How do skydivers hit their marks?

I found that the average skydive lasts 5 minutes.

With the earth spinning at 1000mph, why don’t the divers end up in the next county?

Does the atmosphere travel at the
same pace as the ground?

Mostly, yes. Also, practice.

Pretty much. If it didn’t, the wind would be pretty ferocious.

Yeah. The atmosphere travelling at a different pace as the ground is wind. The wind is not anywhere near 1000mph. Skydiving is normally done when the surface winds are relatively light. The jump plane pilot can monitor winds during the climb and the jump point can be adjusted to compensate.

They hit their marks…

Really, Really, hard.

That greasy spot on the corner used to be Johnny.

You’re about to jump out of a perfectly good airplane Johnny, how do you feel about that? Point Break (1991).

Ever been up in a balloon? I have. It doesn’t move at 1,000 mph either, just wind speed. And skydivers can steer better than balloonists.

The technical term for this in skydiver lingo is going in. Or bouncing.

It is really interesting to me that the worst consequence of constant 1000 mph winds that you can think of is skydivers landing one county over.

Here is the NOAA wind scale for hurricanes: I’ll quote the worst:

So yes, the atmosphere for the most part travels at the same pace as the ground :slight_smile:

IANASkydiver (might be something I try one day since looks saner than bungee jumping) but it seems to me I’ve seen skydivers steering somewhat with cords and vents in the chute? Yes, no?


Older military-style round chutes have a pair of vents in the back that gives them a small forward motion. Pulling on one cord or the other changes your direction, thus providing some rudimentary steering. I’ve only ever jumped a few times when I was young and stupid, and on one occasion recall doing quite a bit of steering to avoid both power lines and a railroad track!

More modern chutes are more like wings and have a controllable and potentially considerable forward speed and so are more maneuverable, but take more skill to operate. The other thing that helps jumpers hit their target is exiting at an appropriate location that takes the wind into account. Sometimes a targeting device will be thrown out of the plane first, a small weight with a long, highly visible ribbon of bright material, that helps determine the amount and direction of wind drift.

Wind drift indicators (those long brightly colored ribbons) aren’t used much these days. When they are it’s usually by demo jumpers at, say, a sports stadium where alternate landing sites are limited and landing in the designated area is a priority (gotta please the crowd). Landing off-site isn’t a big deal on a typical jump. Most drop zones are located at airports away from town and surrounded by open fields. You might have a long walk back to the hangar but most of the time that’s the biggest problem you’ll face.

Some drop zones still use a WDI for the first load of the day if they are dropping static-line students, but the static-line training method is becoming less and less common. AFF (accelerated free fall) is more prevalent. That’s where the student is taken higher and is in free fall on the first jump, accompanied by two trained instructors who hold the student stable until deployment time. It’s more expensive than the static-line method but a student can be cleared to jump on their own in as few as seven jumps.

As Richard Pearse mentioned, these days the pilot can monitor conditions on the ride to jump altitude and select the exit point using GPS. Spotting, where a jump master opens the door, locates the airport and decides when to jump, is becoming a lost art. Even with GPS, landing off-site is not uncommon, especially at larger drop zones with bigger airplanes. Twin Otters are popular and they can hold 22 jumpers. If they are divided into 5 or 6 groups who allow a few seconds between exits they can get pretty spread out. But as I said, most of the time landing off-site isn’t really a big deal.

And a really nice feature is that you can flare out on landing so that your downward speed is really small, or even zero. You couldn’t do that with the old round chutes.

One interesting consequence: the fastest passenger planes (commercial jets) only achieve about 500-600 MPH airspeed, meaning that if they fly into the wind, they’ll have a negative groundspeed. They’ll reach their destination eventually, but only after moving backwards the long way around the globe.

One the plus side, if your destination is downwind, you’ll get there at 1600 MPH instead of 600 MPH. :cool:

Just don’t flare too high or you’ll find your downward speed increasing again when your canopy collapses!

Modern sport chutes also have much greater forward speed and glide ratio than did old ones. So for any given drop point and altitude in any given wind, a modern chute can fly to any touchdown point in a much larger circle than could the older chutes. And can correct for a larger amount of unexpected wind.

Which means the required precision for exiting the airplane is much sloppier than it once was.

Because the maneuverable, high performance canopies of today have greater range, traffic problems near the landing area can result. When 22 (or more) skydivers are trying to make it back, coming in at differents speeds from different directions and altitudes, collisions occasionally happen. It’s easy to lose track of other jumpers in 3 dimensional space.

Most drop zones have established traffic patterns similar to aviation- typically a left hand pattern with a down wind, base and final approach. It can still get crowded when everyone is coming in at once. I never minded walking and I usually had a bigger, slower parachute so I would often land a bit farther away and let the zippy little canopies fight it out.

My experience was from around the mid-70s, so no surprise that a lot has changed, thanks for the info. Newbies like me were all static-line until at least (IIRC) ten jumps. I actually don’t remember if the WDI was always used, or just on initial jumps, but I do recall it being used a lot. The drop zone was basically in open country so in general there was no huge problem in being off target, other than obstacles like the ones I mentioned that you might have to steer around. There were also rumors about irate farmers when an errant jumper landed on his crops, but I never did that or encountered any farmers bearing pitchforks! :smiley:

You can do some pretty cool stuff with a modern parachute, skill, and balls.

On the negative side, these planes (along with passengers, crew, and airport infrastructure) will be ripped into shreds before even getting off the ground.

Actually, I’m guessing human beings wouldn’t exist in the first place :slight_smile: