Reducing Malfunctions - Sub-terminal Slider Up

[jimjenningsmpa 0]

I am trying to reduce the chance of my friends and myself hitting the object on subterminal slider up jumps by reducing the probablility of severe off heading openings and/or openings with line twists. In light of some new evidence... I have a few theories bubbling up in my head. In order to develop and test modified equipment I could use your help. To confirm these SLIDER-UP theories and move forward in the testing phases, I would appreciate some feedback on the following severe off-heading and/or line twist questions:


I. EQUIPMENT CONFIGURATION (slider up only) -

1.) Slider size (was it a larger/smaller than recommended by
the manufacturer slider) and type (small/large hole mesh,
sail/modified sail)?

2.) Slider Control? (single/double rubberband direct control,
indirect control)?

3.) Canopy brand and type (vented/unvented/ZP/F111)?

4.) Pilot chute size and type (ZP/F111/Vented/Unvented)?

II. MALFUNCTION (slider up only) -

1.) Malufunction (Severity of off-heading, number of line
twists)?

2.) Outcome (Object Strike? How was the sitution dealt with?)


III. WIND CONDITIONS AND OBJECT SHAPE - the goal here is to try to
determine the effect of wind during the opening i.e. were
rotors or turbelence a significant factor by figuring the...

1.) Strength of wind (mph)?

2.) Quality of wind (turbulent/clean/consistent)?

3.) Direction as it relates to the object?

IV. THE JUMP

1.) Length of delay/useable altitude ?

2.) Stability, or body attitude, at deployment?


For instance...A few years ago I jumped a nice little 800' cliff in the AZ desert. I was jumping a vented 265 FOX test canopy outfitted with a multi and a normal size (for 265) large hole mesh slider directly controlled on the C lines - each doubly wrapped. I had a 38 inch zp pilot chute. The constant 10 mph wind was from the NE hitting the cliff face at a 45 degree angle coming from my left. The cliff formation has a buttress jutting out about half way down on the right hand side that continues to the bottom. After sitting up top for nearly two hours, the wind appeared to be declining,and wanting to get on with the trip, I decided to jump.


I chose to do a shorter delay to avoid being pushed downwind into the buttress on my right in the event of an off heading in that direction. I did a 3 second delay flat and stable, deployed and looked up at my canopy as it opened into a 450 degree off heading to the left. My body coninued to spin as I was heading directly toward the buttress downwind. I impacted the top of the buttress with one full line twist about 4 or 5 seconds after inflation, pulling on the brake lines through the twist to lessen my inevitable impact. I continued over the top of the buttress and into another cliff area, unspinning, bumping and scraping my down the sheer cliff, landing at the top of the talus without serious injury.

After studying the cliff shape, the winds, and my experience. I determined a "whirlwind" was created by a combination of the shape of the object and the winds from that angle, causing the severe offheading with line twists. In hindsight (as pointed out to me by some more expereinced jumpers), I should have taken a longer delay to avoid the whirlwind, or not jumped at all. Equipment configuration may have played a part in the severity of the off-heading. Ironically, about five minutes after I jumped my partner up top reported that the winds had died down to nothing.

The canopy suffered three cells and the stabilizer ruined and three lines broken just below where it attaches to the canopy. I landed with only one bump on my foot from the initial impact on the top of the buttress. Helmet, knee, and elbow pads definately helped reduce injuries.

By investigating malfunctions we can hope to reduce their occurence. Please take a few minutes to tell us about your sub-terminal slider up malfunction experience. At the very least, please list canopy size, brand, and configuration.

Thanks,

JJ