The Sud-Ouest S.O.1221 Djinn is a French two-seat light helicopter designed and built by Sud-Ouest later Sud Aviation. The helicopter rotors were driven by compressed-air jets at the end of each blade.

Experience with the earlier Ariel experimental tip jet helicopter led Sud-Ouest to develop a practical light helicopter, the S.O.1221 Djinn. It did not use the same tip jet system but relied on compressed air being fed to the ends of the rotor blades. Apart from its method of propulsion the Djinn was a conventional helicopter with a two-seat side-by-side cabin and a Turbomeca Palouste turbo-compressor behind. The aircraft had an uncovered tail-boom with twin fins and a rudder. Because of the torque-free rotor propulsion, it did not need an anti-torque tail rotor.

A single seat prototype (designated S.O.1220) tested the power concept and first flew on 2 January 1953. This was a simple uncovered structure with an exposed seat for the pilot. This proved the viability of the propulsion system and five two-seat prototypes were then built as the S.O.1221, the first flew on 16 December 1953. Within a few days the helicopter had climbed to an altitude of 4,789 m (15,712 ft) to establish a record in its class.

The French Army encouraged the building of a pre-production batch of 22 helicopters for evaluation. The first pre-production aircraft flew on 23 September 1954. Three of these pre-production helicopters were acquired by the United States Army for evaluation as the YHO-1. The French Army ordered 100 helicopters and six were bought by the German Army. The French Army used the helicopter for liaison, observation, training, and with one-pilot and two external litters for casualty evacuation.

Production ended in the mid-1960s after 178 Djinns had been built. Some helicopters were sold to civil operators for agricultural use fitted with chemical tanks and spray bars.

Operators

France: 

French Air Force

French Army, 100 helicopters in two batches of 50

Germany

German Army, eight for evaluation.

Switzerland

Swiss Air Force four helicopters for evaluation.

United States

United States Army, three for evaluation as the YHO-1.