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The World War II Photo of the Week
for 17 January 2005

The Flying Vibrators ...

   The flightline at Randolph Field, Texas is filled with Vultee Valiant BT-13 trainers. In the foreground, a group of air cadets are lectured on the BT-13's virtues as a training craft. The Valiant was the basic trainer most widely used by the USAAF during WW II. It represented the second of the three stages of pilot training — primary, basic, and advanced. Its main use was to transition pilots from a less powerful primary trainer, such as the Piper Cub or the PT-17 Stearman, to the more powerful and complex advanced trainer, the SNJ or Texan. 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 featured a two-position variable pitch propeller. Nicknamed the "Vibrator" by the pilots who flew it, the BT-13 was powered by a Pratt and Whitney R-985 engine. The origins of the nickname are unclear, but three reasons are often cited as the source for the moniker: when approaching a stall, the airplane shuddered noticeably; during more daring maneuvers, the canopy was prone to rattling; the powerful radial engine and fixed-pitch prop caused all the windows of nearby buildings to vibrate whenever a BT-13 took off.

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