Today I had a great flight from BDL-IAD on a United A319, then we boarded a Mesa CRJ (N37208). There was a catering delay, and it was hot, so we sat there with the ground a/c unit connected and the windowshades down. The catering finally arrived and after more waiting the FA closed the main cabin door. I should mention that I was in 3A so I could sort of see what was going on.

Something was wrong because the aircraft immediately started to pressurize due to the a/c still being connected and everyone's ears started popping. Should the outflow valves have opened even if the pressurization system wasn't on? The FA then opened the service door (which must not be a plug type door because she was petite and I don't think she could've opened it otherwise) and it came open with a loud bang and thumped hard against its stops due to the outrushing air. This bent the door and a bit of the sheet metal around the door. Our flight was canceled and 4.5 hours later we finally left on the next flight (which itself was delayed an hour due to thunderstorms on the east coast today).

My question is, once you realize that the cabin is pressurizing due to ground a/c, what do you do about the situation?

Boarding:


No matter how often it was slammed, it couldn't close:


Guys taking pictures:

The outflows need bleed air off the engines to operate properly and therefore the doors are not to be closed when ground air is connected. If the door was closed, the outer handle needs to remain unstowed to keep the pressure valve on the door open.

Thanks, I figured the FA forgot that the ground a/c was connected and closed and secured the door when she shouldn't have.

But how do you relieve the pressure once you get the ground a/c turned off and the cabin is at a higher pressure than the outside air...and the engines aren't turning?

Quoting MD-90 (Reply 2): But how do you relieve the pressure once you get the ground a/c turned off and the cabin is at a higher pressure than the outside air...and the engines aren't turning?

On the MD11F we have a switch where we can controll the outflow valve manually. So just open it electrically and all the air should vent overboard...

WILCO737 (MD11F)
  

Quoting MD-90 (Thread starter): which must not be a plug type door because she was petite

ALL aircraft doors are plug-type doors, otherwise they'd explode out at altitude. Even the overwing exits are plugs.
On pressurized aircraft, I mean.

Anyhow, the over-pressure relief valves won't open until you reach maximum cabin delta-p (difference in pressure between outside and inside). On the ground, max delta-p would be an earsplitting amount. So the "backup plan" in this case won't help you.

So yeah, basically, you've got a situation where an external machine is pumping air in, and the aircraft doesn't have a way to let it out.

Quoting MD-90 (Reply 2): But how do you relieve the pressure once you get the ground a/c turned off and the cabin is at a higher pressure than the outside air...and the engines aren't turning?

The flight crew can manually open the outflow valves with a switch in the cockpit.

The whole thing is fishy- the outflow valves are normally logic'ed to go full open during landing rollout. So, it should have already been open, in other words.

Quoting MD-90 (Thread starter): a catering delay

Lol...... they should have just made every pax buy a can of pop in the terminal!

Quoting MD-90 (Thread starter): Should the outflow valves have opened even if the pressurization system wasn't on?

I don't think the CRJ has a dedicated outflow valve like most airplanes do. I know we always crack the cabin or avionics bay door when an air cart is used to prevent what happened to you. However, I'd assume they have other ways of equalizing the pressure than a regular door. I just don't know what they are.

[Edited 2008-06-30 09:20:09]

Quoting MD-90 (Reply 2): But how do you relieve the pressure once

Emergency Dump Switch..... always fun if you're out on engine runs and the weather conditions are right. Hit the switch and watch it snow inside the plane

Quoting AA737-823 (Reply 4): The whole thing is fishy- the outflow valves are normally logic'ed to go full open during landing rollout. So, it should have already been open, in other words.

There is a nice big placard by the external air connection on all of our CRJ-700's that say have a door cracked open to allow a way out for the air... If IIRC, as I do not have my CRJ training info in fron of me at the moment, T Prop is correct, the outflow valve needs motive flow to operate, thus it needs a bleed air source. If the A/C cart was connected, I am going to assume that the APU was not operating, thus no bleed air was selected. I could be getting my RJ systems confused with the Dash 8, but I believe they are the same.

Kris

Quoting MD-90 (Thread starter): My question is, once you realize that the cabin is pressurizing due to ground a/c, what do you do about the situation?

