Mark James Boyd wrote:
So from the broader perspective of whether a "safety" device
contributes to safety ultimately or reduces it, yes, I
see there is a parallel. I was thinking you were drawing
a parallel in another way, which you weren't.

From reviewing the articles, and what you and Eric said, I
think the combined ideas are that:

1) The spinal compression axis is far more of a factor than
the forward momentum.

2) Parachute weight doesn't increase compression
noticably along the spinal axis (parachute weight doesn't
contribute to submarining significantly).

3) During the impact along that axis, the paracute weight
forces are borne almost entirely by the seat frame under it
rather than by the pilot.

So based on this, the extra weight of a parachute has
perhaps some effect, but this effect is negligible
in sailplane terrain impact accidents.

The key difference here is how the weight causes effects
differently in a car vs. a sailplane. The semi-reclined
sailplane seat position is significantly different than
in most automobiles.

Does this sum up what you all seem to have said?
Is there anything else I missed?

It does for me.


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Eric Greenwell
Washington State
USA