February 2013

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

Issue link: http://experimenter.epubxp.com/i/108002

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Page 29 of 44

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 30 Vol.2 No.2 / February 2 013 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

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