Flight Tests of N.A.C.A. Nose-slot Cowlings on the BFC-1 Airplane
This is a 1939 NACA technical report, issued by the National Advisory Committee for Aeronautics, on flight tests of nose-slot engine cowlings fitted to a BFC-1 biplane fighter, written for aeronautical engineers. The photographs show the cowling in close-up, on the airplane at low and high speed settings, and smoke tests of airflow over and out of the slot, with flat, documentary lighting on plain grey tones.
