No handgun round will cause a decompression failure, and certainly will not cause a massive failure of the airplane's outer shell.  At ANY altitude the pressure inside an airplane is only 1atm, and a small hole would quickly get plugged up as escaping air swept up loose material.

Sorry, just an engineering student venting.

radioman

I'm not an engineer (or even a student for that matter), but what about a bullet hitting one of the many windows?

I'm all for armed Air Marshals, don't get me wrong.

As a practicing engineer, I suggest you try an experiment.  Take a can of Coke or other soda adn shake it up throoughly.  Leave it in the sun for a while.  Then shoot it with a .22.  The resultant explosion of the can should be spectacular.

You need to account for the mass transfer involved.  The pressure differential may seem small, but the mass fo air available to flow out the small hole is large and will force the hole to become larger.  The deHavilland Comet had a problem with catastrophic stress cracks propagating along window frames due to that very small pressure differential..

Agreed!

The DeHavilland Comet is a perfect example.

That which is trying to escape will create for itself a suitable exit.

[size=1]( I found a very interesting page regarding the Comet: [url]http://www.geocities.com/CapeCanaveral/Lab/8803/comet.htm[/url])[/size=1]

As a practicing engineering [i][b]technician[/i][/b], whose day to day job it is to bring down the cold, hard, black heal of reality across the throat of every design engineer's wispy genius:

Radioman's initial statement rings true.  However, while a single handgun round wouldn't cause massive hull failure due to rapid decompression (the hull failures of the Comet were attributed to metal fatigue - and this was back in the fifties to boot), if that stray handgun round were to hit something more critical to passenger survival (like the landing gear, or maybe [size=4]THE PILOT[/size=4]), then you've got something to worry  about.

The soda can model would probably work if you shot out of an airplane's body with a handgun bullet in a caliber, of oh say, 3 feet.

Get your flame suit on, it's gunna get hot.

Take it from an aircraft mechanic of 25 years,  ANY bullet hole in the skin of an aircraft will cause a rapid decompression of the pressure vessel.  

The shin on commerical aircraft is approx. .060" thick.  A .22 size hole in a pressurized cabin will crack and tear (along the ragged edge) to sizes to pull out whole sets of seats out.  

The pressure inside the cabin at cruse altitude is somewhere around 6-9 psi which is enough to make it impossable to even open the e-exit or any cabin door.

Look at the deHavilland Comet disaster or the 737 (?) in Hawaii 15 years ago.  They crashed because of a crack in the cabin skin that caused the aircraft to come apart in flight.

They made glaser rounds to lower the chances of decompression on airplanes.

Radioman and Paul have the only correct answers in this thread.  As a mechanical engineer and ex B-52 pilot, believe me, these cabins already leak like sieves.  

No, the skin won't tear open from a gunshot.  No, you don't need to account for "mass transfer".  It's still air pressure through a small hole.  
No, a pumped up coke can has no relation to an airplane cabin.  The first napkin will stop up any gunshot hole.  
Hit the pilot?  There are two.  Hit landing gear?  Strongest parts on any airplane.  Tires, there's many.  
Hit hydraulic or electric lines?  Critical ones are redundant, up to four parallel on critical systems.  
Hit a window?  They're multi layer & plastic lined.  
Hit the WTC because nobody fought back with any weapon?  You're screwed.

One detail, the cabin is only pressurized to 3/4 atmosphere at the worst case.  Typical cabin altitude is 4,000 feet.  Typical cruise altitude is in the high 30's.  Differential is typically 1/2 atmosphere.  For a real high flyer that breaks 50,000 feet  the differential approaches 3/4 atmosphere.

Norm

I think that flight atendants should be armed with Tazers, and the cockpit crew should ALL have firearms...

Unfortunately, in the instances we've discovered this week ([i]and 2 years ago w/ the Egyptian pilots[/i]), the terrorists may very well be in the left seat to begin with.  Look how many more have been arrested and found with pilots credentials this week alone!

