skydivers have the myth of the spin that remains after the cutaway.
... But the physics suggests one does keep the rotational momentum one has at the time of the chop.
This video illustrates the physics of the situation: a puck on an air table rotates about a central point, attached by a string. When the string is cut, the puck departs in a straight line, but with rotation. This is well known physics (at least to those that understand classical mechanics).
I've had a couple of spinning mals on a Diablo -- they spin pretty good, and in both cased my RSL activated my reserve with neither incident nor line twists.
If you're thrown away from your spinning main, the rotation that was happening around your main is going to stop, because the fulcrum (the main) is gone. If you were also twisting (i.e. either the spinning line twists were twisting up worse or untwisting) that component can stay with you I believe.
My first mal was a tension knot spinner on a Triathlon 135 with an RSL. I did open under a Tempo reserve with a couple of line twists that I had just enough time to kick out of and fly back to the DZ from over the woods, a pond and more woods, clearing the tree line with yards to spare after a 60+ way jump.
I had wondered if the line twists were an aberration or if the main with the RSL caused the freebag to make a couple revolutions before the reserve came out?
I'll admit that there are some very specific circumstance where a jumper could have some 'personal' rotational momentum built up that could remain after the chop. That said, I have never heard of a jumper who got wrapped up in a reserve bridle or lineset, the worst I've heard of line twists. To that end, I've also heard of line twists on an otherwise 'clean' cutaway and reserve deployment.
Those very specific circumstance would certainly be some of the most violent, disorienting and high-speed malfunctions, making it the worst possible time to be concerned with trying to disconnect an RSL, and then playing the losing game of trying to get stable before pulling your own reserve.
I maintain that the best course of action in such circumstances would be an immediate cutaway and reserve deployment. Less altitude loss, less disorientation and more time to kick out of any reserve line twists if they should occur.
Let's remember that a malfunction only occurs after you have decided it was time to end the skydive. Your main might have different ideas, but in any case you're going much faster than you wanted to be at the given altitude. Staying on track, and slowing yourself way down should be your #1 priority, and analyzing the nature of your mal and reconfiguring your rig to match is not conducive to stopping anything.
If you feel the RSL poses a real risk, just don't jump with one. If you choose to jump with one, be ready to operate as if it wasn't there, to include pulling your own silver handle and ignoring it unless you plan to land in water or on top of a building.
My friend Dan went in on 8/3/2008 due to a reserve bridle entanglement after cutting away from a spinning lineover. It was around his waist twice, so there was no rolling out of it either. None of us had heard of such a thing before, or since then. I think the odds of that happening are astronomical.
Here is video of 2 chops I had a couple of years ago. The first one was on a CRW jump - so I opened at 12 grand. It was on a Lightning 113, and I chopped at 9k or so. That is why I took a while to try and get stable before dumping my reserve. The rig was a Racer, and the reserve was a Tempo 120.
The second was after an AFF jump - I probably opened at 3500 or so. Sabre 135 - probably was a lineover but I'm not sure. I slow-mo'ed my actual chop as you can see the reserve bridle launch. I dumped my reserve as soon as I cutaway just because I knew I was getting towards 2k. The rig was a Racer, and the reserve a PD 126. The line twists on the PD reserve were so stable I had a hard time getting them out!
So even though both of these canopies are relatively "docile" in the grand scheme of modern canopies - you can see I was clearly getting thrown around a lot on a spinning mal.
That being said - I do believe in RSLs for the vast majority of jumpers. Better to have a reserve with line twists than no reserve at all. I just don't believe that you are instantly not spinning as soon as you chop.
Line twists on reserve deployments are very common. (see my icon for an example) They are no big problem to deal with. The more altitude you have, the better no matter what your problem is.
On the other hand you could decide to mess with your RSL before cutting away. But your cutaway and reserve handles are large and placed in an easy to find and easy to see location. While your RSL bail clip is a tiny device you can find by feel only and is really only meant for use on the ground or under a good controllable canopy on a windy day.
If you feel you may need to disconnect your RSL before cutting away you should not get into the airplane with it connected. It's not designed to work that way. I mean really, most situations that require a cutaway will involve a spinning canopy of some sort. If you are not willing to cut away a spinner with your RSL you should not use an RSL. You need to make this decision BEFORE you jump.
(This post was edited by gowlerk on May 10, 2013, 12:01 PM)
It's a good discussion, but keep in mind that it is speculation whether or not it has anything to do with this incident.
