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Upward Sliding Cabin Doors Vs. Outward Hinged  
User currently offlineLH455 From United States of America, joined Oct 2004, 87 posts, RR: 0
Posted (8 years 4 months 2 days 1 hour ago) and read 8084 times:

Just wondering about the sliding cabin doors on MD-11s, L1011s and 767s -- these doors are automatic and slide into the upper fuselage. During an accident is it possible these doors become jammed due to structural damage to the upper fuselage or do they have a manual swing-out option?

When the SIA 744 crashed in Taipei in '99 the hinged doors opened despite the damage the fuselage sustained. Same for the AF 340 that crash-landed in YYZ last summer.

The DL -1011 that crashed at DFW in 08/85 was mostly destroyed, and I don't remember if the far aft cabin doors were used to evacuate or if survivors jumped from the open cabin? Also, the Mandarin MD-11 that crashed in HKG in 99 was flipped onto its back so I don't believe the doors were used to evacuate in that incident either.

Do any FAs, pilots, mechanics, or engineers know of any risk with upward sliding doors? I've noticed recent aircraft designs still retain the swing-out doors (777, Airbus models).

Please excuse me if this has been discussed before -- I searched and didn't find the topic.

[Edited 2006-03-30 19:26:43]

32 replies: All unread, showing first 25:
 
User currently offlineJorge1812 From Germany, joined Apr 2004, 3149 posts, RR: 8
Reply 1, posted (8 years 4 months 1 day 22 hours ago) and read 7975 times:

Very interesting question. The only thing I know is that there is some kind of a hydraulic back-up when no power is available to open the door. But I myself wondered about the structural damage thing very often.

Georg


User currently offlineYYZYYT From Canada, joined Apr 2005, 947 posts, RR: 0
Reply 2, posted (8 years 4 months 1 day 21 hours ago) and read 7892 times:

There are some good discussions of the door mechanisms in tech ops:

RE: MD-11 Door (by Edina May 7 2005 in Tech Ops)#ID117334

or

RE: Semi Plug And Plug Type Door On A/c (by DAirbus Oct 5 2004 in Tech Ops)#ID100075


User currently offlineCptGermany From Germany, joined Feb 2006, 86 posts, RR: 0
Reply 3, posted (8 years 4 months 1 day 21 hours ago) and read 7892 times:

Quoting LH455 (Thread starter):
During an accident is it possible these doors become jammed due to structural damage to the upper fuselage or do they have a manual swing-out option?

The chances that the upper fuselage is damaged during a moderate crash are relatively low. I bet that except for fire damage, the upper fuselage on AF's A340 at YYZ was mainly intact. So I would say that the chances that upward sliding doors on L1011 and MD11 become jammed due to damage in the upper fuselage are slim. Furthermore, if the upper fuselage becomes damaged, the entire airplane usually breaks apart, because that would require the fuslage to flip somehow.

On the other hand, there might be a deformation of the fuselage upon impact during a crash landing. However, I am confident that designers at Lockheed and McDonnell-Douglas thought about this possibility when they designed the doors. Again, the chances are also very slim that during such an event all doors become jammed.

We have seen recently during the A380 evacuation test that all people need to be able to leave the airplane within a short period of time even if half the doors are blocked. So even if upto half the doors on a MD11 or L1011 are jammed due to structural damage in the upper fuselage, all passangers should be able to get out of the wreck quickly. But as pointed out, this scenario is rather unlikely.

I believe the initial idea to have the doors retract into the upper fuselage within the cabin originated from the fact that many times swing-out doors have been ripped off the aircraft by gate-bridges. IMO, the mechanism on the L1011 and MD11 is a great idea. Nevertheless, your concern is definitely appropriate. I hope my thoughts are helpful and informative.

I hope this thread receives more attention since it is an interesting topic. Unfortunately, A vs. B threads get most of the attention nowadays.  Sad


User currently offlineRandyWaldron From United States of America, joined Mar 2006, 324 posts, RR: 3
Reply 4, posted (8 years 4 months 1 day 16 hours ago) and read 7750 times:

As a flight attendant that used to fly the DC10 regularly, I can only comment on how those doors operate.

The doors on the DC10/MD11 operate in three ways: normal, emergency and pneumatic override. Opening the door in the normal mode requires electrical power. In the emergency or pneumatic override modes, electrical power is not required.

In normal (slide disarmed) mode, the doors are electrically powered, either by the door control handle (the big silver thing mounted on the aircraft wall) or electric push-button switches located on the flight attendant jumpseat adajcent to each door.

In the emergency (slide armed) mode, the door is opened only via the door control handle, which punctures a bottle of compressed gas which throws the door in and upwards into the ceiling, and deploys the escape chute. (Electrical power is not required).