I propose that during a hi-jacking the planes be equipped with a button that automatically but at a controlled rate cause internal and external pressures to equalize also causing the air masks to drop. To not pass out on the flight they would have to put them on in which a gas to put everyone to sleep would emit. This would assume that the cabin is secure and seperated from the terroists. Any air marshel could then don a small portable air breather to manuver. If shots were fired there would be less risk because there would not be histerical passengers and I THINK a round that missed would not cause a catastrophic failure in the planes skin.

Ok, now how practical is this? Someone must know.
BrenLover

All these references to the Dehaviland Comet miss the point completely.

The Comet demonstrated the problem of metal fatigue caused by repeated pressurization-depressurization cycles.

Better alloys with needle-like inclusions that serve as rip-stoppers (and rounded window corners) solved that problem.

If you really believe that a small hole in the aircraft skin can bring down a plane, then I guess we'd better be worried about someone shoving a sharpened umbrella through the side of the plane!

I know, let's stip all passengers naked, sedate them, and THEN take them aboard the flight on gurneys.

Would that make you'all feel safe enough?

All the talk of depressurizing the aircraft and putting people to sleep raises a concern for me if firearms are present in the passenger compartment. If oxygen or other flammable gases are present and a round fired off, I would think you'd have the equivalent of a flying bomb. Whether it's AirMarshals or the flight crew, I don't have a problem with firearms as long as all the factors concerning safety are addressed.

That is not a bad idea.  Check in, get put to sleep.  You could configure all planes like cargo carries and have people stacked like cord wood in palletized containers.  Just load'em in the side cargo door and off we go.  When you land reverse the process.

Heck, even pepper spray would have worked.

Exactly

Didnt a 747 back in the eighties have a bomb go off in its cargo hold, and it still made a safe landing in Athens?  

On the otherhand didnt a 747 crash in Japan in the eighties because its rear passenger came off in flight?

What is up with this?

My concern isnt about air marshals, they can be given special ammo. My concern is letting passengers carry guns, with the resulting risk that they might have the wrong ammo.

Are you sugesting using an unmeasuredd anesthetic? I have to believe there are very good mecical reasons for not doing that! Shooting the lowlife cockaroach is the answer.


edited to add:
This is a perfect aplication for gun controle. You need to hit what your aiming at!

How does this have anything to do with an aircraft?

In your scenario, you are transferring energy (from the bullet) into a non-compressible medium (the soda).  Of course it blows up. But we are not talking about a Aircraft full of water being hit by a high-speed Volkswagen.

[rolleyes]

If we "harden" the cockpit door they will resort to killing passengers to force the pilot to comply or use explosives

If we arm the staff of a plane they will just place more terrorists on board and know who to kill

If we use Air Marshals they will find out who is he is ahead of time

The only viable solution is allowing carry by passengers onboard. There is no "counter" to that threat.

carry on board no way! 20 pissed of passenger's shooting at someone on board will be a disaster.
this would never happen.

i have one interesting point to add.
In the boeing plant one of the tests that they preform before allowing a passenger plane to be delivered is a pressurized cabin test, basically they seal everything up, with a thin plastic sheet around the plane and "pump" the plane to a given pressure. It is considered BAD to have leaks.
i don't know the real answer yet but whatever the result putting anything through the airplane while in flight will be bad, cabin decompression at the least.
I am shure they have done some sort of testing on a projectile exting the skin of an aircraft, info is on the web somewhere.

So if your on a plane that gets hijacked, and someone shoots a hole in a window... plug the hole with the hijacker.

A disaster like a plane crashing into a building?

Ask a real commercial pilot about the "dangers" of bullet holes.

Hey now, I said I didn't know how practical it was. I'm not a doctor/engineer, and I dont even play one on TV.

Your ultimate deterant will be what it takes to ultimately get on the airplane. How many Izzy Airlines highjackings have you heard of that originated in Isreal? Their security is outrageuous compaired to ours. That is your first and best line of defense. Second string is the armed crew/guards.

BrenLover

The pilots already have that option -- they can just dial down the pressure inside the cabin so that people have a mild case of hypoxia.

