MD-90 From United States, joined Jan 2000, 7041 posts, RR: 14 Posted (3 months 1 week 1 day 10 hours ago) and read 1941 times:
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:
T prop From United States, joined Apr 2001, 804 posts, RR: 1 Reply 1, posted (3 months 1 week 1 day 9 hours ago) and read 1924 times:
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.
MD-90 From United States, joined Jan 2000, 7041 posts, RR: 14 Reply 2, posted (3 months 1 week 1 day 9 hours ago) and read 1916 times:
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?
WILCO737 From Germany, joined Jun 2004, 4024 posts, RR: 67 Reply 3, posted (3 months 1 week 1 day 9 hours ago) and read 1918 times:
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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)
If it ain't Boeing (or McDonnell Douglas), I am not going.
AA737-823 From United States, joined Mar 2000, 3401 posts, RR: 5 Reply 4, posted (3 months 1 week 1 day 4 hours ago) and read 1885 times:
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.
For unto us a Child is born- unto us a Son is given!
KingAir200 From United States, joined May 2006, 725 posts, RR: 0 Reply 6, posted (3 months 1 week 23 hours ago) and read 1824 times:
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]
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EMBQA From United States, joined Oct 2003, 7314 posts, RR: 11 Reply 7, posted (3 months 1 week 23 hours ago) and read 1808 times:
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
"It's not the size of the dog in the fight, but the size of the fight in the dog"
KBFIspotter From United States, joined May 2005, 710 posts, RR: 1 Reply 8, posted (3 months 1 week 23 hours ago) and read 1803 times:
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.
A10WARTHOG From United States, joined Jul 2004, 181 posts, RR: 0 Reply 9, posted (3 months 1 week 22 hours ago) and read 1803 times:
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.
EMBQA From United States, joined Oct 2003, 7314 posts, RR: 11 Reply 10, posted (3 months 1 week 22 hours ago) and read 1788 times:
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]
"It's not the size of the dog in the fight, but the size of the fight in the dog"
A10WARTHOG From United States, joined Jul 2004, 181 posts, RR: 0 Reply 11, posted (3 months 1 week 22 hours ago) and read 1779 times:
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
PGNCS From United States, joined Apr 2007, 821 posts, RR: 1 Reply 13, posted (3 months 1 week 14 hours ago) and read 1686 times:
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.
Jetstar From United States, joined May 2003, 909 posts, RR: 1 Reply 15, posted (3 months 1 week 13 hours ago) and read 1674 times:
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.
AA737-823 From United States, joined Mar 2000, 3401 posts, RR: 5 Reply 16, posted (3 months 1 week 6 hours ago) and read 1628 times:
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.
For unto us a Child is born- unto us a Son is given!
Jetstar From United States, joined May 2003, 909 posts, RR: 1 Reply 17, posted (3 months 1 week 2 hours ago) and read 1615 times:
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.
PGNCS From United States, joined Apr 2007, 821 posts, RR: 1 Reply 18, posted (3 months 1 week 1 hour ago) and read 1601 times:
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.
Type A classification may be derated to Type 1 due to interior configuration.
Electrically operated doors that move upward and outward when operated (Normal).
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