Making Parachute Safety in The Wind Top of Mind at Topgun
When TOPGUN received more flexible rules on maximum wind speeds for training flights, the CNA analyst assigned to the command began to hear concerns. Winds often whipped across the Nevada desert at Naval Air Station Fallon, home of TOPGUN and the rest of the Naval Aviation Warfighting Development Center. Some on the TOPGUN staff knew a fellow pilot who had died when dragged on the ground by a wind-blown parachute after an emergency ejection.
These 2010 instructions eliminated an upper limit on wind gusts. They also gave commanding officers leeway to override limits on sustained winds when deciding whether to allow training flights or not. But neither commanders nor pilots had any scientific data on the risks of different windspeeds. Dr. Robyn Lalime’s analysis would create a way to quantify — and even visualize — those risks. Even today, pilots rely on that guidance.
The aeronautical safety flight surgeon on staff, Commander Becky Bates, asked Lalime to bring physics and mathematics to bear on the problem. The CNA field representative worked closely with naval engineers on computer models of the performance of three different parachutes in varying winds. And she dragged her own weighted flight suit across asphalt and desert sand, measuring newtons of force to establish a coefficient of friction for a Nomex suit. Strangers would approach, asking, “What the heck are you doing?” But TOPGUN staff, already accustomed to her hands-on approach to research, would just comment, “Oh, I see you’re gathering data.”
Lalime employed long, complex equations to reach her conclusions, but she and Bates knew that pilots needed simple rules of thumb. One said that for every additional 10 knots of windspeed, a parachutist could expect to be dragged by an extra 250 feet per 10 seconds. They also used memorable images to evoke the impact of high winds. The CNA analyst had lived through the experience of being blindfolded and dragged through the water by a parachute harness during her own ejection training — in preparation for flights with TOPGUN pilots. She knew it was an intensely sensory experience.
For example, to illustrate wind’s effect on a lightweight pilot with a parachute from an F/A-18, they converted detailed calculations into colorful comparisons of landings at different windspeeds. In no wind, the landing resembles a jump from a 10-foot platform. In a 20-knot wind — the upper limit for sustained windspeed in the official instructions — it’s like that same leap with a case of beer bottles under each arm. At 30-knots — an ordinary gust in those conditions — it’s like that 10-foot fall with giant panda clinging to your back.
Lalime could already see the impact of this work before she departed from TOPGUN. (Today she’s still in CNA’s Field Program, billeted to the Naval Information Warfighting Development Center in Norfolk, VA.) The flight school staff asked for the findings to be widely briefed and published. And her calculations played into decisions about whether to fly on windy days. But she could not have known the work would endure for more than a decade. Navy physiologist Amanda Lippert reports that she still references this study when giving ejection safety briefs to aircrew, in order to convey the importance of obeying wind limits. With CNA analysis, a pilot or commanding officer can make safety decisions backed by science — and keep the panda off their back.