Maximum safe height to jump from? And ancillary question.

Factual Questions
1

I was wondering idly about this today, taking a concrete floor for example and assuming a correct landing, at some point there is a gradation of heights where you go from ‘definitely won’t get injured’, ‘possibly get injured’, ‘definitely get injured’ and ultimately ‘definitely dead’.

Basically what is the maximum safe height to jump from without any of the latter happening?

And the bonus question, assuming a person is going to fall from a significent height what is the best position to be in on landing to at least attempt to minimise injury? I’m thinking its possibly to land on our your side with arms positioned to protect your head? But I may be way off base on that one.

Thanks!

2

You can be injured by a tiny fall on a concrete floor depending on how you land, so the maximum could be less than an inch to avoid all injuries. Assuming you can position your body and absorb and spread the impact it depends on skill, you probably want to land on your feet with legs flexed and continue to fall over and roll out. If you just have to assume some position for landing you probably do want to cover your head, but at the expense of injuring other parts of your body.

3

Yes, I wasn’t sure how to word that, perhaps it would have been better to say ‘even when all things go correctly, at what height are you still going to get hurt?’

Anyway, thanks for the reply, 0320 here and I’m off to (a hopefully safe and secure) bed.

4

Aren’t there known cases of people falling out of airplanes at high altitudes (e.g., skydivers whose chute didn’t open) and surviving?

When my big brother came home from the Army (circa 1959-1962) he told of a guy he knew who did that.

ETA: He also told me of the rescue efforts typical of such cases: The primary equipment being a mop and a bucket. They found the guy, dazed and wandering around (this was apparently in a desert training area) and asked him “Where did he land?” Then the guy said “Here I am” or something to that effect. Then they asked: “Not you! The guy who clobbered in!”

5

We have done this one before and there is no one specific answer. Some people die from falling off of a short stepladder (I knew a fairly healthy man that happened to) and other people have fallen literally tens of thousands of feet and walked away with rather minor injuries all things considered.

The ‘safe’ height has to be determined statistically and it is not absolute by any means but it is much lower than most people assume. I work in an industrial facility and the workers there spend lots of time on high lifts that can go up 30+ feet above the concrete floor. The training that they get emphasizes that, if they ever neglect their safety equipment and manage to fall out, they will probably not suffer long for it but the family they leave behind will.

Here are some stats for falls from height but they include all types of surfaces. Falls to concrete are obviously less friendly than those to sand, dirt or snow. The LD states the ‘Lethal Dose’ followed by the percentage of people that die from falls from that height (e.g., 50% of falls from 48 feet onto all surfaces are fatal).

“LD90 for fall=7 stories The median lethal dose (LD50) for falls is 4 stories, or 48 ft, and the lethal does for 90% (LD90) of test subjects is 7 stories, or 84 ft”.

I have looked for a definitive chart that breaks down deaths from falls by type, surface etc. and never found a really good one. There are lots of scattered ones around but not any truly comprehensive ones that I have found. You can Google search with ‘LD50 for falls from height’ to see more.

Here is a previous thread on the subject. The one constant is that fatal falls tend to be much lower than most people think.

6

Think of it as another kind of quantum physics phenomenon, that falls from 10000 feet are 100% fatal, but still, every so often someone will fall that far and survive.

7

Under the OP’s stipulation of a concrete floor, I’m skeptical that it’s ever possible to survive a fall of even hundreds of feet, let alone thousands.

Examples of people surviving a long fall invariably involve a less-than-instantaneous stop (e.g. hit vegetation, or a snow-covered slope, etc.). Or they include such factors as a partial parachute deployment.

8

I think this question isn’t about the typical “falling” scenario, but rather how high can one safely jump onto concrete under controlled conditions. I’m picturing an experienced stuntman or parachute trainer-type performing a proper controlled landing; whether that be a landing transitioning to roll… or whatever the best method is. Motivated by money and/or some level of fame, they try:

performing the jump/landing at 5 feet… probably quite easy and repeatable.
performing the jump/landing at 10 feet… maybe get hurt 2/10 tries?
performing the jump/landing at 15 feet… ???
performing the jump/landing at 20 feet… ???
performing the jump/landing at 25 feet… ???
performing the jump/landing at 30 feet… ???

