Parachutes in commercial aircraft.

[matthyaouw]

I've been told that commercial aircraft don't provide parachutes due to the fact that depressurising the aircraft suddenly to let everyone jump out would kill them. This doesn't add up... If the plane is at 40,000ft, then fair enough, you can't really blow the doors, but if the plane is in trouble then it's not going to stay at that altitude very long, so as it decends there must be a point where the doors can be safely blown (perhaps the cabin could be decompressed slowly as it decends?)
Anyway, surely the problems caused by decompression must be less than those caused by sudden, flaming "supercompression"?

 

[Entropy]

No it wouldn't kill you. They probably don't put parachutes on because it would be to hard to teach everyone on board how to use them properly.

 

[wolram]

Knowing a little about the industry, i would say airlines would give all sorts of
reasons why they do not have them, but saving weight would be the last thing
they would say.

 

[hitssquad]

Even if it were technically feasible, why would you put parachutes in a commercial aircraft?

 

[outsider]

they lose cargo revenue due to weight restrictions, plus they would have to pay for the parachutes, and will also need to pay to train staff (it's not cheap and there are a lot of staff, some of whom would not want to skydive for training)...

and then there is the actuarial calculation based on deaths to justify their use... remember that the parachute is not a guarantee of life...

and imagine 300 parachutes coming down all around you... is that war or a plane coming down?

 

[Moonbear]

No it wouldn't kill you. They probably don't put parachutes on because it would be to hard to teach everyone on board how to use them properly.

I agree that they aren't terribly useful if you don't know how to use it properly, when to open it, etc. Not to mention somehow avoiding sucking the passengers through the jet engines as they are jumping out of an erratically descending plane that may or may not still have power to some engines (I don't know if that would be part of the problem, but that's because I'm one of those people who would have no idea when to open a 'chute or how to land, or how to steer it away from someone's swimming pool or the high tension power lines or the 4-lane highway. ) I'd rather take my chances with the pilot managing to get the plane back under control or landing with a plane still between me and the ground with emergency crews ready and waiting.

 

[hitssquad]

They would exit out a back door (back doors would have to be designed into all planes)so they wouldn't hit the wings and engines. But 200-600 novice jumpers all trying to get out of a plane at the same time would never work. 90% would freeze up in the doorway. And no one else would be able to get out. There would be panic and riots. It would be basically a holocaust.

Most commercial jet crashes occur on take-off or landing. You can't jump out of an airplane that close to the ground, and if you could, could you get 600 people to get strapped into parachutes and out one door in 5 seconds?

 

[Moonbear]

But 200-600 novice jumpers all trying to get out of a plane at the same time would never work. 90% would freeze up in the doorway. And no one else would be able to get out.

I'm not sure that would be the biggest issue. Afterall, the other 199 people behind them would probably just shove them through the door whether they wanted to go or not. I would think the bigger problem would be once they were shoved out of the plane, all those who balked at the door are going to completely freeze up in panic with the sensation of free-fall, possibly even black out, as they plummet to the ground and will forget to pull the cord or be unable to do so.

Most commercial jet crashes occur on take-off or landing.

Technically, don't they all occur on landing? A really bad, perhaps unexpected, sudden landing, even if it occurs only moments after the initial take-off? Well, with the exception of the rare mid-air collision I suppose.

 

[hitssquad]

the other 199 people behind them would probably just shove them through the door whether they wanted to go or not.

I was thinking of Fluffy the Cat and a bathtub full of water. Besides, it has been demonstrated numerous times in burning buildings that a pile of people trying to get out one door will just create a pile. Fluffy the Cat in front won't help matters.

as they plummet to the ground and will forget to pull the cord or be unable to do so.

Commercial jump companies use a system for novice jumpers that automatically pulls the rip cord as the jumper exits the plane. (You clip your ripcord to a cable strung along the inside of the fuselage at about head height.) Naturally, commercial jets would use the same system.

Technically, don't they all occur on landing?

Good point. But seriously, on takeoff if one of the engines conks out, the plane crashes. Also, an unusual temperature inversion situation where the air near the airport is rushing downward causes some plane crashes on takeoff. For the former, we can make more reliable engines and stiffer maintenance requirements, but nothing can be done about the latter.

