Letters | Aug 01, 2020
Opening Shock

William Grut

The recent accident-statistics report—“Non-Fatal Incidents Summary” by Ron Bell in the May issue of Parachutist—was interesting and prompts me to bring up, once again, the problems of opening  shock. Modern micro-lines of all types have almost zero deformation. It is exactly for this reason that they are used in top-level yachting, where zero stretch is needed to maintain a constant sail aerofoil shape.

The slider was a fantastic innovation, revolutionizing the use of the square canopy. It is highly consistent, yet with the great number of parameters affecting the opening sequence, many of which may not be normal, it is not infallible. Human, elemental, design or just random-chance perturbations in its deployment sequence give everyone a slammer opening sooner or later. In the best case, these may cause a stiff neck or back for a day or so. However, in the worst case they may kill instantly or render the jumper powerless by severing the spinal cord or knocking them unconscious, leading to a completely uncontrolled landing in whatever location the winds take them, which has a high chance of proving lethal.

But there is another, separate problem of hard, poorly damped openings: chronic traumatic encephalopathy. CTE is well documented and seen often in long-term participants of rough, impact-filled sports. Worryingly, the impacts need not be excessive to generate problems down the road. To date, no one has been able to give any specific lower limit for the degree or numbers of impacts needed to cause damage, but repetitive firm opening shocks in parachuting would almost certainly fall within the danger envelope. (I won’t even go into slider-down base-jumping.)

In days gone by, the term “punch drunk” described some of the typical effects of CTE later in life. What many don’t notice is the far more debilitating span of damage that causes changes from the neurological to the psychiatric. While it is beyond the span of this letter to go into full details, an excellent reference is available in the article “Repeated Mild Traumatic Brain Injury” by Brooke Fehily and Melinda Fitzgerald at PubMed Central (ncbi.nlm.nih.gov/pmc/articles/PMC5657727/). Many of the results of CTE almost certainly reduce quality of life and shorten life span. Skydiving tellingly has a skewed distribution toward the young, where there tends to be a predisposition to live for the moment with some dismissal of the consideration that in many aspects they are writing within their lives of the present, much of the text for their own future life chapters.

Hard openings then generate two separate serious danger areas: First, the single killer opening, rare but horrifyingly damaging or lethal (either directly or indirectly). Second, CTE, much more surreptitious but equally destructive in the long term. Our sport has not addressed these concerns to the same degree as other areas, such as potentially deadly low pulls or cutaways. This is surprising, yet most surprising of all is that fact that it would be easy to conceive of designs for damping elements (and/or weak links for the first problem of high-impact “super-slammers”) that could be easily fitted (and retrofitted) into harness systems or risers. Many jumpers (not least this writer, along with a host of camera jumpers and those with bad backs) specify Dacron lines—the only commonly used line which has any built-in elasticity (up to 5 percent deformation)—for their canopies. This, however, is only a very partial solution.

I am confident that the creative and imaginative people in the skydiving community or industry could think up a suitable design that would solve these issues (as did the game-changing slider). Perhaps of most importance for incentive is that anyone who comes up with a simple, effective design will likely have a lot of money coming their way, as not only will everyone buy it, but it is highly likely to become mandatory.

Focus on this problem is long overdue. I submit that almost every other impact sport has or is considering taking counter measures. We love our sport for its thrill, its beauty and its camaraderie, not for playing Russian roulette in unnecessary areas of known physical damage.

William Grut | USPA #1460 and
MSc (biomechanics), MD, PhD
Vancouver, Canada

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9/30/2020 4:25 AM

Great recommendation to the industry. I would also like to see more information on the long term effects on your neck and cervicals of added weight on your helmet... hard to find any specific information on this topic

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