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Model Airplane News, Nov 1999 by Tiano, Frank

Without a doubt, oone of the hottest, newest and fastest-growing segment of aeromodeling today is jet aircraft. Over the past two decades, the interest in jets has been on a steady rise and right now is attracting new pilots by the payload. Just attend a couple of jet fly-- ins and you'll see what I mean!

IN THE BEGINNING

The ducted-fan jet was pioneered in the mid-'70s by the team of Bob Violett and Jim Scozzafava. Working together, they introduced the first no-kidding, ducted-fan unit-the Scozzi-using John Brodbeck's screaming little K&B 40 Formula One pylonracing motor and a lightweight A-4 Skyhawk designed by Bob.

The Scozzi-powered A-4 awed modelers wherever it was demonstrated. Bob Violett spent many years developing that first ducted fan: increasing this, decreasing that, finding which materials would last and, finally, talking K&B* into making a true fan engine-one that had a rear exhaust and gobs more power. Once Bob had a powerplant, he started to design new models to house this powerful new ducted-fan system.

Anyone messing with a ducted fan 25 years ago had his hands full. Mind you, the aircraft designs were as solid as a rock, but those screaming engines with their special tuned pipes and fuel systems had to be working in perfect unison for success.

By 1980, or so, problems had been sufficiently worked out to ensure that with just a little extra care taken in the preparation of the model, ducted-fan success could be expected.

Once the fan unit had been more or less sorted out, fan-engine size grew from .40 to .46, and then Bob Violett jumped dramatically to a .72. While other budding companies introduced a series of hot .60 engines, the Violett engine further grew to .82, and in recent years, this has been followed by the famous .91 and, just recently, the awesome .96. Almost all of the larger ducted-fan engines today are in the .90 to 1ci range.

By the early '80s, several other companies were manufacturing and developing ducted-fan airplane kits, engines and totally new fan designs. For the next 12 years or so, we saw all sorts of weird stuff such as two-stage fans, twin-cylinder engines, diesel-powered fans, mini fans, larger fans; you name it. It took a while for modelers to figure out which products worked best for them.

Even though ducted fans and jet models had progressed vigorously, there were still those who considered them a dubious power source. It took years of continued success to convince them that jets were a stable and fun alternative in our hobby.

After the smoke had cleared, even the most skeptical had to admit that jet subjects with ducted-fan propulsion units have become reliable models that have come into their own. As I said, just go to any jet event and see for yourself.

But enough of that; here's what else has happened during this time. Larry Wolfe, a model airplane designer and a fabulous pilot from California, bought the rights to the Scozzi fan unit, offered it under the name Turbax One and called his company Jet Hangar Hobbies*. Tom Cook had developed a competitive ducted-fan unit with an impeller of a slightly larger diameter; called the Dyna-Max, it uses the O.S. 91 fan engine for power. Byron Originals* entered the scene with some inexpensive, stand-off-scale models that used a pushertype fan unit that worked well but in most cases required a huge cheater hole in the bottom of the airframe to work most efficiently.

Bob Violett introduced a totally new ducted-fan unit-the Viojett. For a time, K&B supplied engines for this new fan. Later, Bob designed his own custom engine, which is the same today.

By 1995, we saw a turbine-powered model or two going through its teething stages. The model jet age had really arrived! Over the next few years, Tom Cook and Bob Violett introduced kits that could handle either ducted fans or turbine engines, and smaller companies soon followed suit. As far as the turbine engine manufacturers went, in the beginning, there were a bunch-everything from simple homebuilts to the sophisticated.

By 1998, only a few major players remained, and all are still with us. We'll cover the turbines in an upcoming segment.

THESE BULLS HAVE NO HORNS

In general, jet models are larger, and their engines-both turbine and ducted fan-are stronger than ever. This combination required that high-quality, specialized support gear be developed for these "upscale" airframes. Suddenly, we needed electronic throttle controls, better fuels, fuel pumps, stronger glow plugs, custom landing gear, metal-gear servos, tachometers, wheels, tires and brakes and a host of other gismos, doodads and accessories.

Someone had to take the bull by the horns and develop the necessary hardware. Remember, the original A-4 was a 5-channel airplane. That's four flight functions plus a channel for retract gear. As the models became larger, we added flaps and servo number six. Then we added mixture control to get more life out of the engine (that's channel seven) and speed brakes for the 20-plus-pound models (we're up to eight now).