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Sikorsky UH-34D Seahorse
The H-34 started as a private Sikorsky Aircraft development, which the military ignored. However, it soon became a true workhorse in service with all branches of the U.S. armed forces, in addition to a host of foreign nations, and a variety of civil operators. The H-34 was also the final evolution of large piston-engine helicopters before the rise of turbine powered designs.
Designated by Sikorsky as the S-58, the H-34 took form as an improvement on the company's revolutionary S-55. That model appeared in the late 1940s, as other manufacturers began to break Sikorsky's hold on large military helicopter contracts with designs such as the tandem-rotor Piasecki HUP-1. Early Sikorsky designs placed the large reciprocating engine behind the cabin. This had the effect of restricting the center-of-gravity of the helicopter to a very narrow range. Igor Sikorsky and his design team discovered that if they moved the engine to the front of the cabin, closer to the axis of the main rotor, the center-of-gravity envelope became much larger. This configuration required the relocation of the cockpit to a position on top of the engine. Sikorsky engineers inclined the engine at a 45-degree angle so that the drive shaft would not run through the main cabin, though this created a partition between the cockpit and main cabin. However, the addition of clamshell doors to the nose of the aircraft made maintenance access to the engine far simpler than it had ever been before.
Shortly after the S-58's introduction in 1954, Sikorsky entered it into the U. S. Army and Air Force competition for a new utility helicopter and the U. S. Navy competition for a new Anti-Submarine helicopter. The S-58 lost both competitions. The Army and Air Force selected the Piasecki tandem-rotor H-21; the Navy selected the Bell HSL-1; and the U. S. Marine Corps, which did not hold a competition, selected the mammoth twin-engine Sikorsky S-56.
Subsequently, the HSL-1 proved unsuitable for the shipboard anti-submarine role, the
S-56 suffered from development problems, and the Air Force absorbed almost the entire H-21 production run. Accordingly, the Marines, the Army and the Navy turned to the S-58 as the only readily available alternative. It proved to be an excellent choice for all three services. Ultimately, even the Air Force used ex-Navy H-34s as Search and Rescue (SAR) aircraft.
Initially the Navy designated the aircraft the HSS-1 Seabat (Helicopter, anti-Submarine, Sikorsky), while the Marines referred to it as the HUS- 1 (Seahorse Helicopter, Utility, Sikorsky), and the Army adopted it as the H-34 Choctaw. In 1962, all the designations changed to a Department of Defense standard and the aircraft became the UH-34. Sikorsky built 1,825 S-58s and UH-34s including the A, C, G, and J models, but the D became the most common. Sud-Est of France built another 135 S-58s under license and Westland of the United Kingdom built nearly 400 of a highly successful turbine-powered variant known as the Wessex .
A nine-cylinder air-cooled Wright R-1820-84 reciprocating engine powered the single-rotor H-34. The massive engine required an elaborate blower system to keep it cool. Shafts and gearboxes situated along the spine of the fuselage and a substantial tail pylon drove the tail rotor. The fuselage was all metal, principally magnesium alloy, for weight savings.
The Navy Seabat relied on sonar dipping gear and an autopilot that permitted low-altitude hover at night or in poor visibility, to perform its anti-submarine mission. The low altitude and airspeed required for this type of operation made successful autorotations unlikely in case of engine failure, and mandated a particularly trusting and courageous aircrew to fly these high-risk missions. The aircraft operated as the mainstay of the Navy Anti-Submarine helicopter force from 1954 until 1962 when the SH-3 Sea King came into service. In addition to the Anti-Submarine role, the H-34 served in the Navy as the UH-34J for VIP transport and SAR duties. The U. S. Coast Guard also acquired six H-34s for the SAR role.
The U. S. Army employed the H-34 principally for general utility purposes, as well as VIP transport flights, and SAR missions. One of the most challenging missions flown by Army H-34s was the evacuation of the Congo in 1964, but Army H-34s did not participate in Vietnam , and did not fly in the assault helicopter role.
Beginning in 1956, the H-34 saw its introduction into combat during intensive operations with the French in Algeria . In 1955, the U. S. Marine Corps received its first HUS-1s as an interim type, ostensibly until the HR2S (later CH-37) entered squadron service. However, the HUS lasted far longer in USMC service, and in much greater numbers, than the HR2S ever did. Ultimately the Marine Corps took delivery of 515 UH-34Ds, asthe HUS-1 was designated after 1962.. From the late 1950s until the CH-46 entered service in 1965, the UH-34 operated as the mainstay of Marine Corps helicopter units.
On April 15, 1962, Lt. Col. Archie Clapp's Marine Medium Helicopter Squadron 362 (HMM-362), know as Archie's Angels, deployed to Soc Trang in the Mekong Delta in South Vietnam as part of Operation SHUFLY. This was the Marine Corp's effort to support the Army of the Republic of Vietnam (ARVN) troops in actions against the Viet Cong. HMM 162,163, 261, 361, 364, and 365 joined the operation later. During late 1962, the SHUFLY H-34s traded places with an Army squadron and moved to Da Nang because the H-34 was more capable in the mountainous terrain of northern South Vietnam than the Piasecki H-21.
