When there’s a group of sky divers holding hands, making a ring or a big formation - how do they join together after they’ve jumped out of the plane? They jump singly, right? so how do they join up? do they “swim” through the air, using their arms and legs?
For big formations they tend to exit in a group, but yes, skydivers can maneuver quite extensively to make a formation. Not “swimming,” but using the shape and direction of their body to modify thier direction and rate of descent. Next time you are driving at speed, put your arm out the window. Put your fingers together and turn your hand. Notice how the air pushes your hand around? That’s what skydivers do. To slow down, they spread their limbs and arch their back. To accelerate, pull limbs together and by side and head down.
Interesting. So that’s how they change vertical speed - how do they change direction horizontally?
Angle of attack. Lean left and theair will push you in that direction. You can get fairly precise control using arms, legs and angle of body, as is evidenced by some of the maneuvers they perform.
Watch this Youtube clip.
You maneuver horizontally by altering the lift on one part of your body. For instance, pulling in the arms and extending the legs will make you go forward (and down); pushing out the arms and pulling in the legs makes you go backward (and down). Tilting your shoulders and/or bringing a leg on one side will make you turn (or if you do it rapidly enough, spin). Maneuvering toward another person can be tricky because of how nonintuitive the motion is; if you’re arched and falling at the same level as another diver, and try to approach them by just going forward to him, you’ll end up underneath him.
You can do a joined egress as silenus describes for a small group–say six or eight, or perhaps even more for a plane with a rear exit ramp–but with much larger arrays they all have to maneuver together, which takes much preparation, practice, and planning, and if it doesn’t come together in a few score of seconds, it’s all done with. Personally, I’d be more than a little concerned to land with such a massive number of other divers coming down at the same time, as most skydiving accidents occur on approach and landing, and aside from broken ankles and tailbones, a substantial number of accidents are the result of two or more skydivers colliding or getting entangled.
Stranger
To put it simply, for horizontal motion the sky diver’s body acts like a very inefficient glider. You can control the angle of glide by adjusting your body in a similar manner to a sailplane adjusting its course with its control surfaces (ailerons, elevator, rudder, etc).
So, rather than swimming, you really are flying… just mostly in a down direction.
Largest formation I was ever on was a 16-way but what I recall is that for the really large loads (we’re getting up in the hundreds of participants) they have designated flight zones for everybody - this quadrant flies and lands here, this other group there, and so on, for precisely the reason you mentioned; keeping everybody out of each other’s way. They also stage the deployments so that the various parts of the formation aren’t all dumping at the same time. If memory serves correctly when they did the first 200-way years ago, one man was the “trigger” at the center, he popped at about 5500’ which was the signal for the various wings to start turning, tracking off to particular altitudes and deploying.
Watch the video I linked to. 400 divers, and you can see each group break away from the formation and head for their designated LZ.
Still, that is a lot of people coming down at once. I get nervous when I see someone a couple hundred feet away from me, and of course, you can’t see anyone above and behind you.
Stranger
Holy smokes. I remember reading about the 300-way a while back and I thought that was huge. When I was actively jumping (1990s) someone did a trend analysis comparing number of current jumpers over time with size of largest formation over time to see when the two would intersect (2027 and it’d be a 15000-way, something like that).
For those of you who haven’t had the opportunity to see a formation build watching from the ground it’s an experience. All these tiny dots coming together in a complex figure and the best part is that you can hear it - the formation makes a noticeable roaring noise as it heads earthward at 120mph, even if it’s 2 miles above you. Go to your local DZ and check it out.