 

[Moonbear]

I was thinking of Fluffy the Cat and a bathtub full of water. Besides, it has been demonstrated numerous times in burning buildings that a pile of people trying to get out one door will just create a pile. Fluffy the Cat in front won't help matters.

The problem/difference with escaping a burning building is that if you try to shove the person ahead of you out of the way, they trip and fall in front of you creating an obstacle to everyone behind them. Someone else trips, starts creating a pile-up, people get trampled, and it's all quite mess. With jumping out of a plane, if you shove the person in front of you out the door, there's nothing there, so they don't continue to be an obstacle.

However, there would be the complication of trying to get everyone into their 'chutes, people still putting them on as they get to the door, the person in the front of the plane who gets theirs on quickly and tries to climb over the people in the aisle still trying to sort out the clasps, etc. I'm certainly not disagreeing there would be major logistic issues that would make it a far worse option than just staying buckled into your seat while the pilot does his/her best to regain control of the aircraft. If you're still at high enough altitute to jump when a problem is discovered, I would think you'd have a lot more chance that the pilot could land the aircraft...dump fuel, try to glide in, have runways cleared and coated with foam if necessary, etc.

Commercial jump companies use a system for novice jumpers that automatically pulls the rip cord as the jumper exits the plane. (You clip your ripcord to a cable strung along the inside of the fuselage at about head height.) Naturally, commercial jets would use the same system.

Hmm..I didn't know that. I always assumed that's why people did tandem jumps when first jumping, so you would be with someone more experienced until you learned how to do it yourself.

Good point. But seriously, on takeoff if one of the engines conks out, the plane crashes. Also, an unusual temperature inversion situation where the air near the airport is rushing downward causes some plane crashes on takeoff. For the former, we can make more reliable engines and stiffer maintenance requirements, but nothing can be done about the latter.

Yeah, I was only joking about them all happening on landing. I understood what you meant about crashes at take-off.

The cost issue that has been raised is also not insignificant. For that one flight every 10 years where it might help to have jumped mid-air rather than crash-landing, it just doesn't make financial sense. Airlines are already struggling with rising fuel costs. If you add more weight and take up space that could have been used to earn revenue with cargo, all the airlines will be going bankrupt because it'll be too expensive for most people to buy a plane ticket.

 

[Evo]

However, there would be the complication of trying to get everyone into their 'chutes, people still putting them on as they get to the door, the person in the front of the plane who gets theirs on quickly and tries to climb over the people in the aisle still trying to sort out the clasps, etc.

Then there would be the morons trying to get their luggage out of the overhead bins.

 

[Moonbear]

Then there would be the morons trying to get their luggage out of the overhead bins.

There's always one of them! I was on a flight with a medical emergency on board (okay, several medical emergencies...half the flight crew came down with food poisoning, or something with similar symptoms about mid-way between Britain and the US). We were instructed to stay in our seats, clear of the aisles and to NOT open the overhead bins until the EMTs were done and had assisted the sick crew members off the plane. And of course there was one moron who got up to get his bag the moment the plane came to a stop and was in the way as the EMTs were trying to get down the aisle.

 

[Ivan Seeking]

One idea that people are toying with is that of parachutes for the airplane itself. This is now done for some small planes, and the technology already pretty much exists to do it for jets - from the space program. The questions are whether or not it would do much good and of course the cost.

Previous thread.
https://www.physicsforums.com/showthread.php?t=26804&highlight=parachute

This system has already saved lives.

 

[moose]

When does everyone think "OK we have to jump now, we won't make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air??

 

[Grogs]

When does everyone think "OK we have to jump now, we won't make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air??

It's not only that. The FAA requires that reserve parachutes get repacked every 90 days, whether they're used or not. This has to be performed by an FAA Master Rigger and the going rate, on a civilian drop zone is about $50 per repack. Multiply $50 by 300 by 4 times per year, and you're looking at an additional $60,000 per year per plane. You'd also have to store the parachutes somewhere that the passengers couldn't get too them during a routine flight, otherwise they'd have to be inspected after every flight to make sure they hadn't been tampered with.

As bad as the financial problems are, they wouldn't be anything compared to the technical problems. You have 300 people scared out of their minds trying to don a piece of gear they are completely unfamiliar with, move to the rear of the plane, and jump out.