Turn off the A/C cart and let the pressure bleed down. It will take a little bit of time but is will come down. Or just dump the cabin as previously said.

Quoting A10WARTHOG (Reply 9): Turn off the A/C cart and let the pressure bleed down.

Yup...aircraft are not without leaks..and they are allowed. On the Ejet you pressurize up to 5.0 psid.... shut off the APU air, drive the valves closed.. and start a stop watch....record your readings and then graph them out. It's been a year, but if I recall.. you record at every 0.5 psid drop and how long it takes to get there. As long as the are good... the leaks are within limits. I did one once that took almost 30 minutes to bleed down... it was WAY good.

....or on the on the flight deck move the pressurization control switch to manual and drive it open.

[Edited 2008-06-30 10:48:40]

Quoting EMBQA (Reply 10): Yup...aircraft are not without leaks..and they are allowed. On the Ejet you pressurize up to 5.0 psid.... shut off the APU air, drive the valves closed.. and start a stop watch....record your readings and then graph them out. As long as the are good... the leaks are within limits. I did one once that took almost 30 minutes to bleed down... it was WAY good. ....or on the on the flight deck move the pressurization control switch to manual and drive it open.

Did something like that on an ERJ. After replacing Door seals and window seals

Quoting AA737-823 (Reply 4): ALL aircraft doors are plug-type doors, otherwise they'd explode out at altitude.

Not so much...cargo doors are typically not plug-doors. You just need to make sure the latch structure can take the load.

Tom.

Quoting AA737-823 (Reply 4): ALL aircraft doors are plug-type doors, otherwise they'd explode out at altitude. Even the overwing exits are plugs. On pressurized aircraft, I mean.

This is not a correct statement. Most non-cargo doors are plug doors, however.

Quoting Tdscanuck (Reply 12): Quoting AA737-823 (Reply 4): ALL aircraft doors are plug-type doors, otherwise they'd explode out at altitude. Not so much...cargo doors are typically not plug-doors. You just need to make sure the latch structure can take the load.

GA aircraft doors typically aren't plug doors either. Even some of the bizjets (to save room, I suppose).

Quoting AA737-823 (Reply 4): ALL aircraft doors are plug-type doors, otherwise they'd explode out at altitude. Even the overwing exits are plugs. On pressurized aircraft, I mean.

Looking at the picture of the CRJ in the original post, the first picture shows passengers boarding via the air stairs, that is not a plug door, its just that the structure around the door frame is very strong and the latches are designed to hold the door closed.

Most corporate jets use non plug doors, some LearJets are certified to 51,000 feet use a non plug 2 section door. Gulfstream jets like the G2 through the GV also use non plug main doors with built in steps along with Falcon jets and Hawkers.

The CRJ is basically an offshoot of the Challenger business jet and except for some early model 600’s which had a door that was hinged on the top and a small lightweight folding steps was used for boarding, the Challenger series has used non plug main doors.

The only bizjets that I remember that used a plug door was the early Hawker’s and the Lockheed JetStar, on the Hawker, the door rolled up into the ceiling and boarding was via a lightweight set of folding steps.

On the Lockheed JetStar the plug door slid back in and then slid aft on tracks and had a 2 section folding set of steps that also when retracted slid aft to allow the main door to be used as an emergency exit without the steps blocking the doors.

Quoting Tdscanuck (Reply 12): Not so much...cargo doors are typically not plug-doors.

I was referring to pax entry doors, considering that's what is actually being talked about.
But I'll count on you to nitpick in the future.

Quoting PGNCS (Reply 13): This is not a correct statement.

Okay, name for me an airliner of decent size (I work on 737s and 747s, so I typically consider anything smaller just a toy) that has MAIN CABIN (again, topic at hand...) DOORS that are not plug-type.

Quoting MD-90 (Reply 14): GA aircraft doors typically aren't plug doors either.

Yes, but the Cessna 150's I've flown aren't, in fact, pressurized... thus removing their tendency to explode out at altitude, as I've stated...

Quoting Jetstar (Reply 15): Looking at the picture of the CRJ in the original post, the first picture shows passengers boarding via the air stairs, that is not a plug door

Just because a door has stairs doesn't mean it isn't a plug. The 737s with aft exit stair-equipped doors are certainly plugs, as are the Fokker 70/100s with built in stairs.

