The C-4 facility is made of a vertical axis jet and used to calibrate pneumatic and fast response directional probes up to the transonic domain. It is installed next to the C-3 blowdown cascade facility, and benefits from the same 40 bar air supply system. The air coming from this high pressure air reservoir enters into a settling chamber through a perforated cylinder. Several grids are installed in this section to control and guarantee the uniformity of the flow and the turbulence. The calibration nozzle is characterized by a contraction ratio of 14.75 and has an outlet diameter of 50 mm, allowing a stable operation, even at high Mach numbers. Large mass flows can be maintained during significant times, up to a few minutes. Three different computerized carriages allow running a detailed angular (yaw and pitch) calibration. The accuracy quoted in the angle calibration is better than +/- 0.5 deg.