THE HIGH SPEED - Chapter 5: High-speed Cowlings, Air Inlets and
Outlets, and Internal-Flow Systems - HIGH-SPEED COWLINGS -  The
NACA cowling was an obvious subject for research in the new
8-foot high-speed tunnel in 1936. It was the center of much
attention in the NACA program and the pressure distributions
obtained in the PRT by Theodorsen's group revealed local
velocities as high as twice the flight speed for the blunter
shapes. Using Jacob's criterion, we estimated that the critical
speeds would be as low as 300 mph at altitude, well within the
performance spectrum of pursuit aircraft of that period (ref.
175). R. G. Robinson planned a high-speed program which would
start by testing five of the cowlings used in Theodorsen's
program and then proceed to develop improved less-blunt shapes.
I was fortunate to be project engineer on the cowling
investigation, my first substantial project assignment. - During
design of the cowl models I had noticed one of the then-new
DC-3's parked on the Army flight line. It h