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Further Reading

RON-1 / QH-50 Gyrodyne DASH

An important step in the development of the Drone Anti-Submarine Helicopter for operation from destroyers was taken in April 1958 when an existing Bureau of Aeronautics contract with Gyrodyne for the RON-1 rotocycle (one man helicopter) was amended to provide for the development, installation and flight test of remote control equipment. The QH-50 Gyrodyne was an small unmanned ASW helicopter, built in 1960. The USN bought more than 300.

The Gyrodyne carried two torpedos. The US Navy has studied the feasibility of operating Vertical Takeoff and Landing (VTOL) UAVs since the early 1960s to overcome the limitation of short takeoff distance from surface vessels, the QH-50 Gyrodyne torpedo-delivery drone being an early example. Nonetheless, high cost and technological immaturity precluded acquiring and fielding operational VTOL UAV systems at that time.

Western trends have concentrated on single main rotor/tail rotor, tandem rotor, and synchropter devices. An exception to this is shipboard launched short-range unmanned aerial vehicles (UAV) where the need for vertical takeoff and landing capability combined with stable handling characteristics has renewed interest in the coaxial configuration. The QH-50 series served as a remotely controlled, weapon-carrying drone used for antisubmarine warfare. Over 700 QH-50s were subsequently built and delivered to the US Navy.

The Hiller Aircraft Company produced the first successful American coaxial helicopter in 1944. Hiller went on to produce the XH-44, which was followed by Bendix (Models K and J), Hoppicopter, Brantly, Roteron, and Jenson. When Bendix dissolved in 1949, they sold their Model K to the National Advisory Committee for Aeronautics (NACA) Langley Research Center for rotor research work and their Model J to the Gyrodyne Company of America. During the 1950s, NACA Langley used their rotor as part of a program to investigate the general characteristics of multiple-rotor configurations in the Langley full-scale tunnel, which was also supplemented by small-scale model tests.

Gyrodyne continuously worked to improve the coaxial rotor helicopter concept over a number of years. After converting the Bendix Model J to the Model 2C, problems arose such as vertical rudders and differential collective failing to provide adequate yaw control in autorotation. March 1953 saw the idea of using "tip brakes," which solved this problem. Gyrodyne went on to develop the XRON and YRON series.

On 23 May 1957 a drone HTK-1 helicopter, carrying a safety pilot, operated from the fantail of Mitscher (DL 2) in the vicinity of Narragansett Bay. These tests and others, conducted in February off Key West, in which a piloted HUL-1 carried Mk 43 torpedoes in flights to and from the Mitscher, demonstrated the feasibility of assigning torpedo carrying drone helicopters to destroyers and led to the development of the Drone Anti-Submarine Helicopter (DASH) which was later embodied in the QH-50C.

An important step in the development of the Drone Anti-Submarine Helicopter for operation from destroyers was taken on 02 April 1958 as an existing Bureau of Aeronautics contract with Gyrodyne for the RON-1 rotocycle (one man helicopter) was amended to provide for the development, installation and flight test of remote control equipment.

In 1961 a test and evaluation was conducted on the Gyrodyne YRON-1 rotorcycle to determine its tactical suitability for Marine Corps use as a vertical lift vehicle portable by one man, simple to maintain, and requiring operator training of a degree comparable to that given motor vehicle operators. The YRON-1 did not satisfy the stated requirement for a vehicle of this type. Maintenance and operator training requirements were considered excessive for the intended operati nal purpose of the vehicle, therefore it was c nsidered unsuitable for Marine Corps use.

In the early 1960s, the Navy laid plans to operate the unmanned DASH, the Drone-Anti-Submarine Helicopter. Dozens of older destroyers were rebuilt to incorporate a small flight deck and hangar. But technical obstacles prevented DASH from becoming operational, leaving scores of ships with new aviation facilities too small to accommodate manned aircraft. The empty flight decks were embarrassing, but the ships themselves retained enough capability to stay in service another decade or so.

Gyrodyne is now a generic term in the FARs, used to describe an aircraft with dual propulsion units for vertical and horizontal flight. A gyrodyne is defined in the National Aeronautics and Space Administration Aeronautical Dictionary, 1959, as follows: "A rotating-wing aircraft whose rotor or rotors provide lift only, the system customarily being powered for take-off, hovering, landing, and for forward flight throughout part of its speed range, but usually autorotating at the higher flight speeds, forward propulsion being provided by a propeller or jet." There is also a company called the Gyrodyne Company of America, an aerospace contractor, which had a trademark, which used the name gyrodyne. The trademark has lapsed. The Gyrodyne concept is currently being pursued under license by Dornier GmbH (Germany) and Israeli Aircraft Industries, Ltd. (Israel).

Coaxial helicopters have been a reality for several decades now - including a series of UAV or RPV platforms (the Candair CL-237, the Westland 'Sprite,' and the Gyrodyne QH-50, among others). The use of two counter-rotating rotors is employed in some helicopters, such as for example, a Kamov helicopter of Russian origin. The use of counter-rotating concentric rotors has the advantage of having a zero net angular momentum thus avoiding the requirement of a tail rotor for torque balancing required in the single main rotor arrangement, as in the conventional helicopters. There is also a saving in power, which is normally consumed by the tail rotor of a conventional helicopter. However, due to the lower rotor being placed in the wake of the upper rotor, there is an interference effect, which results in an increase in the power required for a given thrust, thus nullifying to some extent, the savings in power of the tail rotor.

A rotary wing aircraft with a contra-rotating rigid rotor system is capable of higher speeds compared to conventional single rotor helicopters due in part to the balance of lift between the advancing sides of the main rotor blades on the upper and lower rotor systems. In addition, the retreating sides of the rotors are also generally free from classic retreating blade stall that conventional single or tandem rotor helicopters may suffer from.

To still further increase airspeed, a rotary wing aircraft may incorporate an auxiliary translational propulsion system. Use of a coaxial contra-rotating rotor system in combination with an auxiliary translational propulsion system, allows a rotary-wing aircraft to attain significantly greater speeds than conventional rotary-wing aircraft, while maintaining hover and low speed capabilities.

One system significant to these flight attributes is the design of the main rotor, of which the rotor blades are the primary force and moment generating components. Design requirements for a rotary-wing aircraft incorporating a contra-rotating rotor system differ significantly from conventional rotary-wing aircraft. As with a conventional rotary-wing aircraft, the advancing blades of both the upper and lower rotors produce lift; however, unlike a conventional rotary-wing aircraft, the retreating blades of the contra-rotating rotor are off-loaded commensurate with increasing flight velocity, and need not produce lift to balance lateral (rolling) moments. Rather, roll equilibrium is attained by balancing the net effects of the equal and opposite moments produced by the advancing side blades of the counter-rotating rotors. The ability to off-load the retreating blades from producing lift alleviates retreating blade stall -- a primary cause of speed limitation on conventional rotary wing aircraft -- thereby permitting much greater forward flight speeds to be achieved.

The QH-50 Unmanned Aerial Vehicle (UAV) helo platfrom remained in service into the 21st Century as a target drone and experimental test platform.