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Archimedes Rotorcraft & V/STOL Museum

Autogiros, Autogyros, Gyrocopters, Gyroplanes.

A number of names for the same machine, a rotary-winged aircraft that flys in Autorotation, i.e.- there is no power delivered to the rotor in flight. Air passing upward through the rotor causes both lift and a forward force which keeps it turning. An asymmetrical airfoil with a slight reflex at the trailing edge works best for autorotation, but a symmetrical airfoil will also work.

autorotation diagram

Diagram of autorotation forces

The beginning.

Juan de la Cierva of Spain, with a desire for a safer aircraft, spent many years inventing the Autogiro.

Cierva 1935
Cierva in 1935

On January 10,1923, Juan de la Cierva's C.4 Autogiro made its first crow hop, but unfortunately was rolled over. It was quickly rebuilt and the first public demonstration flight occurred on January 17, 1923. Cierva was not the first to experiment with autorotation, but he did solve the isssue of dissemetry of lift between the advancing and retreating blades. The C.4 flew straight and steady for 600 ft at an altitude of 13 ft at Getafe airfield in Spain. The rotor was fixed and the aircraft used ailerons and elevator for flight controls. The first cross-country flight of an autogiro (Cierva C.6) was made fromCuatro Vientos to Getafe airfield on December 12th, 1924. The flight was 7 1/2 miles and lasted 8 minutes 12 seconds at an average speed of 48 mph.

Cierva C.4
Cierva C.4
Cierva C.4 in flight
Cierva C.4 in flight

Many experiments with allowing the rotor to tilt side to side were performed with the C.4 and subsequent models that followed. The first Autogiro with "direct control" (a universal mounted rotor that allowed tilting all around the azimuth) was the Cierva C.19 Mk.V in 1932. Several tests between March 5th - 22nd were performed without wings or a tailplane. Later versions included small horizontal tails and some were moveable, or with large flaps to direct prop blast into the rotor to aid in prerotation.

Cierva C.19 Mk.V no tail
Cierva C.19 Mk.V without wings or horizontal stab
Cierva flies C.19 Mk.V with horizontal tail
Cierva flying the C.19 Mk.V with horizontal tail

Harold F. Pitcairn

Pitcairn is the most notable of Cierva's customers/licensees and there were many. In August 1928, Harold ordered a C.8 Autogiro fitted with a Wright Whirlwind engine. The C.8 Mk.IV was designated C.8W (NC418) and was the first Autogiro flown in the U.S. on December 19, 1928. Pitcairn conducted flight tests comparing the Autogiro to his famous Mail Wing airplane. He was impressed enough by the flight characteristics and performance that he licensed with Cierva gaining access to Cierva's designs and patents. Pitcairn pushed forward with his own designs, the most famous of which is the Miss Champion PCA-2.

Miss Champion
Miss Champion
Miss Champion flying
Miss Champion flying

The first Pusher Autogiro was the Buhl Pusher. It utilized many elements of the Pitcairn PA-18 and was designed for observation and aerial photography. The first flight was December 15, 1931. The timing amidst the great depression killed off the project.

Buhl Pusher flying
The Buhl Pusher in flight

The advent of direct control and removal of the wings proved rotary-winged flight was viable and paved the way into production of the conventional helicopter. It is unfortunate and ironic that Autogiro technology brought about its own demise. The military wanted the helicopter and abandoned the Autogiro.

Enter Bensen.

Igor Bensen brought new life into the Autogiro. His idea of a small machine for the everyday man grew the Bensen Gyrocopter to become the most sold kits and plans in the amateur built arena.

Inside story: The men in the rotary-wing lab at Wright Patterson AFB were told to participate in a local fly-in in Fairborn Ohio. They decided to take their Hafner Rotorchute for display. Igor Bensen came to this fly-in and asked if he could borrow the Rotorchute for study. They let Bensen have the machine, which was never returned. In July of 1954 there was an article in Popular Science magazine about Bensen's great new invention. It was litterally an almost direct copy of the Hafner Rotorchute. Bernie Lindenbaum of the WPAFB rotary-wing lab wrote to the editors telling them that Bensen did not invent the machine. Bernie's letter was published in the next issue of Popular Science.