They even use it as "crowd control" on rowdy New Year's flights.

As one of the lucky ones allowed to fly out of Canada on Thursday, our Stews gave us all free drinks, probably so any potential terrorists would pass out.

of course, they'll keep coming.  and we keep sending back home in body bags.  point: it doesn't matter what we do.  they'll keep coming.  only one solution:  passengers resist like hell.   maybe, maybe, the terrorists will decide that plane hijacking is no longer a viable option because they can't use the plane in the intended manner.

Funny, this same topic has come up this week on a couple of other web sites.

From [u]The Proficient Pilot II[/u], by Barry Schiff (courtesy of a post by [b]AntiTyrant[/b] on a FreeRepublic thread ( [url]http://www.FreeRepublic.com/forum/a3b9ed38a7e70.htm[/url] ) started by [b]earplug[/b]):

[b]Pressurization[/b]

There probably are more absurd misconceptions about aircraft pressurization than about any other aircraft system.

Consider, for example, the popular belief that a bullet shot through a pressurized fuselage will cause explosive decompression and loss of aircraft control. This is, after all, what happened to Pussy Galore and James Bond in Goldfinger when a stray bullet went through the cabin wall of their Lockheed Jetstar. Not only did they experience explosive decompression, but the aircraft went into a spin, forcing Pussy and James to parachute to safety. Totally ridiculous, but it made for good drama.

And how about the myth perpetuated by the motion picture Airport '77? After the Boeing 747 came to rest at the bottom of the Caribbean, the intrepid captain (Jack Lemmon) allayed his passengers' fear of drowning by proclaiming authoritatively, "Don't worry, folks; this airplane is pressurized!" Apparently pacified, the naive passengers headed for the piano bar to sip martinis until rescued.

Someone should have nominated this movie for the "Best Comedy of the Year" award.
...
Pressurizing an aircraft cabin (the pressure vessel) is similar to pumping air into a tire that has a controllable leak. In the case of piston-powered aircraft, pressurizing air is provided by the engine turbochargers. The "leak" consists of one or more outflow valves at the rear of the cabin. These valves allow air to escape continuously. This prevents excessive pressure from causing structural damage and provides an exit for venting stale air overboard. Pressurization is maintained by pumping in as much air as is allowed to escape.

Many believe that cabin pressure is determined by varying the amount of air pumped into the aircraft. Not so. The flow of incoming air is approximately constant. Cabin pressure is determined by the outflow valves, which modulate automatically to vary the amount of air flowing overboard and maintain the selected degree of pressurization.

In effect, the cabin always has at least one open "hole." The addition of a bullet hole, therefore, would have no effect on cabin pressure. The outflow valve(s) would compensate by closing slightly and automatically to maintain a constant flow of air through the cabin. Larger holes in the structure, however, may result in depressurization.

In the case of jetliners, the ouflow valves are so large that the loss of an entire cabin window may not affect cabin pressure significantly. (It would not be pleasant, however, to be seated next to such a window.)

[i]Barry Schiff, with 20,000 hours in more than 225 types of aircraft, has achieved worldwide recognition for his aviation accomplishments. A verteran captain with Trans World Airlines, currently flying the Lockheed 1011, he is a contributing editor of AOPA Pilot and an award-winning author of eight books and more than 500 articles. — 1987[/i]

IF THERE ARE ANY CIVILIAN PILOTS OF AIRLINERS OR EVEN A MECHANIC FLOATING IN HERE. EMAIL ME, I HAVE QUESTION, THAT I WOULD LIKE TO ASK, CONCERNING THE LAYOUT OF AIRCRAFTS.

THANKS.

I’d think a bullet hole in a fuel line would be a big problem, even if it was a small hole.

I continue to maintain that the cockpit crew should be armed and told “This is your plane, don’t give it up.”  Despite their pressed uniforms and friendly greetings, airline pilots tend to be pretty tough customers.

Right now we seem to be disarming everyone on the plane except the terrorists!!

