The first prototype 004A, which was constructed to run on diesel fuel, was first tested in October 1940, though without an exhaust nozzle. It was benchtested at the end of January 1941 to a top thrust of 430 kgf (4,200 N; 950 lbf), and work continued to increase the output, the RLM contract having set a minimum of 600 kgf (5,900 N; 1,300 lbf) thrust.[5]