Groen Brothers has been working on its Hawk Gyroplane family since 1986. Prototypes leading up to the Hawk 4 include the Hawk I and H2X. The Hawk 4 Gyroplane is the first in a series of near VTOL-capable aircraft and is initially being developed and marketed to government agencies, with FAA certification not expected for at least two years. The RevCon 6G technology demonstrator uses the fuselage of a Cessna 337 as the basis of its fuselage and will be progressively modified into a gyrodyne by the addition of rotor blade mounted tipjets; Groen has offered its GyroLifter gyrodyne to the US Department of Defense. The company has a flight test facility at Buckeye, Arizona, where, on 12 July 2000, the prototype Jet Hawk 4T / Hawk 4 made its initial flight.

In July 2001, Groen announced plans to move to a new 18.580m² facility at Phoenix, Arizona. The plant, which will cost US$14 million and employ 425, was intended to become operational by end 2002 and have the capacity to produce four aircraft per day, however this has lapsed.

In August 2001 the company concluded a joint venture with Al-Obayya Corporation to produce and market gyroplanes in Saudi Arabia. However, economic downturn of late 2001 resulted in 85 of 130-strong workforce being laid off. Earlier plans for Chinese assembly also appear to have lapsed.

Groen is also the parent of American Autogyro (AAJ), whose Sparrowhawk is described elsewhere.

GROEN HAWK 4

TYPE: four-seat autogyro

PROGRAMME: Based on proof-of-concept Hawk One (N4379X) first flown 26 September 1992; design started April 1996 and prototype two-seat H2X (N4412X) first flew 4 February 1997; later converted to three-seat Hawk III standard. First deliveries had been due June 1998, but design changes to H2X and later Hawk III in October 1998 resulted in Hawk 4. Initial aircraft (N402GB) first flew 29 September 1999, powered by a Continental piston engine, and made first vertical take-off on 9 December 1999; had flown 120 hours in 200 sorties by early April 2000. In September 2000 company switched certification effort to turbine-powered Hawk 4T (N403GB), which was renamed Hawk 4 at this time following abandonment of piston-engined version; the following October Groen changed its focus to seek government contracts for Hawk 4, slowing certification process for both piston- and turbine-powered versions until it sees market upturn.

On 28 December 2001, Groen announced contract with Utah Olympic Public Safety Command for lease of Hawk 4, beginning 20 January 2002, for security patrols at Salt Lake International Airport, equipped with video downlink system, Spectrolab SX-5 searchlight and additional radios; aircraft flew 75 hours in 67 operations.

CURRENT VERSIONS:

• Hawk 4: Currently powered by 313kW Rolls-Royce 250-B17C turboprop; first flew (N403GB) 12 July 2000; originally intended for certification late 2001. Other changes include addition of underfins and taller landing gear. Two further prototypes under construction.

  Applications include airborne law enforcement., electronic news gathering, aerial surveillance, utility/passenger transport and aerial application.

• Jet Hawk 4T: Original designation for turbine-powered version. Renamed Hawk 4 by 2002.

• Hawk 8: Proposed eight-seat variant with four-blade rotor and 559kW turboprop engine.

CUSTOMERS: By May 2003, deposits on 148 aircraft had been taken, via 12 dealerships. Fractional ownership programme announced July 2001 but later dropped.

COSTS: Around US$749.000 (2003).

DESIGN FEATURES: Twin tailbooms supported by stub-wings which also house main landing gear; large twin stabilisers and rudders; with fixed horizontal tail surface mounted between the vertical tails. Two-blade, semi-rigid aluminium teetering rotor with swashplate. Rotor speed 270rpm.

FLYING CONTROLS: Patented collective pitch-controlled rotor head allows smooth vertical take-off (zero ground roll) and enhanced flight performance. Rotor brake is standard. Actuation by pushrods. Patented dual-control stack cyclic flight controls.

STRUCTURE: Steel mast and engine mounts; stressed skin aluminium semi-monocoque fuselage, tail unit, hub structure and propeller; composites nose, engine cowling and wingtips; acrylic windscreen and doors; glass fibre nosecone and engine cowling.

LANDING GEAR: Initially fixed tricycle type; with electrohydraulically operated retractable gear to be offered later. Mainwheel tyres 6.00x6; nosewheel 5.00x5; Cleveland hydraulic brakes. Twin safety wheels at rear of tailbooms.

POWER PLANT: Production prototype for Hawk series was powered by a 134кW Textron Lycoming O-360-A4M flat-four. Hawk H2X had one 335kW Geschwinder V-8 aluminium liquid-cooled engine, derated to 261kW at 2.500rpm, driving a Hartzell three-blade constant-speed propeller.

Hawk 4 piston-powered version has air-cooled, six-cylinder Teledyne Continental TSIO-550 rated at 261kW at 2.700rpm; prototype had four-blade MTV propeller but production models will have Hartzell three-blade constant-speed propeller. Engine provides power to rotor for prerotation to provide for short and vertical take-off capability; power to rotor system never engaged during flight. Hawk 4 turbine-powered version has one 313kW gas turbine engine driving three-blade constant-speed propeller.

Fuel capacity 284 litres in single tank at rear of fuselage; refuelling point at top of fuselage. Oil capacity 11.4 litres.

ACCOMMODATION: Pilot and up to three passengers in enclosed cabin in two pairs of seats; rear seats fold to provide baggage space.

SYSTEMS: Electrical system 28V DC.

AVIONICS: Comms: Honeywell KLX 135A GPS/COM, KT 76A transponder with Mode С, РМ 3000 intercom. Flight: United Instruments suite.

Technical data for Hawk H4 Rotor diameter: 12.80m, fuselage length: 7.31m, overall height: 4.11m, empty weight: 835kg, max. take-off weight: 1587kg, max. speed: 238km/h, cruising speed at 75% power: 212km/h max. rate of climb at sea level: 457m/min, service seiling: 4875m, take-off run: 8m, range with max fuel at 75% power: 584km