Model Magic – RS-4 Desford

In the period immediately after the Second World War, the coming of the jet engine saw much innovation in both civilian and military aviation. At the time the possibilities of the jet age were vaguely glimpsed, but largely unknown. However, the arrival of jet power did prompt the need for broader training opportunities, and a number of manufacturers, sensing commercial possibilities, rose to the challenge. At that time there was also much discussion about the effects of fast jet flight on human physiology. This prompted a number of aviation initiatives, which with hindsight now seem rather curious. Into this environment of lateral thinking, one small English manufacturer, Reid and Sigrist, believed that they had a particular contribution to make.

One fashionable idea of the time, was the notion of ‘prone piloting’. In the ‘40s, the idea of piloting whilst lying on ones tummy was thought to be a possible requirement for future fast jets. The reasons were two-fold. First, such a configuration enabled the frontal area of the airframe to be reduced and therefore allowed a useful reduction in drag. Second, physiological research indicated that aircrew could withstand greater ‘g’ forces if they were lying on their stomachs, and not sitting upright. This was thought to be a vital consideration, given the need for future jet combat aircraft to manoeuvre at ever increasing speeds. Of course, from the earliest days of powered flight their had been prone pilots, beginning with Orville and Wilbur Wright. However, throughout the ‘30s and early ‘40s, for both aerodynamic and physiological reasons, a number of experimental German gliders and advanced military prototypes had introduced this unusual control configuration. For many designers of the post war period, then, it seemed the way forward, though looking back, pressure suits and well-designed seating arrangements were to prove more practical.

Just before the Second World War, Reid and Sigrist designed and built the colourfully named RS-1 Snargasher. This 1938 design was an all wood, twin-engine, light aircraft intended for training duties. It was powered by two de Havilland Gypsy Six IIs and was not unlike a Miles Messenger or Gemini. During the War the RS-1, registered as G-AEOD, served in military communications duties. A development of this aircraft, now called the RS-3 Desford, appeared in 1945. It was generally similar to the RS-1, but with the powerplants up-rated to twin de Havilland Gypsy Majors. The RS-3 first flew on 9th July 1945, registered as G-AGOS. Designed as a two-seat conversion trainer the prototype was evaluated for this important role by the RAF but, alas, no orders were placed.

In 1949, the Ministry of Supply, wishing to assess the effects of fast jets on human pilots, bought the RS-3 and converted it to the dual-control RS-4 Desford, dubbed the ‘Bobsleigh’. It was so called since one of the two pilots was to fly the aircraft lying prone in the newly lengthened and glazed nose section. This version first flew in June 1951. Given the serial number VZ 728, it remained at Farnborough, where it was used for tests until the mid ‘50s. It was sold to Air Couriers in 1956, who removed the nose control position, and re-engine the airframe with two 145hp Gypsy Major 1C-2 engines. Used until 1972 for aerial photography, it was subsequently bought in 1974, for the Strathallan Collection, at Auchterarder.

To modern eyes the Reid and Sigrist Desford may now look like a fanciful dead end, though for many it is part of that romantic era when British aviation cut its own distinct furrow. The idea of prone piloting was quietly dropped, only to make the occasional re-appearance over the years in a number of odd experimental aircraft, including the tiny American WeeBee and the curious prone-pilot Gloster Meteor F8. The RS-4 Bobsleigh prototype still exists in storage and non-flying condition, though there are moves afoot to return it to full flying capability. Whatever its lasting contribution, the Desford remains an intriguing footnote to British post-war aviation.

Long-time modeller, sometime Nats scale judge, and Cotswold Kits supremo, Syd King is the designer of the Bobsleigh model. He describes the Desford as the ideal twin model: “Two rudders – both in the prop’ wash – and a fixed undercarriage!”

Syd worked from photographs to arrive at his own plan, using what he cannily terms ‘reverse isometrics’. The model certainly looks convincing, though Syd refers to it as a typically  “sport-scale / large scale model. The construction is of largely traditional built-up structure with the addition of Syd’s own-design / own cut foam wings. This is hardly surprising, given Syd ownership of Cotswold Kits, famous amongst other things for their foam and fibregless pylon racers such as the Tracer. The fuselage is entirely built up on conventional frame formers, and then skinned using 1/8 balsa. The tailplane, fins, and rudders are built to the ‘Brian Taylor method’ with a central core of 1/16 balsa, skinned in 1/6 balsa riblets. Overall finish is traditional tissue and dope, topped with Flair Spectrum paints.

Turned on a Myford lathe by Syd’s mate John Parker – he’s the engineer in their little group – the undercarriage legs are damped with 1/2” springs bought in a bagful from one of the shows. Wheels are Flair Tiger Moth types.

Ultra-reliable, the two Zenoah 26s feature standard silencers that are conveniently accommodated within the cowlings. The tanks are 500ml each side, allowing 14 minutes duration – easily long enough for an LMA flying slot.
Highlighting the only disadvantage of the twin fin configuration is the fact that an extra servo is required to drive the steerable tail wheel. This is operated by the rudder channel, via a three-way lead. As Syd wisely observes: “You really need a steerable tail wheel with a twin…”

The RS-4 is fitted with flaps, which are small but effective. They deploy to 70°, giving a usefully steep approach. Pitch is neutral on deploying the flaps, conferring virtually no trim changes. Apparently the aeroplane is delightful to fly, very stable, with crisp controls. Syd has even tried deliberate one-engine landings, and noted hardly any trim change. In flight, the Desford looks appropriately quirky and British.

Wingspan: 34 feet
Length: 26 feet 9 inches
All-up weight: 3,300 lbs
Max speed: 162 mph
Power: 2 x 145hp de Havilland Gypsy Moth Major 1C-2 piston engines

Wingspan:    11 feet 4 inches
All-up weight:    36 lbs
Radio:    Multiplex Royal Evo / 12 servos
Power:    2 x Zenoah 26 petrol
Props:    18 x 8” Menz