Explosive Decompression

[News Shooter]

in the movie Airport to blame for this. It may have been in Bond as well, but I know I held this misconception for many years thanks to old George

[Redworm]

Originally Posted by Charlie Golf

Normal Max Pressure +7.8 psi (also why there's no need to freak when the wacko in 10A starts pulling on the Exit Row Door at 37,000.....)

Yeah, I've been wondering about that...so if someone opens the emergency exit door at cruising altitude the only person that's going to get hurt is the guy doing it? Would any passengers or crew standing nearby have to worry?

[Charlie Golf]

Yeah, I've been wondering about that...so if someone opens the emergency exit door at cruising altitude the only person that's going to get hurt is the guy doing it? Would any passengers or crew standing nearby have to worry?

Most doors on modern commercial jets are "plug-type" doors which must be pulled in first, then rotated to fit through the opening or they have some portion of the door that is hinged so it folds to make the door smaller than the opening.

The emergency exits on the airplane mentioned are straight plugs and about 24" wide by 48" tall, giving them an approximate surface area of 1150 sq. inches. At 7.8 pounds per square inch (PSI) that equates to roughly 9000 pounds of force that would need to be exerted on the door to get it to budge.

That door ain't goin' anywhere and the only person who may get hurt is the wacko when the rest of the passengers pummel his ass

[Redworm]

I don't understand...if emergency exit doors are so difficult to open then what use are they? Or is the difficulty only present at high altitudes?



oh wait....hah, as I was typing this reply I pictured the design in my head and understood

[silverandgold]

Another pilot here. Looks like the inquiry about decompression has been addressed.
My only problem with armed pilots is the fact that in the front of the plane are the pilots, behind them is the hijacker(s), and right behind the hijacker are 200 passengers. Personally, I think a plane full of people is a rather undesireable background to be shooting against.

[JohnKSa]

Personally, I think a plane full of people is a rather undesireable background to be shooting against.

Of course you realize that if the pilots/marshalls fail to maintain control of the aircraft, there is a very good chance that EVERYONE aboard will die. Besides the obvious threat of suicide hijackers crashing the plane, I believe that the current doctrine for dealing with hijacked aircaraft is to have the military shoot it down to prevent it's being used as a flying bomb...

Which means that even if you kill a BUNCH of the passengers but manage to regain control, you're far, FAR better off than if the hijacking is successful. Whether the hijackers crash the plane of an F16 splashes it, everyone's going to die.

[Ozzieman]

They dont carry parrachutes in comercal flights. Other than the one in the 70's the guy hijacked the 737 and had the pilots fly below 10,000 feet then opened the rear starway so he could jump out. He was never seen or heard from again.
Explosive decompression is a very dangerious condition, but the chances are slim and the one and only reasion I dont like hearing that pilots are caring guns. Taking out one of the forward windows would be enough that if it was blown out would probably take both pilots out of the aircraft, and is also why one of the pilots up front are required to have belts on at all time.
The biggest danger other than being unable to breath I think would be from flying garbage.
There are few known loss of aircraft from decompression.

[Wyo Cowboy]

OK. One more time...

Shooting a SIDE window will leave a hole the size of the bullet. No other damage. The side indows are double laminate with a additional protective inner plexiglass pane (protects against scratches, crayons, etc). The FORWARD windsheilds are multi-layered glass, vinyl and acrylic with an extreamly fine wire mesh for heating. The windshields are rated to take a 8 pound bird at speeds in excess of 345 mph (300 knots). If the outer pane is damaged there is NO restriction on pressure differentual (the difference between the pressure inside vs outside of the aircraft - normal cruse diff is 7.6 psi... 37,000 ft outside = 8200 ft inside). If the inner pane is damaged the aircraft is restricted to 5 psi differental or about 26,000 feet cruise altitude. And if BOTH are damaged, the aircraft is restricted to 2 psi diff or 15,000 feet. Also, the windshield is sloped, so any round fired in an aircraft will most likely strike the windshield at an angle. The police have found that firing a bullet at a car's windshield will have difficulty in penitrating. An airliner's windshield is considerably thicker, stronger and better enginered than any car windshield. I sincerely doubt that a pistol round would penitrate through an airliner's windshield. And, as you can see, even with damage to the entire depth of the windshiel there is very little danger.