Quoting Jetstar (Reply 15): Hawker’s and the Lockheed JetStar, on the Hawker,

And the NA Saberliner.... MAN, what a pain in the neck, that one.

Quoting Jetstar (Reply 15): Challenger series has used non plug main doors.

I suppose it's possible, and if true, then I've learned something.
But I've never heard of an aircraft of decent size that didn't have plug doors. Whoda thunk.

Quoting AA737-823 (Reply 16): And the NA Saberliner.... MAN, what a pain in the neck, that one.

I forgot about the Sabreliner, that stupid airstair design cost North American some sales. After walking up the steps you had to step down about 10 inches into the cabin entranceway while slightly hunched over, this was uncomfortable for women with heels or tight skirts and I heard that some executives wives did not like the steps so they pressured their husbands not to but the Sabreliner.

When NA introduced the Saber 65, which was a model 60 with 731 engines and a redesigned wing, they were pressured to redesign the steps and get rid of the small teardrop cabin windows, but NA did not do so because of budget reasons.

Quoting AA737-823 (Reply 16): Quoting PGNCS (Reply 13): This is not a correct statement. Okay, name for me an airliner of decent size (I work on 737s and 747s, so I typically consider anything smaller just a toy) that has MAIN CABIN (again, topic at hand...) DOORS that are not plug-type.

Well you didn't SAY main cabin doors. You said ALL doors.

The 744 upper deck doors open outward although they translate upward during the opening process. I haven't flown it since 1996, but I do seem to recall that for a "Door [L/R] Upper Dk" EICAS you had to check the pressurization system and then call the FA to ensure that the door was latched properly. I believe that below 3 PSID that a FA had to be stationed near the door as it was possible to open it in flight. Above that differential I think that the bottom face of the door ensured it would stay closed. I posted a relevant and interesting site about aircraft doors below, if anyone is interested.

I am unsure about the 73NG overwing exits. I have never flown the NG, but I know they do open outward. I am unsure if they are locked closed with a weight on wheels or PSID activated mechanism, or if they must translate upward before rotating outward.

Since you're the 737 and 747 mechanic, I'm sure you know far more about these doors than I do.

http://www.tc.gc.ca/CivilAviation/co...96/scheduleA/section2.htm#section6

B-747- 400 Main Deck Doors

Upper Deck Doors (Type A)

Type A classification may be derated to Type 1 due to interior configuration.
Electrically operated doors that move upward and outward when operated (Normal).
Pneumatic operation (Emergency). Pressure gauge above door.
Never used without slide inflation (Single Channel Slides).
Manual Inflation Handle under clothes cover.
Slight mechanical difference in operation of Slide Arming Lever from Main Deck doors (lever is moved Up/Down to Arm/Disarm) (lift cover).
Cover will not close unless lever is properly in either mode.
Opened in Emergency by rotating Door Control Handle upward fully.
Approximate force required to move door control handle from closed/locked position to open position (Normal & Emergency): 18 kg. (40 lbs.).
Door Ground mode Light.
Battery OK Light.
References

Boeing 747 Operations Manual
Air Canada F/A Manual 356
Canadian F/A Manual
Boeing - Airworthiness Division

[Edited to add information about 747-400 Upper Deck doors.]

[Edited 2008-07-01 07:40:20]

[Edited 2008-07-01 07:54:33]

Quoting AA737-823 (Reply 16): The 737s with aft exit stair-equipped doors are certainly plugs,

I'm a little confused here. I thought that the optional airstairs on a 732 were an entirely different assembly to the door, (which as you say is of the plug type).

My understanding of plug doors is that they go in, then turn, then rotate out. I really can't see how this would work with the aircraft in the picture above. Are you sure it isn't designed the same way as a business jet? Those locks and braces do, as Jetstar says, look very substantial. I'm just curious is all.

Quoting AA737-823 (Reply 16): Yes, but the Cessna 150's I've flown aren't, in fact, pressurized... thus removing their tendency to explode out at altitude, as I've stated...

Do any pressurized Cessnas, Pipers, or Beechcraft have plug doors? Pretty sure they don't, although I've never researched it.

Here is a nice view of the Gulfstream 4 main entrance non plug door.


