Gadgetopia

I'll have to catch this one. My favorite so far has been their repeated attempts to determine whether a frozen chicken, when used as a projectile, carries more penetrating force than a thawed chicken. They finally pulled it off a couple of weeks ago, and found that frozen chickens make better bullets.

No. They found out that the energy trasfer time from a frozen or thawed chicken is the same. i.e. there is no difference in that speed.

The explosive decompression experiment is not complete. When the situation occurs in a jet flying at approximately 500 to 600mph, there is also a tremendous suction that occurs as the air moves along the fuselage. This will likely contribute to sucking out suff and people.

I have opened the window on a Piper Cheroke (single engine) flying at 2000- 3000 feet and the suction is strong enough to empty a bottle with the opening located in the openend window (20 sq in).

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 from Justin

A shaped charge is an explosive that is shaped so that its explosvie force is directed in a specific direction. A Bazooka's charge from World War II (and most anti-tank weapons) uses a shaped charge so that the force is directed into the armor of the tank instead of going in all directions.

You don't need to take into account the movement of the airplane because the air pressure at 30,000 feet is only 4psi. Even if there was a Bernoulli effect that made the outside pressure seem like a perfect vacuum (going from "inside air pressure"->0 instead of "inside air pressure"->4), it would have made little difference in the explosion because it is only a fraction of the total psi difference.

Besides, the effect is not an important factor in real life. If SL in his Piper really saw an effect from Bernoulli effect from the open window, he would have passed out because the air in his aircraft would have been sucked out. Instead, I am quite sure the air pressure in his aircraft was very close to the air pressure outside it.

Many pressurized aircraft have been shot up (for example, B-29's over Japan and Korea, and B-52's over Vietnam) and have made it home. Sometimes the people inside don't even know it happened until after they landed.

I am a flight attendant and have alot of knowledge with aircraft decompressions. It is true that you would get different results if you had 500mph wind going over the fuselage. MANY people in the past sadly proved this when a flight attendant was sucked out of a 737 over the pacific and 9 passengers in their seats were sucked out also over the pacific on a different airline. Some of these people went into the engine. I am not sure if I would say this is a MYTHBUSTED.

There was a demonstration of decompression in a Convair airliner in the 1960's. It was filled with water to simulate compressed air. A few Convairs had had their roof blow off during flight. Those planes, of course, crashed. After a lot of tests, the roof blew off. The diagnosis was metal fatigue in the skin of the airplane. I forget what precautions have been mandated since then. I suspect that the shaped charge was the 'last straw' , especially since it was the fourth rapid decompression of the cabin of a retired 737.

i was in an explisive decompression and yes the ai rushing past the hole is strong enough to tear a piece of the fuselage off and that is what happened- there was a bomb on board and it went off and the hole wasnt that big but then the air rushed into the cabin and tore a 10 foot section and sucked 2 passengers out

I completly agree with steve. If you have a 500 mph rushing past the plane it would change the results darasticly. The pressure of layer of wind rushing by the plane/hole would be less than that of the air pressure of an object sitting still, there for the pressure and according to Bernoulli the rate of decompression would decrese.

sry (typo) there for the pressure would be less and according to bernoulli the rate of decompression would increse.

If you have a 500 mph rushing past the plane it would change the results [drastically].

I mentioned this in the original post, but everyone seems to have missed it. I said:

[...] they didn’t address one thing: the drop in air pressure caused by the velocity of the air outside the plane. You see, the entire concept of flight is based on the fact that air pressure goes down as the speed of the air goes up.

So when a hole gets blown in the side of the plane, even after all the air rushes out and the pressue of the plane is equal to the ambient air pressure at that altitude, you now have 600 m.p.h. air rushing past the hole, which would have a much lower air pressure than the stationary air inside the plane. Does this make sense to anyone else?

I've been thinking about this question for some time and still can't male up my mind.

There seem to be real stories about holes in planes that give conflicting evidence: some say people have been sucked through holes; some say it is harldy noticable.

I wonder whether military aircraft have a different set up - they may have less pressure inside than commercial aircraft. They don't have to be as comfortable as commercial aircraft and they must be prepared get bullet holes from time to time.

In response to John's point about the 737 that lost alot of it's upper fuselage over the Pacific, that was cause by micro fractures in the skin of the airplane. Which allowed it to open up with a zipper effect. It was NOT a result of a small hole. You also have to take into account True Airspeed and Indicated Airspeed. By this I mean that when your higher up in the air, there is less air. So you can move faster with less drag. An airliner moving at 500 knots is actually true airspeed. The indicated airspeed will vary but will be around 300 knots maybe less, depending on altitude. Indicated airspeed is the measure of actual air moving over the airframe. Speed over the hole, imho, will have a negligible effect in and of itself. Think of the space shuttle, it is in orbit flying at Mach 25, but has zero indicated airspeed.

