 Two Gyron Juniors, with afterburners, were also used on the Bristol 188 Mach 2 supersonic research aircraft.The 188 was originally intended to have the Rolls-Royce Avon but the half ton lighter Gyron Junior was substituted in June 1957 .This engine was one of the first in the world to have infinite variation of thrust right up to full reheat.Other manufacturers using thrust increase in discrete steps.