Here's another take: Step 1: a propeller is like a wall or (straight on, no wing stuff) sail moving forwards forever. When the wind pushes on a propeller it's

Here's another take: Step 1: a propeller is like a wall or (straight on, no wing stuff) sail moving forwards forever. When the wind pushes on a propeller it's like it's pushing against a sail or wall, but instead of moving forward it turns in place. Virtually, it's still like a wall moving forward. So it converts linear push to a rotational motion. Step 2: Wheels are the opposite for solid surfaces: they couple rotational motion to linear motion on the ground. Step 3: the propeller on the vehicle is connected to the wheels. The gearing makes the "virtual wall" of the propeller move backwards as the vehicle moves forwards. This cancels out the forward motion of the vehicle from the point of view of the air. So from the point of view of the wind, the propeller is like a wall or sail that isn't moving with the vehicle. It's stuck stationary on the ground, or moving slower. The reason why the wind can't push a vehicle faster than the wind is that once you get to wind speed, there is no more speed difference to impart a force on the vehicle. Here, even when the vehicle is at wind speed, there is still a difference between the (slower) virtual speed of the propeller and the wind. So it still gets pushed, and can further accelerate. TL;DR the vehicle uses the wheels and propeller to make itself appear to be running slower relative to the wind, and so it can continue to accelerate when its real speed has reached the wind speed. Another way to visualize it is: instead of a traditional propeller, imagine it like a water wheel, or an impeller, with vanes the air hits. As the vehicle moves forward, the vanes move backwards. With the vehicle at wind speed, the vanes moving backwards cancel out some of its speed, so that there is still a relative difference between the wind speed and the vane speed, so there is still a force exerted.