Here is a story that leads to a completely different type of speculation. My last cutaway, several years ago, I had an RSL. I checked on the ground, and on the plane that it was connected. When I cutaway, I was pretty high (~5k ft) so I waited a couple seconds to pull silver. I ended up being nearly knocked unconscious (not really related to this discussion), and because of that didn't think much about my RSL until I landed. It was then that it occurred to me... "why was I able to delay those few seconds?" So I looked down on my rig and sure enough the RSL was still in place with the shackle wide open. I did a lot of digging and eventually found some info that IIRC was corroborated by Bill Booth: the RSL shackle is the "weak point" in the system (weak in terms of bulletproof design, not in terms of force transfer capability) and has been known historically to sometimes come disconnected on its own in an actual use scenario.
So it's completely possible the jumper in this incident had a similar occurrence, and this has nothing to do with midair rigging attempts. The take home from that speculative branch is of course the old "if you have an RSL, don't rely on it."
The take home from that speculative branch is of course the old "if you have an RSL, don't rely on it."
I have the small Wichard snap shackle (same as used for RSL) on my camera wings. There have been a few instances where they've come undone mid jump, even though the spring has been lubed and the pull tab changed out for a smaller tab. Yes, they can come undone.
Cutting away from a spinning malfunction with an RSL gives you a good chance of winding up with numerous line twists on your reserve. It's actually a good decision to disconnect the RSL before cutting away, in that situation, but not if it takes you more than 5 seconds to disconnect it.
The moment you cutaway, you fly away from the canopy feet-first in a straight line. The relative wind is blowing from your feet toward your head.
You can simulate this by tying a weight to the end of a cord, then spinning it overhead and letting it go. The spin ends the moment it is released.
Oh, I dunno.
My limited experience in the matter involved being under a violently spinning main, on my back, with the left steering line half-hitched over my altimeter (I'd tried to clear a lineover).
Since it struck me that I should do something very quickly, but that the steering line could well remover fingers if I wound up hanging under it, I executed a gunslinger cutaway (cutaway and reserve pulled simultaneously).
The freebag cleared the trash with the better part of a foot to spare (judging by the video), and the reserve opened with four line twists. The steering line was twisted up in the reserve suspension lines until I kicked out of the twists, and I wound up landing while still towing the main by the knot around my left hand (I regained feeling in my left ring fingertip about a year and a half later).
YMMV, but I still had plenty of angular momentum after chopping - but I also had plenty of altitude with which to work to get under control and land in one piece.
I have no interest in doing it again, so you will please excuse me for my scanty knowledge of the subject.
P.S.: No RSL, jumping camera on a 1992 Racer.
(This post was edited by winsor on May 10, 2013, 6:01 PM)
But your cutaway and reserve handles are large and placed in an easy to find and easy to see location. While your RSL bail clip is a tiny device you can find by feel only and is really only meant for use on the ground or under a good controllable canopy on a windy day.
Your observation leads to another important point: We lose fine motor control under stress, so because we use our fingertips to deal with the teeny tiny RSL release, doing that in the middle of a malfunction will automatically be harder to do because of that, independently of position, tension, etc.
On the other hand, we do not use our fingertips to deal with the release and reserve handles; we use the larger muscles of the hand and forearm, so stress-related "dexterity degradation" is minimal.
When you add this factor to everything else involved with handling a spinning malfunction, it doesn't seem like a very good idea to me to try to disconnect the RSL in the middle of the maelstrom -- unless you were initially open at 3,500 feet or higher, in which case you would have more time and less stress to disconnect it.
I think the big debate here is because the "you don't rotate after a cutaway" people are thinking in "ideal", 2D, point-in-a-vacuum physics and have either never been in a big-G mal or got very, very lucky when they were.
In the real world, a skydiver with asymmertric mass, asymmetric surface area and drag profiles moving not only tangentially (upon cutaway) to the spin but also with the non-trivial (esp under an HP main) vertical componant and resultant quickly changing relative wind.
And even all that doesn't take into account any delay in the release of each set of risers -- a delay built-in in order to make sure that the (potential) RSL-equipped riser will always release last in order to avoid the RSP deploying the reserve with one side still attached. It may be a very-very short delay, but physics doesn't have a grace period. Unser normal circumstances this has a negligible effect but in high-G situations it doesn't take much to induce a spin
Also... as preciously stated, when someone chops they are released at a tangent line to their rotational disk.. this is NOT feet first... rough sketch: http://cl.ly/image/2k1f3H331d2X Even if you start on your belly you still have all of the above to take into account AND you're not in a particularly non-rotation-producing body position right away. best case... more likely you're on your side or back
You are absolutely true. The rotational momentum of your body (a body that is forced to move in a circle due to canopy) will stay after you cut away and it will keep you spinning after the cutaway. HOWEVER, your rotational speed is not that high that it will introduce multiple line twists. For arguments sake, lets say that a jumper ended up with 4 twists and the approximate time for reserve deployment is 2 seconds. That means that the jumper must have spun around his own axis 4 times during the reserve deployment. In order to do this, the spinning malfunction must also rotate around its axis 4 times per two seconds. That is a rotational speed of 2 revolutions per second. Assuming that your body is 2 meters away from the center of rotation, the G-forces would be in the order of 30 G! I think it is pretty clear that a malfunction does not rotate this quickly and the number of line twists on the reserve has a huge number of other factors (body position, etc.) other than just the small rotational momentum left after the actual cut away.
