The HUP Retriever, built by the Piasecki Helicopter Corporation, was the first helicopter produced in large numbers for the U.S. Navy. Called the “HUP-mobile” in the fleet—the name recalling an early automobile name—the HUP was a refinement of Piasecki’s earlier Navy HRP series, prototypes of which first flew in 1945. The HRP-1 Rescuer (22 built) and HRP-2 (4 built) served with the Navy, Marine Corps, and Coast Guard, evaluating antisubmarine, search-and-res- cue, amphibious assault, and minesweeping roles for helicopters.
The U.S. Army and Air Force purchased several hundred HRP-2s (redesignated H-21) with the names Shawnee (Army) and Workhorse (Air Force). After successful trials with the HRP, the Navy ordered an improved version— the HJP—for shipboard utility and rescue duties, especially for use in the plane-guard role for aircraft carriers. The designation was changed to HUP in 1949, when the Navy adopted the letter U in place of J for utility; the P, of course, indicated Piasecki.
Following the two XHJP-1 prototypes, the first of which flew in 1948, the Navy procured 32 HUP-1 and 394 HUP-2 variants. The HUP-1 had vertical tail fins fitted on the large rotor pylon, although these were deleted on later models, which in turn were fitted with autopilots. Some HUP-2 helicopters got the HUP-2S designation, indicating that they were fitted with the AN/AQS-4 dipping sonar for submarine detection. No weapons were carried.
HUP-mobiles entered Navy service in January 1949; in January 1951, Utility Squadron (HU) 2 became the first operational squadron. Old timers will recall that fleet HUPs were used mainly as plane guards, and for carrying chaplains, admirals, and mail between ships.
Although employed primarily in these utility roles, the Navy’s first helicopter ASW squadron, HS-1, was established on 3 October 1951. The unit was scheduled to get 18 HUP-2S helicopters, but Piasecki could not meet Navy deadlines and the squadron did not receive its first helicopter until February 1952 when an HUP-1 was accepted for tests. Two months later, the first HUP-2 arrived and that summer the squadron went aboard the escort carrier Siboney (CVE-112) for carrier qualifications with nine HUP-2s.
HS-l’s helicopters were put through their paces during June 1952. One HUP-2 was lost at sea when its engine failed and several others were almost lost; the squadron found the HUP unsuitable for ASW operations. There were more carrier tests in August with more problems—three HUP-2s went down at sea although all were salvaged.
The Army procured 70 similar Piasecki helicopters designated H-25A, but they were considered too small for the service’s requirements and 50 of those were subsequently transferred to the Navy where they became HUP-3s. The Marines flew 13 of the Navy HUP- mobiles, while 15 of the HUP-2s went to the French Navy and 3 HUP-3s went to the Canadian Navy.
The Navy-procured helicopters were powered by a single Continental R-975 piston engine rated at 525 takeoff horse power for the HUP-1 and 550 horsepower for the HUP-2. They turned tandem rotors 35 feet in diameter, which eliminated the need for an antitorque tail rotor. The rotors folded for shipboard storage.
The crew consisted of a pilot and copilot plus a third crewmen in some roles. The helicopter’s payload was four passengers or two litters and an attendant. A hatch in the bottom of the fuselage permitted personnel to be hoisted directly into the cabin.
The Bell HSL, a larger helicopter, was developed later specifically for ASW. It had a gross weight of 16,800 pounds compared to the HUP-2’s 6,000 pounds. It was not successful and all helicopter ASW squadrons received the Sikorsky HSS-1 Seabat beginning in 1955.
The HUP-mobile was an effective helicopter and served in the fleet until September 1964—a lengthy career for a pioneer in naval aviation development.
Note: In the 1962 redesignation of U.S. military aircraft, the HUP-1 became the UH-25A, the HUP-2 the UH-25B, and the HUP-3 the UH-25C.