The Federal Aviation Administration (FAA) shares the Environmental Protection Agency's (EPA) concerns about lead emissions from small aircraft. Owners and operators of more than 200,000 piston-engine aircraft operating in the United States rely on aviation gasoline (avgas) to power their aircraft.
Symmetry (noun). a due proportion of the several parts of a body to each other; adaptation of the form or dimensions of the several parts of a thing to each other; the union and conformity of the members of a work to the whole. Symmetry (noun).
Symmetrical means, a shape or figure cut to where the same shape/s is on both sides. For instance if you cut a circle in 2, you have a biosphere on both sides. 1  having similarity in size, shape, and relative position of corresponding parts. 2  When two halves of an object are mirror images of each other.