3

Let's say a plane is going to crash and all people on board know this.

Why can't they jump from the aircraft when the plane is near the ground?
They would have higher chances of surviving, right?

voretaq7
  • 68,398
  • 8
  • 226
  • 337
why
  • 33
  • 1
  • 1
  • 3
  • Higher perhaps, but the improvement would be insignificant: see this question on physics.SE which is the same scenario, and consider that an aircraft would probably start 'falling' from much more than the 10m or 20m described in the some of the answers. And that's without considering practical difficulties like opening the door and fighting off the other passengers who want to jump too. – Pondlife Nov 21 '14 at 18:15
  • 3
    Your question is extremely closely related to In the event of a crash over thick snow or a forest, would it be safer inside the aircraft or free-falling? - While your question is not about forest or thick snow, the factors at play deciding the fate of your body already seems to be answered in the other topic. – Karl Stephen Nov 21 '14 at 18:30
  • 2
    Mythbusters already addressed this with jumping in a runaway elevator. Buster fared no better jumping--and a plane crash involves a lot more speed than an elevator. – Loren Pechtel Nov 22 '14 at 03:42
  • sure, Bugs Bunny has done it lots of times. Seriously, a case of a british bomber at about 500 feet and the crew ejected. The low altitude, net vector of the forward motion & falling airplane & upward ejection caused one guy to hit the ground still strapped to the seat, the chute never had a chance to deploy yet he skid safely to a stop and walked away uninjured. – radarbob Nov 25 '14 at 06:32

2 Answers2

13

Why can't they jump from it when the plane almost reaches the ground?
They would have higher chances of surviving, right?

Wrong.

Remember your body still has roughly the same momentum it did when it was in the vehicle - just because you jumped out doesn't mean you're not still moving forward at a rate of speed the human body simply isn't designed for.

Let's reframe your question:

If you were in a car doing 60 miles per hour and you knew the car was about to crash into a brick wall, would you jump from the vehicle, or would you remain strapped into your seat where the car, seat, seatbelt, and airbag will all help absorb the impact?

As with a car, being inside an aircraft and properly restrained will afford you substantial protection from the initial impact, and some of the crash energy will be absorbed damaging the aircraft. That increases the length of time it takes to decelerate your body and gives you a better chance of survival.

If you jumped out of your friend's Cessna because it's going down and might hit some trees your unrestrained body would be decelerated far more abruptly when you hit the trees (or the ground).
You might survive, but you've lessened your chances considerably (and the Cessna is a best-case scenario - your forward speed would be around 60mph as in the car example. For something like a 747 you'd be in the 150 mile-per-hour range or faster when you jumped out, which is almost certainly not survivable).

voretaq7
  • 68,398
  • 8
  • 226
  • 337
  • 3
    The only time it's safe to jump out of a crashing airplane is if you have a parachute and sufficient altitude to use it. – Dan Pichelman Nov 21 '14 at 19:26
  • Unless you're Nicholas Alkemade... https://en.wikipedia.org/wiki/Nicholas_Alkemade (Or one of the other people referenced from the same page) – Jon Story Nov 21 '14 at 19:35
  • 3
    @JonStory 7-to-(some really big number of people who have died from falling off things) odds . . . I tell ya what if my neighbor jumps can I have their seat cushion to help absorb impact in my brace position? :) – voretaq7 Nov 21 '14 at 20:42
  • 3
    @DanPichelman Even that isn't a certainty. Ejector seats are carefully designed to blast you clear of the plane; regular parachute jumps are done at low speed and often from a door at the rear of the plane; test flights of commercial planes have an escape hatch, again designed to guide people clear of the plane. None of these conditions is likely to be met in a situation where they weren't deliberately made to happen. You don't want to jump out of the plane and turn into a very large bird-strike. – David Richerby Nov 21 '14 at 22:04
  • @voretaq7 hey I wasn't saying it was a good strategy, just that a few have made it work :p – Jon Story Nov 21 '14 at 23:35
  • @voretaq7 just to play devil's advocate, air resistance will slow a person down more than it would slow a 747 down in the time before hitting something solid :) – hobbs Nov 22 '14 at 01:59
  • 2
    @hobbs That's true, though it depends on when you jump. (Of course if you jump out high enough that air resistance will substantially reduce your forward velocity you'll now have your freefall velocity to contend with, which is usually enough to have you make a mighty SPLAT when you hit the ground…) – voretaq7 Nov 22 '14 at 06:03
3

No, jumping out of a plane just before it crashes wouldn't help you, for the same reasons that jumping off the floor in a free-falling elevator wouldn't help you.

Community
  • 1
David Richerby
  • 11,875
  • 4
  • 46
  • 86