Assuming that's no problem, when 300 people run to the rear of the plane, the Center of Gravity will shift beyond the Aft CG limit and the plane will stall, the people will be pinned to the ceiling until the pilot recovers from the stall (if he can,) then slung to the floor. The plane probably isn't in very good condition in any case (everyone's jumping out after all) so this problem is more likely.

Next you've got exit speed. A commercial airplane cruises at about 400-500 knots. Standard parachutes are made to open at speeds more along 110 knots. No parachute I know of is designed to open at 4-500 kts. It would either rip the fabric of the canopy to shreds, break most of the lines on the chute, or rip the harness out from between your legs (maybe taking them along.) The only way to slow down to the proper speed would be to jump out and freefall for a while until you reached a slower speed, then deploy. Obviously, this isn't possible with a static line system, and even if you did give the passengers a manually deployed chute, how many of them are going to wait more than a nanosecond before they pull the ripcord or throw out the pilot chute.

Back when I jumped every weekend, I carried my rig on a commercial airliner a couple of times. I thought about every conceivable scenario, and the only time I could see using it was if the plane disentigrated around me and I was able to don it before I passed out from hypoxia. I ended up just putting it in the overhead bin.

 

[Pengwuino]

When does everyone think "OK we have to jump now, we won't make it" and actually have time to jump out and get everyone out? Most of the time you wouldn't know you are definitely going to crash, and once you do, well, you wouldn't have time for parachutes. Plus, the added weight would make airplane tickets cost more because of more fuel usage. Why make something safe only slightly safer, yet uneconomically? I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air??

Yah! In what situation are you really going to have the pilot thinking that this is an unsurvivable situation yet be level enough and high enough to start parachuting people out? All i can think of is having a fuel leak occur in the middle of the ocean.

 

[hitssquad]

All i can think of is having a fuel leak occur in the middle of the ocean.

No one would survive a parachute jump into the ocean. Oceans are great for ditching planes, though.

 

[Pengwuino]

Oh yah good point...

Those peopel look awefully happy for having their aircraft bail into the ocean.

 

[Townsend]

They would exit out a back door (back doors would have to be designed into all planes)so they wouldn't hit the wings and engines.
But 200-600 novice jumpers all trying to get out of a plane at the same time would never work. 90% would freeze up in the doorway. And no one else would be able to get out. There would be panic and riots. It would be basically a holocaust.

Most commercial jet crashes occur on take-off or landing. You can't jump out of an airplane that close to the ground, and if you could, could you get 600 people to get strapped into parachutes and out one door in 5 seconds?

All of these problems are easily solved...ejection seats. The pilot can arm the seats before a crash and as a passenger, if you want to eject then you may do so...if you want to take your chances with landing then that is up to you. Babies and young children would of course not have the same options.

This would also make it easy for the pilot to let people escape an aircraft hijacking.

 

[Pengwuino]

All of these problems are easily solved...ejection seats. The pilot can arm the seats before a crash and as a passenger, if you want to eject then you may do so...if you want to take your chances with landing then that is up to you. Babies and young children would of course not have the same options.

Wouldn't that require opening up a massive amount of the aircraft's body thus making it almost a joke of an idea to try to fly that thing?

 

[Townsend]

Wouldn't that require opening up a massive amount of the aircraft's body thus making it almost a joke of an idea to try to fly that thing?

I don't think it would really affect it very much at all...I could be wrong though. Any aircraft engineers want to comment?

Honestly, I have seen aircraft land with half a wing and most of the empennage blown off...you would be surprised how well a plan can fly with missing parts..

 

[hitssquad]

This roofless plane flew just fine. A flight attendant got sucked out, though.

 

[Pengwuino]

haha well then that's cool.

Really screw up a terrorists day when everyone just flies out once they pull their guns.

 

[hitssquad]

Really screw up a terrorists day when everyone just flies out once they pull their guns.

If they're using the plane as a cruise missile, they wouldn't mind. 9/11 used virtually empty planes on purpose -- it was easier to control the passengers that way.

 

[Townsend]

If they're using the plane as a cruise missile, they wouldn't mind. 9/11 used virtually empty planes on purpose -- it was easier to control the passengers that way.

That is a good point...perhaps the pilot could set the system to autopilot and the plane could then fly to a secure location and then the pilot could just eject himself...this could all be done with the press of a single button which would also enable the passengers to eject themselves... of course the situation would look pretty grim for the youngins...

