A chap who was a well-known TP told me of his course at ETPS when they still had the test Javelin there. Off he went to wild West Wales to do some TP thing involving rudder doublets, SPO excitation or somesuch. After a while doing this, there was a strangled yelp from the back seater; he suggested that they RTB'd fairly schnell. Some gross cock-up about fuel flow, fuel volume - and the ac having 2 engines rather than 1! Off they went at best range cruise, approaching Green One they were given the usual (for those days) "Turn right 60 for ident" from the Air Traffickers...... "Madam", quoth TP chum, "I am flying the world's last remaining Javelin. If I do what you ask, the world will soon have one less. Non-deviating direct please....."
Apparently they just made it home on fumes....