This kind of experiment would probably never actually happen, but at some height nobody would even try to perform the stunt. So where is that max height you can’t pay a person to jump from (because it can’t be done safely no matter what), and at what height in between would a pro politely decline the offer (because in their experience at such jumps they’ll probably break something with better than a 50% chance)?

I doubt anyone would try a controlled jump and landing on concrete at much over 20 feet.

9

The Parachute Landing Fall is probably one of the best bets as it distributes the shock over several non vital parts of the body.

10

I always heard the 50 percent mark was 3 stories, but I don’t have a cite for it. I’ll take Shagnasty cite of 4 stories as a better answer since it is actually cited.

There were several guys who basically got shot out of their bombers in WWII and survived. Here are the ones I remember off the top of my head.

Alan Magee was a gunner when his plane was basically shot apart. His chute was also ruined in the attack. He had a choice of riding the wreckage down (and likely burning to death) or jumping to his death. He chose to jump. He jumped from around 20,000 feet up or so (a common altitude for bombers at the time), and couldn’t tell you how he managed to survive as he passed out from a lack of oxygen on the way down. He came crashing down through the skylight of the St. Nazaire train station and landed in a heap on the floor. He broke quite a few bones and had a fairly lengthy recovery, but survived.

Ivan Chisov was a Russian navigator whose plane was also shot apart. Ivan however jumped with a perfectly good chute. He thought that if he pulled his chute right away, he would just make himself an easy target for a pissed off German fighter pilot, so what he intended to do was drop down below the level of the battle and then pop his chute. What he actually did was pass out, and never opened his chute (he had also jumped from roughly 20,000 feet). He hit the side of a snowy ravine, and bounced, rolled, and slid down to the bottom. He was also badly injured.

The most amazing story I think though was Nicholas Alkemade. Nicholas got the order to bail out, and found his chute in flames. Like Alan, he had a choice of burning to death in the wreckage on the way down, or jumping to his death, and also chose to jump. Nicholas also passed out on the way down. However, he landed in fir trees, bushes, and a bit of snow, and basically walked away from the whole thing with little more than a few scratches and a slightly sprained knee. He’s the only one I know of that fell 20,000 feet or so and didn’t break anything.

None of them landed on concrete, but still, falling 20,000 feet kinda proves that there really isn’t an upper limit to how far you can fall. That’s more than high enough to reach terminal velocity, and after that you’re just showing off. :stuck_out_tongue:

I’ve also read about a few skydivers who have fallen with failed chutes. Most had at least part of the chute partially out, maybe in a tangled mess which was certainly not as effective as a chute opening properly, but it did probably slow them a bit. One story that really stuck in my mind was a skydiver whose main chute tangled, then the reserve chute also tangled, and he slammed into someone’s back yard at a pretty high rate of speed. The article described his legs as “telescoping” so that his feet were up where his knees were. Needless to say, he had a bit of a recovery, but he did survive.

Another story that stuck with me was a skydiver who talked about how they train to roll when they hit so that they spread out the damage over several different points of contact (the parachute landing fall in Fubaya’s link). The guy said he broke all of the points of contact, so he figured he did it right.

11

The great motorcycle jumper Evel Kneivel when he would jump would always land on concrete so he always had bad injuries. Evel also had no protection other than a helmet.

Nowadays motorcycle jumpers land on dirt ramps which have more give than concrete. They also wear special suits that are padded in some areas, hard in others like the heart.

12

I have my copy of John Templar’s “The Staircase” right here. It has some data on falls (mainly staircases, but the principles are useful for small falls).

There isn’t a monotonic relationship between height and risk. Very short falls are actually more dangerous than falls of a few feet, because there isn’t time to brace or adjust balance.

There are three phases: The reflex answer, the answer of will, and the functional stretching reflex.

The reflex answer takes 5 cm (2 inches) to kick in. No muscular contraction, very hard jolt.

More than 18 cm (7 inches) is needed for a deliberate reaction for a well controlled landing. Not a jolt, but no control.

More than 30 cm is needed to be able to react on landing to absorb shock and recover balance.

So falls under 30 cm have surprisingly high risk. After that there is quite low chance of injury for a normal child or adult until you get high enough to twist muscles or fracture bones even in a controlled landing.

I can’t answer with good data for longer falls. In practice it depends far more on what you hit and your orientation than the height you fall from. You can probably specific LD50s for particular surfaces, but I don’t have the tables to hand.

