Re: This sounds a bit odd.
Most of the things in the article point to the heavier helmet being the problem. That is not an Ejector seat problem.
That is also my reading of it; the rest seems to detract from the proper identification of the problem. That said I can see how body mass could be a determining factor.
At the risk of stating the obvious an ejection seat works by firing an explosive charge under the seat, after first shattering the canopy (again explosives are used) because unless the canopy is blown the result is a dead pilot. There are other things that happen, such as the pilot's legs being drawn back against the seat, much like car seat belt pretensioners. The seat is firing upwards, and the primary point of contact between seat and pilot is his (or her) derriere. That sudden acceleration is transmitted up the pilot's spine, and if the helmet is heavier that "standard" that heaviness becomes increased inertial mass. That increased mass can only be accelerated by the force transmitted up the spine and neck bones, thus adding to the extreme compression stress to which the entire spine (ncluding the neck) is subjected.
If the pilot and all his (her) component parts survive that, the compression stresses are repeated when the parachute deploys; this time the heavier helmet is forced downwards on to the neck bones and thence to the spine. (I cannot recall - if I ever knew - the point at which the pilot and the seat become separated.)
It is well known that pilots who have had to eject often land about 2" shorter than when they took off because of the compression of all the disks in the spinal column, and IIRC they have a specified number of weeks during which they have to return to within a certain precentage of their previous height; fail to return to "normal" and flying duties are cancelled.
I suspect that the pilot's weight comes into the equation simply because a heavier pilot will have a heavier bone structure that is better able to cope with the severe compression to which the spine and neck will be subjected; lighter pilots will have a lighter spine that is less well able to cope.
Ejection (I had to be careful there!) must come pretty close to the limit of what the human body can tolerate and survive and any additional factors such as increased helmet weight could easily pose a problem. If one answer is to specify a minimum body weight for pilots then that would seem to be perfectly sensible.
So Martin Baker are being threatened because of a problem that isn't their fault seems to be a perfectly fair point to make.
Biting the hand that feeds IT
