Experimenter

JAN 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/101874

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Te best way to think about safety in your cockpit is to think about an egg inside one of those cardboard cartons at the grocery store. If you drop the carton on the ground, the cardboard crushes pretty readily, and the egg breaks, resulting in a need for a cleanup in aisle six. you to stay as close as possible to the way it was originally, in all directions. Loss of volume can happen in several ways. The engine may be shoved back into the cockpit, or up and back. The risk of this can be minimized by designing the structures in the cockpit to keep the engine in its place. The use of a slanted "A" pillar at the sides of the windshield (as seen in cars) is not always standard in light aircraft. This is one of the main components to keep the engine from moving upward and should be included in all aircraft. We will look at the first of these points in this article and the rest in following installments. The "container" here is the volume within your aircraft's cockpit. The best way to think about safety in your cockpit is to think about an egg inside one of those cardboard cartons at the grocery store. If you drop the carton on the ground, the cardboard crushes pretty readily, and the egg breaks, resulting in a need for a cleanup in aisle six. Now, if you place an egg in the center of a plastic bottle filled with shredded cardboard and drop it on the floor, the egg is much less likely to break. One of the major reasons for this is because the "passenger" in the bottle is not directly exposed to a sufficient decrease in the volume of the cabin or forced to directly impact the sides of the container. The same holds true for your aircraft. Ideally, you want no more than a 10-percent reduction in the volume of your cockpit in the event of a crash. This means you want the frame protecting In fact, short of the wing spar, this pillar should be among the most robust structures in an aircraft. Assuming a frontal impact at the lower side of the engine compartment, you want to have structures in place that are going to keep the engine out of the cockpit for a few reasons, the most obvious being that if the engine tears loose, it is likely to take the firewall and anything attached to it (such as the instrument panel) with it. While not having such a pillar may offer a major improvement in forward visibility especially in a taildragger, it also is an almost sure way to increase the severity of injury especially to the front-seat occupants' legs. Secondly, if the engine does break loose, you have probably just created a fuel leak in most aircraft. (The few of us who spend the extra cash for lines fitted with quick disconnects like the ones that the military uses on its helicopters are spared that problem.) Having the engine mount designed to absorb energy in a manageable way by controlled ductile or frangible failure modes but still transmit any remaining energy around the cockpit in as straight as a direction as possible without causing failure of the cockpit structure is the most ideal option here. EAA Experimenter 33

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