Abstract: Portable RCS versus azimuth measurement apparatus for an aircraft to be tested has a dolly attached to the aircraft at a location on a supporting surface. A nose wheel adapter mounted on the dolly temporarily replaces the nose wheel of the aircraft with a spare nose wheel. An electric motor on the dolly coupled to the spare nose wheel rotates the spare nose wheel. A beam structure has a first end removably affixable to the dolly and a spaced opposite second end extending under the axis of rotation of the aircraft and between the main landing wheels. A synchronizing gearbox, mounted on the second end of the beam structure at the axis of rotation of the aircraft, has an output shaft and senses rotation of the aircraft about the axis of rotation, sensed rotation of the aircraft being indicated by rotation of the output shaft. Rotation of the output shaft of the gearbox is restrained relative to the surface by an anchor.