S a f e t y W ir e
Overview of the wreckage of an experimental aircraf.
Experimental Aviation
Part 3: Restraints
By Stephen L. Richey
In this article, the third in the series, we continue
our discussion of how to improve the crash survivability of experimental aircraft. Given that we have
gone over the reasons why we need to pursue such
improvements and what we can do to improve the
design of the cockpit or cabin, let us move on to the
subject of restraints.
Restraints serve a couple of purposes in an aircraft.
The first is to keep the seat occupant from being
thrown either completely out of the aircraft or being
flailed forward or laterally into the structure of the
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cockpit. There remain some resistant folks who still
think a lap belt without shoulder restraints is sufficient
to protect them in a crash. To them I offer the following diagrams taken from a NASA article on human
biomechanics. The first (Figure 1) shows the distance
an adult man can be thrown about in a crash type
deceleration when restrained by just a lap belt. This is
known as the "flail envelope" or "strike envelope."
This demonstrates why in aircraft without shoulder
restraints, it is not uncommon to find a distinct imprint
of the face of the pilot or front seat passenger in the