 

[hitssquad]

of course the situation would look pretty grim for the youngins.

Tandem jump. Just strap them to your belly.

 

[Townsend]

Tandem jump. Just strap them to your belly.

You mean a tandem seat ejection? Interesting idea...

 

[hitssquad]

You mean a tandem seat ejection?

Yeah.

Interesting idea...

As these all are, but an airline implementing any of these ideas might not inspire passenger confidence.

 

[Moonbear]

As these all are, but an airline implementing any of these ideas might not inspire passenger confidence.

Really good point! If I heard an airline was packing parachutes, I think I'd have second thoughts as to why they felt they needed them.

 

[Ivan Seeking]

The only chance for parachutes is for the planes themselves. The rest is academic.

 

[outsider]

It's not only that. The FAA requires that reserve parachutes get repacked every 90 days, whether they're used or not. This has to be performed by an FAA Master Rigger and the going rate, on a civilian drop zone is about $50 per repack. Multiply $50 by 300 by 4 times per year, and you're looking at an additional $60,000 per year per plane. You'd also have to store the parachutes somewhere that the passengers couldn't get too them during a routine flight, otherwise they'd have to be inspected after every flight to make sure they hadn't been tampered with.

As bad as the financial problems are, they wouldn't be anything compared to the technical problems. You have 300 people scared out of their minds trying to don a piece of gear they are completely unfamiliar with, move to the rear of the plane, and jump out.

Assuming that's no problem, when 300 people run to the rear of the plane, the Center of Gravity will shift beyond the Aft CG limit and the plane will stall, the people will be pinned to the ceiling until the pilot recovers from the stall (if he can,) then slung to the floor. The plane probably isn't in very good condition in any case (everyone's jumping out after all) so this problem is more likely.

Next you've got exit speed. A commercial airplane cruises at about 400-500 knots. Standard parachutes are made to open at speeds more along 110 knots. No parachute I know of is designed to open at 4-500 kts. It would either rip the fabric of the canopy to shreds, break most of the lines on the chute, or rip the harness out from between your legs (maybe taking them along.) The only way to slow down to the proper speed would be to jump out and freefall for a while until you reached a slower speed, then deploy. Obviously, this isn't possible with a static line system, and even if you did give the passengers a manually deployed chute, how many of them are going to wait more than a nanosecond before they pull the ripcord or throw out the pilot chute.

Back when I jumped every weekend, I carried my rig on a commercial airliner a couple of times. I thought about every conceivable scenario, and the only time I could see using it was if the plane disentigrated around me and I was able to don it before I passed out from hypoxia. I ended up just putting it in the overhead bin.

This was a riot to read! Thanks ...

 

[Pengwuino]

That is a good point...perhaps the pilot could set the system to autopilot and the plane could then fly to a secure location and then the pilot could just eject himself...this could all be done with the press of a single button which would also enable the passengers to eject themselves... of course the situation would look pretty grim for the youngins...

haah that would be rather hilarious. I think the terrorists would catch on pretty quick and start hijacking ships or something. I wouldn't want my insurance to just fly the coop if I am tryen to hijack an airplane.

 

[russ_watters]

Most commercial jet crashes occur on take-off or landing.

This really is the point. Can anyone name the last time a jetliner became fatally stricken at a high enough altitude that people could have jumped to safety? I can - October (?) of 2001, when the vertical stabilizer came off that Airbus over New York. But it would not be easy to put on a paracute in a frisbee-ing plane. Frankly, I can't think of a crash in the past 20 years where parachutes would have helped (perhaps the ValuJet crash in the Everglades, but probably not).

Parachutes and ejection seats... uh, you guys know that these things take a five-point harness, right...? Can anyone say that they could strap-on a 5-point harness in a frisbee-ing plane? How 'bout a burning one? It's just unreasonable to think that it's possible.

 

[matthyaouw]

Alrigh, many many good points, so I'll be quiet now.

I mean, couldn't cars have ejection seats, so that when you crash, instead of airbags, you get ejected in the air??

One word- Tunnel

 

[Pengwuino]

One word- Tunnel

And what if you simply flip?

