The Groen Hawk 4 was a single engine,

pusher configuration In an aircraft with a pusher configuration (as opposed to a tractor configuration), the propeller(s) are mounted behind their respective engine(s). Since a pusher propeller is mounted behind the engine, the drive shaft is in compression in n ...

, four seat

autogyro An autogyro (from Greek and , "self-turning"), also known as a ''gyroplane'', is a type of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. Forward thrust is provided independently, by an engine-driven propeller. Whi ...

built in the United States in the late 1990s. Three prototypes, two piston engined and one turboprop powered, were flown but the Hawk did not go into production.

Design and development

Design work on the Hawk utility/passenger autogyro began in 1996 and the first prototype, the two seat H2X, first flew on 4 February 1997. It was later modified to include a third seat and renamed the Hawk III. The production prototype, a four-seater named the Hawk 4, was significantly different from the Hawk III in detail but retained the pod and mid-line pusher engine configuration, combined with low stub wings, twin booms and

fins A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...

. Changes between the Hawk III and 4, apart from cabin revisions to accommodate the extra seat, included a new constant chord, aluminium rotor in place of the earlier tapered, composite blade. The rotor was also lowered and the pitch control levers enclosed within a shallower fairing. The wings and fixed

tailplane A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplane ...

were cropped, so that they no longer extended beyond the booms and fins, the

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally aircraft, air or watercraft, water). On an aircraft the rudder is used primarily to ...

s were shortened so that the tailplane no longer needed cut-outs for their movement and extra, short, inboard rudders were added. Successive engine changes increased the power by almost a factor of two. The Hawk 4 had a steel rotor mast and engine mountings but was mostly aluminium elsewhere, including the rotor, rotor head and

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

. The

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

was an aluminium

semi-monocoque The term semi-monocoque or semimonocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement. Semi-monocoque construction is used for, among ot ...

. Some components, such as the nosecone, engine cowling and cabin door were formed from

composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...

s. The rotor was a semi-rigid or teetering design with a swash plate, rotating at up to 270 rpm. Yaw was jointly controlled by the balanced rudders on the endplate fins and the all-moving inboard rudders. It had a fixed,

tricycle undercarriage Tricycle gear is a type of aircraft undercarriage, or ''landing gear'', arranged in a tricycle fashion. The tricycle arrangement has a single nose wheel in the front, and two or more main wheels slightly aft of the center of gravity. Tricycle g ...

with mainwheels mounted at the tips of the stub wings. Two rows of seats accommodated the pilot and up to three passengers; alternatively, the rear seats could be folded to provide baggage space. The Hawk 4 was powered by a 261 kW (350 hp)

Continental TSIO-550 The Continental IO-550 engine is a large family of 9 liter fuel injected six-cylinder, horizontally opposed, air-cooled aircraft engines that were developed for use in light aircraft by Teledyne Continental Motors. The first IO-550 was deliver ...

air cooled

flat-six A flat-six engine, also known as a horizontally opposed-six, is a six-cylinder piston engine with three cylinders on each side of a central crankshaft. The most common type of flat-six engine is the boxer-six engine, where each pair of opposed cy ...

piston engine, which provided pre-rotation power to the rotor for jump starts and drove a four blade propeller in forward flight. The Hawk 4 first flew on 29 September 1999 and had logged 120 hours by the following April. A second aircraft, initially designated Hawk 4T and powered by a 313 kW (420 hp)

Rolls-Royce 250 The Allison Model 250, now known as the Rolls-Royce M250, (US military designations T63 and T703) is a highly successful turboshaft engine family, originally developed by the Allison Engine Company in the early 1960s. The Model 250 has been pro ...

-B17C

turboprop A turboprop is a turbine engine that drives an aircraft propeller. A turboprop consists of an intake, reduction gearbox, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. Fuel ...

driving a three blade propeller first flew on 12 July 2000. It was redesignated Hawk 4 when development of the piston engine version was dropped. It had a taller undercarriage, high set tailplane, endplate fins with rounded extensions below the tailbooms and modifications to the inboard rudders. The Hawk 5 was a planned five seat development. Despite optimistic sales predictions before the 2000 recession, the Hawk did not reach production.

Operational history

In 2002, the

Winter Olympic Games The Winter Olympic Games (french: link=no, Jeux olympiques d'hiver) is a major international multi-sport event held once every four years for sports practiced on snow and ice. The first Winter Olympic Games, the 1924 Winter Olympics, were he ...

contracted with GBA to provide aerial security over Salt Lake International Airport. The Hawk 4 second prototype bearing the acronym ''UOPSC'' (Utah Olympic Public Safety Command) was used for this assignment.“Olympic Security Aided by Groen Brother’s Hawk”, Aero-News Network
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Specifications (Hawk 4, piston engine)

References

External links

{{ external media , align=left , video1 ={{youtube, XCEYfW8DyxQ , Hawk 4 Gyroplane Takeoffs and Landings

Hawk Hawks are bird of prey, birds of prey of the family Accipitridae. They are widely distributed and are found on all continents except Antarctica. * The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks and others. Th ...

Single-engined pusher autogyros 1990s United States civil aircraft