An ultrasonic railroad rail inspection system, apparatus and method for in situ rail inspection including a wheel assembly containing a fluid-filled tire and an ultrasonic transducer mounted within the wheel assembly. The transducer is supported in the tire such that the ultrasonic beam generated by the transducer has a beam axis that intersects a head of a railroad rail at a position offset from the longitudinal median plane of the rail to the side of the head penetrated by the ultrasonic beam. The ultrasonic beam is reflected by flaws in the rail in the form of echoes. The echoes return to the transducer identifying the location of flaws.