SINGLE pilot operation with one or two observers, depending on the work to be done, has been adopted for all test flying. Required loadings are achieved by adjusting fuel quantity and lead ballast. The observer is positioned aft of the pilot where he can scan all the pilots' flight and engine instruments and also monitor an observer panel mounted behind the second pilot's scat and facing inboard (FIG. 1). The other observer is in the second pilot's scat where he has a parallax‐free view of the engine and starboard flight instruments. Thus for performance flying the forward observer has all the basic instruments within a narrow are whilst the aft observer can concentrate on special pressure and temperature instrumentation on the test panel, the two sets of readings being co‐related during performance climbs by time and altitude.