A non plug door is life the A320, it extends outward, then forward. This door like all doors (plug included) when closed, interface with the fuselage via stops/fittings usually at stringer/longeron locations. As posted above, rigging the door is crucial to its operation.

Next time you board an airplane, look for these structural elements, you'll see them.


User currently offline320tech From Turks and Caicos Islands, joined May 2004, 491 posts, RR: 5
Reply 3, posted (10 years 1 month 4 weeks 15 hours ago) and read 9635 times:

A better illustration of a non-plug door would be an A320 (and many others, no doubt) cargo door. The door has a piano hinge at the top, and hooks at the bottom. There are also locking pins that extent from the sides when the door handle is closed. The door opens outwards.

The A320 pax door is a plug door, really, because it must be lowered into position. The door doesn't open straight out, it is lifted clear of door stops, and then can be swung out.



The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
User currently offlineAPwannabe From Hong Kong, joined Oct 2004, 17 posts, RR: 0
Reply 4, posted (10 years 1 month 3 weeks 6 days 14 hours ago) and read 9592 times:

Thx all for your details information. Now I know which is which.  Smile

So does that mean a plug door could only be opened inward because of the size of the door is bigger than the frame?

Is 747 using Plug type door?
so which type of door is now widely in use and which one is better? other than in civil aviation, do these kind of doors popular?



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User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 5, posted (10 years 1 month 3 weeks 6 days 14 hours ago) and read 9590 times:

The B747 is indeed a plug door. If you look closely at the top and bottom you will see panels we call "gates". These gates retract as the door opens and allows then door to pass through the opening.

User currently offlineAPwannabe From Hong Kong, joined Oct 2004, 17 posts, RR: 0
Reply 6, posted (10 years 1 month 3 weeks 6 days 8 hours ago) and read 9575 times:

So a plug type door system still needs a mechanical door frame for it to operate?

Sorry to keep asking, these questions has been on my mind for more than half a year already Big grin



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User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 7, posted (10 years 1 month 3 weeks 5 days 21 hours ago) and read 9546 times:

No problem.

The difference between a plug door and a non-plug door is simple how it sits in the door frame. I don't know if one is better than the other.

All still need some way to lock. All still have to be held in the door frame mechanically. Remember, when a door is closed, it becomes part of the structure and is thus subject to the same forces.

The door frame is not mechanical per se. It usually houses the hinge and the tracks that the locking rollers engage. There is uaually quite a bit of "monkey motion" in the door in order to make it work. Take for example the B747 (classic) door. The mechanism must be able to:
1. open the upper and lower gates,
2. rotate the rollers out of their tracks,
3. first move the door inboard a little and then swing out like a conventional door,
The door also has a mechanism installed to arm or disarm the slide and the air assist bottle.

Doors are complicated.


User currently offlineDAirbus From United States of America, joined Nov 2003, 593 posts, RR: 2
Reply 8, posted (10 years 1 month 3 weeks 5 days 14 hours ago) and read 9531 times:
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Another type of plug door mechanism is the doors on the 767, L-1011, and the DC10/MD11. To open the doors on these aircraft, the door moves in a short distance on tracks and then retracts into the overhead.

For cargo doors on large passenger aircraft, there are three basic types. The first type is the plug type door which opens inward. The 737 and DC-9/MD80 are good examples of this type of door. The CRJ and ERJ have a door similar to the 767 cabin door where they move in slightly and then go up into the cargo bin on tracks.

The second type is found on the 727, 757 and 767 where pulling on the door handle (or pushing the switches on the 767) first raises the door and is then opened the rest of the way either electrically or manually. This is similar to the mechanism of the entry door on the A320 described earlier.

A third type is the non plug type door with a "piano hinge" usually found on larger airliners such as the 747 and 777 as well as most Airbus aircraft. These doors open and close either electrically (Boeing and McD) or hydraulically (Airbus). What is interesting that although these doors are power actuated, they still have some kind of manual handle or interlock as a safety feature. Also, to ensure that the door is locked properly, they have some kind of feature allowing a visual check of the locks.




"I love mankind. It's people I can't stand." - Charles Shultz
User currently offlineApwannabe From Hong Kong, joined Oct 2004, 17 posts, RR: 0
Reply 9, posted (10 years 1 month 3 weeks 1 day 8 hours ago) and read 9460 times:

wow thx soooooo much for your clear and details explanations, Air2gxs and DAirbus. I believe that I have some idea of the operation on those 2 types of door. thanks a million!!!!! =)


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User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 10, posted (10 years 1 month 3 weeks 1 day 1 hour ago) and read 9458 times:

We may call them plug doors, and say that they are larger than their openings but that is only partly true. Most are only wider than the opening, not taller. The only shape that cannot pass through its own opening is round. That is why manhole covers are round - it is the only shape that cannot fall down the hole.