In the pneumatic override mode, the door is opened by moving the arming lever past the armed detent and moving the door control lever to the open position. This opens the door without slide deployment and is used to open the door when there is a total loss of electrical power.

There is also a manual lift bar on the DC10 door when either of those three methods fail.

I hope this helps.



"Flaps 20, gear down, landing checklist please..."
User currently offlineRandyWaldron From United States of America, joined Mar 2006, 324 posts, RR: 3
Reply 5, posted (8 years 4 months 1 day 16 hours ago) and read 7738 times:

Additional info:

Most aircraft doors have this feature called "power assist". Becaue aircraft doors are extremely heavy (doors on the 747 weigh hundreds of pounds), in an emergency, when time is of the essence and the door could be obstructed due to debris or structural damage, power assist applies brute force to the door to ensure it opens.

All Airbus Aircraft and Boeing 747's, 757's, and 777's have a power assist feature. 727's, 737's, DC9/MD80's and B717's do not.



"Flaps 20, gear down, landing checklist please..."
User currently offlineMarkHKG From United States of America, joined Dec 2005, 960 posts, RR: 2
Reply 6, posted (8 years 4 months 1 day 15 hours ago) and read 7667 times:

Upward sliding doors are also known for their "unforgiving" nature during accidental slide deployments, as you can't really stop the door from opening during emergency mode. A particular offender is the B-767, because of its slide arm/disarm "inboard/outboard" indication that can be hard to look at.


Release your seat-belts and get out! Leave everything!
User currently offlineLH455 From United States of America, joined Oct 2004, 87 posts, RR: 0
Reply 7, posted (8 years 4 months 1 day 14 hours ago) and read 7618 times:

Quoting RandyWaldron (Reply 5):
power assist applies brute force to the door to ensure it opens.

Aha -- this is what I was wondering.

Your response is super informative!


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 8, posted (8 years 4 months 1 day 14 hours ago) and read 7582 times:

Quoting Jorge1812 (Reply 1):
The only thing I know is that there is some kind of a hydraulic back-up when no power is available to open the door.

The L-1011 passenger doors are electrically operated in normal operation. If electrical power is not available they can be cranked open (from inside on all doors and the the outside for the L-1 door).

However, in an emergency the each door is equipped with a spring loaded counterbalance. This counterbalance can open the door and deploy the slide in under five seconds.


User currently offlineIkramerica From United States of America, joined May 2005, 21474 posts, RR: 60
Reply 9, posted (8 years 4 months 1 day 13 hours ago) and read 7553 times:

Quoting CptGermany (Reply 3):
However, I am confident that designers at Lockheed and McDonnell-Douglas thought about this possibility when they designed the doors. Again, the chances are also very slim that during such an event all doors become jammed.

In respect to that, the normal way that anything is engineered when part of it must still work properly after being damaged is to make the important area the strongest part of the structure (relatively), and the spots right next to it a great deal weaker so that if stresses are concentrated anywhere near that spot, buckling/damage will occur around the vital area, but not in it. This is not to say the surrounding areas are weaknesses, they are just designed to be the first areas in that region to fail.

This type of design is used for modern car doors, for example. The goal is for a car/truck to sustain a front crash test and still have fully functioning doors. Many car makers have achieved this.

One can assume that these jets also have this type of design. So if the fuselage buckles around the door, the door "pocket" would be the strongest area of that section of the plane. It would take near break apart of the plane for that section to buckle, as the energy would instead otherwise be absorbed by the non-critical section of the fuselage.



Of all the things to worry about... the Wookie has no pants.
User currently offlineLH455 From United States of America, joined Oct 2004, 87 posts, RR: 0
Reply 10, posted (8 years 4 months 1 day 5 hours ago) and read 7443 times:

Quoting Ikramerica (Reply 9):
So if the fuselage buckles around the door, the door "pocket" would be the strongest area of that section of the plane. It would take near break apart of the plane for that section to buckle, as the energy would instead otherwise be absorbed by the non-critical section of the fuselage.

Hmm ... so that suddenly makes those legroom-plentiful door seats seem much less desirable!


User currently offlineNzrich From New Zealand, joined Dec 2005, 1521 posts, RR: 1
Reply 11, posted (8 years 4 months 1 day 4 hours ago) and read 7401 times:

Quoting RandyWaldron (Reply 5):

All Airbus Aircraft and Boeing 747's, 757's, and 777's have a power assist feature. 727's, 737's, DC9/MD80's and B717's do not.

They all do its called Muscle power



"Pride of the pacific"
User currently offlineNzrich From New Zealand, joined Dec 2005, 1521 posts, RR: 1
Reply 12, posted (8 years 4 months 1 day 4 hours ago) and read 7392 times:

But i have to say i did also wonder sometimes what would happen in a crash if you could get out ...Mind you if the door frame was buckled any door would be difficult to open ..


