Jump 456 Debrief

Skydance 09-13-2025

Hi so ... I figured that since I organized the jump, I owe you a debriefing. This was a really fun jump and thanks for jumping with me! I was not sure really why it did not go as planed but once I saw the video, I think I understand a little better. So here's my take on what we could learn from the jump.

The Exit

Forgive me if you have heard this before but when you get out of the plane, down is not really straight down. We fly a parabolic arc for a while since we have some forward momentum (the plane's speed) and gravity pulling us down. So we start with about 85 MPH in the horizontal direction (V_h) and no speed in the vertical (V_v). Once we get out, the air friction slows down our V_hwhile gravity speeds up our V_v. So we end up on a flight path that is slowly changing from forward to down. Therefore, in order to fly stably on this path, we need to have our bellies perpendicular to this path when we let go of the plane and we should expect that angle to slowly change from a forward facing direction to a downward direction. What adds to this difficulty is that 85 MPH is not really much wind and so your normal control surfaces of your body have less effect until we fall far enough to reach terminal velocity. This stuff makes exits challenging.

In a 4 way group, the names of the positions correspond to the place you are in the door. Point (Yeheun's position) is towards the point of the plane. Tail (Ana's position) is towards tail of the plane. Inside Center (Seth's position) is the person inside the plane in the center. Outside Center (me) is the person outside in the center. In a 4 way exit, those three outside people want to exit is such a way as to lay themselves out on that imaginary slope we call the "hill". To do that, you want just a split second difference in the time each of them let's go. You want the outside center to count and leave right on "Go". The Tail, leaves just a little early, like just as the knee of the person giving the count turns to go the outer direction. The Point leaves just a little late, like almost letting the Outside Center pull them off the plane a little. The Inside Center wants to push on the Outside Center so that he is out the same time as the Outside Center. Staging the exit this way will lay everybody out hopefully on an angle matching the hill's angle.

Looking at the above picture, it seems like we did just the opposite. The Point left a little early, the Tail left a little late and the Inside Center is still on the plane. LOL! Now I admit, I could have reminding everybody of this when we were dirt diving. And I probably told Seth to "just dive out" but I did not say when. I almost never get to organize, so this is where I get to learn.

The Hill

In this picture, you can see that Seth although he left a little late, he is belly to the wind which is great. You can also tell that the plane is moving away from us which means we are slowing down in the horizontal direction. But look how far Seth is behind us! We are really accelerating downward. He is at the beginning of the hill and we are about half way through it.

In this picture, I think that since Yehune has a good arch, we can tell from that where the hill is currently. Ana and I should be more in that orientation. What is happening now is that since I am falling sideways, there is a burble starting to grow behind me. Soon, Ana is going to fall into that burble and flip to her back and loose altitude. And again, you can see we are in the wrong order. Point should be high and Tail low.

Freefall

Yehune is still in a good arch, you can tell that we are off the hill now by her orientation. Since I am below Ana, I am stealing all her air. Because of that, she has no lift and no control and hence flips to her back since she is still holding on to me. At this point of the exit going wrong, it might be better for the sake of control to all let go, get clean air and try to regroup. We might actually loose less altitude doing that. It's hard to give up trying to fix that exit though. I'm still holding on and should not be.

Finally, I let go of Yehune. Now, I am in Ana's burble and we fall below Yehune.

The Video

For the rest of the dive, it's easier to see on the video what is going on.
0:20: It's great to see Kurt, a very seasoned jumper, still practicing his EPs on the plane.
1:11: After the door is open, it's the best time to spot. It seems like Ana and Yehune are just watching for the green light. Eventually, they spot after the green light is on. Trust the pilot, but verify. :-)
1:57: Great recovery by Ana, getting back up to level with the rest of us.
2:01: Ana is so close but attempts to doc when she is just a little high. Remember, there is a swirling vortex of doom right above my back called a burble and it wants to drag you in to it! Got to be on level to dock.
2:11: I think what happened here is that Yehune did a great job of tracking to get to the formation and on level, but tried to use the dock to slow her down. Bring your legs in to slow down before you get there.
2:12: The docking with speed put a lift and twist into her trajectory sending her over Seth on her back, so that his burble curved her path down between us. Weeeee! LOL.
2:19: Ana comes in to dock, but I think Seth and Reed move down and turn just as she gets there. You can't see it in this Video, but in the 360 version, you can see Seth's legs going quickly from flat, to knees bent just when she gets to us. The base should be trying not to move or turn so that we make ourselves an easy target to dock on.
2:20: While Ana is getting ready to try again to dock, Yehune flies under her. So Ana falls into her burble, hits her leg and spins Yehune so now she is pointing away from the formation.
2:30: Break off time, but Yehune pulls in place. This turns out perfectly fine and safe this time. But pulling in place is usually reserved for photographers. Unless this is a solo, we should be in the habit of always tracking away from the center of the formation before deploying just so that everyone knows what to expect. In general, there is nothing wrong with pulling in place, but it should be planned for during the dirt dive. Because, here's the thing: if two people during the break-off decide to pull in place, then we have a problem. So always communicate before you get on the plane that you plan to pull in place, not at break-off.

Summery

Thanks for reading this through. I know its a lot of words. Not that a lot went wrong here. A lot went right! Nobody got hurt and it was a lot of fun! But skydiving is an expensive sport and I think we should try to get as much learning out of every jump that we can. So that's why I am pointing out every little thing. This was not a bad jump at all! I've seen much worse and been the cause of much worse. And, take this all with a grain of salt because I am not a coach nor an instructor. I'm just a B-License guy that just happened to be the most experienced guy on this jump and felt like analyzing this one to death! LOL.

So some points to remember from this one:

Be like Kurt and practice your EPs on the plane. I'm not saying anyone did not, but he is such a good example, had to point that out.
Spot when the door opens before the green light is on. Sometimes a pilot will turn that green light on way early!
Work on the exit timing: Tail first, then centers, then point.
Let go if the exit is not working.
LSD Level Slot Doc. Don't try to doc too high or that burble of doom of the guy next to you will suck you in!
Be mindful of the burbles. We burbled each other about 4 times on this jump! Avoid the burbles!
The base should be stable. Try to be an easy target and predictable so that others can dock on you.
At break-off, track away from the center before pulling unless something different has been agreed upon before the jump.

Thanks for the Jump!
- Reed