Piasecki YH-21-PH Workhorse One of 18 SAR (Search and Rescue) service test models built. This one, assigned to the Wright Air Development Command, has a triangular device fitted to the windshield. Seen at a Dayton, Ohio air show in May1955. Later models, with their Arctic winter capabilities ( the H-21A and H-21B) were put into service by both the U.S. Air Force (USAF) and the Royal Canadian Air Force (RCAF) to maintain and service DEW (Distant Early Warning) radar installations stretching from the Aleutian Islands and Alaska across the Canadian Arctic to Greenland and Iceland.