People, we are talking about a BULLET hole, not something from an explosion. The person up there reference a hole from an explosive that "wasnt that big ", but I'll bet it was much, much larger, surface area wise, than a bullet hole. We are talking a hole with an area smaller than 1/2 square inch..

there are already holes in every airliner in the sky. They aren't "air-tight". I guarantee there are tons of leaks in every door. Airliners are designed to still provide decent cabin pressure with SEVERAL windows missing.

Pressurization works kinda like this on a modern airliner (until they start using the bleedless technology enmasse)... Air is compressed in the compressor stages (front end) of the engines as we all know.. A portion of that now high pressure air (the rest goes into the combustion chamber, gets mixed with burning fuel, heats up, expands, drives the turbine section of the engine, spits out the nozzle, providing thrust, etc.) is "bled" thru valves and tubes (this is called "bleed air") called "bleeds" into the cabin (thru heaters/air conditioning packs). you can use it for many purposes, pressurization, starting engines, etc. Any excess pressure from the cabin is let out thru an "outflow valve" in the back of the cabin. A big adjustable hole. The outflow valve operates automatically. As the engine RPM changes, altitude changes, holes get punched in the skin of the cabin, windows get blown out, etc. Only when you are not getting as much bleed air as is being blown out will you get decompression.

Think of it more like blowing up a balloon with an automatically adjusting hole in it that wont let you blow it up past a certain point.. Air in minus air out = cabin pressure.

Ok take a baloon fill it up with hot air (easier if you are a politician). Put a piece of tape on the baloon. Push a pin through the tape and baloon. you will see that the air comes out but does not tear the baloon. Planes are not made of rubber and will not tear like rubber. A bullet hole in aluminum will not cause it to tear apart and rip people apart.

A small hole (like a bullet hole) will cause decompression but no explosion (se balloon example above).

The air passing over such a hole will cause some extra underpressure but the amount limited.

Every single case where people have been sucked out of an aircraft has happened after some form of drastic structural failure. Like the cargo door latches failing, entire cockpit window being removed or worse.

// anders

I recently saw this episode. OMFG! Apart from being surprised that they really showed in detail exactly where to place a bomb to effectively destroy an such a big plane with only 100g of high explosive (!!!) and how to improvise a shaped charge with commercially widely available detcord and some paper I really liked it a lot. I wonder how that episode made it past the homeland security censors, considering that the Lockerbie jumbo was destroyed by several hundred grams (almost a pound) of high explosive.

Now imagine someone managed to simultaneously detonate TWO or more such small bombs, e.g. by radio, one in the freight compartment (Lockerbie style) and another one in the passenger compartment, then that jet is guaranteed to crash. Richard Reid, the British shoe bomber, might have succeeded in bringing down a jetliner if he had seen that episode and his lighter had worked.

If people really think hard this episode of Mythbusters should be a huge wakeup call. How hard is it to get 100g of well sealed and hidden high explosive on board? That's only two liquid ounces. How hard is it to hide a detonator? How difficult is it to get some sheet metal past the security at airports into the plane? Two small linear shaped charges assembled in flight and placed at the right position (as shown on Mythbusters), or a slightly modified maglite with some hidden "goodies" (metal reflector with exposives packed behind it), or a shaped charge without metal and filled with water(!!!), or a flying plate charge, or a can of coke with a liquid explosive with its bottom producing the shaped charge effect... there are endless possibilities. Add some bad weather and a 737 including its passengers is toast. You just need to know where to place that charge. Which already was obvious to some of us (plus every damn engineer), butnow everyone can find out. Well done!!!

And BTW, it wasn't a Boeing 737 they blew up. It was an old DC7 or DC9.

Okay... If people needed Mythbusters to see how to blow up a plane, they REALLY need to pay more attention in physics class - not to mention most of the Internet should be banned, 'cause you can find easy recipies for explosives, blueprints for airplanes and more out there.

My point is: If someone wants to kill you, they WILL SUCCEED - it's not hard to kill somebody, and it's not particularly hard to blow up a plane.

All it takes is some determination. A shaped charge in the cargo department isn't going to work, btw, unless you have controll of the placement of the cargo (and if you do, then there wouldn't really be any problem placing charges at all...) and a shaped charge in the cabin is a little more troublesome to fix - unless you're about to go up in smoke with the rest of them - never been much fan of self-sacrifice, myself. But then again, you could probably manage to hide away a shaped charge in one of the toilets, or pack it into one of the meal-trays (I used to work at a caterer who made airplane meals - NO CHECKING WHATSOEVER of the meal-trays - they were put on the plane by us at the caterer, and we also did the cleaning and preps of the inside of the planes - wouldn't been hard to hide something).

And for Mythbusters - I think perhaps the program wasn't entirely to-the-point on the decompression issue - I would much more like it if they took a plane up there in the sky and tested it :D