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Photo © Jerome Zbinden


All legacy Gulfstreams from the turbo prop G1 up use the same system. Latching is via large pins that extend out of the door and into holes in the door frame. You can see in the door frame the openings and around just above the gray door seal on the door the pins which are retracted in the door when opened. All the force on the door in flight is entirely on the door pins and latches, so the door frame is reinforced to take the pressurization loads, and considering the later models of the Gulfstream series are certified to FL490, thats a lot of stress on the door frame

The door is hydraulically closed using the aircraft auxiliary electric hydraulic pump with the switch in the nose wheel well for external use. As the door closes, the lower section of the steps folds upward in the upper section and the hand rails, which are not disconnected fold and retract with the door. The steps are an integral part of the door so they are not movable away from the door during flight. The door is considered an emergency exit and is outlined in paint to conform with the regulations.

Opening is done be releasing the door lock handle either inside or outside and the door uses gravity to open, it is slowed by the force of the hydraulic fluid in the system being returned to the reservoir.

The weight of the door when opened is not supported by the airframe, but entirely on 2 small wheels mounted on extensions that sit on the ground and care must be taken so the wheels are not blocked or in ruts on the tarmac because as the airplane is being refueled, the airplane will settle down lower and the door will walk slightly outwards on the ramp, which is why there are wheels instead of a block.

For towing the airplane with the door open, a set of cables is used to raise the door off of the ground and support the door, they are normally stored in a small compartment on the aft side of the door. One person can easily lift the door a few inches off the ground to connect the cables. They are hooked onto the door frame and the bottom of the door raising the door a few inches off of the ground. Also when the airplane is on jacks, the door if open must have the support cables installed as the airplane is jacked up and before entry into the cabin a platform or a wooden box has to be placed under the door because the cables are not designed to take the weight of a person, milk crates or a wooden box make a great door support.

First off, OUCH!

So heres the deal with this situation....

The CRJ-200 does have various ways of equalizing its pressure with the outside air, namely the outflow valves (there are two located below the floor of the cargo compartment that vent into the non-pressurized aft equipment bay, you cannot see them from the outside of the plane), a ram-air valve, and a pressure release flap on the main cabin door.

This is a very tricky situation to end up in. There is a limitation imposed by Bombardier that external air must not be connected and in use without the avionics bay or main passenger door open. Why? Because, even using all the methods combined to relieve pressure, the external air can still pump air into the cabin at a rate greater than you can dump air out of every possible vent, flap, and valve in the fuselage. Every captain should, prior to authorizing the FA to close the door, verify that external air is no longer plugged in. If there is confusion and the door is closed for some reason prior to air being disconnected, I would do my quickest to turn off both packs, open the outflow and ram-air valves, instruct the ground crew to turn off the air, and instruct the flight attendant to very carefully open the pressure release flap on the passenger door. Once thats all done and the pressure is equalized, the main cabin door can be re-opened.

If this isn't done right, you could end up with a situation such as what was described by the original poster.

Quoting AA737-823 (Reply 16): I was referring to pax entry doors, considering that's what is actually being talked about. But I'll count on you to nitpick in the future.

I will nit pick as well. He was talking about the cabin service door when he mentioned the FA's petite stature.

Quoting AA737-823 (Reply 16): Okay, name for me an airliner of decent size (I work on 737s and 747s, so I typically consider anything smaller just a toy) that has MAIN CABIN (again, topic at hand...) DOORS that are not plug-type.

Borderline off-topic but I'm 99% sure that the over-wing exits on the 737 NG (e.g. the spring loaded "gull wing" doors) are not plug type; there is an electronic latch that engages at around (IIRC) V1 [if you're in the window seat of an exit row you listen carefully during the takeoff roll you can hear it click to prevent the door from being released in flight.

Lincoln

Interesting event. I've seen this happen but never on an RJ. We almost never used GPUs on our CRJs but if the APU was deferred we would have to.

In the case of our ATRs, it's all a part of parking the a/c to connect a/c and power so that they can shut down the engine. If we did for some reason have to button her up for a while during the day (next flight in 2hrs or more and no crew) we would close the boarding door and also close the cargo door but we won't latch it so you could feel the rush of air through the handle.

