**Scale Speed**

Scale speed has more to do with the visual perception of flight characteriatics than the theory of fluid flow and Reynolds number.

In judging scale competition flights, flying in a scale like maner garners additional points.

For example: For a 1/4 scale plane to appear like its scale counterpart in flight it would have to:

1. Be 1/4 the distance from the viewer as the full scale plane it was being compared to.

2. Cover the same visual angle as the fullscale plane (at 4 times the distance) in the same elaped time.

This means that to appear scale like in flight the 1/4 scale model must fly at 1/4 the speed of the full scale plane. If the wind is blowing at 5 MPH and the full scale plane stalls at 44 MPH, the ground speed of the full scale plane will be somewhat above 44-5=39 MPH.

In the same 5 MPH headwind the 1/4 scale model will have an airspeed a little in excess of 11 MPH and a ground speed a little in excess of 11-5=6 MPH. To have a ground speed 1/4 of full scale, the wind speed can only be 1.25 MPH for the model.