"Pride of the pacific"
User currently offlineTod From Denmark, joined Aug 2004, 1724 posts, RR: 3
Reply 13, posted (8 years 4 months 1 day 4 hours ago) and read 7358 times:

Quoting Ikramerica (Reply 9):
In respect to that, the normal way that anything is engineered when part of it must still work properly after being damaged is to make the important area the strongest part of the structure (relatively), and the spots right next to it a great deal weaker so that if stresses are concentrated anywhere near that spot, buckling/damage will occur around the vital area, but not in it. This is not to say the surrounding areas are weaknesses, they are just designed to be the first areas in that region to fail.

Not the case with the 747. The fuselage structure a few framebays forward and aft of the doorways is reinforced and is stronger than the regular fuselage sections.

Tod


User currently offlineClassicLover From Ireland, joined Mar 2004, 4627 posts, RR: 23
Reply 14, posted (8 years 4 months 1 day 4 hours ago) and read 7343 times:

Quoting Nzrich (Reply 12):
But i have to say i did also wonder sometimes what would happen in a crash if you could get out ...Mind you if the door frame was buckled any door would be difficult to open ..

You'd just use the overwing exits if the main doors were inop. Besides, there's a reason for that many exits on planes.

The sliding up door isn't a new concept anyway... the Lockheed Electra (1959) had doors like that.



I do quite enjoy a spot of flying - more so when it's not in Economy!
User currently offlineFlyboy80 From United States of America, joined Jul 2001, 1876 posts, RR: 3
Reply 15, posted (8 years 4 months 1 day 4 hours ago) and read 7341 times:

I still think that safety videos, and safety information cards on commercial aircraft need to emphasize more specifically on the power assist. I know that if the F/A wasn't present, and one of the PAX had to open a door, indeed they would and they wouldn't let go of the door control handle and probabaly be thrown.

User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 16, posted (8 years 4 months 1 day 3 hours ago) and read 7304 times:

Quoting LH455 (Thread starter):
Just wondering about the sliding cabin doors on MD-11s, L1011s and 767s -- these doors are automatic and slide into the upper fuselage. During an accident is it possible these doors become jammed due to structural damage to the upper fuselage or do they have a manual swing-out option?

I can add a little more detail, as I was (still am, I guess) certified on door rigging and inspection on the MD11. It was a good way to get in the plant off the flight line during the California winters.

The MD11 passenger door works as our F/A colleague described it. The structure is pretty robust and as a matter of fact the door fits in the guides rather loosely so even a fair amount of structural deformation wouldn't keep the door from opening. As it is a floating plug door, no locking bars or other such stuff is needed.

The cargo doors and airpack doors, of course are entirely different. I was certified to rig and inspect them as well.

When opening under normal conditions the door is opened by an electric motor operating a windlass that raises the door with cables. The pneumatic backup system has a valve, rather than a puncture feature. There is a flask of N2 under high pressure in the overhead, and you can see the pressure gauges in the ceiling panel as you enter. When you throw the emergency lever, the door IS going to open and damned fast, too. It is raised by a powerful pneumatic motor. At the same time the girt bar is retained in the floor and that's what starts the slide deploying.

I always thought the opposite-that doors that translate inward on a central pivot would be problem areas in the event of structural deformation. I am informed that the A380 uses an electric backup powered by some large storage capacitors. Perhaps one of the Airbus folks around here can bring me up to speed on that.


User currently offlineLH455 From United States of America, joined Oct 2004, 87 posts, RR: 0
Reply 17, posted (8 years 4 months 1 day 1 hour ago) and read 7225 times:

Quoting Dougloid (Reply 16):
I always thought the opposite-that doors that translate inward on a central pivot would be problem areas in the event of structural deformation.

I've thought the same thing too -- you need to move 'em inward a bit and then out, right? Regardless -- if the outside is blocked or damaged they may not go out but it seems all systems have a force option that'll get 'em out or up regardless.

Since 76s are still being manufactured the system certainly must be safe. Wonder what main factor is in choosing one over the other when designing the plane? I'm sure there are many factors going into it.

Thanks to all you FAs and engineers who have chimed in


User currently offlineCtbarnes From United States of America, joined Mar 2000, 3491 posts, RR: 50
Reply 18, posted (8 years 4 months 1 day 1 hour ago) and read 7207 times:

Thread got moved to tech-ops while I was reading it.  Confused You can't say the Mods aren't on top of things...  Wink

This thread has, for me, been one of those questions I've always wanted to know about but was afraid to ask for fear of being seen as too much of a hardcore geek.

