In 1945, the Navy issued requirements for a compact utility/rescue helicopter to operate from aircraft carriers, battleships, and cruisers. The industry wide paper competition was won by single-rotor Sikorsky (XHJS-1) and Piasecki overlapped tandem (XHJP-1). A side-by-side flight/mission evaluation by the Navy was held. The XHJP-1 won and became the HUP-1 in production.
| Mission | Rescue and Utility |
| Crew | 2 |
| Passengers | 4 |
| Engine | Continental R975-42 |
| Horsepower | 550 |
| Rotor Diameter | 35 ft |
| Fuselage Length | 32 ft |
| Weight Empty | 4,100 lb |
| Useful Load | 1,650 lb |
| Maximum Speed | 108 mph |
| Cruising Speed | 84 mph |
| Range | 360 miles |
| Ceiling w/ Normal Load | 10,200 ft |
The shipboard requirements, particularly the small carrier elevator, presented a difficult rotor folding problem to allow rapid storage below deck. An overlapped rotor configuration previously designed by Piasecki for a more compact tandem fuselage configuration was ideally suited to fit these elevators by placing the blade tips of the two, 3 bladed, 35′ diameter rotors in each corner. Blade folding was not required for carrier operations, expediting movement to the hanger deck below. The blades were foldable for smaller cruiser elevators, making it the most compact helicopter for its weight. This was the first overloading tandem rotor helicopter to fly.
The HUP was a six place, single engine helicopter. The fuselage was an all metal semi-monocoque construction with conventional fixed landing gear and powered by a continental R-975-46 engine with an initial take-off rating of 550 horsepower, later reduced to 450 horsepower.
The copilot’s seat was foldable forward and an electrically operating hatch door lowered to drop a rescue sling from an overhead hoist and effect a live rescue without crew assistance. A stokes litter could be lifted directly into the cabin with a crew assistant. For ease of maintenance, the engine and its mount, fan cowling, oil system, accessories, etc. was removable as one unit through an overhead hatch in the rear fuselage. The HUP-2 was the first production helicopter to be equipped with an auto-pilot which permitted ifr and hands off flying, including hovering.
The rugged hup was built to higher load factors than previous helicopters. It was the first helicopter to perform a loop, unintentionally, when demonstrating its “g” capabilities. The missions of the HUP were shipbased rescue, observation and utility, personnel and cargo transport. A total of 339 HUP1/2/3/4 and the Army version, the H-25 helicopters were delivered to the United States Army and Navy, the Royal Canadian Navy, and the French Navy. Over their 20 years life, these helicopters were responsible for the saving of countless lives.
