 Because of this it also proved difficult to land, and if an engine failed during takeoff, TF33 main engine thrust was limited to 70% power to maintain directional control.Despite some shortcomings the design had shown exceptional performance and "Big Safari" authorized the "First Chip" production program in August 1963 for the fabrication of 19 more RB-57Fs from existing B-57 airframes.After its flight test program, the two RB-57F prototypes were sent to Rhein-Main AB, West Germany in late 1963 for operational testing and evaluation (OT&E) with the 7407th Support Squadron, where they proved their effectiveness in flights along the German border at over , taking long-range photographs over the border into East Germany.