SAFA Skysailor Magazine

34 SKY SAILOR March | April 2021 Recently, we’ve seen trends in paraglider harnesses to be lighter, easier to pack, and more streamlined. While all of these aspects are desirable, it’s hard to create a light and slim harness with maximum safety performance. Safer harnesses usually have thick foam back protectors, or a big airbag (or both) beneath the pilot’s butt. Another aspect mentioned in the ejection seat literature also isn’t really addressed by paraglider harness tests. The ejection seat researchers found that although their testing was based around an 80kg pilot, a heavier pilot places more stress on his/her spine in an ejection scenario, so it follows that a paraglider pilot heavier than 80kg also places higher forces upon their spine in a seated, vertical direction accident. In addition, researchers found that by the age of 60, a pilot’s spine will only take about half of the force that a young, fit, 18-year-old’s spine can before injury. This is a definite concern when the average age of a SAFA pilot is 52. As you all know, being a pilot is all about risk man- agement, and if you are older and weigh more than the standard 80kg, your spine cannot tolerate the same G forces a younger or lighter pilot can. Pilots may want to factor this information into their risk management and their equip- ment selection. References: Jones, Thomas C., 2014, Certified Ejection Seat Weight Ranges and their Effects on Personnel Selection Karl Slezak / Peter Wild, 2011, Back protectors report, DHV Technical and Safety Department Martin Eiband, 1959, Human Tolerance to Rapidy Applied Accelerations: A Summary of the Literature, NASA Footage of the first Martin Baker ejection seat test Further Reading: Back Protection Survey and Results Para-test Reports What do paragliding harnesses and jet fighter ejection seats have in common? by Peter Allen – SAFA Projects Officer Both are built to provide a form of safety protection. With fighter aircraft ejection seats, it’s obvious – the ejection seat is designed to allow the pilot to eject from the aircraft quickly in case of an emergency. The paraglider harness… I’ll tell you further down… The first ejection seat was designed in 1910 but not widely adopted. After WW2, it was noted that at high speed a pilot couldn’t exit the aircraft easily or without injury. It was then that the Martin-Baker company began to work on developing ejection seats in earnest. One problem an ejection seat de- signer has to deal with is that the forces applied to the pilot have to be low enough so the pilot isn’t injured, but at the same time high enough for the seat and pilot to clear the aircraft tail. Also, in the case of ejection on the ground or during take-off, the ejection seat needs to reach sufficient height for the parachute to deploy. There are many reports of pilots having to recover in hospital from spinal injury after using an ejection seat. The force acting upon a pilot in an ejection sequence is similar to the force a paraglider harness tries to dissipate in an accident where the pilot hits the ground vertically in a seated position (i.e. stalling just before landing). During certification testing, a test dummy (torso) is placed in a paragliding harness and dropped from a height of about two metres. This tests the effectiveness of the ‘impact pad’ or airbag under the seat and behind the pilot’s back. The test measures the instantaneous ‘G’-loading applied to the test dummy when the harness is dropped to the floor. The G force happens over quite a short period of time – around 20 milliseconds. The lower the G rating, the better. The research that the armed forces undertook in conjunc- tion with the Martin-Baker company in the early 60s is still available, and it is no surprise that the human limits they ascertained are the same that paraglider harness testing still uses. Statistically speaking, spinal injuries can happen from 25G and are almost guaranteed at 50G. This is why para- glider harness manufacturers are working towards getting the lowest G measurement in the test. Sampling the tests done in recent years show a range of 22G up to 34G. Rob Holmes launches at Shelley Beach, WA, early one morning