 

[Moonbear]

Parachutes and ejection seats... uh, you guys know that these things take a five-point harness, right...? Can anyone say that they could strap-on a 5-point harness in a frisbee-ing plane? How 'bout a burning one? It's just unreasonable to think that it's possible.

Well, I'm sure I have sufficient skill to do that, but I can't be so sure about most passengers, and I expect the airline would get a lot of customer complaints if they even changed to a 3-point seatbelt system.

I think Grogs pretty much made the best argument against parachutes so far. I think people are just fantasizing about ejection seats now, knowing it's not at all realistic to do.

 

[FredGarvin]

This has to be the silliest conversation I have seen so far. Next time you're on a flight, take a look around at the winners around you. 95% of the people have a tough enough time with the seat belt and figuring out the bathroom doors let alone putting on a parachute (which I think very few people would be able to do when they needed to).

Ejection seats would probably kill more passengers than they would save. Especially the elderly. Then there are the "denisty/gravitationally challenged" that would require an extra boost on their seats. Although, I am sure Martin-Baker would love to outfit all of the world's airlners though. Let's fill a commercial airliner with 300 or so explosive rocket engines. Yeah. That's the ticket.

 

[Moonbear]

This has to be the silliest conversation I have seen so far. Next time you're on a flight, take a look around at the winners around you. 95% of the people have a tough enough time with the seat belt and figuring out the bathroom doors let alone putting on a parachute (which I think very few people would be able to do when they needed to).

I was thinking that they can't even get their bags up into an overhead bin without help. There are some seriously spatially-challenged people. On the last flight I was on, there was this guy standing in the aisle in the back of the plane trying to get against the flow of passengers getting onboard to find a space for his carry-on because he couldn't find space near his seat...I looked up at the bin right next to him and suggested if he just turned the other roll-away in it so it was turned the other direction, his bag would fit right next to it. He seemed to marvel at this revelation a moment before deciding to try it.

Then there are the "denisty/gravitationally challenged" that would require an extra boost on their seats.

I was trying to think of a nice way to say that. I don't think ejection seats come with seat-belt extenders. And what do you do about those people who have to use two seats?

The suggestion of ejection seats on a car is even funnier though. How fun to have them shoot you up into the air so close to the ground that there's no way to cushion your fall, and then you can land without the protective cage of your car smack in the middle of traffic. Sounds fun, huh?

 

[russ_watters]

The suggestion of ejection seats on a car is even funnier though. How fun to have them shoot you up into the air so close to the ground that there's no way to cushion your fall, and then you can land without the protective cage of your car smack in the middle of traffic. Sounds fun, huh?

Ejection seats on military aircraft are "0/0" - ie, they operate just fine at zero speed and zero altitude. They rocket you up to ~1,000 feet, so you're high enough for the parachute to deploy.

But again - before you can eject, you need to strap on your harness, lest you follow in the footsteps of that hapless boy who was the last person allowed in the cockpit of a military fighter jet at an air show...

 

[outsider]

This has to be the silliest conversation I have seen so far. Next time you're on a flight, take a look around at the winners around you. 95% of the people have a tough enough time with the seat belt and figuring out the bathroom doors let alone putting on a parachute (which I think very few people would be able to do when they needed to).

omg... I'm dying... LOL! this is the ultimate answer!

Ejection seats would probably kill more passengers than they would save. Especially the elderly. Then there are the "denisty/gravitationally challenged" that would require an extra boost on their seats.

Oh.. your killing me now... Especially since more and more people want to fly, more and more people are "gravitationally challenged", and the boomers are only going to get older...

Come to think of it, the escape hatch in the back of the plane would cause a panic due to the fact that there are first class passengers sitting in the front who would "expect" to have the right to jump first.

Someone laterally challenged may have difficulty getting out of their seat and into their parachute given the cramped aisles... nevermind... i couldn't imagine everyone being able to get into their parachute all at the same time while in a panic without some human factors to cause a chain reaction...

FredGarvin, thanks for making my day!

 

[Moonbear]

Come to think of it, the escape hatch in the back of the plane would cause a panic due to the fact that there are first class passengers sitting in the front who would "expect" to have the right to jump first.

I'm just enjoying the momentary thought of the look on those first class passengers' faces when they realize that person with the cheap ticket stuck sitting by the bathroom at the rear of the plane will be the first one to escape the doomed plane. Ah, it would be such sweet revenge.

