The test section ceiling is on tracks and can be moved by an electric drive system sideways across the tunnel. On the ceiling is a carriage, likewise on tracks and motor driven, which may be moved fore and aft. The carriage supports two struts, which can be driven on vertical tracks. Probes can be mounted to the end of the struts allowing accurate three-axes positioning anywhere in the test section within the physical limit while the tunnel is operating. Traverse speed and position is computer-controlled for each axis. Speed and acceleration in each axis can be changed to fit the customer's needs. The maximum positioning speed for either the X (up/downstream) or Y (left/right) axis is 5 inches per second. The maximum speed for the Z (up/down) axis is 10 inches per second.