Re: F4 Phantom - Flying Bus???
One other significant difference between J79 and Spey was the spool-up time. The old technology axial flow turbojet was rapidly responsive to throttle demands whereas the by-pass Spey was very slow in comparison and the reheat light-up even slower. The use of idle power if high and fast on the approach would invariably be followed either by a touchdown in the undershoot or a change of underpants as the people got bigger quicker than rate of descent could be reduced. Pulling G whilst selecting reheat could wash off 50 kts in no time before the burners lit so it was always useful if the bogey could send 5 secs notice before manoeuvring.
The only good thing about the Spey in the RAF Phantoms was the British jobs saved/created - perhaps a worthwhile price to pay?