Analytical Materials

Autogyros (Brief historical overview)

The autogyro (after Latin “autogyro”, that is, self-revolving) was invented in 1920 by Spanish engineer Juan de la Sierva. The autogyro is a flying vehicle heavier than air, with lifting capacity originating on the lifting rotor revolving freely under the action of running-on air flow passing through the lifting rotor disk, and the thrust is created by the power unit. Specifically, it ensures reduction of the take-off and landing speeds, take-off and landing runs.

The probability of a crash related to the construction strength or sudden outside impacts of the environment is considerably lower than for other types of piloted flying vehicles, according to the statistics of the last hundred years.

In the first models of the autogyro, actuation of the lifting rotor revolution before the flight was done manually by way of spin-up or from a tractor propeller, and its revolutions number increases at taxiing and take-off running. Later, there have been developed special drives to the main rotor from the autogyro engine.

The autogyro needs a runway (50ё100 meters) and a ground of a minimal size (run up to 7 meters). A pusher propeller is used to create horizontal speed in the autogyro. In case of faults in the autogyro engine, the vehicle can continue flying by means of parachuting.

Advantages as compared with an plane:

• safety in case of speed loss

• insensibility to air turbulence

• absence of flight limitations at wind of up to 20 m/s

• 180 degrees turn, practically, in position

• possibility of landing without running

• good field of vision

The main advantages as compared with a helicopter:

• lower cost

• reduction of vibration level

• lower operational expenditure

• absence of dangerous altitude in case of the engine failure

• absence of flight limitations at wind of up to 20 m/s

In the 1930s, the autogyro received wide acceptance in many countries, including the USSR.

The first Soviet autogyro KASKR-1, tried in 1929 by pilot I.V.Mikheyev, was designed and built under the supervision of practical designers N.I.Kamov and N.K.Skrzhynskyi.

At that time autogyros were adopted by nearly all European armies as well as navies, where they were used as reconnaissance vehicles and “headquarters couriers”.

Since the beginning of World War II five standard battle autogyros A-7-ZA were used in defensive fighting at Elnya. The machines were used only at night, and, mainly, for leaflets delivery to scatter over the rear positions of the enemy. M.L. Myl, N.I. Kamov’s student, the future helicopter general designer, was the engineer of the battle autogyros squadron.

At the same time, starting with 1930s, interest in autogyros began to wane notably. The reason was inability of these vehicles to compete with helicopters which featured a considerably broader range of flying characteristics. In late 1940s - early 1950s interest in autogyros practically dissol-ved against the background of achievements in development of helicopters. Autogyros turned out to be restricted by the speed range limitations (30-35 ё 220-250 km/h). Besides, helicopters are capable of performing any manouevre, including vertical, which is unattainable for the autogyro.

Interest in autogyros resumed in 1950s in the USA owing to effors of DSc Igor Bensen.

While working for the General Electric, he was engaged in investigations of Hafner “rotachute”, a small gliding motorless flying vehicle with a windmilling propeller.

The design of a small autogyro with a pusher propeller and direct control by the lifting rotor bushing, he developed, became commercially successful due to simplicity, low cost, easy control and fabrication.

The Bensen Aircraft firm, he set up, was developing autogyros named “gyrocopters”, primarily, for non-commercial use.

As opposed to autogyros by de la Sierve, Bensen’s “gyrocopters” featured a simple truss-beam fuselage design, McCulloch (later modified VM) pushing engine, direct control by the lifting rotor with the help of a handle at the top, making control “reverse”, three-support undercarriage with a nose wheel and tail additional support.

At present, the major part of autogyros are developed using Bensen’s “gyrocopter” designs. The distinguishing feature is use of the preliminary spin-up system, as well as upgrading of the design embodiment. Only vehicles Roto-Pup, LW-2, LW-3 of the firm Little Wing Autogyros and Pitbull of the firm Nort American Rotowerks use the tractor propeller and a three-support undercarriage with a tail support.

The market of light autogyros impresses by a variety of designs which, nevertheless, feature no fundamental differences. Some firms offer finished, adjusted and tried vehicles. Besides, a customer can buy at low price an autogyro design to suit his requirements and fabricate it from parts he buys or produces himself. It is possible to buy either a complete set or specific parts as well.

There is a great variety in constructional embodi-ment of the fuselage and the design styling (fairing, plating). In this respect autogyros can be compa-red to motorgliders. There are beam, truss-beam or truss designs available. Cover plating fixing can be complete, partial or absent.

The autogyros flying and technical characteristics range is relatively narrow and has stable, strictly determined limits. The minimal speed of horizontal flight is 13-20 km/h for vehicles with low specific load on the bearing surface (Air Command Single Place, Bumble Bee, Gyrobee, Dominator, SnoBird Exciter, Sport Copter Lighting and Vortex), up to 48-54 km/h at considerable specific load (Commander 147A, Barnett J4B and J4B2, Super Bandit, Sycamore Mkl).

Maximum speed is determined, primarily, by specific load on the bearing surface, resistance of non-bearing parts and rated capacity of the power unit, and is in the limits from 96-104 km/h for ultralights, corresponding to FAR-103 (Air Command Single Place, Ken Brock KB-2, KB-3, Bumble Bee, Gyrobee, Little Wing Rotor-Pup, SnoBird Explorer, Sport Copter Lightning, Rotor Wing 3D-RV) up to 160-200 km/h for autogyros with powerful engines and fairing (Commander 147A, Air&Space ISA, Barnet J4B and J4B2, Falcon, Magni M-14 and M-16, Marchetti Avenger, Montgomerie Merlin, RAF-200, Sport Copter Vortex, Sportster, Sycamore Mkl).