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Comment by Implicated | Hacker News Reader

Why are they breaking legs/vertebrae upon landing? I assume it's due to the velocity in which they hit the ground - but having parachutes I'm not sure why.

Anyone have insight?

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I think just the ejection force can break bones if you are unlucky. A friend of mine had to punch out of a Harrier at low altitude. When he got out of the infirmary months later he was 2cm shorter from vertebrae compression than when he joined the RAF.

AFAIK traditional (WWII) and most military type of "round" parachutes come down "fast", much faster that what you may be used seeing in modern videos with "sport" rectangular/directional parachutes, where they can "brake" and practically land while practically at a standstill.

Paratroopers have some intensive training, and the standard is to land with a sort of somersault, see this (British Army) video:

https://www.youtube.com/watch?v=Lu2f1u928xk

exactly to minimise the risk of fractures, see also:

https://en.wikipedia.org/wiki/Parachute_landing_fall

Probably pilots (that may have additional issues with the G suit and the seat) cannot in many case do the same.

And also many "normal" users may fail at making a "good" landing:

https://en.wikipedia.org/wiki/Parachuting#Most_common_injuri...

I was a civilian student sport parachutist in the late 80’s before square canopies were in widespread use. We used Vietnam-vintage ejector-seat round parachutes that were modified to include a ‘double-L’ hole on the rear panels [0]. This created forward motion and gave some steerability, albeit at the cost of increasing the sink rate. We always landed with a parachute landing fall because the downward speed was a potential ankle-breaker. Basically you kept your feet and legs together, and as you came in the inevitable lateral motion automatically dragged you over sideways, and you could roll back on to your feet. I landed about 70 jumps, and by the time I stopped I could achieve good accuracy in low wind conditions (landing within a yard or two of a target after deploying at 2500 feet).

[0] http://www.parachutehistory.com/round/combo.html

I think it's the set of compromises. You'd want a round parachute because the pilot might be unconscious for some or all of the descent - but that makes it harder to control the horizontal velocity.

I'd also think that an ejection being unplanned matters. Skydivers and paratroopers can try to plan their drop zones, while pilots can't. (There's a famous story of an ejection from an SR-71 where the Pilot wasn't sure which of about 5 different states he was in.)

Pilots are probably also a lot less experienced with landings than skydivers would be.

As I recall from my 1 solo-ish skydiving experience: The standard rectangular parachutes let you move at a max of 20mph (or km/h?). And that's relative to wind. If the wind is 21mph, you can't go against it as an amateur.

I figure the round chutes are even worse at this, so you could be forced in one direction against your wishes.

From what I can see here: the chute deploys as soon as you eject at some hundreds of mph. It's probably big and therefore not very controllable.

Finally, I think you land in the seat, so it's hard to control your landing.

I believe the chutes are set not to deploy above 15,000 feet. Also, many of the ejector seat have a seat-man separator motor so you don't land in the seat.

I think ”Legs may get broken, vertebrae may be compressed.” doesn’t just refer to the sentence immediately preceding it (”you and the seat part company, and you land—hard”), but to the entire paragraph, starting with ”Ejecting at up to 65,000 feet from an aircraft flying at 700 mph is a violent process.”

Having jumped out of a plane exactly once, the speed at which you approach the ground is actually still pretty fast even with the parachute purpose-made for beginners. I imagine also being strapped into a 200lb chair complicates landing gracefully as well.

The seat is designed to fall away after the parachute deploys.

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