This might help Colin, same series. These (and yours) are Heli radios
and so old not even listed in the Futaba obsolete section. I have 2 even older FP-T5NLH non computer heli radios
I used for my planes before going 2.4. You can use the heli radios
for anything but the rotary knobs are for trimming pitch and tail rotor, throttle etc and work together with other switches. You can probably use the normal std functions plus throttle hold, throttle cut (which also works in conjunction with the rotary trims and a few others but it might take a bit of mucking around to get them to do what you want.
I used a few functions for things they weren't meant for in the planes, like throttle cut, idle up (toggle sw turns on pre set throttle hold level- for auto rotation). This manual should give you a rough idea and the rest will be suck and see.