Freewheel
You might like to look at the BoI / accident report of the mid-air collision in January 2007 at RAF Ternhill involving two Squirrels.
The QFI in ZJ263 was sadly killed but the "stude" survived with serious head injuries and there is no doubt that wearing a helmet saved his life....The other crew of two also survived, albeit with less severe/minor injuries
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Many moons ago I knew an RAF Medical Officer (Wg Cdr David Anton) who must have retired some time ago but he was an aviation pathologist and an expert in accident investigation where aircrew injuries were being assessed. Apart from identifying cause of death
in fatal accidents he had the happier task in others of seeing first hand how improvements in crash-worthiness, fire mitigation, aircrew clothing/helments etc. actually worked.
I haven't a clue where his is now but I am sure he is very well known in av med circles. Martin Baker may be another source worth contacting, apart from making ejection seats they also design and manufacture crash-worthy seats for both FW and RW ac. (Thankfully I have never had recourse to use either apart from a one-off "ejection" up the gantry rig then at North Luffenham before the joys
of being let loose with a JP at Linton!)
MB