Photos Kevin Carroll
An unusual bird with remarkable flight performance
The Durafly Auto-G2 is a well-engineered design that flies great. Autogyros never fail to attract attention at the flying field, and this one is a ball to fly!
Long before helicopters took over my life, I was fascinated with RC autogyros. For at least 25 years, I've watched the state-of-the-art progress from dual-rotor outrigger designs to gradually more practical single-rotor versions. However, with all the other projects on the bench, I never got around to building one. With the Durafly Auto-G gyrocopter, available in an ARF version for just $75, I finally decided to do something about that. Here was an autogyro I could have flying in an hour!
⊕ Outstanding flight performance
⊕ Quick and simple assembly
⊕ Clever engineering details
⊕ Unusual and eye-catching
Assembly is minimal, as the servos, electronics and motor are all installed.
The rotor is mounted on a sturdy plywood pylon, and aileron control is via two micro servos in a pull-pull arrangement. The motor drive uses a flex-shaft and one-way clutch to spin up the rotor for takeoff. Ideally, this should be assigned to a momentary switch, but a toggle will suffice.
The installed 41mm brushless outrunner provides plenty of power for very short takeoffs. I do most of my flying below half-throttle, allowing flights of over 10 minutes.
The Auto-G V2 comes almost totally assembled and includes some neat design features, chief among these a flex-drive to spin up the rotor for takeoff. This drive plugs into the flight battery's balancing plug, and it's connected to a spare channel on the receiver, ideally a momentary switch like a push button. The drive has a one-way bearing so that the rotor can uncouple in flight, and the drive shaft is flexible to allow for tilting the rotor for roll control. This should only be used prior to takeoff, as the rotor should freewheel in flight.
Assembly is minimal, as the servos, electronics and motor are all installed. The landing gear snaps in place, the horizontal stab mounts on the tail boom with two clamps, and the vertical fin is glued in place with supplied glue. The rotor blades are screwed to the hub, which has built-in flapping hinges. Finally, the rotor and prop are mounted on their shafts. All that's left is to install the pushrods and bind the receiver. It's a good idea to put the flight battery on charge before you start assembly, as you're likely to have the airframe finished before the battery is charged. With the minimal assembly completed, it's time to head to the field.
In the Air
I really had no idea what to expect from the test flight, which naturally took place on training/club meeting night (no pressure here!). Initial takeoff was a breeze! I hit the switch to spin up the rotor and then cut the rotor as I added power. The Auto-G accelerated smoothly, and I eased it off the runway. Once in the air, it handled much like a high-wing airplane: all flight controls were normal, and it showed no bad habits.
GENERAL FLIGHT PERFORMANCE
Stability: With its tall rotor pylon, the Auto-G has a natural tendency to level itself. I find turns are better with a healthy amount of rudder. Autogyros won't stall in the conventional sense, but you need to manage pitch and power to keep the rotor speed up. Don't be afraid to shove in some down-elevator if you see the rotor getting slow.
Tracking: This is one of the Auto-G's most remarkable traits. Even on minimum distance takeoffs, with the rotor powered and full throttle, it tracks straight as a string. This was really unexpected.
Aerobatics: Aerobatics are hardly the purpose of an autogyro, and yet the Auto-G has proved reasonably capable. It does very nice chandelles and stall-turns and is even capable of loops. Do bear in mind that the rotor blades are not designed for high-G maneuvers, and you can crease the foam if you overstress them.
Glide and stall performance: While the Auto-G can do normal landing approaches like a regular airplane, the real fun is steep short-field landings. Fly the traffic pattern at what seems way too high altitude. After turning final, pull throttle back to near idle and use down elevator to keep the rotor rpm up. The Auto-G will sink like it's on an elevator, but won't pick up speed. About 10 feet above the runway, add a little power to arrest the sink and it will land like a butterfly.
This little gyrocopter exceeded my expectations in every way. The powered rotor makes takeoffs a snap, and handing in flight is much better than expected. Landings are where the Auto-G really shines, and I can do touch-and-gos for as long as the battery lasts.
AUTOGYROS: A DIFFERENT PATH TO ROTARY WING FLIGHT
The Auto-G is an odd-looking bird, but the flight performance is remarkable. Tracking on takeoffs is straight as can be, and handling is honest and predictable. The model has loads of power for short-field takeoffs but flies happiest around half -throttle.
The Cierva C.6 was the world's first truly successful rotary-wing aircraft, capable of cross-country flight. Based on the fuselage from an Avro 504, it used stubby wings for roll control. This photo shows how the rotor was spun up by men pulling on a rope, just like a toy top! (Photo via Wikimedia Commons)
The C.6 demonstrated full 3-axis control, and the Spanish press called its 7-mile flight in March 1924 “the leap into glory.”
From the earliest days of powered flight, ambitious designers attempted to build rotary-wing aircraft. In 1909, before he had built a successful airplane or even learned to fly, Igor Sikorsky built two unsuccessful helicopters. Given the incomplete knowledge of aerodynamics (and the limitations of structures and powerplants) true helicopters simply weren't yet practical. Even Sikorsky, a man passionate about the possibilities of hovering flight, turned his attention to more conventional fixed-wing designs for the next 30 years.
There was, however, a simpler middle road to rotary-wing flight. Just 10 years after Sikorsky's unsuccessful attempts, Spanish engineer Juan de la Cierva began work on a rotary-wing concept in which the rotor was not powered but simply windmilled or “autorotated” as the aircraft flew through the air. With a freewheeling rotor there was no torque to deal with and no need to wrestle with the complexities of controlling cyclic and collective pitch.
While not capable of true vertical takeoff or sustained hovering, de la Cierva's “autogiro” showed important advantages over conventional aircraft. It could take off from short fields, fly safely at very slow speeds and could make extremely steep landing approaches with minimum rollout. Pitch and yaw could be controlled by conventional tail surfaces.
After moving to England in 1925, de la Cierva steadily improved his designs, which were licensed to manufacturers around the world, including U.S. companies Pitcairn and Kellett. One major improvement was the development of direct rotor control—a forerunner of cyclic pitch control. Later designs could use engine power to spin up the rotor and then “jump” into the air. By the mid-1930s, the autogyro was well on the way to evolving into a true helicopter.
Ironically, de la Cierva, who embarked on his autogyro designs in an effort to improve flight safety, died in 1936 in an airliner crash. It would be left to others to perfect the helicopter, but gyrocopters remain in use to this day as light recreational aircraft.