Ejection seats on military aircraft are "0/0" - ie, they operate just fine at zero speed and zero altitude. They rocket you up to ~1,000 feet, so you're high enough for the parachute to deploy.

Oh, goody! It'll be something new and exciting for the stupid teens to challenge each other to do. Why go to the amusement park when you can play with the seats in daddy's new beamer. Just watch out for the trees overhead.

 

[outsider]

I'm just enjoying the momentary thought of the look on those first class passengers' faces when they realize that person with the cheap ticket stuck sitting by the bathroom at the rear of the plane will be the first one to escape the doomed plane. Ah, it would be such sweet revenge.

bulkhead & "close to the front" seat requests will be replaced by seats nearest to the back of the plane... everyone will claim to have a bladder problem

Oh, goody! It'll be something new and exciting for the stupid teens to challenge each other to do. Why go to the amusement park when you can play with the seats in daddy's new beamer. Just watch out for the trees overhead.

oh.. that wouldn't happen *sarcasm* LOL

 

[EnumaElish]

Most commercial jet crashes occur on take-off or landing. You can't jump out of an airplane that close to the ground, and if you could, could you get 600 people to get strapped into parachutes and out one door in 5 seconds?

That's a fact. But suppose govt. regulations mandated numerous and wider emerg. exits and just like you can't board an airplane without a picture ID, suppose that you couldn't board without a basic training in para. jumping? I know this goes against the deregulatory spirit of our times, I am just hypothesizing here.

I also think bicycle helmets could be made mandatory for car passengers and they could end up saving lives.

P.S. Then again, after reading Grogs's post, I am not so sure about para. jumping's feasibility. But I still think helmets in cars would be a good idea.

 

[Moonbear]

I also think bicycle helmets could be made mandatory for car passengers and they could end up saving lives.

Not likely. At the speeds involved in car collisions, bicycle helmets are pretty useless.

Under US standards bike helmets are tested in 2 meter drops that achieve about 14 miles per hour (22.5 kph) on the flat anvil. In Europe the drop height is only 1.5 meters. Why so low, when bicyclists frequently exceed 14 mph in forward speed?

http://www.bhsi.org/limits.htm

Seat belts and airbags work much better by ensuring your head doesn't hit windshield or pavement.

 

[hitssquad]

I also think bicycle helmets could be made mandatory for car passengers and they could end up saving lives.

Helmets are intended not to save lives, but to reduce brain injury.

 

[hitssquad]

Not likely. At the speeds involved in car collisions, bicycle helmets are pretty useless.

Then how do people come away from car accidents with brain damage, or in comas, instead of dead?

 

[Moonbear]

Then how do people come away from car accidents with brain damage, or in comas, instead of dead?

Luck? If you still come away with brain damage, how has the helmet helped? That's what it's supposed to be preventing.

Helmets only protect at low speed collisions. Now, when a bicyclist is hit by a car, I would suppose the driver is usually slamming on the brakes and not hitting them at a full 50 or 60 mph.

Also, bicyclists are not hit by cars directly head-on. I found this and a lot of interesting information on this site:
http://www.helmets.org/henderso.htm

3.2 The kinematics of a bicycle collision

A careful field study of real-world cycle accidents was conducted in Germany (Otte, 1989). The predominant collision was between a cyclist and the front of a car. The subsequent kinematics were shown to be similar to car-to-pedestrian or motorcycle collisions. The primary impact is with the bicycle and the lower limbs of the cyclist. The body of the cyclist is then thrown up over the front of the car. Impact with the windscreen of the car is common at impact speeds as low as 25 km/h. In this study the mean collision speed was 36 km/h. The cyclist's head almost always hits the hood, the lower centre part of the windscreen or the A pillars that support the ends of the windscreen. The body of the cyclist is further injured by contact with roof structures, and at impact speeds of 55 km/h and over the cyclist is likely to be thrown completely over the car. This, of course, presents a renewed risk of head injury as the rider hits the ground.

However, I've also found contradictory information to the information cited by my first source regarding the reduction in injuries in Australia following implementation of the helmet laws, which instead suggests the reduction in injuries was actually due to a reduction in the numbers of people riding bicycles due to safety fears sparked by the initiation of helmet laws. One such site offering such evidence is this one:
http://www.magma.ca/~ocbc/hfaq.html#A4
(That site is pretty anti-helmet though, but it sure does provide an alternative view on things. Their reasons seem mostly that helmet laws deter people from riding bicycles, or for those who do wear them, gives them a false sense of security so they engage in riskier behavior.)

