CRJ Door / Pressurization Question
 

Hey guys…. So I have a question… which has somewhat been explained to me, but I’m still a little fuzzy!

I’ve been told that it’s next to impossible to open a cabin door in-flight, due to the pressure differential. Now this makes perfect sense on the over-wing exits (which are plug type); however, the MCD (and possibly the service door?) on the CRJ are not plug type – they don’t have to come back in before going out. (Or do they, and I just never noticed?)

But if they’re not plug type, and they do just open straight out… then theoretically the only thing holding them closed are the locking pins?!

So yea…. I’m probably missing something! Any of you guys that fly the CRJ want to offer an explanation?

Thanks! =)

The CRJ main cabin door is NOT a plug type door. It does NOT have to open inward first.

The only thing holding it in place is the pins and cams.

I am not aware of any pressure-based safety interlocks, so I would assume that if you pulled the handle open, the cabin door would open, and probably depart the airplane, possibly entering (and destroying) the left engine.

You would follow the cabin door into the engine in about 25 milliseconds.

Look at the slots on the door that engage the posts. If I remember correctly, the door actually has to move inward a few inches before moving upwards to clear the posts.

I think the term I saw was semi-plug type door. Either way it's red on the EICAS vs yellow like every other door/hatch.

I've wondered this myself.

Wouldn't the airflow about the fuselage "hold" the door closed? I've had a Seminole door open in flight and it is impossible to close in the air due to it not being a completely airtight vessel. So, since the CRJ is pressurized there would be nothing pushing the door open aside from the person opening the door. And I doubt that person is strong enough to overcome the outside pressure holding the door closed.

Maybe?

Maybe if the cabin was depressurized first. If the cabin is pressurized...

Lets say 8 psi...

The door is about 3ft x 6 ft (approx)...

3 x 6= 18 Square feet

Convert to inches: 18 x 144 = 2592 square inches

8 x 2592 = 20,736 pounds (over ten TONS)!

My bet is the door would pop right open...

That is the same amount of pressure on the pins, I'm going to say it would be near impossible to rotate the cams with that much pressure on it...the handle would snap first.

Good math... I don't remember that in ground. You could be making that all up and I would still beleive you.

Isn't there a story floating around of a Comair FA who accidentally tried to open the door in flight? Something about the outer handle popped out in cruise and the crew asked her to pull it back in, instead she actuated door lever thingy (technical term).

Don't forget the MCD and the emerg. exits on the CRJ have pressure panels that open when you pull the handle. The MCD handle has two positions when you pull up. The first opens the panel and releases the pressure. The second click actually releases the door.

Haven't heard that one.

I have gotten the PAX DR OUTR HANDLE caution before (not sure if that is the proper wording)...we didn't ask the FA to touch it in fear of that very confusion. We were in the terminal area anyway.

I worked at Comair for 8 plus years and never heard about a story like that. However a Comair flight attendant had a finger severed as she tried to close the door from the outside. It was a windy day and the door slammed shut with her hand clutching the inside of the door. I never met her but she would come into ground school and talk about the incident.

Holy Crap. Why would you grab the inside/side of the door? I'm not tall enough, so that isn't evne an option for me...I just shove and walk it up with my hands.

Wrong! The static coeffecient of friction for steel-on-steel (coated in grease) is amazingly low. Those pins would slide right out.

The PSEU sensor for the cabin door cannot be MEL'ed (I tried last week). It's a red message.

CHQ had an incident in IAH where a FA was injured by opening the main cabin door while the A/C had a small amount of pressurization remaining. The door came open so fast and with so much force, she was thrown onto the ramp. She was badly injured.

As a -200 PIC for a while, that was my 2nd least favorite thing about the A/C. (inability to disconnect the engine driven HYD pump was #1 - it forced an in-flight shutdown and RTB once).

The coeffeicent of friction doesn't have to be very high when your talking about 20,000 pounds.

Looking at a couple of websites, the Co-efficient of friction for steel on steel lubricated is around .15 (http://www.carbidedepot.com/formulas...icient.htm)for about 20k pounds that would take about 3000pounds of force to break it free. given about a 3 foot door handle (a lever) it would take possible 1000 pounds exerted by the FA to pull the handle.

I'm sure as hell not going to go and try it, but I still think it isn't very easily done.

Except that incident involved the galley door.

Hard steel is less than .10, maybe half that. I don't know, but I'm assuming that those pins are not mild steel or iron.