A "true plug" type door will be wider than the opening but not taller. To open, you typically will pull it inward, then rotate so that it is, in effect, narrower than the opening. Or, better yet, it will roll up inside the fuselage out of the way, as described by Dairbus above.

What is often called a "semi-plug" is the passenger door on an A-320 for example. What makes it plug-type is that lugs on the door rest directly against hard points on the door frame and the pressure differential holds it securely against those metal lugs. Like a true plug type door, if all the latch mechanism failed in flight, pressurization would hold it in place.

Non plug types, like most aircraft cargo doors latch up to the exterior, in effect. In flight if the latches failed, it would fly away.

Now a trivia question: On the DC-9 in passenger configuration, one door in the pressure vessel is NOT a plug-type door. Which one? Bonus points, what safety feature does it incorporate to compensate for this?




Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 11, posted (10 years 1 month 3 weeks 17 hours ago) and read 9435 times:

Slamclick,

I beg to differ, but the B747 (at least the classics) do have true plug doors. The gates at the top and bottom open or retract making the door smaller in hieght so that it may pass through the opening. When locked the gates fully close or extend and complete the seal.


User currently offlineApwannabe From Hong Kong, joined Oct 2004, 17 posts, RR: 0
Reply 12, posted (10 years 1 month 3 weeks 11 hours ago) and read 9419 times:

err..... in case the mechanic parts fail to operate, a non-plug type door will have a better chance to be opened?

one of the exit on the wing? cos there is another door next to it for faster evacuation while emergencies. Shouldn't be the one near cockpit as the door size is too big to operate without complicated mechanic system on locking and openning safely(in a pax mode)?

just a wild guess  Laugh out loud


[Edited 2004-10-10 06:57:26]


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User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 13, posted (10 years 1 month 3 weeks 1 hour ago) and read 9402 times:

Now a trivia question: On the DC-9 in passenger configuration, one door in the pressure vessel is NOT a plug-type door. Which one? Bonus points, what safety feature does it incorporate to compensate for this?

I'll guess this is the aft door with the airstair since it just pops down. Safety feature: the extra door on the inside of this (opening to the aisle) that opens inwards.

Just a guess. It's been a long time since I walked up or down a DC-9 airstair  Big grin



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 14, posted (10 years 1 month 2 weeks 6 days 23 hours ago) and read 9396 times:

Well, we are even because I never flew a DC-9 with the aft airstair. I believe but may be wrong, that the pressure seal there was at the aft bulkhead, though, and that the area around the retracted stair was not pressurized in flight. (?)

I was referring to the forward airstair door, below the 1 Left door. That stairwell is pressurized but the door simply latches to the airframe. In the event of a blowout there, the floor in the forward galley should collapse around the stair and prevent it being drawn out into the slipstream.

Air2gxs I have to stand by that statement. The gates at the top and bottom that you refer to are not part of the door frame (except for being bolted to it) but are actually to be considered a part of a mechanical latching mechanism. The door "frame" has no moving parts. To pass through an opening the same shape as the door, but smaller, the door would have to be pulled inward, rotated through two axes and passed out either head first or foot first.

Maybe it is a matter of semantics but the frame itself has a set of inside dimensions that cannot be decreased without deforming. The door has a fixed height and width that cannot be decreased without deforming. On the 747 as described, the height of the door is less than that of the frame, therefore not a "plug" in the vertical sense.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineNORTHSEATIGER From United Kingdom, joined Sep 2003, 432 posts, RR: 5
Reply 15, posted (10 years 1 month 2 weeks 6 days 2 hours ago) and read 9363 times:

Now, The super puma has plug doors but is kept closed in the way you would say is a non plug door i.e latches/hooks/rollers, it is bigger than the opening but is outside of the airframe. A non plug door in this respect is one which just slides and locks.


T's And P's look good....Rotate
User currently offlineFrancoflier From France, joined Oct 2001, 3818 posts, RR: 11
Reply 16, posted (10 years 1 month 2 weeks 2 days 13 hours ago) and read 9265 times:

Hey SeaTiger!

Quick question there, you got me confused a bit:
Is the Super Puma pressurized?

If it helps the topic, most small aircrafts (turboprops or bizjets) don't have plug doors because the mechanism and complexity of it would make it too big and heavy. Plus those doors often swing outward and provide you with the steps to climb in. Most of those doors have little windows on the sides to visually check the locks at all times, plus the usual microswithches to provide you with a warning if one or more locks are not in place.

The mechanism within the door provides a geometrical lock that pretty much never fails.

However some plug type doors can be found, like in emergency exits for instance, which swing inward, then are removed from their open hinges and can be thrown outside.



Looks like I picked the wrong week to quit posting...
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