How bomb-proof is an airliner?

My brief experience with airplane engine manufacturing suggests that, in general, airplane manufacturers are as fanatical about redundancy as the phone company is.

Suppose what-sis-futch gets his baggies of explosive on board and, rather than setting his testicles on fire, he actually got them to blow up. If Richard Reid’s shoes actually detonated rather than smoldered, what kinda force is involved?

How likely is aircraft failure? I guess I’m thinking that, unless you have a bag full of explosives in the cargo hold, it’s more likely you’d just blow a hole in the floor or the bulkhead and depressurize the plane.

We these guys a credible threat to the plane’s passengers beyond the blast damage to those immediately around them?

At the simplest level, yes. Then again if that ordinary hole in the floor or bulkhead were to sever vital components (hydraulic lines, fuel lines, electrical systems, structural systems) and/or cause the aircraft to become aerodynamically unstable, it’s all over. While there are big events that have occurred and the aircraft landed safely, it does come down to location, location, location on an aircraft and the size of the explosive event.

I’m sure the SDMB Dope flight crews will be along shortly to offer more expert information.

The goal of these “small bombers” is to make a hole in the fuselage above the center fuel tank, igniting the fuel, and causing a catastrophic explosion. Note that not all planes have center fuel tanks.

Hard to say, without knowing exactly how much he had on him. Keep in mind though that we’re not talking about plain ol’ combustible gunpowder, but high explosives. 35 grams (a little over an ounce) of high explosive, properly contained, is enough to shred a 1-foot diameter concrete column. Place an amount like that near an aircraft hull, and I think you’re fairly guaranteed to experience a hull breach. Whether it would be a catastrophic event with loss of aircraft would depend on a number of factors: size/composition of the explosive, proximity to the hull and/or particular components of the hull (e.g. ribs or skin), possible damage to critical hydraulic/electrical lines, and the question of what wind blast damage might do.

All of this has been under study for quite some time.

The recent attempt (the underwear bomber) had about 80 grams of PETN on him. This is more than enough to blow a hole in an aircraft. The shoe bomber had 50 grams on him and government tests showed that that would blow a hole in a passenger aircraft. I don’t know how they did this test though. With this recent attempt it was just wrapped in plastic which would not allow any pressure to build up nor direct the blast at all. I’d still guess it would have made a significant hole in the plane though. After that? Depends. The top of the fuselage can get blown off and the plane can still fly. If the hole destroys structural areas where the wing meets the fuselage you could have some catastrophic problems. If the blast severs fuel lines or a fuel tank you’re toast. Equally dangerous would just be starting a large chemical fire with an incendiary chemical. A fire on a plane could be a nightmare if it couldn’t be put out through normal means (i.e. phosphorous based incendiary chemicals).

As has been mentioned, it comes down to location, location, location. There have been airplanes that suffered catastrophic damage and landed safely, and airplanes brought down by teeny-weeny component failures.

Depressurizing the airplane by itself won’t bring it down, but having vital personnel sucked out of a large hole or passing out from lack of oxygen could - which is why there are very strict rules about pilots having oxygen masks on hand/wearing oxygen masks.

Explosion + fuel tank = very big explosion and probably everyone dies

Explosion + severely damaging/severing a wing or tail = probably everyone dies (although the current record for surviving an extreme fall without a parachute is held by an airline attendant who rode an airplane fragment down from tens of thousands of feet)

Explosion + severing vital control components = likely everyone dies (though at least one airline has been landed with no functioning hydraulic-powered flight controls where a significant number of people survived, though not all)

Small explosion that starts a fire, filling the fuselage with smoke, may kill all aboard even before a crash as burning airplane parts generate highly toxic gasses and lots of smoke. If the fire burns through vital controls you will probably crash. If it burns to a fuel tank the airplane will likely explode and kill everyone on board. However, not all small fires will get so out of control, there is a limited fire-fighting capacity on board, and the the fuselage can be flushed with fresh air after a fire to improve the air quality (though that doesn’t happen instantly).

It’s impractical to “bombproof” airplanes by armoring them because the weight would increase to the point that you can’t get the thing off the ground. Hence the focus on trying to keep bombs off the airplane in the first place.

Where the hypothetical bomber sits may be significant as far as results are concerned or how long you have to fight a small fire before it does something you can’t fix in flight.

Of note is that the latest attempt was during landing. This is naturally a critical time. Unlike a hull breach at altitude, the pilots might not have had time to recover control had the bomb detonated successfully.

This was the point I was attempting to make WRT to high explosives.

