Piasecki Helicopter Corporation YH-21-PH Work-Horse 50-1231, first flight 11 April 1950 Published on April 10, 2012 in 11 April 1952Full resolution (432 × 218) Next → Piasecki YH-21-PH Work-Horse 50-1231, first flight at Morton Grove, PA. (San Diego Air and Space Museum Archives)