The Federal Flight Deck Officers (armed pilots) are trained very heavily in shooting extreamly accurately in a very confined area, and are held to a very high standard of marksmanship. So, one of those pilots firing towards the windshield is highly unlikely. Besides, the terrorists would be behind them, not sitting on the instrument panel!

Pilots are required to wear their seatbelts at all times which the are at thier duty position unless the belts would restict them from preforming their duties correctly. By the way, so are flight attendants, that's why the are not moving around during takeoff/landing or near the ground. The requirement is there for turbulance. Having the aircraft run into clear air turbulance with the pilots unstraped would be dangerous as the pilots might not be able to get to the controls in case of an upset.

"Where did he get this info?"
Boeing 737-300 Aircraft Operating Manual and Federal Aviation Regulations.

[Limeyfellow]

The main problem with firing guns come not from explosive decompression anyway. It comes from hitting the electrics since they are all thrown by wire. You of course will have a similar problem if you missed with the taser and hit the instruments in the cockpit.

[Wyo Cowboy]

Currently, only the Airbus family and, I think, the Boeing 777 are "fly by wire". Also, there is quite a bit of systemand wiring redundancy that a single round would do little damage. Even with several rounds, they would have to specificly placed.

I'd heard that United Airlines experimented with the taser and stungun onboard an Airbus A320. Both on the ground and inflight. The story which I heard had maintenance check pilots flying and a third person "fired" the stungun and the taser into the instrument panel and the circuit breaker panels. No serious flight control annomilies were reported. Not a flight that I would have liked to be flying!

[Pat Rogers]

Ozzieman,
That was a Northwest 727 that was hijacked by a M/W who called himself D.B. Cooper.
He didn't bring the rag with him. He requested it on the ground and FBI complied, getting it from a local rigger.
Just FYI.

[JohnKSa]

The main problem with firing guns come not from explosive decompression anyway.

At the risk of re-re-re-repeating myself, I will point out once again that the debate about damage to the aircraft from pistol fire is MOOT.

Even if an armed pilot kills everyone aboard and crashes the plane, he has achieved a BETTER result than the hijackers intended (by not allowing them to aim it at a populated target and THEN crash) and has done no worse than the U.S. military intends to do (shoot down the hijacked jet with all aboard to prevent a 911 scenario).

THEREFORE, the main problem has nothing to do with how a pistol might damage an airliner, or how many passengers might be killed by an armed pilot. The MAIN problem, is, in fact, NOT REGAINING CONTROL OF THE AIRCRAFT--regardless of what the cost in passenger's lives may be--even if it results in the loss of the aircraft.

Failure to prevent the hijackers from gaining control will mean the certain death of all aboard--AND possibly the death of many on the ground as well.

[USP45usp]

I don't know how many "but, but, but" folks here have access to the Internet, but if you do, check out some of the designs for aircraft.

You think a "double tap" or "triple tap" is bad (when you post but you hit the submit key because you think you had trouble and then.... poof, you have two to three of the same posts), the system is a redundant system. There is more then one (up to four in some cases, depends on the aircraft) system for each that will bring the plane down safely.

If you notice, most aircraft are brought down by total engine failure, lack of power (due to engines), and things falling off (like the tail or a wing).

Then you have to check out the aircraft that were used in war. Big planes like the bombers and even the fighters. Sure, a missile (which is a high explosive) will bring them down, and in the old days, many rounds (unless a lucky hit) would bring them down. Then check out what type of rounds they were using and at what amount they were being sent at the plane.

And not all of them fell from the sky, many made it home so riddled that people wondered, how the heck did they make it home. They did so because the plane was made for it.

Air Force in case you are wondering .

Guns on planes (and if it were so bad, why do the AM's get to have guns? ) are not the problem and before 1960's (I don't know the year that they banned guns from Aircraft, commercial) they were never a problem.

From what I've seen, people of another country with box cutters, were the problem.

Wayne

[MeekAndMild]

When I was in the Air Force they used to teach explosive decompression survival techniques. This involved having the students crowd into a small altitude chamber and then the big chamber next to it was pumped up to 32000 feet pressure altitude. They opened a 12 inch valve but it still took a couple of seconds for the pressure to equalize.

