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Take an electricity pylon, exit points on either side, both good. True crosswind, straight down the wire.

Ideally, on a short(ish) delay, it would be preferable to jump with the wind blowing from the left so that the pilot chute is blown away rather than towards you. Possibly worse for hand-held over stowed. This has to be considered as the jumper is accelerating slowly to match the velocity of the windmass down the wire, whilst a PC will reach that velocity much sooner (thankfully too! )

At some stage, therefore, the jumper will be moving across the ground with the airmass and so the above considerations no longer apply.

Question is: at what sort of delay does the crosswind effect stop being important?

Answers on a post(card)!

Richard

it depends on how much wind you have

I at some point jumped really high x winds in a SL,on the video you see that the packjob turns 90 degree towards the wind.I do belive that thouse kind of winds would blow any slider off deployments to an offheadding..

But if its a pylon you considder you should most of the times drop by the elektrical wires and therefore it wouldnt be an issue as you then has a overhung A whith no wires on.. giving you plenty(despite the lz and altitude)of time to land at a safe spot..

Just my experience not based on much so read it reconsidder and do what you will about it

I've seen such crosswinds have an effect at two or three seconds even with a pretty mild crosswind (10-15 mph, say). Offhand, I'd say the answer is in the 3-5 second range for most crosswinds...

Of course, there are two effects at play. First, the relative horizontal wind is getting smaller as you get pushed along with the airmass (as you point out). This one would be difficult to calculate. More important, I suspect, is the fact that the relative vertical wind is getting dramatically bigger.

Suppose, three seconds in, you've still got a 10 mph crosswind. That PC is going to take off deviated by less than ten degrees. My experience has been that a 10 mph wind doesn't get a person moving more than maybe 1 or 2 mph i the first rhree seconds -- a small contribution compared to the above.

Edit to add: As noted above, the effect on heading is really much more important -- a fact that supports the observation that a person just isn't pushed that much by the wind in the first few seconds.

So, heading-performance aside, you're saying that the delay (unless going terminal I presume ) makes little difference with respect to the danger of throwing your PC into a crosswind and ending up with a possible entanglement or hesitation?

Certainly I'm saying that I'd be cautious about it right up until three seconds -- maybe a little more -- even with a moderate crosswind. It surprised me how little it took to be on a two-way watching the other guy quickly work a bridle off of his right arm.

Rule of thumb: when your fall rate exceeds the absolute wind speed.

So if you are falling 15mph, and the wind is 5mph, you're in control. If you'r falling 5 mph and the wind is 15mph, the wind is control.

Tom as usual is on the money...dont forget in high winds you will subconciously turn into it as well...which could exacerbate your problem...best bet isif it makes you wonder...either get gus to go first...get him to daisy chain you or go to the pub...

 
>>Since you have exit points on either side of the A, why not do a side floater into the wind? Just exit from the side that keeps your PC hand opposite the tower, and be quick if you have a 90 toward the tower.

Like Tom said, also..
Why not go hand held with the PC in your other hand, the one on the downwind side? Also note that on lighter crosswinds/short delays that one tends to turn into the wind due to the shoulders being parallel to the horizon and and the extraction angled rather than perpendicular.
With stronger winds this can do the opposite.
Easiest to explain is that at lighter crosswinds, you influence the canopy, and at higher it influences you.
take care,
space

Cheers guys.

It was hypothetical, but based on recent experience. I was curious to know what people had observed in such conditions - so that I may continue in my quest for "good judgement"

Do you mean in freefall, or under canopy?

Is potential bridle entanglement only really an issue for hand-held, and not for stowed (good throw taken as a given) iin crossw-wind conditions?

So, hypothetically, short-delay slider down in a strong crosswind from an overhung "A" - would stowed always be preferable?

WTF??

A PROPERLY rigged and executed hand-held deployment ALWAYS has LESS bridle entanglement potential than going stowed.

