Whilst I appreciate that the thrust is coming from the propellor, and not the wheels, what I feel is key to the question, is the very moment that the A/C would start to move, it not only has to overcome the drag of the tyres,(the sum total of which is a calculation of the AUW of the A/C and the deflection of the tyre) together with the friction of the brake pads,and wheel bearings, as it normally would, but that drag is multiplied by (to me at least) an unknown factor, and as it has no inertia, to break it free from this drag, (which increases the faster the conveyor moves) it will not move.

I have been in a light A/C which got stuck in a rut, that a child could have got a tricycle out of , with a combination of thrust and inertia; no amount of thrust (full power) would move it ,and yet when we got out and pushed, it was unbelievably easy to move.

So I suppose the question is, does this A/C have enough power to overcome a force of drag which increases, the more power is applied?

The length of the conveyor belt is irrelevant, beyond the point where any given A/C makes contact with it (with however many wheels).

A man on a walking maching doesn’t need a longer treadmill because he starts to run ,because the speed increases pro rata with his (and he remains in the same place); if someone was to turn the speed up to his maximum running speed, could he move forward to turn it off….no

The absolute key to this is windspeed, which is either generated by the, er wind,(which we are assuming there isn’t any) or else the A/C’s forward speed, creating lift, and so flight.

If the A/C had retractable U/C, (and was at full takeoff power on the conveyor), and retracted the U/C would it fly…. no because it isn’t moving forward.

Don’t you just love hypotheticals…. if you accept that the conveyor belt can match the speed (full power thrust)that any given A/C can reach, then it will never move forward, and with zero windspeed, it will have zero lift, and so will not fly; in reality no conveyor belt system could respond in speedchange as fast as say the thrust of a rocket motor could be delivered , and so the difference between the two would be your forward speed, if that was great enough to provide lift then, even partial lift, would reduce drag from the conveyor, and with that, the full effect of its rearward motion, allowing greater forward speed to be achieved.

Is the A/C facing into the wind?

Undercarriage lever a little sticky is it sir?

I would have thought it would need fixing to the front of the engine, especially if the engine mounts are in anyway flexible.

How right you are old boy, well spotted, we certainly are a posh lot down here in Somerset and never swear;) .

The prop now there is a challenge, the Hyd motor and torque hub(gear box) are great but the torque hub is designed to drive large industrial machinery and not cope with THRUST. having stripped it there is only a circlic holding the two halfs of the TH together. Clearly we cannot bolt the prop straight to the TH, the pull from the prop would rip it in half and you would have a prop doing 800RPM ripping through the air. I spent a few days working out a design to attach a shaft to the TH with a thrust bearing, even if the shaft hub connection and bearing fails the prop cannot detach. The drawings a bit rough and i havent worked out the dimensions yet. Would welcome any constructive critisism (holds breath:o ) or any other design ideas. Remember that it has to incorporate the TH.

Nice use of colour, Tony Hart would be proud of you!

I think you are right to be cautious r.e the hyd motor,I have seen them shear the output shafts , if they run out of line, and a side load is imposed; you either need to get it perfectly in line or else use a slip ring or something similar to join the motor to the propellor drive shaft, allowing a slight difference in alignment.

What is the frame that holds the propellor drive shaft fixed to?