AP 118 · No. 10 Section II · Aircraft Plate 140 / 178

Plate 140 of 178 · Cold War · Light observation and training helicopter

Sud-Ouest SO.1221S Djinn

SO.1221S Djinn, painted as FR108 ‘CDL’, The Helicopter Museum’s Sud-Ouest SO.1221S Djinn, built in 1959 for the French Army’s light aviation (ALAT) and flown until the end of 1968: Sud-Ouest’s two-seat light helicopter and the first tip-jet helicopter to go into production, with a Turbomeca Palouste compressor behind the cabin blowing cold air up the mast and out of nozzles at the tips of its two-blade, 11 m rotor, so it needs no tail rotor, an open lattice tail boom carrying a stabiliser and a single rudder in the engine’s exhaust, and skid undercarriage, shown with the blades parked fore and aft and the museum’s ground-handling wheels clamped to the skids: French Army olive drab overall with a bright green cockpit, a large white ‘C D L’ behind the cabin with a small black ‘108’, a French roundel with a yellow outer ring on the lower nose, a grey rudder with a dark green top band carrying a yellow ‘CDL’, and dark blue-grey blades with yellow bands at the roots (no photograph shows the port side, so its markings mirror the starboard).

3D model

Turn it over

A procedural model built in Blender from published dimensions, drawings and photographs, painted as FR108 ‘CDL’, The Helicopter Museum’s Sud-Ouest SO.1221S Djinn, built in 1959 for the French Army’s light aviation (ALAT) and flown until the end of 1968: Sud-Ouest’s two-seat light helicopter and the first tip-jet helicopter to go into production, with a Turbomeca Palouste compressor behind the cabin blowing cold air up the mast and out of nozzles at the tips of its two-blade, 11 m rotor, so it needs no tail rotor, an open lattice tail boom carrying a stabiliser and a single rudder in the engine’s exhaust, and skid undercarriage, shown with the blades parked fore and aft and the museum’s ground-handling wheels clamped to the skids: French Army olive drab overall with a bright green cockpit, a large white ‘C D L’ behind the cabin with a small black ‘108’, a French roundel with a yellow outer ring on the lower nose, a grey rudder with a dark green top band carrying a yellow ‘CDL’, and dark blue-grey blades with yellow bands at the roots (no photograph shows the port side, so its markings mirror the starboard). Drag to orbit, scroll or pinch to zoom · download .glb (611 KB)

Data plate

Specification

First flight, number built and top speed are for the whole family (); engine, crew and dimensions are for the SO.1221S Djinn modelled here.

History

The Djinn

A conventional helicopter drives its rotor through a gearbox, and the rotor’s torque has to be cancelled by a tail rotor. Sud-Ouest’s answer was to drive the blades from their tips instead. In the Djinn a Turbomeca Palouste, a small gas turbine used as an air compressor, sits behind the cabin and blows compressed air up the hollow mast and along the blades to nozzles at their tips. Because the rotor is pushed round from the tips there is no torque on the fuselage and no tail rotor; a rudder placed in the Palouste’s exhaust gives the pilot control in yaw.

The single-seat SO.1220 test bed flew on 2 January 1953, and the first two-seat SO.1221 followed on 16 December 1953. Within weeks it had set a height record for its class, and a pre-production batch of 22 began flying in September 1954. The Djinn was light, simple and cheap to build, with an open steel-tube tail boom and a small glazed cabin, and it became the first tip-jet helicopter to go into series production. About 178 were built.

The French Army’s light aviation, the ALAT, took 100 for observation, liaison and training, and some were tried with anti-tank missiles. The West German Army took six, the US Army evaluated three as the YHO-1, and others went to civil operators, many as crop sprayers with spray booms either side of the cabin. Cold tip jets are noisy and thirsty, and later helicopters went back to shaft drive, but the Djinn showed that a jet-driven rotor could work in everyday service.

This airframe

Djinn FR108 ‘CDL’

FR108The airframe modelled

FR108 is an SO.1221S Djinn built for the French Army’s light aviation, the ALAT, and coded ‘CDL’. It is now part of The Helicopter Museum’s collection at Weston-super-Mare. The model shows it as it is displayed there, with its blades parked fore and aft and ground-handling wheels clamped to the skids: French Army olive drab overall with a bright green cockpit, a large white ‘C D L’ behind the cabin with a small black ‘108’, a French roundel with a yellow outer ring on the lower nose, and a grey rudder with a dark green top band carrying a yellow ‘CDL’. No photograph shows its port side, so those markings mirror the starboard.

See it at The Helicopter Museum

Where to see one

In the gazetteer

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

Every airframe and serial All 178 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.