Ordinary combustion (deflagration) proceeds at subsonic velocities, and you will not be able to produce a destructive shockwave this way unless you contain the combustion gases and suddenly release them. This is how cheap little firecrackers work: they are flash-powder tightly wrapped in several layers of paper.

Detonation is a different beast altogether, and is the domain of high explosives. The chemical reaction proceeds through the explosive at supersonic speeds, resulting in the emanation of a destructive shockwave, even in the absence of any containment at all. For reference, a stick of dynamite contains 35 grams of nitroglycerin wrapped in paper. Here’s what one stick of dynamite can do for ya; an explosion like that within a couple feet of a thin aluminum hull would pretty much guarantee a rupture.

All this stuff about ignition of explosives, but no one ever seems to think about simple nitroglycerin that could just be thrown against a wall one time and go off, right??? What would be the power of 3 ounces of that in a glass gift bottle or something easy to throw hard? Are there other things that can go off in that fashion too?

This is why we need profiling and searches of the kind of people whose religion says they are at war with us, because that is who brings all this stuff onboard every time I can recall.

I just can’t follow why some people want everyone super searched when it is always people of this religion. I support fairness, and if/when Methodists start doing it too then yes we ought search them totally as well. Meanwhile stick to those doing it, that is fairness.

Pure nitroglycerin is far, far too unstable to transport. That was why Dynamite was invented. Nitroglycerin has been known to explode just due to rapid temperature changes. Three oz of nitroglycerin is equivalent to more than 6 sticks of dynamite, (maybe more, depending on the percent), and would easily blow a hole in an airplane.

Anyone remember the bombing of United Flight 629?

This happened in 1955, a guy wanted to kill his mum (who was on the flight) so he blew up, her, the plane, and everyone else in it

Modern explosives are awesomely powerful. At work we use shaped charges that contain around 25 grams of RDX. The leading shock wave from the explosion measures around two or three million psi, enough to instantly bore a three-foot long hole in solid rock. The primer cord we use to set it off detonates at a speed around eight kilometers per second. Astounding numbers.

My friends ask me if I ever play around with that stuff. I usually say, “Are you @$%# crazy?”

It is not necessary to bring the plane down to achieve the terrorism goal. Look what happened with an “unsuccessful” suicide bomber. If a bomb was detonated successfully, the fact that the plane landed safely would be a footnote compared to the havoc it would cause to air travel and homeland security.

“Excuse me sir, are you a Muslim?”
“No, I’m Catholic”
“OK then, come aboard”

Sounds foolproof to me.

It is this sort of childish presentation of profiling that distorts discussion around why we should implement it.
The Israelis have been remarkably successful considering that they are very desired targets.

As a frequent flyer who has to deal with the annoyance of our pitifully inadequate “look-for-weapons”-based security (and my name, unfortunately, is on the TSA no-fly list) I support profiling. Off-topic, here, though.

Though they are very directed and would mostly make a small hole in the fuselage, and likely not cause a catastrophic failure.

Profiling is fine. The idea that you are going to know who is a Muslim by looking at them is silly. Looking at terrorism in the US, a better profile is men between 18 and 50. I don’t think any 50 year-old Muslim women have hijacked a plane or blown up a building.

If I were the FBI I’d put you high up on the list. I presume you are a male between 18 and 50 who is politically inclined enough to post on message boards.

Actually, one of these devout idiots would be easy to separate out. Often by what they have on, but you could also do it much better by having passengers just step on a Koran as part of boarding ramp choice.

These nut cases have some big aversion to feet and stepping on stuff that we don’t. You wouldn’t need a real Koran either, just a square in the floor with the word Koran on it (and the arabic symbols too) and big enough one could not step around it. The line going by that would be the minimal search line thru just metal detector.

The other line open without the square would lead to the total search patdown, etc area. Regular passengers would just ignore it and walk right over the square, it would not add any time to the boarding process, but the nut cases would either go be searched totally or turn around and leave.

It is not unfair to peaceful moslems either, think about the choices, either do this and search just them totally, or search everyone totally. Either way moslems get the same treatment, see? But they benefit from it too by the shorter boarding time for all of us regular folks and the plane takes off quicker for them as well. Everyone comes out ahead, except the suicide bomber.

Who is “we”? Are Muslim Americans not part of we? Are the 15,000 Arab Americans who fought in WWII not part of “we”? If so, I don’t want to be part of “you”.

But maybe it will work. Can we put Bibles on the ground in front of abortion clinics too? Maybe we can see if people will burn their NRA membership card before we allow them in schools and Lubys’.

Folks, could you please take your policy discussion to Great Debates? This is the GQ forum, and this thread is about the mechanics of blowing up an airliner, nothing more.