Classic Rotors

Following the relatively successful U.S. Navy trials with the HRP, the Navy ordered the improved HJP for shipboard utility and rescue duties, especially “plane guard” for pilots who crashed into the sea during carrier landings or takeoffs. The HJP designation was changed to HUP in 1949 when U was substituted for J in aircraft and squadron designations. In the fleet the HUP was known as the “hup-mobile” or “shoe” (because of its shape). The U.S. Army procured 70 of these helicopters as H-25s but subsequently transferred 50 to the Navy. Nineteen were procured for foreign use, mostly by the French and Canadian navies.
The HUP/H-25 had the Piasecki tandem-rotor design, with a smaller and more streamlined fuselage than the HRP/H-21 design. The two three-bladed rotors overlapped, thus reducing the size of the helicopter to facilitate shipboard operation. The HUP could fit on aircraft carrier elevators without folding its blades, and on most cruiser elevators with blades folded. The pilot and copilot sat in the nose, below the forward rotor, as in the HRP/H-21. Behind the cockpit the cabin could accommodate four passengers or three stretchers, with the single Continental engine mounted aft. The tubular, metal-covered fuselage rested on a fixed undercarriage. The HUP-1s had vertical tail fins on the after rotor pylon. They were deleted in later helicopters (which had auto-pilots fitted). The Navy variants had all-weather instrumentation, and some had AN/AQS-4 dipping sonar fitted for ASW operations (designated HUP-25). A hatch in the bottom of the fuselage permitted personnel to be hoisted directly up into the cabin.
After trials with two XHJP-ls (BuNo. 37976/977), the Navy ordered 32 HUP-1 variants for shipboard operation. These were followed by 165 HUP-2s, some fitted with dipping sonar. The Marines flew 13 of the Navy HUPs. The Army procured 70 helicopters similar to the HUP-2, designated H-25A. These were too small for Army requirements and 50 were transferred to the Navy as HUP-3s. The Navy HUP-2/3 survivors were redesignated UH-25B/C, respectively, in 1962. Another 15 HUP-2s went to the French Navy and 3 HUP-3s went to the Canadian Navy.