All in all, yes, the body will have some rotational momentum after the cutaway (this is the laws of physics, so no need to debate this) however, the momentum is too small to have a major impact on exactly how the reserve deploys. Just as a guess, I would say that if the left and right risers release with a small delay, it will introduce a much higher momentum on your body compared to the rotation from the cutaway.
In any case, regardless who is right or wrong on the physics part of this, I would much rather have a reserve with line twists at 300 feet than no reserve at all at 100 feet. The more altitude you have, the more time you have to deal with the line twists, but if you cut away low, you have no choice but to deploy your reserve asap regardless if you have a RSL or not.
Obituary for Mr. Santiago Pedro Rosell Sr Santiago (Sandy) Rosell passed away on Wednesday, May 8, at the age of 62.
He was born on September 11, 1950 in Havana, Cuba, and raised in Miami, Florida.
After earning a Masters of Arts Degree in Communications from the University of Central Florida, Sandy attended Naval Aviation Officer Candidate School, in Pensacola, Florida, and became a U.S. Navy jet fighter pilot. He was aircraft carrier qualified aboard the USS Lexington, and, while flying T-28’s, T2C’s, and A-4J’s, rose to the rank of Lieutenant Commander.
Following distinguished service with the U.S. Navy, Sandy continued his extensive aviation career by founding an aviation maintenance management firm. There, as Chief Pilot for Venture Airways, he flew both jets and helicopter aircraft for United Medical Corporation.
Most recently, he was the Chief Pilot for A-OK Jets, Inc., flying internationally for John W. Henry & Company and the Boston Red Sox baseball team.
He was a consummate pilot, a pilot’s pilot. Involved in world-wide international flight operations, he was rated in Challenger, Falcon and Gulfstream aircraft, and was dual rated in rotorcraft.
Besides his extensive aviation career, Sandy’s vast interests spanned many activities, from photography to motorcycles and sports cars, and much more. In the world of parachute jumping, he was Advanced Free Fall certified, and enjoyed the sport immensely.
Sandy never met or knew a stranger, and his friends were many. He made each one feel special, so special that many felt Sandy was their closest friend.
He left behind a loving wife, Linda, son Sandy Jr., and step son Kenneth.
His enormous presence of spirit, and his unbridled joy for life and living, will never be forgotten.
He will be deeply missed.
A funeral will be held 2:00 p.m. Tuesday, May 14, at the Annunciation Catholic Church, 1020 Montgomery Road, Altamonte Springs, Florida, followed by a church reception.
A Memorial Fund has been established to help carry on an effort of great, great importance to Sandy. His fervent wish was to see his son, Sandy Jr., graduate from Embry-Riddle Aeronautical University, and after to accrue sufficient aircraft hours to become a highly employable commercial pilot.
To further Sandy’s loving dream that his son follow in his aviation footsteps, contributions are warmly welcomed.
Checks may be made payable to the Santiago Rosell Memorial Account, and mailed to BMO Harris Bank, 129 E. Gore Street, Orlando, FL 32806. Arrangements entrusted to DeGusipe Funeral Home & Crematory.
Has the experience and main canopy size been confirmed?
The original post made reference to a "highly experienced" jumper probably on a 200+ canopy but later posts indicate 400-500 jumps (maybe a little more) and a 150 main. I am assuming that the latter posts may be accurate but would be interested to find out for sure. Thanks.
FWIW I have had 2 mals where I found myself spinning wildly. Both times I had an RSL fitted.
When I cut away the first (line twists, about 8 years ago, from memory on a Pilot 150, when I had between 200 and 300 jumps) I found myself under a reserve with about 6 line twists. Although I was pretty stressed about this, the canopy flew straight while I kicked them out. My equally low-jump number, non-rigger friends advised me to ditch the RSL as being the likely cause of the reserve line twists. For a while I did then I researched RSLs in more detail and decided to use one again.
The second "spinning" mal like this was last year, when I had a lineover on a Pilot 124. This time, the reserve flew perfectly straight on opening - no line twists.
My knowledge of physics is very limited so I cannot contribute to that debate but perhaps my experience is of some relevance. Bottom line for me is that my next rig will most likely have an RSL.
I had a really hard opening, damaged canopy.. cut away and pulled the reserve... I told my buddy I could believe how fast the rsl pulled the pin.. till he pointed it out that it was still on the rig open.. when I left the plane it was connected. Though it was a large brass one.. my first cutaway.. tony