Improved apparatus, systems, and methods for inspecting a structure are provided that use a pedestal robot mounted on a rail system, a probe extension coupler, and an inspection probe capable of performing pulse echo ultrasonic inspection. A probe may also include sled appendages and an axial braking system to inspect over holes and off edges. A probe may also include an ultrasonic pulse echo transducer array for high rate inspection; the transducer array may be mounted in a bubbler shoe for individually coupling each of the transducers in the array. A rail system may also include an optical encoder for providing location information for the robot and axial braking system. A probe extension coupler presses the inspection probe against the structure for adjusting to changes in surface contours.