It also seems there are issues regarding which standards are used by various countries for certifying bicycle helmets. From the first source I provided, it seems Australia has changed their standards to address concerns with earlier helmet designs, but it seems more variable elsewhere. I'm not sure this site has the most recent information, but the Snell Memorial Foundation, which is a non-profit organization that certifies helmets claims the standards required in the US are lower than their own standards, so not all helmets are created the same.
http://www.smf.org/articles/bcomp.html

Again, this UK site concurs regarding the impact speeds for which bicycle helmets are tested:
http://www.whycycle.co.uk/safety-helmets.htm

What can a helmet do?

As with most safety orientated products, bicycle helmets have to pass certain standards prior to being allowed to be sold. What may be surprising is the exact nature of those standards.
Cycle helmets are only designed and tested to withstand an impact equivalent to an average weight rider traveling at a speed of 12 mph falling onto a stationary kerb shaped object from a height of 1 metre.
This is the equivalent of falling from your bike onto the road or the kerb edge.

Helmets are not tested nor expected to be able to offer full protection if you come into contact with a vehicle which is moving.

I have been entirely unable to find information regarding the actual speed of impact (even a good guesstimate) of a person's head with the car in collisions resulting in head injury and collisions in which the helmet prevented head injury, so I don't know how much of the effectiveness of bicycle helments preventing head injury are due to the rest of the body taking the initial force of impact and reducing the impact of the head with the car when the head finally collides.

According to Snell, there is a compromise/limit to improving the helmets further:

The other problem is, how much helmet will you wear. A good motorcycle helmet will generally provide more protection than just about any other helmet, but they are heavier and do not provide as much venting. This is OK for riding a motorcycle because in general you are not exerting as much physical energy as you would be on a non-motorized vehicle.

I also read in one of these sites, and now can't find it again (maybe it was one of the links I already closed) that if the helmets were designed to be more effective in higher speed impacts, they'd lose some effectiveness in lower speed collisions, such as a kid falling off his bicycle.

Anyway, all of this is probably pretty different from what would happen to the driver or passenger in a car who is in a crash at higher speeds and their head slams into the windshield at the full 55 mph they are traveling when the car comes to a sudden stop, or when they and the entire weight of the car crushes down on their head as the car rolls. Maybe a motorcycle helmet would help, but then it would probably limit posture with a seat back behind you that you wouldn't have on a motorcycle (the seat head rest is there to prevent neck injuries), might be restrictive of how well you can turn your head to look for obstructions, etc. Plus, cars aren't designed with all that much head room...I don't know if a tall person could fit in some cars with the added height of a helmet on their head.

I guess the bottom line is bicycle helmets are designed for the impacts that bicyclists are likely to experience, not the impacts motor vehicle drivers are likely to experience.

 

[hitssquad]

Car drivers wearing bicycle helmets to reduce injury potential

I also think bicycle helmets could be made mandatory for car passengers and they could end up saving lives.

Not likely. At the speeds involved in car collisions, bicycle helmets are pretty useless.

Then how do people come away from car accidents with brain damage, or in comas, instead of dead?

Luck? If you still come away with brain damage, how has the helmet helped?

We were talking about potentially helmeting car passengers. As far as I know, car passengers do not generally wear helmets. If that is indeed the case, asking 'how has the helmet helped' is an instance of the complex question fallacy.
datanation.com/fallacies/distract/cq.htm

 

[Moonbear]

We were talking about potentially helmeting car passengers. As far as I know, car passengers do not generally wear helmets. If that is indeed the case, asking 'how has the helmet helped' is an instance of the complex question fallacy.
datanation.com/fallacies/distract/cq.htm

Oh, I misunderstood. I thought you were talking about bicycle helmets on bicyclists colliding with cars since, as you point out, car passengers don't wear helmets. Oh well, I learned a lot more than I ever would have otherwise about bicycle helmets in the process.

 

[Ivan Seeking]

Here's the newest high speed impact resistant helmet.

http://66.132.232.61/prodimages/R13014.gif