Jul 19, 2001, 12:16 AM
Post #1 of 14
I thought the jump run order case was solved and the jury's verdict was is in but, it seems some DZ's have other ideas. Recently I visited Empuriabrava in Spain (the Perris of Europe) and another well reputed French DZ. They were both putting freeflyers out before RW loads. Twice I had RW four ways drop all around me. Granted, at Empuriabrava the run in is always north, becasue they can't drop people over the town (no outs), so when the wind is from the sea, it's fine. But when the wind is from the north, they still put free flyers out first so everyone ends up over each other. Should freeflyers have to dump lower than usual to accomodate this policy and stay safe? Do some DZ's not get or read the articles and studies about jump run order? So until things change, it seems like people should watch out for the drift when you jump some places in Europe. Anyone know anywhere else they put tandems out first, then freeflyers then RW? And what is their reasoning?
I'a a flat flyer and I've been in this situations (close to others, bot flats and head downs) with both configuration: FF 1st or last.
I think the key is to make sure there is adequate seperation and not to track along the jumprun (Empuria has clear rules for tracking). I know there's been some studdies into this, and I've never really agrred with the validity of the assumptions that were used in them (its been a while, cant remember what they were). In the end, take it upon yourselft to make distance...
And I've been to US DZs that swear by both rules (FF 1st or last)...
Other than that it is a great dropzone. And yes, of course they do have rules about tracking (same as anywhere else). However, on the seperation note, you don't always have control of those jumping after you. Especially when you get those guys at the back that like to shout, "Go, Go" and goad less experienced jumpers into leaving too soon because they are worrying about a long spot. So I still say, read the winds, talk to people and watch out.
Jul 19, 2001, 6:09 PM
Post #6 of 14
I recently looked at a study with animation and everything on this. The general theory being that a FF spends less time in a given altitude therefor is less affected by the winds at that alt. hence less lateral drift. Now this does not take into account the Jump run heading relative wind direction and any jumpers actions while in free fall. (Like the ability of a free flyer to attain much higher horizontal speeds) Geoff= sorry about you having to thread through but if someone comes through your canopy right after opening that will be the last thing on your mind....Know what I mean Vern?
If the RW jumpers are drifting over you in freefall, then there is definately not enough seperation. Freeflyers may have a little less drift, but not that much. Differences in drift would seldom push an RW jumper over a freeflyer unless they started out way too close. It would take some serious wind gradients for that to happen, and is not your everyday conditions. If those kind of conditions do exist, then that information should be as important as the wind velocity and direction on the ground, and extra seperation should be used.
Not to say that this is right, but I believe this is the reasoning to sending out freeflyers first. If RW goes first, he falls slower and a freeflyer exiting after him could pass through him in free fall. Also, typically the freeflyers open at a slightly lower altitude.
There has been HUGE discussion over on wreck dot (that's rec.skydiving) in the past on the whole thing, if you did a search over there, you would see the endless arguments. the animation on http://www.omniskore.com/ is from a college professor (physics). There is also a really good article written by Bryan Burke on the subject there. It is the current accepted practice to put belly out before head down in an upwind jump run condition. In a cross wind scenerio it really doesn't matter. Of course the perfect jump run is a 360 degree circle .5 mile radius from the "correct" spot. some flat flying groups can cover huge amounts of horizontal distance - tilt a formation a little sideways and off it goes. The short story is horizontal seperation is the key.
Weid14....Exactly, seperation is the key. Also God gave you two...not one but two eyes to scan below and above you. I dont know if it's just bad luck but lately I have had to avoid jumpers while in free fall. One jump I had one below me. I had given a nice 7 sec seperation but he still ended up below me (sitflyer). I tracked and dumped avoiding him by about 100-200 ft lateral. The other was a flat flyer above me Sunday. Luckily I FF most of the time and have ample opportunity to clear airspace both above and below about 1,000 ft prior to pulling. Something I hope everyone is doing.