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QH-50 Drone Anti-Submarine Helicopter (DASH)
DSN Drone Anti-Submarine Helicopter (DASH)
XRON/YRON-1 Rotocycle

The QH-50 (originally designated DSN) family, produced by Gyrodyne were unmanned rotary wing aircraft initially developed to meet the requirements for the US Navy's Drone Anti-Submarine Helicopter (DASH) program. QH-50s operated from US destroyers, capable of carrying one or two torpedoes or a single Mk 17 Nuclear Depth bomb depending on the model. Over 700 QH-50s were subsequently built and delivered to the US Navy. The QH-50s were later used as target drones and for a number of special programs.

Western trends in the development of rotary wing aircraft almost entirely concentrated on single main rotor/tail rotor, tandem rotor, and synchropter devices. An exception to this was shipboard launched short-range unmanned aerial vehicles, where the need for vertical takeoff and landing capability combined with stable handling characteristics renewed interest in the coaxial configuration.

Gyrodyne, the name company responsible for the development of the subsequently system, became a generic term in the Federal Aviation Regulations, 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, dated 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." The company, called the Gyrodyne Company of America, had had the term trademarked, but it subsequently lapsed. Other companies subsequently pursued the "gyrodyne" concept, such as Dornier GmbH (Germany) and Israeli Aircraft Industries, Ltd. (Israel).

Coaxial helicopters were a known quantity, with many types being built and fielded by militaries and civilian concerns, including a series of unmanned or remotely piloted platforms (the Candair CL-237, the Westland 'Sprite,' as well as the Gyrodyne QH-50, among others). 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 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. From this experience, Gyrodyne went on to develop the XRON and YRON series of rotocycles.

On 23 May 1957, a drone HTK-1 helicopter, carrying a safety pilot, operated from the fantail of USS Mitscher (DL 2) in the vicinity of Narragansett Bay. These tests and others, conducted in February 1958 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).

An important step in the development of the Drone Anti-Submarine Helicopter for operation from destroyers was taken on 2 April 1958 as an existing Bureau of Aeronautics contract with Gyrodyne for the RON-1 rotocycle (a one man helicopter) was amended to provide for the development, installation and flight test of remote control equipment. The US Navy subsequently acquired 9 DSN-1s and 3 DSN-2s for developmental purposes.

In Summer 1959, the US Navy's Ships Characteristics Board determined that gasoline engines presented a fire hazard for ships. As a result, planned purchases of additional gasoline engined DSN-1s and -2s were cancelled. The decision was then made to acquire a turbine-powered variant, the DSN-3. Still, the existing stock of DSN types continued to be used in evaluations. On 1 July 1960, a DSN-1 landed on the USS Mitscher, with a safety pilot aboard. On 7 December 1960, a DSN-1 made a completely pilot-free landing on the USS Hazelwood (DD-531).

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 operational purpose of the vehicle, therefore it was considered unsuitable for Marine Corps use.

However, Gyrodyne continued to work on the DSN series for the DASH program. To support the program, dozens of older destroyers were rebuilt to incorporate a small flight deck and hangar for the helicopter. In 1962, as part of the change in designation practices for aircraft and missiles across the department of defense, the DSN-1 was redesignated the QH-50A, the DSN-2 was redesignated as the QH-50B, and the DSN-3 was redesignated as the QH-50C. The QH-50C was still in development, only making its first flight on 25 January 1962.

The USS Buck (DD-761) received the first QH-50C on 7 January 1963, but further deployment of the DASH was slowed by vibration problems in the initial batch of 80 aircraft. The fleet was grounded on 5 June 1963 to correct the problems, resuming flight operations on 1 July 1963. In late 1963, Secretary of Defense Robert McNamara approved a budget that provided funding for 2 operational DASH systems and another backup DASH system for each of the 240 destroyers the Navy planned to upgrade as part of the 2 phases of the Fleet Rehabilitation and Modernization (FRAM) program. In 1964, the US Navy ordered an improved QH-50D, which included an improved engine and lower maintenance fiberglass rotor blades. The new rotor blades were subsequently retrofitted to existing QH-50Cs. In 1968, Boeing ceased production of the T50-BO-12 engine being used in the QH-50D, leading to the development of the QH-50E, which used an Allison T63-A-5A, Model 250-C19A. Only 3 QH-50Es were produced before the US Navy decided to terminate the program.

The US Navy deployed the system in destroyers around the world, with the system seeing service during the conflict in southeast Asia. In January 1965, the US Navy explored using the QH-50C/D as reconnaissance platform by fitting video and film cameras to the aircraft as part of Project Snoopy. A telemetry system to allow remote operators to monitor their actions and a transponder to track location were also installed. QH-50s modified under Project Snoopy were used for missions like spotting for naval gunfire support. Under a program conducted joint by the Advanced Research Projects Agency (ARPA; now the Defense Advanced Research Projects Agency or DARPA) and the US Navy, called DESJEZ, using the QH-50 to deploy sonobouys and relay the information back to its mothership was also explored in 1969. In 1970, the US Navy ended DASH operations service-wide, citing the systems cost and its failure to meet requirements. The bulk of the ships that had been modified to carry the DASH had been decommissioned as well.

Though the US Navy decided to stop pursuing DASH, QH-50s had been modified by the APRA for reconnaissance and strike missions as part of Projects Nite Panther and Nite Gazelle. The Navy had also experimented with the QH-50 as a gunship, as well as looking at whether it might be possible to use it to rescue personnel or deploy electronic countermeasures. The Paris Peace Accords, which ended the bulk of US operations in Vietnam in 1973, ended the immediate requirement for QH-50s capable of performing these missions. In 1974, ARPA stopped their work with the type, passing some remaining aircraft to the US Army.

The Navy transferred its remaining QH-50s to the Naval Air Warfare Center at China Lake and to the US Army's White Sands Missile Range, where they served as target drones. The Navy explored restarting QH-50 production in 1986 as its supply of drones ran low, but the costs were determined to be too high. In 1995, the QH-50 target drone program was transferred entirely to the US Army. The system remained in service into the first decade of the 21st Century as a target drone and experimental test platform. Also, in addition to its US service, the QH-50 was operated in the anti-submarine warfare role by the Japanese Maritime Self-Defense Force between 1965 and 1977, when it was removed from service due in large part to logistical issues arising from the US Navy decision to cancel the DASH program.




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Page last modified: 10-04-2012 13:25:23 ZULU