I've been reading the few publicly available articles I can find on Google Scholar. Alas, most of them are behind paywalls so I’m often limited to summaries.
One drawback is that many of the papers, such as
Analysis of injuries among pilots involved in fatal general aviation airplane accidents
(Wiegmann and Tanaja), seem to focus on fatal accidents, where 50-60% of pilots suffered head/brain/facial injuries. However 36% had also fractured their pelvises and 50% had liver injuries and 30% splenic injuries etc... It’s no use surviving your head injury if you’re going to die of half a dozen other things simultaneously.
Li and Baker (
https://www.researchgate.net/profile...fc.pdf)suggest that polytrauma causes 42% of deaths, and head injuries 22%. About 6% of fatal injuries are isolated head injuries. Burns – 4% and drowning, 3%.
However the more interesting accidents from our perspective are those where the participants either survived with a significant injury, or where the participants suffered an isolated fatal injury that might potentially have been prevented.
This FAA report (
Crashworthiness Studies: Cabin, Seat, Restraint, and Injury Findings in Selected General Aviation Accidents,), unfortunately rather old from 1982, looks at 47 ‘survivable’ accidents. They found that 25% of their pilots/co-pilots had suffered facial/head injuries. They also found that hardly anybody was bothering to wear an upper torso restraint (shoulder or harness) - arguably if they had been, these injuries might have been less common. It’s not quite clear to me how they defined ‘survivable’accidents. I suspect it’s in the small and illegible print at the end.
Baker, Brady, Shanahan and Li (
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2810202/)
alarmingly state that there are about twice as many fatalities as hospitalisations for serious injury! About 14% of hospital admissions were for head injuries, and 4% for burns. A more general figure seems to be that 20-25% of accidents result in a fatality.
Of interest to me was Wiegmann and Tanaja's observation that brain injuries are more correlated with facial injuries than skull fractures. I’d been thinking of getting a lightweight helmet with no visor, but on this basis I’m reconsidering that.
Wiegmann and Tanaja stated that 7.3% of occupants had suffered ante-mortem burns. Obviously that’s not the same as stating that 7.3% of occupants could have been saved had they been wearing Nomex. However it implies there’s some value in the stuff.
All the papers that mention it are unanimous that upper torso restraint makes a big difference to survivability and that if it's there, it should be worn.
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So for my own safety equipment budget:
Nomex clothing and leather gloves – weight neutral; cost £150 (the new Nomex underwear was more expensive than the grow-bag)
Helmet - £300 for a budget/Ebay version – about 600g heavier than a headset alone.
Shock absorbing foam seat – about 500g heavier than the previous version. £60 + labour
Life-Jacket - £80; 800g
PLB - £180; 150g
Total cost of safety gear: 2kg additional weight. Price: £770
Looking daft: priceless
Obviously it’s not going to make anybody invulnerable (and one of the drawbacks of safety gear is that sometimes it makes people think they’re invulnerable) but I think you can argue it will make a significant dent in the risk of dying from a head injury, burn or drowning and should also reduce the injuries suffered in already survivable accidents.