RE: Nelson allowed in Q-500
c. The manufacturer or other source has given the notice required by subsection 6 of this section, Availability of Engines and parts, and received a letter of approval from the chairman of the RC Racing Contest Board; and:
Or this
RCR-3 Engine: A two-stroke cycle, glow ignition, reciprocating-piston internal combustion engine. For purposes of events requiring stock or commercially available