The planes we flew had a ram dump valve in the cockpit so you could remove air pressure before opening the top. Even with the big valve, not 12 inches but still big, it took several seconds to bleed off pressure when you needed to.


For a bullet sized opening there would be plenty of time to stuff something in the hole, perhaps a sandwich bag with a half eaten PBJ?

[IZinterrogator]

Only one person was sucked out of this hole, a stewardess who was not buckled in.

I wouldn't worry about a bullet.

[guntotin_fool]

Mr Wyoming Cowboy.

A question for you;

I have been told that today it would be very difficult to hijack a plane knowing with what we know as you as a PIC could simply just dump cabin pressure and put every one behind you to sleep.

by the time Ahmed wakes up you could have him in flexcuffs.

would this be a viable feat?

[Charlie Golf]

I have been told that today it would be very difficult to hijack a plane knowing with what we know as you as a PIC could simply just dump cabin pressure and put every one behind you to sleep.

by the time Ahmed wakes up you could have him in flexcuffs.

would this be a viable feat?

In theory it could be done. In practical application probably not...and it would be foolish to do so IMHO.

Intentionally dumping cabin pressure places everyone on board at some risk.
And of course that places the airline, and the pilots involved as some level of liablilty risk. Kinda like when the Russians gassed all those people in the theater to put the kidnappers to sleep and ended up killing quite a few hostages in the process.

The hijackers are coming in with a plan. In the time they attempt their breach, a pilot would have to go from "What the F@#$ was that?!?!" to DON the O2 mask and dump the cabin pressure.

That could/would take some time unless the pilot is constantly in Condition Red (and then he's one of those guys no one else wants to share the flight deck with ) with one hand on his O2 and the other on the dump switch.

Furthermore, most transport category aircraft have both a automatic and a manual pressurization mode. Auto is the standard setting. In the aircraft I fly, if you dump the cabin in auto mode it actually only takes the cabin up to an altitude of 14,500' (from 8,000') and if the hijackers are in decent shape, they may slow down a little bit but they aren't gonna konk out.

In order to dump the cabin completely you'd have to go to manual and then run the outflow valves full open which adds more time to the pilots reaction -- then the cabin would climb, but it would not be instantaneously.

Now if these guys were just killing people in the back but had not attempted to breach the FD well then it could be an option in theory........but the practice has been advised against by most every airline managment as well as the Air Line Pilots Association.

Todays FD doors are bulletproof but not necessarily breachproof although they have various locking mechanisms, most of them are only going to slow a breach attempt rather than prevent it. One could only hope that the able-bodied passengers get involved while the one of the pilots initiates an Emergency Descent and the other maintains the integrity of the FD and FD door and prepares to defend it with use of deadly force.

[Wyo Cowboy]

Charlie Golf has is spot on. The crew could dump the cabin using the manual over-ride but the cabin would "climb" to meet cruise altitude at about 6,000 feet per minute. 8,000 ft cabin, 34,000 ft cruise at 6,000 fpm comes out to about 4 minutes and 21 seconds. Not real fast. Manually dropping the masks might be a thought to cause confusion to the terrorists. The O2 masks automaticly will drop when the cabin altitude passes 13,800 feet and there is no over-ride in the flight deck. So, trying to dump the cabin in order knock them out would just deploy the exact means for them to remain alert and funtional. Even dumping the cabin and decending to 13,5000 to avoid the O2 mask deploy wouldn't work. Sea level tourists go hiking in the 13,000 foot mountians around here all the time and have little problems.

All this being said, if I had terrorists killing people in the cabin and/or trying to breach the flight deck, I would use any and all dirty tricks that I can think of to confuse and confound them as we are trying to get the plane on the ground as fast as posible. One option discussed is to shut down an engine and kill the autopilots. Any trained airline pilot can easily fly the plane on one engine. Mr. Terrorist probably didn't get that far in thier "training". If the terrorists get control of the plane, it still goes down, but at least not where they had planned.

[IZinterrogator]

How do you "kill" an autopilot? Do you slit its throat and let it deflate?

[Wyo Cowboy]

Ah, come on! Didn't you see "Airplane"? Otto was self delating until Julie Haggerty blew in to his... ah... well... hump... ah, yeah. Slitting his throat would probably work.