Gallery/Beechcraft King Air C90
Mike Barbee’s award-winning twin-engine electric
Mike Barbee’s award-winning twinengine electric
If you’ve ever thought that electricpowered airplanes weren’t all that exciting, then check out Mike Barbee’s Top Gun Scale Invitational entry: the Beechcraft King Air C90 twin. Pilot Frank Noll flew this 1/4-scale entry in Team, and the duo placed first in their class. After the impressive finish, we caught up with Mike to chat about his amazing aircraft and get its impressive backstory. Here’s what he had to say.
Gerry Yarrish: Mike, congratulations on your impressive Top Gun Team win. Please tell us about yourself and your model.
Mike Barbee: Thanks, Gerry. The King Air C90 is a twin-engine private aviation aircraft built by Beechcraft in the 1960s. I built the 1/4-scale
King Air from a Bob Patton design. It has a 155-inch wingspan, is 110 inches long, and weighs 960 ounces (60 pounds). As you mentioned, my pilot Frank Noll and I won first place in Team, with a static score of 96.833 points and a total final score of 193.416. We also won the Team High Static, Best Military (Pilots’ Choice), and the Critics’ Choice Runner-Up awards.
This was my 27th year attending Top Gun and during that time I have entered 10 different airplanes. I have been flying RC for 37 years and specifically with scale aircraft for the past 30. I am the president of the National Association of Scale Aeromodelers (NASA), the special-interest group of the AMA that supports and promotes scale in RC, control line, free flight, and helicopters. I’m from Delaware, Ohio, and I am also the East Coast chairman for the U.S. Scale Masters Association.
What about the model’s construction?
Basically, the fuselage is made of fiberglass and resin. I laid it up using Bob Patton’s original molds. The wings are made with a foam core and then sheeted and finished with fiberglass as well. The build time was about 1,700 hours over a two-year period. There aren’t any plans, so really the King Air isn’t a kit build. It’s in a Navy Military Heritage scheme, so it qualifies as a warbird, and it’s modeled after the only King Air painted in these colors.
What radio gear do you use?
Frank flew the King Air with a Futaba 18MZ transmitter, with a 12-channel Futaba receiver, using 12 Futaba S9177 SV servos. We also used a Demon Cortex three-axis flightstabilization system.
What power system is used in the King Air?
The model is powered by a pair of Kontronik KSG 4:1 geared electric motors turning two 3-blade variable-pitch propellers. These are ground adjustable, and my setups have 21.5x16 settings. The electronic speed controls are Kontronik S-145 300-amp equipped with Bluetooth for programming. I am using Venom 6S 5000mAh flight batteries, with four in each engine nacelle wired with two in parallel and two in series.
Tell us about the landing gear.
The pneumatic landing gear for the King Air were designed by Bob Patton for the model. I did modify them to include the use of larger air cylinders. I use a Robart air system and tanks; the gear doors also operate with air cylinders. The brakes, wheels, and tires are all from Robart.
Mike, we saw that your power system included a scale engine start-up sequence. Tell us about it and your model’s flight performance.
This is pretty cool. During the startup, one engine [motor] starts at a time, and it’s all part of the programming in the speed controllers. The first motor spools up to idle speed, just like the full-size aircraft, then the second one spools up to idle speed. I also disabled the prop-brake function. The overall effect is very scale and impressive. They almost sound like real turbo-prop engines.
Tell us about the flight performance.
Well, the full-size King Air aircraft can cruise at about 240mph.
So I worked backward and tried for 80mph model airspeeds. I also needed to get flight times that would allow me to complete nine flight maneuvers. With the ground-adjustable props set with a 16 pitch, I got a realistic
speed with consistent flight times of 12 minutes while still having about 38 percent of the battery voltage remaining for a safety margin.
Flaps are used for both takeoffs and landings, and I am pleased that they don’t cause any flight trim changes. Putting the King Air through its paces, we found its flight characteristics are very maneuverable and it’s easy to fly. We’ve rolled it.
What’s next?
Since Top Gun, Frank and I have competed at other events including the AMA U.S. Nationals, again in Team. We won the Team class as well as the Grand Champion award. This award is given to the highest aggregate score in the Expert, Team, Sportsman, and Open classes. We will also be competing in the NASA Scale Classic in October held at the AMA site. Next year at Top Gun, I am planning to compete with the King Air in the Expert class.
“I BUILT THE 1/4-SCALE KING AIR FROM A BOB PATTON DESIGN. IT HAS A 155-INCH WINGSPAN, IS 110 INCHES LONG, AND WEIGHS 960 OUNCES (60 POUNDS).”