I remember in early safety videos produced in the 80's they used to show actual pictures of the door being open and the slide being deployed, both from the inside and outside. I always thought these pictures looked really cool, but it probably got too expensive, the computer animation nowdays just doesn't seem the same.

Charles, SJ



The customer isn't a moron, she is your wife -David Ogilvy
User currently offlineDavid L From United Kingdom, joined May 1999, 9523 posts, RR: 42
Reply 19, posted (8 years 4 months 1 day 1 hour ago) and read 7199 times:

Quoting Ctbarnes (Reply 18):
but was afraid to ask for fear of being seen as too much of a hardcore geek.

Hardcore aviation geeks, eh? There's no place for their sort on a.net.  Smile


User currently offlineTristarSteve From Sweden, joined Nov 2005, 3981 posts, RR: 34
Reply 20, posted (8 years 4 months 1 day 1 hour ago) and read 7195 times:

The Tristar and B767 doors have a counerbalance. In normal operation this balances the weight of the door plus slide. In emergency opening, the slide is attached to the floor. As soon as the door opens, the weight of the slide is taken off the door. The now much lighter door moves up under the counterbalance at high speed.

Quoting ClassicLover (Reply 14):
the Lockheed Electra (1959) had doors like that

and the Dh Trident series.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16999 posts, RR: 67
Reply 21, posted (8 years 4 months 23 hours ago) and read 7161 times:

Quoting RandyWaldron (Reply 5):
Most aircraft doors have this feature called "power assist". Becaue aircraft doors are extremely heavy (doors on the 747 weigh hundreds of pounds), in an emergency, when time is of the essence and the door could be obstructed due to debris or structural damage, power assist applies brute force to the door to ensure it opens.



Quoting Flyboy80 (Reply 15):
I still think that safety videos, and safety information cards on commercial aircraft need to emphasize more specifically on the power assist. I know that if the F/A wasn't present, and one of the PAX had to open a door, indeed they would and they wouldn't let go of the door control handle and probabaly be thrown.

Thrown? Actually more dramatic than that. One 777 F/A told me when she briefed me that it would break my arm if I didn't let go as soon as the handle started moving by itself. This would happen after a very brief part of the arc (she indicated about 30-40 degrees). She added that "unless the girl sitting in front of you is DEAD [her emphasis] you won't need to do it, but just in case". Big grin



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 22, posted (8 years 4 months 22 hours ago) and read 7150 times:

Quoting TristarSteve (Reply 20):
The now much lighter door moves up under the counterbalance at high speed.

Steve,

This is not recommended, the L-1011 door (with slide pack removed) can go up so fast and with such force the upper stops can and have been sheared. Something like a 1 1/2 seconds to completely open.


User currently offlineLTU932 From Germany, joined Jan 2006, 13864 posts, RR: 50
Reply 23, posted (8 years 4 months 19 hours ago) and read 7102 times:

Quoting Dougloid (Reply 16):
I can add a little more detail, as I was (still am, I guess) certified on door rigging and inspection on the MD11. It was a good way to get in the plant off the flight line during the California winters.

What about DC-10s? Don't those share the exact same door types as the MD-11s?


User currently offlineLH455 From United States of America, joined Oct 2004, 87 posts, RR: 0
Reply 24, posted (8 years 4 months 19 hours ago) and read 7100 times:

Quoting 474218 (Reply 22):
the L-1011 door (with slide pack removed) can go up so fast and with such force the upper stops can and have been sheared. Something like a 1 1/2 seconds to completely open.

This is interesting too since you mostly think of these sort of force openings as being the result of pressure differences -- like the time the AA A300 made an emergency landing at MIA and the FA was killed when he opened the cabin door too soon.


25 Sfomb67 : If I remember right, UA's 767's have a power assisted door at 1L, the rest use a counterbalance mech. Is this true of all 767's, or is this a option w
26 Dougloid : I believe they are. When I started the last DC10 was being finished for Nigerian-that would have been hull number 446. The doors were the same.
27 474218 : Dougloid, If I looked long enough I think could find my L-1011 Passenger and Cargo Door Rigger/Inspector Certification Card. But I am sure it has exp
28 Dougloid : I'm sure they do. Douglas required people who worked on doors to be certified as well as the inspectors. They were awfully sensitive about it ever si
29 TristarSteve : They still have a counterbalance as well. Our B767 have electric motors at L1 and L2. It replaces the little push you have to give the door on its wa
30 Post contains links Ctbarnes : I remember hearing about that too. From what I remember he was sucked out when he opened the door because the cabin had not been depressurized. Also,
31 Litz : Most airlines I've been on have the animated videos, but America West still used an actual airplane and deployed a slide for their video, including d
32 Starlionblue : Agreed. But on the other hand most people pay zero attention to the video. So having a hip, fun animated video (like VS) will ensure that more people
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