In terms of orientation on striking the ground:
“The location of the impact point on the body is significant” p23.
Basically: Don’t hit the head, maximise the area over which the initial force is distributed, try to hit with flesh instead of bone. In other words, landing on your side with your head covered isn’t a bad intuition if you have control over orientation.

For moderately short falls, absorbing shock by landing with the legs and immediately collapsing is even better, so long as the secondary fall doesn’t hit the head.

For short falls, keeping your balance and avoiding sticking out your hands to get broken if you do stumble is better than trying to change your orientation.

13

This reminds me of something that I saw on TV, IIRC, Maximum Exposure(???)
Guys were, for sport, jumping off of 3 story buildings; the instant that their feet hit the ground they jumped/sprung away from the point of impact, apparently with no ill effect.

I don’t think I imagined it, but, who knows?

14

Stories of people falling 20,000 feet onto snow or branches etc. reminds me that “It’s not the fall that kills you but the landing.”

15

Concrete might be an exception. I speak from experience here. I was practising PLFs on thick mats over a concrete floor and my elbow and arm went between two of the mats and onto the concrete floor. :eek: :eek: :eek: Fortunately one of the other participants was a nurse, but I didn’t get to jump that day.

16

Didn’t die did ya? :slight_smile:

17

I’ve told the story before of a gal I knew in high school who fell off a second story balcony railing and landed on the sidewalk on her face/forehead. So her center of mass fell 10-12 feet. She wasn’t killed, but it was a very close thing; she was permanently damaged. So that’s close to the limit for very bad landing technique.

OTOH, for good technique: …

When I was in pilot training we learned to use USAF standard parachutes. This included jumping off about 8 foot platforms into a sand pit and practicing the Parachute Landing Fall (PLF) as the approved technique for minimizing risk of injury landing on any flat surface. The explanation was the speed of impact after an 8 foot freefall was about the same as the fall speed of the tactical emergency 'chutes we’d be using for real.

USAF selected the size and speed of fall of their chutes with an eye to keeping folks mostly uninjured upon landing on unforgiving surfaces. At the same time, unlike sport chutes, there is a premium on minimizing size of chute & maximizing speed of fall to minimize exposure to the elements and enemy action. Which also supports the idea that somewhere in the 8 foot area is where they expected a knee in the curve of landing injuries, albeit minor. Recognizing there’s a big difference in survival consequences between breaking an ankle during a daredevil show or weekend skydiving event and breaking an ankle 200 miles deep into enemy territory in winter.

Jumping 8 feet into a sandbox was pretty low injury risk for folks still learning the good technique. So I’d WAG that onto the OP’s concrete surface that’d be getting close to the threshold of spraining/straining something for a skilled jumper.

In free fall and ignoring atmosphere, impact speed goes up at the square root of the height. But IIRC deceleration forces go up at the square of the speed. So for round numbers, forces are directly proportional to height of fall. Which leads me to WAG that 20-30 feet = 2 to 3 stories of fall is all-but guaranteed significant injury.

18

Late Add: I just remembered something.

I had a friend who was a fire department Captain (RIP Andy; you were a good man). He once said that falls from 30 feet off a ladder where pretty much a guaranteed disability retirement, if not a funeral. His jurisdiction was urban, so almost all his experience with people falling would be onto hard surfaces.

And no, he wasn’t killed in a fall.

19

Ok, I found a few studies. This one is pretty good, and references the others I found:

Daniele Risser, Anneliese Bönscha, Barbara Schneiderb, Georg Bauera (1996) Risk of dying after a free fall from height, Forensic Science International

32 deaths and 60 emergency room cases from Vienna, restricted to people aged between 20 and 50, all onto concrete or pavement.
Floor - Survived / Dead
Ground - 11 /0
First floor - 10 /2
Second floor - 18 /2
Third floor - 10 /8
Fourth floor - 7 / 9
Fifth floor - 2 / 7
Sixth floor - 0 / 4

The authors also reviewed similar literature, and say that their conclusion matches the consensus that the fifth floor is the limit for landing directly onto a hard surface. The two fifth floor survivors were 24 years old.

For older victims (50+) there are lots of victims even under five metres (that’s me paraphrasing the authors citing another study that I haven’t read).

The authors also mention that bodies in free fall tend to hit the ground head first, so you may not have a choice regarding impact.

20

I saw that, too. It was pretty impressive. Weren’t they Korean?