Ever seen a radio-controlled model aircraft do 300 mph? Visit Metropolis, Missouri, this fall.
- By Ed Regis
- Air & Space magazine, September 2004
(Page 5 of 6)
Violett’s star product is a scale F-100F Super Sabre, which, in pictures at least, is indistinguishable from the real thing. And, Violett says, it flies even better. “We use gyro augmentation on these jets, on the vertical axis and the rudder,” he says. “As in all swept-wing airplanes, they have something innate: Dutch roll. Anytime the airplane is upset, one wing is always advanced in angle of attack, so it’ll pitch up a little bit, and that causes more drag, and so it starts an oscillation.” The airplane ends up wagging its tail from side to side like a happy dog. To dampen the oscillations, Violett and his engineers attached piezoelectric gyros to the rudder, devices that sense Dutch roll and cancel it through slight rudder movements.
“They make you look like a much better, smoother pilot,” Violett says of the gyros. “They take all the wiggle out of the airplane.” The resulting stability is much in evidence when Violett maneuvers his Super Sabre through a flawless four-point roll, a maneuver that, because of its difficulty, is rare among jet modelers.
At 5 p.m., free beer and pizza are served in a tent near the food stand where, earlier in the day, $3 elk burgers were sold. One of the last to fly is Gary Jefferson, a packaging materials salesman from Monroe, Ohio. He wants to get in just a couple of more flights before he has to quit for the evening.
It’s getting cold and overcast now, not to mention gusty, and Jefferson’s wife, Sandy, has pulled on a coat, though it doesn’t seem to help much. Even the family dog is wearing a red blanket.
Jefferson, undaunted, blasts his FiberClassics Rookie around the pattern and goes through the customary show of wild aerobatics until he can barely tell which side of the model is up. “See, you can still tell the fin’s on top,” he says, squinting into the gloom. Finally it’s too dark even for him. He makes one last, perfect landing. The engine spools down. Time for a beer.
Sidebar: The Primordial
In the 1950s and ’60s, the Dyna-Jet Red-Head pulse-jet engine was the hot ticket in control-line model airplane circles. Based on the same operating principles as the engine that powered the German V-1 buzz bombs of World War II, it produced self-sustaining resonant shock waves. A mix of lantern fuel and air was ignited in a combustion chamber, and the resulting explosion would force a spring-steel valve (the sole moving part) behind it to slam shut. As the blast exited the exhaust tube, a wave of low pressure rippled back toward the chamber, sucked open the valve, and drew in another charge of fuel and air. The mixture, ignited by the heat remaining in a spark plug, repeated the cycle until fuel was exhausted.
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.