Nearest I ever got to "maintenance" or any test flying was doing "trim checks" on the Canberra. Involved flying to ISTR 450kts at relatively low level. If aircraft was trimmable at that speed all was OK. If not you had to leave the trim where it was and fly back holding the out of trim force which was considerable and land like that. Ground crew filed a bit off the strip at the back of the trim tab and you went and did it again - good way for the JP to get hours, more likely minutes, but a change from bumbling around at 250kts