The High "A"

[Lee846 0]

Hello everybody!

We just came back from the new A. It's 330 m high and has the 6 levels of wire cables attached to each of 4 corners of construction.
It's athumn now in Russia and weather isn't good.
We just wondered how strong was the wind on the top of that A. It began on approx. 70m and turned down the wire on approx. 120m.
2 days we've been grounded by the rain and finally made the decidion.
The canopy performance wasn't enough to land on the tight area under the wires. Another landing area was far away from the A, but it was possible to get there upwind after the very conservative delay.

The jumps went great, but we have a couple of questions now.

We want to know your opinions, guys!
What wind conditions make it non-jumpable?
What wind conditions are perfect for such objects?
Does anybody have the acidents on such objects like antenna strikes or canopy malfunctions? Was that related with the wind conditions?
Please, tell as about your sub-300m A experience.

Between two evils always pick theone never tried

[outrager 6]

Yo !

This is something i have posted on the subject on Blinc some time ago. In your case with 4 sets of wires you only have 90 degree sector to work with, instead of 120. Be very careful!!!

>"stronger the wind the higher necessity for the wind to perfectly bisect the wires"

This is a very common misunderstanding about antennas. Let's have a look:

The most dangerous condition is no wind at all (just when it feels so peaceful and safe...). After an off-heading opening you will be flying towards either of the wire sets at your canopy's speed in brakes.

Any wind down the wire is a much better case. If you open facing the downwind wire, you speed vector towards it is still your canopy's forward speed. If you open facing the upwind wire you are flying roughly at your canopy's speed minus the wind speed. Stronger the wind, safer you are. In a strong wind (at or above you canopy's speed) exiting almost parallel with the upwind wire (0..30 degrees off) gives you the most safety margin: 90..120 degrees free sector on the downwind side. The upwind off-heading is safe because you have no penetration and/or your canopy will be backing up. You will also open a bit further away from the downwind wire.

Obviously, the safest situation is a strong wind exactly between the wires.

Draw yourself a little picture with 3 lines at 120' angles representing the wires and 2 vectors representing speeds and directions of your canopy and the wind. Add these 2 vectors and everything will suddenly make sense. If their sum is pointing away from both wires no matter what direction is your canopy, you can throw a monkey off safely. Otherwise some prompt steering response will be required in case of an off-heading opening.

You must consider the wind at your opening altitude - NOT at your exit point. The wind will frequently turn as you climb up (usually to the right in the Northern hemisphere and to the left in Oz). Sometimes it turns enough to cross into another sector, and will be a big mistake to follow the wind and exit on the wrong side of the wire.

bsbd!

Yuri.