why my main parachute spun violently

[ethan_tan 0]

Today 2019-11-03, I had my 1st cutaway at jump 93. I was doing belly in a 6 way. Separated at 5500ft, tracked and then deployed.

 

My main started spinning right after opening. The spinning was violent as you can see in the video. I did not have time to pull toggles and I cut away around 2700ft.

 

After the jump, The rigger at my DZ and I found the main parachute and confirmed that toggles are perfectly set at that time. We checked the main and there are no tension knots at all. So toggle fire and tension knots should not be the reason for spinning. It makes me really uncomfortable about jumping in the future because I do not know if the mysterious spinning will happen again. I would like to ask other skydivers for ideas about the spinning. Many thanks.

 

Main: Pilot 168 ZP

DOM: 2018-Oct, 50 jumps on it.

Wingload ratio = 1.15

 

Edited November 3, 2019 by ethan_tan

[davenuk 7]

hmm, looks kinda pulled down on the left. is this what a tension knot would cause? 

[gowlerk 1,903]

I don't know what caused your malfunction, but tension knots are still a real possibility. That is the the nature of tension knots. Once you cut away the tension is released and so is the tension knot. Of course the other possibility is a line over. Do a careful examination of the topskin of the canopy to look for signs of line burn. The friction of a lineover will nearly always cause some damage.

Edited November 3, 2019 by gowlerk

[pchapman 261]

 One gets a somewhat decent view of the canopy in that video from the other jumper. (Even if it gets a bit confusing with full speed, zoomed, and slow mo at different times.) The canopy does look pretty symmetrical; looks like brakes set as you confirmed later.

Could still be a tension knot; they don't always cause a big deformation in the canopy. Could it have been an uneven opening sequence that snapped the canopy into a diving turn as it took flight?  Although Pilots especially at low wing loadings are fairly stable canopies that don't use a lot of brake on opening, so I would have thought they would naturally pull out of the spiral on their own fairly quickly. (You could test that some time, pulling risers to spiral with brakes still set after opening.)

Sometimes one just doesn't know what the mal was, if one didn't have time to look at the canopy closely or have video. At 2700' one still had time to grab risers or toggles to try to slow or stop the spiral. But just plain chopping when you are spiralling down after opening is perfectly OK too...

 

[ethan_tan 0]

4 hours ago, gowlerk said:

I don't know what caused your malfunction, but tension knots are still a real possibility. That is the the nature of tension knots. Once you cut away the tension is released and so is the tension knot. Of course the other possibility is a line over. Do a careful examination of the topskin of the canopy to look for signs of line burn. The friction of a lineover will nearly always cause some damage.

thanks for comments. I looked up the canopy while spinning, and it was square (no obvious line over).  I pumped my riser twice before cutaway but it did not help. 

I rushed my pack job for this jump and probably I made some packing error(s). What would typically cause tension knots in packing? I always un-twist my brake lines in the last pack job of every jump day. I am trying to figure out how to prevent it from happening again. 

Many thanks.

 

[ethan_tan 0]

2 hours ago, pchapman said:

Could it have been an uneven opening sequence that snapped the canopy into a diving turn as it took flight? 

Thanks for commenting. This is possible. I single-stow the rubber band and I use a semi-stowless D bag. I probably should have double-stowed the two rubber bands on my D bag. I remember I have read a thread mentioning single-stow could result in out-of-sequence releases of rubber bands. 

Thanks again for answering.

[20kN 93]

13 hours ago, ethan_tan said:

Thanks for commenting. This is possible. I single-stow the rubber band and I use a semi-stowless D bag. I probably should have double-stowed the two rubber bands on my D bag. I remember I have read a thread mentioning single-stow could result in out-of-sequence releases of rubber bands.  

Thanks again for answering.

Bag strip (the mal you're talking about here) does not cause spinning canopies, it causes an explosively hard openings that can seriously injure/ or kill from the opening shock. If you had bag strip you'd for sure know it. My best guess is tension knots. Actual examples of knots in the lines is rare with tension knots. Usually once you cut away the knot disappears and so you're left with a canopy floating to the ground that has no malfunction in it. Tension knots are not typically caused by packing, they are caused by twisted or worn lines combined with bad luck. The most common place to get a tension knot is at the cascades on the brake lines which is why untwisting your brake lines is important. Highly worn and fuzzy lines tend to get tension knots more often than new, slippery line. Some would argue that careful stowing your lines will prevent tension knots, but my argument is that the only things known for sure to reduce the risk is untwisting the brake lines and keeping the lines in the best shape possible relative to their jump numbers. Other than that, it's a malfunction that's largely based on luck.

Edited November 4, 2019 by 20kN