A Gyro Primer

As the Bensen Days fly-in commences in the skies over the central Florida hamlet of Wauchula, some onlookers are confused about the exact nature of these curious craft buzzing above them. At first, they might assume that they are small helicopters because of the rotors spinning over their heads. Although the craft appear to be agile, they are certainly not fast.

In reality, these often misidentified flying objects are designated gyroplanes by the FAA. They are distinguishable from helicopters by the fact that their main overhead rotors are not powered, but are spinning freely in the air. Well, actually, the rotors can be powered up to speed on the ground and then disconnected from that power upon commencing the takeoff roll, but we’ll get back to that later. What is powered on these machines is a propeller, which pushes the aircraft forward through the air. Confused? Hang on, we are almost there.

Remember toy pinwheels when you were a kid? When you placed them in a breeze, they spun up, which looked cool when you were that age. Some of us were daredevils back then. We would sneak the pinwheel into the car and, when Dad was cruising along, we would roll down the back window and hang the pinwheel out the side, turbocharging the whole process. When the pinwheel was turned parallel to the wind, you could feel lift generated. Even though it took the power of the wind to spin up the pinwheel, the whole process generated lift. You did not put a motor on the pinwheel to spin it up. You used the power of the car’s propulsion to supply the spin, which generated lift.

At this point, if the spirit of Juan de la Cierva can read stuff on the internet, he is spinning in his grave. You see, Juan, a brilliant Spanish engineer, invented what he called the autogyro in the 1920s. He applied actual physics, math, and aeronautical engineering to the problem of airplanes crashing when they flew too slow for their wings to generate enough lift to fly. If the aircraft flew at a speed that was not sufficient for the wings to generate enough lift, the wings would “stall,” resulting in the aircraft plummeting to the ground and crashing. Brilliantly, de la Cierva determined that a scaled-up version of the air screw (propeller) could be forced through the air, generating lift. If the forward motion through the air was removed, as through an engine failure, then the spinning rotor would still generate enough lift in a glide to descend to the ground at a reasonable speed.

Juan’s first designs placed four rotor blades above the fuselage of a regular-looking aircraft (think biplane with the top wing removed). The rotor was canted a little aft and spun freely in the slipstream. Darned if it worked. The first successful flight came on Jan. 17, 1923. He improved his design over many iterations, leading to developments in how the rotors connected to the hub, allowing them to flap, lead, and lag in reaction to the slipstream. These were crucial developments that later led to the invention of the modern-day helicopter (with a powered rotor) by Russian aeronautical engineer Igor Sikorsky.

Interestingly, Juan de la Cierva’s invention became popular in the 1920s and 1930s. The American Pitcairn Autogyro Company built several models, one of which carried Amelia Earhart to a women’s altitude record of 18,415 feet in 1931. Pitcairn’s aircraft was a tractor model, with the propeller in the front of the fuselage, pulling it through the air. Amelia’s record-breaking aircraft now lives in the Smithsonian National Air and Space Museum.

Once Igor Sikorsky developed and flew the first controllable helicopter in 1939, autogyros became the red-headed stepchild of rotorcraft, basically ignored for years. Enter another Igor, Igor Bensen, an engineer who was fascinated by autogyro flight. He believed that the simplicity of an autogyro’s design requirements for flight could be used to develop a cheap and easy-to-construct recreational aircraft that would be fun to fly. And he was right. Igor founded the Bensen Aircraft Corporation in 1953 and based it at the Raleigh-Durham Airport. This autogyro, which he deemed the “Gyrocopter,” was a basic, stripped-down design with an engine and a rotor mast mounted to a box aluminum keel. Power was supplied by a four-cylinder, two-stroke McCulloch war-surplus drone engine (yes, they had drones back then, but that’s another story). Like the rest of the craft, the two rotor blades were handmade. The cabin consisted of a lawn-furniture seat, a stick (rotor heads call them cyclics), rudder pedals, and a throttle. The Gyrocopter was simple, cheap, and easy to build. A story in Popular Mechanics magazine pushed interest and demand through the roof. Builders could purchase plans for $30 or a complete kit for $1,795. It has been estimated that over 12,000 plans sets and kits were sold before Bensen went out of business in 1987.

What happened? Well, guys were building Gyrocopters by the thousands, but gyroplane instructors were few and far between. Many intrepid builders reasoned that this was a safe design and that they could teach themselves to fly a Gyrocopter. Not so much. As it turns out, the Gyrocopter had some aerodynamic quirks that were not readily apparent. The engine’s thrust line fell below the center of lift, forcing the aircraft to pitch up when the throttle was cobbed (like in an emergency). Also, the rotor system gave up in the lift department if subjected to negative G-forces. Although thousands of pilots safely flew Bensen Gyrocopters, and many still do, a large number of ill-trained and unwary pilots rode them to their graves.

However, gyroplane enthusiasts are nothing if not adaptive, resourceful, and innovative. Along came two major developments that improved safety and ease of flying: centerline thrust and horizontal stabilizers. Today’s generation of gyroplanes are considered easier to control than traditional fixed-wing aircraft and helicopters. In addition, the development of more powerful and lighter engines (pronounced “Rotax”) has given rise to two-place aircraft. Innovators also developed prerotator systems, which spin up the rotor blades before departure, shortening the takeoff run.

Modern-era gyroplanes have gravitated into a few prominent categories. First, there are the experimentals. These are kits sold to builders who accomplish at least 51% of the tasks necessary to complete them. Many kit companies have come and gone. Notable survivors are TAG (Titanium Autogyro) out of Australia and Gyro Technic, based in Kasota, Minnesota. Both of these companies are well represented at Bensen Days, and we hope to bring you in-depth stories about them later this week.

A new revolution has all but overtaken the Gyrocopter world: that of certified aircraft with composite fuselages, fancy (often enclosed) cabins, and a hefty price tag. Produced mainly in Europe, they are affectionately referred to as the “Euro-Tubs.” Some of the main players in this realm are AutoGyro out of Germany, Magni, based in Italy, and ELA (an American company). These six-figure-plus aircraft are sold ready to fly. They are sleek, sexy, and currently outselling everything else in the market. Like the Cirrus in the fixed-wing world, these aircraft are the ones that a wife will examine and then proclaim, “We’re buying that one!” All of these major players in this realm are present at Bensen Days. More information to come.