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Brock KB-2 “Gyroplane” Autogyro – N2303

Ken Brock was a leader in the development and promotion of autogyro flight and homebuilt autogyro kits. The museum’s 1970 KB-2 Gyroplane™ was one of Brock’s personal demonstrator aircraft and was donated by Ken Brock. It has appeared in motion pictures, television commercials, and countless air shows in the United States and Canada. Brock’s air show routine included steep chandelles, 90-degree banks, “lazy eights,” spins, vertical descents, and dead-stick landings, amply demonstrating the maneuverability and safety of homebuilt autogyro design.

This stock KB-2 achieved several world records for autogyro flights, including the first coast-to-coast autogyro flight in 1971, flying from Long Beach, California to Kitty Hawk, North Carolina (3,400 miles) in ten days. In 1968, in an identical KB-2 demonstrator (without floats), Brock flew a round trip between Long Beach and Catalina Island, 35 miles off the California coast.

Brock introduced his first KB-series Gyroplane kit in 1957. It was similar to the Benson “Gyrocopter™” kit, first offered in 1953. Brock made several refinements to the Benson design, including a modified control system that made his Gyroplane handle more like a fixed-wing airplane.

Powered by a 90-horsepower McCulloch engine, the KB-2 Gyroplane can take off in 100 to 200 feet, land in 10 feet, and cruise at 65 to 70 mph. Plans and kits for the Brock KB-2 and KB-3 Gyroplanes are still offered by Brock Manufacturing. Like many other autogyro kits on the market, the KB-3 can qualify as an ultralight under FAA rules.

Autogyro Construction and Performance

An autogyro has a powered pusher or tractor propeller to provide thrust and an unpowered main rotor to provide lift. As the propeller moves the aircraft forward, air passing over the main rotor causes it to spin, creating a disk that provides lift like a wing. Though an autogyro cannot hover, it can make vertical landings. In a vertical landing, the KB-2 will descend 15 to 20 feet per second, about the same speed as a parachutist. If the engine quits, gliding the aircraft forward will keep the rotor spinning, allowing a safe dead-stick landing.

Some autogyros have adjustable-pitch rotor blades that allow them to “auto-rotate” like a true helicopter. In auto-rotation during a dead-stick landing, the rotor blade pitch causes the rotor to “windmill.” As the aircraft nears the ground, the pilot changes the pitch to provide lift, and the rotor’s momentum keeps it turning long enough to allow the aircraft to safely flare and land.

With variable pitch, some autogyros have a “jump” feature for vertical takeoffs. In a jump takeoff, the autogyro’s engine is temporarily coupled to the main rotor. With rotor pitch flat, the rotor is spun up to high speed. Then the engine is de-coupled from the rotor, rotor pitch is changed to lift, and the rotor’s momentum keeps it spinning long enough to lift the aircraft a few feet off the ground, where forward motion takes over to keep the rotor spinning. The jump-takeoff system is complex, heavy, and expensive, and is rarely found on homebuilt or sport autogyros.

Autogyro History

The first autogyro, predecessor to the helicopter, was invented in 1923 by Juan de la Cierva, a Spanish pilot and aeronautical engineer. His early autogyros featured a powered tractor propeller, an unpowered rotor on a mast, and a vertical stabilizer. Parnall & Sons, a British airplane builder, built many of Cierva’s autogyro designs, though none of them in any quantity.

Cierva’s C-11 autogyro introduced the jump-takeoff feature. His C-19, which had an airplane-like fuselage, short fixed wings, and a mast-mounted rotor, was built under license by several manufacturers. In the United States, Harold Pitcairn began building Cierva C-19s in 1928. Three years later, Amelia Earhart flew a Pitcairn PCA-2 to 18,415 feet—a world altitude record for autogyros.

PITCAIRN AIRCRAFT INC

By the mid-1930s, the first true helicopters were being built and flown in Europe. Interest in autogyros faded. During WW II, the Japanese Kayaba Ka-1 autogyro was used for reconnaissance, artillery spotting, and anti-submarine defense. The Germans developed very small gyrogliders (unpowered autogyros) to be towed by submarines for aerial surveillance. Reports note that when the submarines were forced to dive quickly, the gyroglider pilot was sometimes left hanging.

With advancements in helicopters, autogyros were mostly forgotten until the early 1950’s when Igor Benson saw a gyroglider from a captured German U-Boat. Benson was a Russian émigré to the U.S. who had worked on early helicopter research at General Electric Corporation and Kaman Aircraft Company. He saw the potential for a safe, inexpensive, kit-built autogyro for sport aviation. His 1953 Benson Gyrocopter™ was the first of the modern autogyros. Today, EAA’s AeroCrafter guide to homebuilt aircraft lists more than 30 autogyro kits on the market.

brock_kb-2

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