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I understand that this will vary depending upon the equipment used, the bodyweight of the jumper, barometric pressure etc, but what is the approximate equivalent height of landing from a parachute jump? I have heard people say the impact is equal to jumping from 6 feet up onto the ground - and yet I have seen members of the Red Devils land seemingly as easily as stepping off a kerb.

(Mods: I have seen this question which is why I ask here, please relocate to the appropriate SE if off-topic)

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  • $\begingroup$ Surely depends on your horizontal speed too. $\endgroup$
    – user
    Oct 7, 2017 at 23:10
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    $\begingroup$ Don't forget then those most likely to use the classic round chute these days (paratroopers), are usually carrying gear -- up to 150 pounds worth. Load up and then jump from 6 feet; it makes a difference. $\endgroup$
    – Brock Adams
    Oct 8, 2017 at 0:09
  • $\begingroup$ Can't you stop almost all your velocity with a correctly executed flaring? Most modern parachutes allow you to control your lift. Do it too early and you'll stall. Do it at the right moment and you touch the ground gently. $\endgroup$
    – vsz
    Oct 8, 2017 at 9:16

2 Answers 2

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As you have intimated in the question, how hard you hit the ground is very dependent on a number of factors.

When I did my training to jump using a classical tethered round chute we practiced landing from a platform of about 5 feet, so six is perhaps a hard landing. That's, roughly, hitting the ground at 12mph.

Folks like the Red Devils typically use an parafoil chute. Basically a self inflating wing. These can be steered and pitched upward to bring the trooper to a stall or even go up if they have enough forward velocity. So yes, you will often see them stop in mid-air and step down. This means this type of parachute has NO equivalent jump height. In fact if flown incorrectly you can crash into the ground at serious speeds.

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Regular "military style" parachutes provide no control over lift and only minor control over direction. With these your descent rate is totally dependent on size, weight and air quality.

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Interestingly, with a regular chute, what makes landings "harder" is not so much the effective height but the amount of horizontal velocity.

You are trained to drop and roll when you hit the ground to absorb the impact.

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This works great if you have any horizontal velocity to help you initiate the roll. If however you are coming straight down it's not so easy.. and your knees end up in your chest... as I found out the one and only time I jumped out of an aging Cessna. Too much horizontal velocity and that roll gets rather violent.

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There is probably no equivalent, since there's a fundamental difference: when hitting the ground descending with a parachute, you are moving at a constant speed, with zero acceleration, but when you hit the ground after jumping from a given height, you're moving at a speed that increases with time, since your acceleration with respect to the ground is not zero, but 9,8 m/s/s

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    $\begingroup$ I think that "equivalent height" is defined based on speed and acceleration is neglected, i.e. "you hit the ground with the same speed you would have if you were jumping from an height of X" $\endgroup$
    – Federico
    Oct 8, 2017 at 6:54
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    $\begingroup$ @Federico When you hit the ground after jumping from a given height, you first touch the ground with your feet, that stop moving at once, but, at that moment, your chest, arms and head, to cite the most distant anatomical structures, are still increasing their speed. As a consequence, the landing sensation is different. In my experience, landing with a parachute is different, very different, from landing after jumping from a given height. I think that most people having experience with parachute jumping will believe the same... $\endgroup$
    – xxavier
    Oct 8, 2017 at 7:06
  • $\begingroup$ In that case equivalent jump from which height of a train going at which speed? $\endgroup$
    – Vladimir F Героям слава
    Oct 8, 2017 at 8:35
  • $\begingroup$ @Vladimir When descending with a parachute, you do always have a horizontal velocity component (that may be zero, if it's a calm day). Vertical and horizontal velocities add up as vectors, and the resulting speed may be quite high... $\endgroup$
    – xxavier
    Oct 8, 2017 at 8:40
  • $\begingroup$ I didn't say anything against that, did I? $\endgroup$
    – Vladimir F Героям слава
    Oct 8, 2017 at 8:52

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