The motor driving the movement of the belt is providing the applying force against the imparted force of the aircraft that’s being applied to make the wheels turn.

:confused:

I think you are confusing force and motion…and the belt cannot apply a force to the aircraft, the airframe that is, but only to the wheels which are free to turn.

Hang on, the wheels are free to turn yes, but they are attached to the aircraft, therefore the motion (motion is an applied force) of the belt is being applied to the not just the free spinning wheels but the aircraft that they are attached to.

A scale model would be something like a person standing at the back of a treadmill holding the handles of a wheelbarrow. The freespinning wheels of the wheel barrow is on the belt of the treadmill.
The person is the engine, the wheelbarrow is the airframe, the wheel is obviously the wheels.

ok A person can push a wheel barrow off the front of the treadmill as long as he pushed the wheelbarrow with sufficient force that the wheel rotates faster than the speed of the treadmill.
If like the original question the treadmill is able to instantaneously match the speed of the wheel of the wheelbarrow no matter how hard the person pushes he won’t be able to push it off the front.

Scale that up no matter how much thrust against the air the engine generates and imparts through the airframe to make the wheels rotate, as long as the conveyor belt is able to match that speed of the aircraft wheels ithe aircraft will remain stationary.
No forward movement, no lift, no take-off

ok, with the aircraft sitting stationary on the belt thrust is applied by the engine, this would normally be imparted through the wheels in order to create ground speed.

The problem – or rather the clever bit of the question – is that from an early age riding bicycles, being driven round in cars and buses, we understand that the driving force goes through the wheel. We rely on “intuition” that we learn early in life but the question catches us because an aircraft applies the force to the air. The wheels are passive.

I actually clarified that in a subsequent post:

The propellor generates the “thrust”. Whilst the aircraft is on the ground that thrust must be imparted against the ground. The point on contact being the wheels.
The forward thrust makes the wheels turn. I took that as read but never mind.

The propellor generates the “thrust”. Whilst the aircraft is on the ground that thrust must be imparted against the ground. The point on contact being the wheels.
The forward thrust makes the wheels turn. I took that as read but never mind.

The motor driving the movement of the belt is providing the applying force against the imparted force of the aircraft that’s being applied to make the wheels turn.

we are told these balance since the belt can match the speed of the wheels

Therefore the forces are balance, and the aircraft isn’t going anywhere

Here’s my take on the aircraft and the conveyor belt.

ok, with the aircraft sitting stationary on the belt thrust is applied by the engine, this would normally be imparted through the wheels in order to create ground speed.

But we are told that the belt matches the speed of the aircrafts wheels.

Therefor as soon as the wheels begin to rotate the belt is right there moving matching it.
Newtons Laws … equal and opposite forces means either stationary or at a constant speed
movement of the belt = thrust impelled rotation of the wheels. so either the aircraft is stationary or at a constant speed.

Since the aircraft was stationary to begin with, and there has been no un balanced forces acting on it, the aircraft will remain stationary with it’s engines screaming.

If I may make my forum debut with what is probably a very silly question, but here goes.

Firstly why on earth it too so long for anyone in Military circles to realise that there was a tactical (and with Air-to-Air refueling Strategic) need to to fill the gap that the Short Belfast left many years ago?

Secondly how on earth it takes so long to design and build a new aircraft in the A400M that has very similar dimensions and would fulfil a similar role to the afore amentioned Short Belfast?

With regard to the C17, I think it’s an excellent aircraft in what it does, and a NATO (the EU owning military aircraft doesn’t appeal to me) purchase and operation in the same style as the E3 fleet would solve a great many C17/A400M issues for many countries.