• Uspa Sim 2019 Pdf

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A subreddit for those interested in skydiving and BASE jumping.Skydiving is a highly addictive sport which has been known to cause loss of money, wuffo friends, and all of your free time. Viewing this subreddit is likely to cause the need to skydive. We can not be responsible if you spend all your money at the dropzone because we are doing the same! RULES:(violating these will get you banned).Be civil and please refrain from name-calling. Skydiving is already full of large egos, we definitely don't need that on the sub.Do not request or give medical advice. We don't know you or your history, your doctor does.No graphic depictions of BSBD. We know it happens, we don't need to see it.

Discussions regarding an incident are allowed after a certain time but please stick to facts, speculation helps nobody. We must learn from an incident, not just gossip about it.No blogspam. If your video contains the words 'like, share and subscribe' or any variation thereof, do not post it. We'll be happy to watch your skydiving video, we are not interested in everything around it.No suggestions of safety violations.

Suggesting pencil packing, altering logbook records, or anything that violates any BSR or FAR will get you a permaban.FAQs:Questions about your first jump?Before asking in the sub, please read our FAQ.Want to become a skydiver?Awesome! Read our FAQ (coming soon).Four-way head down?Read our to decode our language. This weekend, a pilot told me that the common belief that groundspeed determines exit separation is BS, and that all that matters is air speed. His argument was such: Imagine exiting a plane at 100 kts groundspeed vs exiting a balloon at 100 kts groundspeed. Would you leave 6 seconds, according to the chart? Of course not.

Airspeed is all that matters for opening separation between groups.I agreed he had a point, but it somehow still felt wrong, mostly due to different wind speeds at different altitudes (e.g., nobody jumps from a balloon if they are gonna land in 100kt winds). Maybe we should use the difference of airspeed at exit vs. The wind speed at opening instead?We don't open at ground level, so why does ground speed matter?. Are people still arguing about this.

Uspa Sim 2019 Pdf

This horse has been beaten to death, beaten some more, resurrected by the devil himself and then beaten again. Airspeed matters oh so very much. Someone even built a cool little program where you can play with the numbers.Think of it. If the plane had 100kts airspeed into a 100kt headwind. Ground speed 0. Your are jumping from a stationary point over the ground. Wind near the ground is 0kts.

Everyone will open at the same point over the ground. Add variables like flat vs free.

Canopies that fly up jumprun. Tracking and it gets even messier. Oh yeah and to kill the other myth. You will NEVER reach 45 degrees like the old times used to say.edit: Fixed link to simulator. Agreed on all points.I think of it more intuitively like this:You have an arcade machine that has a moving mechanical arm dropping plastic skydivers onto a conveyor belt. There is a fan blowing air across both from the side. The arm moves at some rate equivalent to the ground speed of the plane.

The conveyor belt moves at the ground speed of open canopies, which is basically equivalent to air speed at opening. The fan is blowing air equivalent to the wind speed at altitude. Now - you want to drop the plastic skydivers from the arm onto the conveyor belt with good spacing. Initially suppose the plane ground speed is zero - the arm does not move - and the conveyor is also stationary - equivalent to zero wind speed at opening altitude. No matter what speed the fan runs at and no matter what rate you drop them at, all the plastic skydivers will end up at the same spot on the conveyor belt. The fan speed only changes how far they all blow, but they land on top of each other. Now start the conveyor belt moving - and now they are spaced at some distance set by the conveyor speed and the drop rate.

But still independent of fan speed. Move the arm at some rate opposite the conveyor direction and it increases the spacing further - but still does not depend on fan speed. It only matters what the relative speed of the arm is with respect to the conveyor.So in summary, and to echo the conclusion of the dropzone article - take the ground speed of the aircraft and the wind speed at opening altitude and add them together if they are moving in opposite directions and set your time spacing accordingly. Of course the upper wind speed does determine the ground speed of the plane, so that's the reason you need that data.With the balloon versus plane issue - there is no wind flowing past the balloon. But so long as the balloon is moving relative to the air flow at opening altitude then you will have spacing. This is still not understood by hardly anyone at my DZ. I even wrote my own simulator, to show people.

Not as nice graphics as the one above, but I can change any variable to show what scenario I want.Speaking of why the myth endures: The notion that the DIFFERENCE in wind speeds at different altitudes effects the separation between groups, and NOT a total constant wind speed, same at all altitudes, has alluded basically everyone. It does not help that the 'Welcome to your A-certificate'-magazine new jumpers get has a faulty explanation of the physics involved, even though the conclusion is correct.The second point: I still hear new jumpers talking about the 45deg rule. And I'm sure as hell they did not come up with it by themselves. It infuriates me. I managed to change some minds, but not the minds of the old dogs telling people to do it.

At least they put out their head and look out the airplane, and think about exit separation. That's something.

I've had a lot of debates with a friend over this, and what we are pretty sure that it's not ground speed that matters, but speed relative to the winds at opening altitude, like you suggest. However, since those winds are typically fairly low, using ground speed is a reasonable approximation that's easy to measure and communicate to people.In your example, if the 100 kt winds continued all the way to the ground, you're right that ground speed would be irrelevant.

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That's because when you open, you will continue to drift at 100 kts so by the time the next group arrives at that same location over the ground, you will be far away. Since the entire air mass is moving as one, ground speed doesn't matter one bit.However, imagine that you have 100 kts airspeed and no ground speed on jump run. These 100 kt winds continue all the way down to about 4000 feet where they drop to zero. No matter how much time you leave between groups, people will take the same freefall path and open in the same place. Since the winds at opening altitude are zero, they won't continue to drift. That means that you will have people opening on top of each other.

This is a more realistic scenario - typically (at least where I jump), even when you have really strong uppers, they are reasonably low at opening altitude. So, using ground speed to determine exit separation is a reasonable approximation. Although your conclusions are correct, the explanation is lacking.In scenario 1 with a lot of head wind, the horizontal separation is the same between groups as scenario 2 (for the same exit time interval), if the wind speeds are THE SAME at all heights.The horizontal separation generally suffers in the scenario with a lot of head wind because the wind is NOT the same at all altitudes. Generally it is lower closer to the ground, where you fly your parachute.I can show you pictures of a simulation I did with the same wind speed at all altitudes (a really unrealistic scenario), and that separation between groups is completely unaffacted. But I fear that it will be misconstrued by people. I can PM it to you if you are interested.