Tiny Turbines

Ever seen a radio-controlled model aircraft do 300 mph? Visit Metropolis, Missouri, this fall.

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Whether one mounted it on a hardwood stick fuselage with tiny wings and went for straight speed (Dale Kirn set the first Academy of Model Aeronautics record for jet speed, 154.98 mph, with a Dyna-Jet in 1954) or encased it in a model F-86 or MiG-15, producing a Dyna-Jet-powered model at the local flying site drew a crowd faster than a bag of free money.

Everything about the Dyna-Jet was abrupt. It was either completely off or way-the-hell on. It took a ground crew and a certain finesse to evoke just the right conditions for the pulsing explosion cycle to become self-sustaining. An old Ford ignition coil fired a spark into the combustion chamber while a bicycle pump ushered a blast of air and white gas through the intake nozzle; the latter more often than not would just drizzle out the tailpipe. It was usually easier to set the grass on fire than to get the Dyna-Jet lit. Once a few loud burps got the combustion chamber hot enough to ignite the next charge, one lucky start attempt would result in a sudden and devastatingly loud roar, and the model would strain in the holder’s hands while the pit crew attempted to maintain their wits long enough to disconnect the starting apparatus and clear the launch area. The previously curious cluster of spectators would scatter for cover. Just getting a Dyna-Jet-powered model airborne was its own pinnacle of achievement—unlike stunt, combat, or any of the other categories that require actual flying.

When the pilot gave the signal for release, the model would lunge forward and roar around a circle defined by the control lines until velocity overcame the high wing-loading (the amount of weight the wing had to lift). In due course the craft would climb to cruise altitude (shoulder height). For the next few minutes, there was little for the pilot to do but hang on, hope the control system did not come apart, and wait for the fuel to run out. The series of gasoline explosions caused 250 individual pulses to cascade out the tailpipe every second, creating a Doppler-shifted wail of indescribable proportions while the hapless model was flung by its gigantic blowtorch, constrained by two improbably slender control wires and the grim determination of the pilot.

About the time spectators began to creep closer, the concussive roar would abruptly cease. The model would then best be flown onto the ground as quickly as possible. In the silence that ensued, all present would absorb the event and then store it in the little alcove of memory reserved for Truly Remarkable Incidents.

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