I think the logic behind Cecil’s explanation is lacking in the matter of airflow. If the thrust of the engine were applied only to airflow over the wing, then the plane would indeed take off. However, most of the lift is generated by the airflow over the ENTIRE wing, not just the part of the wing over which the thrusted-by-the-engine air is moving. Indeed, on an aircraft with jet engines mounted under the wings, the airflow directly impelled by the engine does not touch the wing at all.
The thrust of the engines is about moving the entire aircraft forward, which provides airflow over the wings (well, really it provides wingflow through the air, but relative to the wing, it is airflow), which allows lift to be generated by the entire surface of the wing. The motion of the wheels is indeed incidental to the thrust of the engines, but is certainly not irrelevant, as it is the motion of the wheels which allow the motion of the aircraft, which allows the relative motion of the air across the entire wing. The way Cecil states it would require that the entire airflow be the dynamic motion of the air across the motionless wing (because the forward motion was cancelled by the conveyor), instead of the motion of the air being relative to the moving plane. (I know, I know, all motion is relative, but I am using these terms to describe which item, the aircraft or the air, is having kinetic energy applied to it as a result of the thrust of the engine.)
If this is not the case, then what about those large passenger jets which have an engine in the very back end of the plane, at the base of the stabilizer? Those would be rendered completely pointless by your explanation, Cecil.
Love your column, by the way.
C.B., Georgetown, Kentucky
