Vectoring Backwards

Frederick H. C. Schultz

It was the summer of 1942 at the University of North Dakota and I was teaching physics in the Army Air Corps pre-flight program in which men were sent to colleges to learn all the basic science and math they could while waiting to get into actual flight training. Their educational backgrounds ranged from high school to graduate school and many had some flight experience as aircrew members. The teacher had a group for three hours each day for anywhere from three weeks to three months to give as much physics as possible. It was a great teaching situation because the men wanted to learn all they could to make flight training easier and success more certain.

I had just started to discuss vectors with a group and was demonstrating how the combination of two velocities results in a third: the vector velocity of the plane with respect to the air + the velocity of the air with respect to the ground = the velocity of the plane with respect to the ground. After showing several ordinary examples, I proposed the possibility that this resultant velocity could possibly be negative. This started a vociferous discussion. Those with flight experience flatly declared that no airplane could go backwards. Then the bell rang for a break.

It was a hot summer day, so the class moved out of the Science Building to the shady side entrance porch to enjoy the gentle Red River Valley breeze during the allotted ten minutes. The discussion continued all the way out and while we got comfortably settled. Then came the sound of a small airplane at about 2,000 feet directly overhead, where the breeze was much stronger. It was a Piper Cub moving straight backwards across the sky at about ten miles per hour!

When we returned to the classroom, a sergeant said he had understood and agreed with everything I had presented even before the “demonstration.” He had been the tail gunner on a B17 stationed in the Aleutians and was returning from a mission, all shot up, with a maximum air speed of 110 mph and barely enough gas left to get back to the base. His wonderful pilot had landed the plane safely, while maintaining the 110 mph speed straight into the wind and moving backwards with respect to the runway.

 

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