Quoting AA737-823 (Reply 16): Quoting Tdscanuck (Reply 12): Not so much...cargo doors are typically not plug-doors. I was referring to pax entry doors, considering that's what is actually being talked about. But I'll count on you to nitpick in the future. Quoting PGNCS (Reply 13): This is not a correct statement. Okay, name for me an airliner of decent size (I work on 737s and 747s, so I typically consider anything smaller just a toy) that has MAIN CABIN (again, topic at hand...) DOORS that are not plug-type.

Gripe all you want but this is a.nut. We tear vague statements apart.  



BTW I'll pretend to be the Clicker and ask you all what door on the DC-9 is not plug type.

Was the aft stairway on the 727 plug type?

Quoting Dragon6172 (Reply 27): Was the aft stairway on the 727 plug type?

Correct me if I'm wrong, (and its been a long time since I was on a 727) but it swings inward into the cabin. It reminds me more of a bank vault door than the plug type doors at 1R/L 2R/L.

Quoting Starlionblue (Reply 26): BTW I'll pretend to be the Clicker and ask you all what door on the DC-9 is not plug type.

I don't have a clue, but given the way you phrased it I'm gonna guess the tail cone!  

Quoting PITIngres (Reply 29): Quoting Starlionblue (Reply 26): BTW I'll pretend to be the Clicker and ask you all what door on the DC-9 is not plug type. I don't have a clue, but given the way you phrased it I'm gonna guess the tail cone!

Nope. IIRC it is the integral passenger stairway door (ok hatch) under the L1 door.

I hope I got that right.

[Edited 2008-07-03 21:49:10]

Quoting AA737-823 (Reply 16): Okay, name for me an airliner of decent size (I work on 737s and 747s, so I typically consider anything smaller just a toy) that has MAIN CABIN (again, topic at hand...) DOORS that are not plug-type

A320 family.

Quoting MD-90 (Reply 20): Do any pressurized Cessnas, Pipers, or Beechcraft have plug doors? Pretty sure they don't, although I've never researched it.

Can't think of any.

Quoting PGNCS (Reply 18): I am unsure about the 73NG overwing exits.

Quoting Lincoln (Reply 24): Borderline off-topic but I'm 99% sure that the over-wing exits on the 737 NG (e.g. the spring loaded "gull wing" doors) are not plug type

737-NG overwing exits ARE plug-type doors. I've just been through six weeks of gen-fam training. Trust me.
They actually open DOWNWARD, PGNCS, and they spring out and up! Interesting design. Makes closing them very tricky if you don't know what you're doing.

Quoting BAe146QT (Reply 19): I'm a little confused here. I thought that the optional airstairs on a 732 were an entirely different assembly to the door, (which as you say is of the plug type).

I think we're thinking of two different sets of stairs!
I think you're thinking of the stairs built into the aircraft for the L1 door. Yes, they're entirely separate.
I was referring to the stairs actually built into the doors on some aircraft, particularly those operated by Aloha and Alaska Airlines. These were a must have for the combi, which placed cargo forward, and passengers aft of the movable bulkhead.

Quoting AA737-823 (Reply 32): Quoting PGNCS (Reply 18): I am unsure about the 73NG overwing exits. Quoting Lincoln (Reply 24): Borderline off-topic but I'm 99% sure that the over-wing exits on the 737 NG (e.g. the spring loaded "gull wing" doors) are not plug type 737-NG overwing exits ARE plug-type doors. I've just been through six weeks of gen-fam training. Trust me. They actually open DOWNWARD, PGNCS, and they spring out and up! Interesting design. Makes closing them very tricky if you don't know what you're doing.

That's why I said I was unsure, that I had never flown the NG, that I was sure you knew more about the system than I did, and asked you to elaborate on the mechanics of the system.

Quoting Starlionblue (Reply 26): BTW I'll pretend to be the Clicker and ask you all what door on the DC-9 is not plug type.

The forward stairway door? Do I win a prize?  

Quoting AA737-823 (Reply 32): Makes closing them very tricky if you don't know what you're doing.

You can say that again. You wish you had three hands, to do close it.

Quoting PGNCS (Reply 33): Quoting Starlionblue (Reply 26): BTW I'll pretend to be the Clicker and ask you all what door on the DC-9 is not plug type. The forward stairway door? Do I win a prize?

