The “Valiant” was the basic trainer most widely used by the United States Army Air Force (USAAF) during WWII. It represented the second of the three stages of pilot training—primary, basic and advanced. Compared with the primary trainers in use at the time, it was considerably more complex. The BT-13 not only had a more powerful engine, it was also faster and heavier. In addition, it required the student pilot to use two-way radio communications with the ground, operate landing flaps and a two-position variable pitch propeller.
Nicknamed the “Vibrator” by the pilots who flew it, the BT-13 was powered by a Pratt & Whitney R-985 engine. But to counter the shortage of these engines early in the BT-13 production program, 1,693 Valiants were produced in 1941-1942 with a Wright R-975 engine and were designated as BT-15s. By the end of WW II, 10,375 BT-13s and BT-15s had been accepted by the USAAF.