The linear calculation applies to two flat surfaces with all force applied perpendicular. Since the pins and their holes are cyclindical, the math would be different (I'm not doing calculus on saturday :rolleyes: ). But I wouldn't want to try it either.

Sounds like a new episode for Mythbusters...

Why not, there are enough Rj's in the desert to try it out on.

i don't know about popping open in flight, but the door can obviously fall off.

Jet's Door Falls Off During Takeoff - Denver News Story - KMGH Denver

i do think though that it would be impossible to open the door inflight. the door has a plug type pressure valve built into it that swings inward. remember when you lift that handle that pressure release valve opens at the same time. i would imagine that while in flight there is enough pressure on it to keep it from opening, and inturn jamming the lever in the down position.

The negative pressure relief valves prevent the door from opening in flight.

ok so i dug out the ole systems manual. the "door vent flap" opens and closes when the exterior or interior handle is closed or opened. this flap opens inward and acts as a pressurized plug when the aircraft is pressurized.


so i am going to go with the door would be nearly impossible to open inflight because of all the pressure that is being exerted on the door vent flap.

Wow.... I never imagined this would prompt such a wide response! Thanks guys, it's been really informative! So... from what I've gathered, it would be hard because the door vent flap has to open inward. Does this apply equally to the service door?

Also, ignoring the fact that you couldn't manipulate the handle, it would be more than possible for the door to come open if the pins (for whatever reason, either defective or not closed properly) were not properly installed?

Gives me something to think about while I sit jammed between the two doors... =)

The service door is a plug door, it opens in-then-out. The MCD has negative pressure relief valves which prevent the handle from being moved up with the A/C pressurised.

That's good to know.

Ok I normally don't buy into the "this is a security issue" bs especially on forums but I think in this case it doesn't serve our collective good to theorize that cabin doors could be opened in flight. That's probably me being paranoid but just doesn't seem like a good idea. An in depth discussion of aircraft systems is better suited for pilots lounges if you really get that bored.... Lets just stick with "you can't open it and why would you want to try"

Don't agree

Point taken... the thought didn't even cross my mind. Sorry!

If someone tries to open the door they won't get too far... In an RJ what would a passenger be doing up in the front anyways?

Well at least on the CRJ900 the passenger could be up waiting to drop a deuce. Or bailing out from the person in front of them doing so.

Yeah, that is correct. There's a reason that the handle is connected to the cams and pins with a cable. That cable is meant to break (I've seen it happen, doesn't take much to break it) before the door is opened.

On a side note for the CRJ drivers, here's a quick fix that a lot of guys don't know. I don't know if it does it on the 70s and 90s, but the 50s this was a common problem at some gates (depends on the orientation of the gate). If you ever pull into a gate and cannot open the pax door, do not panic, do not call maintenance. Have the ramp crew push you back 25 feet and pull you back in. The airframe is torqued and the door gets stuck in its opening. By towing you back and forth, it usually untwists the airframe and all should be good. There are 4-6 gates (I don't remember which ones) at CVG concourse C that will do this.




Are we forgetting the 700?

MesaFA - Why do you want to know that? Is your name Ahmed by any chance? ;)

The latest interesting door story I read was in the June issue of Professional Pilot.

Apparently a mechanic had just replaced the VSI in a King Air and had the pilot take it up on a test flight. After the plane taxied in from the test flight, the mechanic attempted to board the plane with the engines still running (which is very doable in a King Air.) When he opened the door from the outside, the plane was still pressurized enough to force the door outward fast enough to hit the mechanic in the head and kill him.

I like this one better. ;)

Also in a King Air, a Co-pilot was removed from the aircraft inadvertently after getting up to investigate a "Cabin Door" light. Upon grabbing the door handle the door popped open and he was pulled out of the aircraft. His arm caught in the door cable (luckily) and he hung out there with the door until the aircraft was landed. Memory items for door light in the King Air are for all occupants to stay seated and seat belt fastened. Seems to me that it wouldn't be too hard...I'm sure a negative pressure valve could fail...its normally just a diaghram, and it likely wouldn't be a known failure until it was tried.

I recall, from my Comair days, that prior to opening the main cabin door pilots were suppose to check that cabin differential was less than .1 psid. I do recall now an FA telling me that the door jerked right out of her hand as she was opening. I guess I forgot to check the psid that time.

Some may recall an American Airlines Airbus accident a couple of years ago. A FA was sucked out when, he or she, opened a door on the ramp and the aircraft hadn't depressurized properly. The FA was killed on contact with the tarmac.