No but I can give you a hurrah:

"HURRAH!" 

Quoting AA737-823 (Reply 16): But I'll count on you to nitpick in the future.

And we'll count on you in future to talk down to others in a condescending and patronising manner.

Quoting Jetstar (Reply 15): Looking at the picture of the CRJ in the original post, the first picture shows passengers boarding via the air stairs, that is not a plug door, its just that the structure around the door frame is very strong and the latches are designed to hold the door closed.

Does the CRJ door slide axially to provide the final locking? Assuming it does slide axially, it thus appears to be similar in design to Airbus and B777 passenger doors as well as the rear 767 cargo door. That is, all these doors hinge toward the fuselage, and then slide axially such that the door fittings slide behind the doorway fittings.

Would these be classified as plug doors? I can see how the 747 passenger door would be considered a plug door, but I'm curious as to whether the other doors would be considered as such   .

Regards, JetMech

[Edited 2008-07-04 22:06:16]

Quoting JetMech (Reply 36): Does the CRJ door slide axially to provide the final locking? Assuming it does slide axially, it thus appears to be similar in design to Airbus and B777 passenger doors as well as the rear 767 cargo door. That is, all these doors hinge toward the fuselage, and then slide axially such that the door fittings slide behind the doorway fittings.

Nope, the CRJ main pax door does not slide at all. It is not a plug door. There are a series of bolts around the door frame that rotate and lock into place when the handle is closed which hold the door in place.

NTSB report for a similar circumstance with Air Wisconsin:

http://ntsb.gov/Recs/letters/2007/A07_96.pdf

Quoting Starlionblue (Reply 35): Quoting PGNCS (Reply 33): Quoting Starlionblue (Reply 26): BTW I'll pretend to be the Clicker and ask you all what door on the DC-9 is not plug type. The forward stairway door? Do I win a prize? No but I can give you a hurrah: "HURRAH!"

Coming from you a "Hurrah!" is high praise indeed! 

39 replies and no just writing it off as Mesa being Mesa? You can tell this is in tech ops and not in civ av.

Quoting Silentbob (Reply 40): 39 replies and no just writing it off as Mesa being Mesa?

You know, that's what I thought. The FA didn't seem to be terribly professional.

Quoting PGNCS (Reply 39): Coming from you a "Hurrah!" is high praise indeed! Big grin

Heh. At least I'm almost famous somewhere. 

Quoting Flyf15 (Reply 37):

I see, thanks for the info! How many locking elements are there in total? What delta P is the door rated for?

Regards, JetMech

Quoting JetMech (Reply 43): I see, thanks for the info! How many locking elements are there in total? What delta P is the door rated for? Regards, JetMech

In these photos you can pretty clearly see the locking bolts corresponding to the door frame and door. They alternate between two types, one is a fixed bolt in the frame in which a C shaped cup on the door fits around it, then rotates 180 degrees. The other type is a bolt that slides out from the door into the door frame. If memory serves me correctly, there are 10 such devices around the door frame, 4 on each side and 2 on top. Not sure about the door itself, but the fuselage is rated to 8.7psi.


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Photo © Thierry Deutsch



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Photo © Idle Photography

I think if you open the pax door handle to the first detent (from the outside), it will open the overboard cool valve.

Quoting Ballpeeen (Reply 45): I think if you open the pax door handle to the first detent (from the outside), it will open the overboard cool valve.

It opens the flap on the door visible in this picture. This flap is plug type and therefore cannot be opened at pressure differences you would find in the air but can be opened with the pressure differences you may encounter during ground operations.


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Photo © Allen Yao

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Photo © Gerard Helmer


Original CL-600 door design.

She probably forgot to ask the Captain before closing the door...

Quoting AA737-823 (Reply 16): Okay, name for me an airliner of decent size (I work on 737s and 747s, so I typically consider anything smaller just a toy) that has MAIN CABIN (again, topic at hand...) DOORS that are not plug-type.

That, and especially the middle part, is what I typically consider as just a pretty ignorant statement!

Now (again, topic at hand...), this discussion was about the CRJ 200 door. I'm very happy for you that you're an adult and only get to work on airplanes, while some other's actually get to play with them (I have heard that the 73 and 74 is quite a nice "toy").

J.