Östrich instead accepted the French invitation, and by September had been set up at the former Dornier factories in Rickenbach in the French Zone. Here they were soon joined by other former BMW engineers, as well as those from a number of other German firms, bringing the team to about 200 members. The group was named the Atelier Technique Aéronautique Rickenbach (Rickenbach Aeronautical Technical Workshop in French), or ATAR. They had re-engineered the 003 design as the ATAR 101 (model R.101) by October, and granted a production contract on the proviso that actual production would be carried out in France. In January a further five-year contract was offered to the entire team, including protected wages, provisions for their families, few travel restrictions, and the possibility of French citizenship. The contract was signed on 25 April 1946, and the drawings for the ATAR 101 were sent to SNECMA for production. The first engine took some time to assemble. The first parts were available as early as May 1946, but a complete compressor or turbine was not ready until the middle of the next year. The first complete engine finally ran on 26 March 1948. By April 5 it had been brought up to thrust and was continually improved until it reached by October. During this time a new turbine made of solid high-temperature steels replaced the earlier air-cooled models, allowing for better aerodynamic shaping and an improved compression ratio. By January 1950 several additional engines had joined the program, bringing the total running time to over 1,000 hours, and a thrust of , making it among the most powerful engines of the era. The BMW 003 that it was developed from provided only , less than a third of the Atar. The ATAR 101B introduced Nimonic turbine blades and more stator blades as well as a number of changes to fix minor problems seen in the earlier experimental models. The first B model passed a 150-hour endurance test in February 1951 at . A flight test followed on 5 December 1951 in the Dassault Ouragan, and starting on 27 March 1952, under the wings of a Gloster Meteor F.4. After delivering the initial production run of B models, the Atar 101C used an improved compressor and combustion chamber, raising the thrust to . The Atar 101D featured a slightly larger turbine with new high-temperature alloys that allowed the exit temperature to rise to 1,000 °C and the thrust to .