I am astonished at the number of people in this thread alone that profess to support the Right to Keep and Bear Arms, except on an airplane!!

Exactly!

They seem to be unable to make that last logical step and accept the fact that disarming victims is ALWAYS bad!

This is a terrible choice to make but it would be better to shoot/kill the terrorist, taking you changes that the plane holds together.  IF the place disintegrates and everyone on board is killed its still better that what happened in NYC and Virginia.

I agree with armed pilots and air marshals but no CC for passengers.  What would prevent the terrorist from put several people on the flight with valid or forged cc permits?  

Good point.

Have they needed to do this yet? The problem with arming only the crew and air marshalls is that you've narrowed down the field for the terrorists. They'll be able to tell who [b]isn't[/b] an air marshall - the John Candy-sized guy, the mother with 3 kids, the guy pounding back the drinks - and these guys didn't last as long as they have without being able to spot a cop in a crowd. The terrorists on the 4 doomed flights apparently separated the passengers into groups, so the odds of a marshall overcoming the terrorist guarding his group then overcoming the others who've been warned are pretty slim. The only way I can see that will help eliminate skyjackings is for the terrorists to know that a good percentage of people on board are, or might be, carrying firearms. Letting only the air marshalls and crew carry is no more of a good idea than only letting cops carry. Besides, how do we decide which flights get air marshalls? Do you have any idea how many we'd need in order to put 2 or 3 on EVERY flight?

Arm the officers and put up a strong door, problem solved.
Give the flight attendants stun guns (although I have seen some that were totally irrational at times). A weapon invokes a hightened sense of responsability to most. It most definately has with me.

Current security is sufficiant (if implemented correctly, no women playing with their 6 inch long fingernails at the security check) and there is no need to kill the airlines with the rediculous new measures that have been implemented.

I can see no purpose or rationale to the new measures. No outside checked baggage? No parking near the airport? No passenger drop offs? Can someone explain to me what good these will do or how they would have prevented what happened? I mean they may prevent bombs from exploding in the parking lot but save no more people than if Walmart had the same policy.

Is anyone listening to Norm-G or Skibane? These guys have it right. The aircraft isn't going to suck everything off the carpet because of a few bullet holes. Damn that Goldfinger movie! [;)]

Sure, there's chance of hitting another passenger,someone of the flight crew or part of the system but my guess is that if you're packing, you'll at least know how to shoot the weapon and that chance is remote.

If I have a flight of 100 passengers and twenty may be CC, I'm going to think twice before I try to hijack this aircraft.

NH2112


You haven't answered my question.  What would keep several terrorists from establishing residency in the US and obtaining CC permits? Lets assume that 5 terrorists board an aircraft legally armed and 5 regular joes board carrying.  Further lets assume the pilots and an air marshal are also on the flight,  We now have 13 armed people on the flight.  It don't see many positive outcomes from a gun fight between 13 people in such a confined space.

When the terrorist attempt to take over the plane how will you identify all the bad guys.  Are you going to shoot everyone with a gun?  What if an Arab American also tries to stop the highjacking?  Are you going to shoot him.  What if he thinks you are one of the terrorists and attempts to shoot you.  Who should the air marshal or pilots try to shoot?  

What if only half the terrorist begin the highjacking while the other half wait in the rear of the aircraft to identify and shoot anyone attempting to stop them?


If I was on a flight that was highjacked I would kill to have a handgun but it won't happen.  The best bet is to prevent everyone from bring any weapons on the plane.

The difference between those two incidents lies in what components of the aircraft were damaged.

An explosion could occur in the cargo that may do significant damage to the aircraft, even causing decompression, yet not damage any critical control functions. Similar cases would be the Aloha Airlines 737 that lost a large section of the top of it's fuselage due to metal fatigue or the United Airlines 747 that had a good chunk of the side of it's fuselage torn away in flight because of a cargo door that was improperly closed and secured. In both of these cases rapid depressurization obviously occured and some unfortunate folks near the areas of damage were indeed expelled from the aircraft to their untimely deaths, but the airframes and control systems remained intact and both aircraft remained able to be controllably flown and landed.