Think about it Sam; cross-wind from right to left (rather than left to right ). short delay - bridle is being blown over your arm... hence my question.

uhm, OK

I have thought about it.

I have jumped those conditions plenty too.

Who cares if the bridle gets blown OVER your arm? Or even your whole body? I don't, because as long as it blows OVER you it doesn't matter, the PC will pull the bridle up and off you. If you are stable and not flailing, nothing to snag on there.

Whereas if you go stowed and throw even a little low (in a serious right-to-left crosswind), your PC is now going UNDER your body or your arm.

Also fun to watch are people doing their first floaters and side-floaters stowed, many exit way too head high, pitch in the 'normal' direction and end up with the PC going in front of them under their arm. That makes for some entertaining window-washing type arm action.

I have seen plenty of bad pc throws. Why add the additional risk if you don't have to?

both freefall and under canopy..

 

Is it just that a fixed point of reference would appear to be moving (as the jumper moves with the airmass) in a crosswind, and so a jumper subconciously turns into wind to "fix" the point?

Just curious. It was exactly that kind of real experience I was looking for.

You'll have to supply video-footage of the "window-washing" type action though,

my VERY limited experience of jumping in highish winds was that the wind acting on the jumpers body made it turn like a wind vane. i.e. launching head high with wide legs makes you turn into the wind.

on one particular load, the same effect was noticed by both jumpers, there was no noticeable side drift so i don't think it was anything to do with focusing on a fixed point. or a subconscious turn.

the delay was short, about 2 seconds, a further turn in the same direction was observed by both jumpers on opening.

look at the perfect box,then blow at it from the side what happens?
it will rotate as your legs will act like rother. also add that you exit headhigh which is rather more unstabel than if your falling at your belly at full speed..

its not anything i know,its my own teorhy and it aint tested or proved.

One thing for sure is that if you jump high winds(my define of high winds through) down the wire slider off,you rather want your canopy up against the wind(ie looking into a narrow corner) than getting a downwind into the wires,which also could happen..

I have jumped an Electric Pylon quite a bit in cross winds (out of 25+ jumps I would say about 70% of them have been X winds) with exit at 220ft. I have done this in quite high cross winds both from left and from the right, As you can tell from the exit height my delay is not getting much over 1 sec (nowadays) and my freefall speed is not normally higher than the X wind speed. What I have found is that in a pure X wind at low delays my heading openings are "more often than not" on heading even up to quite strong wind speeds, whereas with a slightly longer delay in strong winds my off headings seem to increase. This seems to happen with jumps in the 300+ft range with 2+ sec delays, that I will put the money on that I open toward the wind on those - I put this down on slight turning toward the wind in freefall as 621 mentions so the X wind no longer becomes a pure X wind. (This assumes pure wind and not wind effected from objects in the path of the X wind)

The general rule of thumb I have always lived to is make sure your freefall speed is faster than the actual wind speed...........as anything else will just be a lottery anyway...........

Oh, going stowed at sub-terminal will both help your possible bridle entangle problem and increase your off-headings in a sub-terminal deployment environment......... in my opinion anyway

There was an interesting post on BLiNC some years ago from DW who referenced the "tea bag analogy" about Crosswinds. I have been unable to find it, and hoped that someone has it in their "BASE DataBASE"........

Anyone?
Anyone?
bueller?
bueller?

So you are saying that going stowed while subterminal decreases the chances of a bridle entanglement?

If so, can you elaborate please? It makes no sense to me and I have come across a few jumpers with this misconception. I am curious as to why.

A few other questions also:

- What do you classify as high winds? I would like a number and units here. I know every jumper has different ideas on high winds.

- Were you going stowed in high right-to-left crosswinds from 220 ft?

thanks

Sorry this read incorrectly, I meant it help increase the problem.


Cant really give numbers / units - its just something I judge


Nope, I dont go stowed at low delays / Heights, and most of my jumps are low delays / heights