Q Branch - Hafner Rotachute

Raoul Hafner had created his first aircraft design in Austria in 1929, a helicopter. He came to England where he proceeded to develop a somewhat successful gyroplane. He continued with other designs, some tendered to requirements of early Air Ministry helicopter specifications.

By 1940 he was in charge of a rotorcraft team at the Airborne Forces Experimental Establishment at Ringway, Manchester, where the idea of using a rotor instead of a parachute to more accurately deliver personnel into enemy territory was developed.

On October 3, 1940, work began on what would become the Rotachute; practical testing began only eight days later with 3 ft. (0.91 m) rotor blades attached to lead ballast. Test drops from a Whitley bomber showed that, whilst the models lacked strength, a properly ballasted rotor could achieve stable flight.

A new model with two metal blades and a total weight of 5 lb. (2.26 kg) was built, and launches from a Whitley on October 16th and from the interplane struts of a Tiger Moth on November 7th were only partially successful, but on November 15th a good descent from a Tiger Moth was achieved.

The next step was to build a larger model with 10 ft (3.05 m) rotor span and weight of 1000 lb. (45.3 kg). After stability tests on the ground on February 19,1942, the model was successfully launched from a special structure on the interplane struts of a Boulton Paul Overstrand bomber, near Manchester on March 14. The model descended from 2,000 ft. (609.6 m.) at 1,500 ft/min (7.6 m/sec).

Meanwhile, from late 1940, Hafner had been working on the designs of a full-scale Rotachute. One concept was to carry several in a rail on the top of a modified troop-carrying aircraft and launch them rapidly, one after the other, from the tail end, to land in as tight a group as was required.

The Rotachute was designed to fit criteria of simplicity, light weight and reliability. It comprised a steel tube frame to seat the pilot, a two-bladed rotor with freely flapping blades, and a rubber mounted skid. The rotor hub was also rubber-mounted, to dampen vibration and to function as a control hinge. The fuselage was open at the front. A tapered fairing behind the pilot stabilised the craft, and this was made entirely of rubberised fabric, with no framework, and was inflated to shape, with the intent of minimising stowage space.

Control was by means of a single stick fixed to the rotor hub. Turns were simply a product of banking. As designed, the Rotachute had a weight of 50 lb. (22.7 kg) and a useful load of about 240 lb. (109 kg.), which might comprise the pilot, his parachute and a Bren gun Mk.1 with 300 rounds.

The rotor diameter was 15 ft. (4.57 m.), making it the smallest man-carrying vehicle capable of controlled flight ever built to that time. Contracts for Rotachute production were placed. Before flight trials began, tests were made with rotors and a complete unit fixed to moving vehicles. Early in 1942, the first flights took place.

Two trials at Ringway in February ended with heavy landings, the craft overturning and breaking the rotors. A third run on a longer runway at Snaith was a little better, and it was decided, at least for training, to fit a three-point wheeled undercarriage (rather than a jettisonable trolley), and aft stabilising fins. This required an extension of the tail fairing, which could no longer retain strength sufficient to avoid fouling the rotor without additon of a frame.

A light frame and tailplane were added, the whole being inflated by ram effect from forward movement. This, the Rotachute Mk.II, first flew in late May, 1942, towed behind a Jeep for about 15 seconds of flight. Further tests led to satisfactory ground-initiated flights of two or three minutes. Work now began on the Mk.III.

Tests began at Ringway of the Mk.III in June 1942, with towed flights of around four minutes ending in controlled landings. A totally free landing followed. The Rotachute was then towed behind a Tiger Moth until it, but not the tow aircraft, achieved takeoff. Further flights led eventually to towed air launches, the Rotachute reaching altitudes of up to 3,900 ft. (1189 m.), and reaching 93 mph (150 km/h) and flight duration of up to 40 minutes.

Subsequent tests using the Rotachute were concerned with development of the Rotabuggy, a Jeep fitted with a rotor and tail unit in much the same configuration. The Rotachute was developed to a Mk.IV, with vertical fins added to the tailplane.

The Rotachute was found to be a fairly simple machine to fly and to land in a restricted area. However, the operational needs for which it was designed never materialised. Rotachute experience did provide a basis for much of today's knowledge of light rotorcraft.