The crash of the Japanese Airlines 747 was the result of rapid decompression that did damage critical control systems. The pressure dome at the rear of the fuselage had been improperly repaired, a faulty riveting job if I recall correctly, and it failed under pressure at altitude, causing a catastrophic decompression that damaged the systems that control both the elevators and rudder. The aircraft was essentially rendered unsteerable and went into a sort of lazy turn. I believe it circled for approximately 45 minutes before slamming into the side of Mt Fuji and killing all 500 or so people on board.

[size=2]... Yeah what [b]Norm_G[/b] said, he know what he is talking bout here. He's right on the money.[/size=2]

Actually, that would be an interesting way to ID Moslems (or Quakers, Fundamentalist Baptists, etc.) Since they don't drink grape or grain based alcohol.

Just a strange idea...

Tom
[beer]

Nothing would, other than immigration laws, or doing away with CC.




I don't see many positive outcomes from letting the terrorists fly the plane into a building because nobody was armed to stop them, or because they spotted the air marshalls before they even got on board the flight and killed them first upon beginning the hijacking.

I highly doubt that if your 13 people armed people were on board, EVERY one of them would be in a position to open fire. After all, the pilots had BETTER stay up front and fly the damn plane, not set the autopilot and come out the cabin door into an ambush.

It might just be how I'm reading your post, but you seem to think that if there were 5 armed bad guys and 8 armed good guys on board the plane, the good guys' guns would be out and blasting at everything that moves as soon as the bad guys made their intentions clear - that the scene on the plane will look like something from one of the recent shoot-em-up action movies. I may be giving people a little too much credit, but I think that they'll wait for the "best" time to take action before taking action. After all, they want to survive the hijacking, and will therefore take care in what they do.




I'd say that you take out anyone walking around and threatening or harming pasengers, announcing he has a bomb, or trying to force the cockpit door. Nothing's 100% accurate, but I think my above criteria have 99.9% of the possibilities covered.



Everyone with a gun who's menacing the passengers or crew, yes. If I see a guy 5 rows ahead of me put a bullet into the head of a guy with a knife to a stewardesses' throat, then no, I'm not going to shoot him.



A lot of "what ifs" here. The fact is, a slim chance of survival because you're able to fight is better than NO chance of survival because you're completely disarmed. What happened on board the 4th plane to be hijacked was preferable to it crashing into its intended target, but if some of the passengers had been armed and had taken the hijackers out sooner, that plane just might have landed safely with several very dead hijackers on board.

This link might help with the discussion.
[url]http://communities.prodigy.net/sportsrec/fam-lawman/gz-aircrew.html[/url]

Gunslinger. Thanks for the interesting link. It was a good read.

On the subject of five terrorists boarding a plane I'll have to add that the flaw of this scenario is we are assuming that the terrorist's already know how many people may be armed on board the aircraft before they board.

I would think in reality, the terrorist wouldn't know if one person or 30 people were armed. Even if each passenger was required to check his or her weapon with the flight officer before boarding. It would make it tough to plan on how many of your fellow terrorist you need to take along for the one way trip.

Omar! Go back to the van and get us four more men, it looks like we're outnumbered [;)]

Personally, I'd rather see the flight crew armed but then that takes the guess work out of who is who for the terrorist group.

[i]What would prevent the terrorist from put several people on the flight with valid or forged cc permits?[/i]

In the absence of a really good background screening process, nothing would keep them off the flight. However, you'd also have maybe 7 or 8 armed non-terrorists also the flight — none of which would be apparent to the terrorists. Makes things a WHOLE  lot  more complicated for the bad guys...

That's why the fictional movie Die Hard was so entertaining. Despite all the planning of the bad guys, one guy with a gun screwed up the whole works.

Sure, it's just a movie but there's a small parallel we can learn from.

I would rather have a small, however remote fighting chance, then ride the plane down to my death.

Then again, wouldn't the same process of elimination help the air marshalls spot the terrorists?