Hafner Rotachute
Hafner Rotochute
Hafner Rotachute flying
Hafner Rotachute flying
Bensen B-6
Bensen B-6 Gyroglider
Bensen B-6 in Museum
Bensen B-6 in Museum

There were several things novel to the Bensen B-6 Gyroglider however. Bensen realized that the retreating blades flapped downward an equal amount to the advancing blades upward flap. Instead of using individual flapping hinges on the rotorblades, he mounted them solid and used a pivot, or flapping hinge, at the center of the rotor hub. This simplified construction for the home builder and worked equally well to combat disymmetry of lift. Also, the B-6 Gyroglider was constructed out of 3/8 and 1/2 inch water pipe, which was readilly available at one's hardware store. The airframe of screwed together water pipe was not well accepted by the aviation communtity. Bensen quickly developed the B7- Gyroglider made of round aircraft quality aluminum. This was followed by the B7-M, a motorized variety enabling free flight. He used the Nelson H-59 engine which with its 40 hp was barely enough to fly the machine. The machine presented other difficulty to the home builder. Drilling the holes on center of the round tube and plugging the tubes with wood anywhere a hole was drilled was a challenge. He then developed the B8-Mc, a square tube construction utilizing the McCulloch 72 hp Target Drone engine. The square tubing was easier for the home builder and did not require pluggin with wood. Sales of kits and plans boomed.

Bensen B-7M
Bensen flying the B-7M with Nelson H-59 engine
Bensen B-8M
Bensen flying the B-8M with McCulloch engine

We happen to have Bensen's personal Gyrocopter in the museum. It was taken when Bensen Aircraft went out of business in 1984 and later donated to the museum.

Bensen's machine
Bensen's personal Gyrocopter sitting outside the museum

Bensen's success stirred renewed interest in Autogiros and two new entries came into the Gyroplane realm. Type certified machines, the Umbaugh 17 and the McCulloch J-2 were brought into production.

The Umbaugh was tandem seating pusher Gyroplane with jump take-off ability. Ray Umbaugh hired Gilbert Devore to design the machine in 1958. The first 5 machines for testing and type certification were constructed by Fairchild in Maryland. The first flight of N43U was in August 1959. The first machine used a T-tail which proved to be inadequate. They also tested a V-tail which also was inadequate. They ended up with the Tri-tail configuration. Umbaugh went bankrupt and his investors stepped in and took over. Air & Space company was formed and production set up in Muncie, Indiana. (Archimedes museum has the remaining husk of #1(N43U), and also the first machine off the assembly line in Muncie, #6) Air & Space eventually went bankrupt after producing 68 of the now 18-A Gyroplanes in 1966.

Umbaugh U-17
Umbaugh U-17, N43U, with T-tail 1959
Umbaugh 18-A Tri-tail
Later Umbaugh 18-A with Tri-tail
Air & Space 18-A
Air & Space produced 18-A
# 6 in museum
Air & Space #6 in museum

The McCulloch J-2, side by side 2 place, was designed by Drago Jovanovich in 1962. McCulloch purchased the rights in 1969 and started production. The J-2 suffered from ground resonance with the original head and blades. To save money on development they got approval to use the Hughes 269 head and blades. Between 1969 and 1974 when production ceased 83 machines were produced.

McCulloch J-2
The McCulloch J-2
McCulloch J-2 blue
Another J-2 in Blue

Within the Amateur Built category, a great many Gyroplanes have been designed, built, and sold. Most are modifications of Igor Bensen's designs. Air Command, Barnett, Bumble Bee, Carr, Dominator, Holmann, Honey Bee, RAF, Sport Copter, just to name a few. There are many new designs out there today - Check them out!