AP 118 · No. 10 Section II · Aircraft Plate 256 / 280

Plate 256 of 280 · Cold War · Experimental light twin-engined helicopter

Cierva Grasshopper III

Grasshopper III, G-AWRP, painted as G-AWRP, constructor’s number GB-1, the first prototype of the Cierva Rotorcraft Grasshopper III (CR.LTH-1, later called the CR Twin), first flown on 18 August 1969, shown at the Farnborough show in 1970 and last flown in October 1971, now displayed at The Helicopter Museum, Weston-super-Mare: a five-seat light helicopter with two contra-rotating, two-bladed coaxial rotors and no tail rotor, powered by two 145 hp Rolls-Royce Continental O-300 flat-six engines in egg-shaped nacelles standing out either side of the tail cone behind the cabin, a rounded cabin with a one-piece glazed dome and four doors, a tapered tail boom with a plank tailplane and a fin and rudder running above and below the boom, and skid landing gear with bowed cross tubes, shown on its black display trolley: ivory overall with black ‘G-AWRP’ under the rear doors, white blades with red tips and grey metal rotor heads, as displayed (shape from a side-on 1970 photograph of the aircraft and widths from cameras solved for museum photographs, as no three-view is known; the rotor-head spacing follows the museum’s figure of 68.5 cm, and the starboard engine bay, which no museum photograph shows, is assumed to match the port one).

3D model

Turn it over

A procedural model built in Blender from published dimensions, drawings and photographs, painted as G-AWRP, constructor’s number GB-1, the first prototype of the Cierva Rotorcraft Grasshopper III (CR.LTH-1, later called the CR Twin), first flown on 18 August 1969, shown at the Farnborough show in 1970 and last flown in October 1971, now displayed at The Helicopter Museum, Weston-super-Mare: a five-seat light helicopter with two contra-rotating, two-bladed coaxial rotors and no tail rotor, powered by two 145 hp Rolls-Royce Continental O-300 flat-six engines in egg-shaped nacelles standing out either side of the tail cone behind the cabin, a rounded cabin with a one-piece glazed dome and four doors, a tapered tail boom with a plank tailplane and a fin and rudder running above and below the boom, and skid landing gear with bowed cross tubes, shown on its black display trolley: ivory overall with black ‘G-AWRP’ under the rear doors, white blades with red tips and grey metal rotor heads, as displayed (shape from a side-on 1970 photograph of the aircraft and widths from cameras solved for museum photographs, as no three-view is known; the rotor-head spacing follows the museum’s figure of 68.5 cm, and the starboard engine bay, which no museum photograph shows, is assumed to match the port one). Drag to orbit, scroll or pinch to zoom · download .glb (860 KB)

Data plate

Specification

First flight, number built and top speed are for the whole family (Grasshopper 1, Grasshopper III / CR Twin); engine, crew and dimensions are for the Grasshopper III, G-AWRP modelled here.

History

The Grasshopper III

The Grasshopper began as the design of the engineer J. S. Shapiro, whose small company built a two-seat coaxial helicopter of that name at Redhill in Surrey in the early 1960s. Its two rotors turned in opposite directions, one above the other, so that their torque cancelled out and no tail rotor was needed. In 1965 the Cierva Autogiro Company, the firm Juan de la Cierva had founded in Britain in the 1920s and which the Weir family of Glasgow had backed ever since, took over the Grasshopper’s sponsors and became Cierva Rotorcraft, with Shapiro’s design as its main project.

The Grasshopper III, also called the CR.LTH-1 and later the CR Twin, kept the coaxial rotor system but put it on a new, streamlined five-seat pod-and-boom fuselage, an early example of modular composite construction. It had two engines, one in each of the egg-shaped nacelles behind the cabin, to meet the worries of the late 1960s about single-engined helicopters, and the two rotors were set only 68.5 cm (27 in) apart to cut height and drag. The Ministry of Technology paid for research, and the first prototype, G-AWRP, flew on 18 August 1969. A second, G-AXFM, followed later that year, and G-AWRP was shown at the Farnborough show in 1970.

A third Grasshopper III, G-AZAU, flew in 1971 with more powerful Continental IO-360 engines, and Cierva drew up larger versions, the CR.420 and the CR.640, for production. The money to build them never came. Air Commodore James Weir, who had financed Cierva since the 1920s, died in 1973, no other backer could be found, and the project was abandoned by 1975. The Grasshopper III was the last aircraft to carry the Cierva name, and none of the three ever went into production.

This airframe

Grasshopper III G-AWRP

G-AWRPThe airframe modelled

G-AWRP, constructor’s number GB-1, was the first of the three Grasshopper IIIs, built by Cierva Rotorcraft at Redhill. It first flew on 18 August 1969, was shown at the Farnborough show in 1970 and made its last flight in October 1971. It is now displayed at The Helicopter Museum, Weston-super-Mare. The model shows it as it is displayed there: ivory overall, with a black ‘G-AWRP’ under the rear doors, white rotor blades with red tips, grey metal rotor heads and black skids, standing on its black ground-handling trolley. No three-view of the type is known, so the shape comes from a side-on photograph of G-AWRP taken at Farnborough in 1970, scaled to the published length, with the widths taken from cameras solved for photographs of it in the museum. The rotor heads are set 68.5 cm apart, the museum’s figure, which makes the model a little taller than the 3.02 m usually quoted. No museum photograph shows the starboard engine nacelle, so it is assumed to match the port one.

See it at The Helicopter Museum

Where to see one

In the gazetteer

The gazetteer records the Grasshopper III in one UK collection. The airframe modelled here is marked.

Every airframe and serial All 280 plates

Profiles and models are procedural interpretations built in Blender from published dimensions, three-view drawings and photographs of each airframe. Treat the museum aircraft as the reference.