Country of origin:

United States of America

Description:

Light utility helicopter

Power Plant:

One 168 kw (225 hp) Textron Lycoming HIO-360-F1AD turbocharged four-cylinder horizontally-opposed air-cooled engine

Specifications:

History:

The Enstrom Corporation of Menominee County Airport, Michigan, was formed in 1959 by Rudy Enstrom to undertake the development and production of a small helicopter for private and commercial operation. An experimental machine with an un-covered steel-tube fuselage and two-blade main rotor was built. The production version, fitted with a three-blade rotor, became the F-28. It had a fully enclosed fuselage and tail-boom. A further change involved the use of a fully articulated main rotor in place of the earlier rigid type.

The prototype, known as the F-27, was first flown on 12 November 1960, and the production prototypes (F-28) were flown on 27 May 1962 and 15 May 1963 respectively, certification of the F-28A being granted in 1968.

The fuselage was a steel-tube pylon structure, with the external surfaces of the cabin being of laminated fibreglass reinforced plastic. The tail-cone was of aluminium alloy semi-monocoque structure with a fixed horizontal stabiliser. The three-blade fully articulated main rotor was of bonded construction, with each blade consisting of an extruded aluminium spar and two heavy-gauge aluminium alloy skins. The rotor was driven by a single belt from the engine to a rind and pinion reduction gear.

The first production model, the F-28, was followed in 1968 by the F-28A, which had a modified drive ratio to allow an increase in the useful load by 91 kg (200 lb). Experience showed the F-28A was under-powered and in 1976 a turbocharged engine and an improved tail rotor were installed.

The F-28B was released in 1970 fitted with a 168 kw (225 hp) Lycoming TIO-360 engine, and the F-28C was the next model to appear. By 1979 about 600 Enstrom light helicopters had been delivered. At that time it was being produced in four basic versions: the F-28C and the 280C Hawk, both fitted with the turbo-supercharged Avco Lycoming HIO-360-E1AD engine; and the F-28F Falcon and the 280F in 1981, both with the more powerful Avco Lycoming HIO-360-G1AD engine.

The F-28 series was classed as the work-horse of the fleet, and could be supplied with a cargo-hook, crop-spraying kit, and single or double stretcher kits. The 280 series, known as the Shark, was a streamlined high-speed version designed for fast economical transport of persons. The F-28P Sentinel was a model aimed at the police-work market.

Enstrom decided to exploit the market in the late 1970s and develop the 280L Hawk, this model flying in January 1979, but it was shelved. In January 1985 the 280FX was introduced and replaced the 280F on the production line.

More than 1,000 examples of the series have been built and production has continued. In 1989 the turbine 280FX was followed by the TH-28 the next year, each powered by the Allison 250-C20 turbine, the former going into production as the 480 and seating five. Top of the range was the 480, fitted with a 213 kw (285 shp) Allison 250-C20W turboshaft, and the similarly powered TH-28 three-seat trainer, the first of which flew in 1989. The latter was entered in a US Army competition for a pilot training helicopter. The first military contract was for five 280FXs for the Chilean Army for pilot training, followed by Colombia, Peru and the Venezuelan National Guard.

In the early 1980s Heliflite of Castle Hill, NSW was appointed as the distributor for Australia and New Guinea, initially importing a turbocharged model for demonstration as a machine suitable for operations in rural areas, particularly in the spraying and mustering roles. In the former role the F-28F had booms and two 364 litre (80 gal) tanks. Heliflite acquired the range of spares held by the previous distributor, Forrestair of Essendon, VIC, a Division of H C Sleigh. Australian operators included Hookway Aviation and Cruse Air.

In New Zealand four examples have appeared on the register. The first imported to New Zealand was an F-28A ZK-HIE (c/n 049 – ex N4923) for demonstration, operated by Canterbury Helicopter Training. It was involved in an accident in Lake Rotorua and was rebuilt. At one time one ZK-HKQ (c/n 422), owned by Lilburn Farms of Raetihi, was used on spraying work. Later a 280C Shark was imported, becoming ZK-HSE (c/n 1186) for Crater Lakes Helicopters, and a 280C Shark ZK-HVJ (c/n 1081) was registered to Range Helicopters in August 1985.