At one point in the trials, an RAE Varsity was fitted with both LLTV and FLIR sensors side by side in the optical 'flats' in the bomb bay. The OC Flying at the time rather took to this system and one night, on returning from a trip through Wales, decided to do a couple of circuits.
He did a circuit carefully observing the features visible on the ground via the CCTV screens on the flight deck and on the tape afterwards, I heard him say 'yes I'm very happy to do a landing on that'..
On his 'go for it' final landing, he positioned the aircraft on final and lowered the gear, only to find (amongst the expletives on the tape) the nosewheel effectively blocked the view of the runway so he had to do a visual landing after all.
Initially we (ATC) would 'kill' the airfield lighting before takeoff using the 'airfield blackout' selection on our lighting panel however it was quickly found that the pilots flying the trials kept telling us the airfeld lighting was still on. When our techies looked at the wiring, they realised the 'airfield blackout' had been designed for wartime use and there was still a very tiny current running through the wiring (to keep the lights warmed up and avoid blowing transformers) and thus a small amount of IR radiation was being emitted so in future, they made sure the lighting circuits were really cold and then put out 4 low powered 'glim' lamps (one either side of each threshold) on the runway for reference.