Pilots of H-34s flying in Vietnam discovered in the combat zone that some of the design's innovative features carried penalties. The high cockpit made it an obvious target, and the drive shaft created a partition that made it difficult for crew chiefs to come to the aid of the cockpit crew if they became injured. The H-34's magnesium skin resulted in very intense fires, and contributed to significant corrosion problems. The airframe was also too weak to support most of the weapon systems that allowed the UH-1 to become an effective ad-hoc gunship. Nonetheless, the H-34 demonstrated an ability to sustain a substantial amount of combat damage and still return home.
Early in 1965, Operation SHUFLY ended as U. S. Marine and Army units landed in Vietnam , following the Tonkin Gulf resolution, and took the lead in the war against the Viet Cong. In March 1966, the more capable turbine-powered CH-46A began to replace the UH-34s. However, in August 1967, several fatal crashes caused by tail pylon failures resulted in the grounding of the CH-46As, and the somewhat haggard but reliable H-34 remained in service until engineers resolved the CH-46 structural problems. In August 1969, the last Marine UH-34D in Vietnam was retired from HMM-362 at Hue Phu Bai. It had served the Marine Corps in Vietnam for seven years. During that period, enemy action and operational accidents downed 134 of the venerable helicopters. To this day, whether they were pilots, crew chiefs, gunners or maintenance troops, the Marines who operated H-34s (which they affectionately labeled the "Dog") all fervently believe that "When you're out of H-34s, you're out of helicopters."
An example of the actions experienced by UH-34 crews occurred on 27 and 28 April 1964 with the helicopters of HMM-364, commanded by Lt. Col. John Lavoy. The squadron received orders to insert a regiment of ARVN troops into a Landing Zone (LZ) that they believed to be unoccupied. Upon arrival at the LZ, the aircraft became the target of an ambush, which presumably occurred because of leaked information. A South Vietnamese Air Force (VNAF) A-1 Skyraider (see NASM collection) attempted to dive-bomb one of the many gun positions but was shot down. Later, courageous Army pilots, flying armed UH-1 Hueys (see NASM collection) suppressed some of the fire, but .50 caliber guns and hundreds of smaller weapons continued to pour fire into the landing zone. Despite the intense fire, Lt. Col. Lavoy led his helicopters into the zone, disembarked the ARVN troops, and departed. Every Marine H-34 suffered from damage inflicted from the ground fire, which resulted in the loss of one aircraft. An H-34 specifically tasked to rescue downed crews immediately picked up the crew.
During the course of the day, HMM-364 entered the zone four times, suffering further damage on each flight. On the fourth assault, ground fire claimed a Vietnamese Air Force (VNAF) helicopter. Once more, the rescue H-34 came to their aid. At the end of the day, every helicopter that participated in the operation displayed battle damage. Miraculously, not a single HMM-364 crewmember suffered an injury. For this action, every Helicopter Aircraft Commander (HAC), including Lt. Col. Lavoy, received the Distinguished Flying Cross. The pilot of the rescue helicopter, John Braddon, also received the Silver Star for the action. This operation was the first action in Vietnam that included multiple lifts of troops into a heavily defended LZ and foreshadowed the hundreds of similar operations that followed.
In the late 1950s, Air America , a CIA-created airline, began flying S-58s in Laos , manned by crews on leave from the Marine Corps. When the last military UH-34 left Vietnam , Air America was still in operation with the type, including upgraded S-58Ts powered by the powerful turbine PT6T-6 "TwinPac."
Military H-34s also provided sterling service outside the war zone. Beginning late in 1957, and continuing through the early 1960s, millions of people around the world witnessed H-34s transporting the President of the United States . This was the first regular use of helicopters in that role. Army and Marine Corps H-34s and HUS-1s replaced the H-13Js (see NASM collection), which had pioneered Presidential helicopter transport. Another starring role of the H-34 was the recovery of the Mercury astronauts and their capsules.
Ultimately the S-58/HUS-1/H-34 was flown by all branches of the U. S. military and also by the armed forces of Argentina , Belgium , Brazil , Cambodia , Canada , Chile , Costa Rica , France , Germany , Haiti , Indonesia , Israel , Italy , Japan , Katanga , Laos , Netherlands , Nicaragua , Philippines , Soviet Union , Thailand , United Kingdom , Uruguay , and Vietnam . In addition to its military service, the H-34 still performs a number of civilian duties including air taxi and fire fighting. The S-58T remains one of the most popular helicopters in the aerial crane role because of its large lifting capacity and relatively low operating costs compared to those of other aerial crane platforms. The abundance of ex-military H-34s, retired in favor of higher-performance turbine models, allowed many operators to acquire a powerful helicopter quite easily.
That an aircraft, initially rejected by all the armed services, should ultimately serve for so long and in such numbers is remarkable. Even more commendable is the genuine affection with which the aircrews who flew it in combat recall their service. Every year thousands of Marines who flew the H-34 in Vietnam still meet at venues all around the country to recall their experiences in a magnificent flying machine and one that meant so much to them.
In 1974, the Marine Corps transferred a UH-34D, Bureau No. 148768, to the National Air and Space Museum as a representative medium-sized assault helicopter. This helicopter entered Marine service on March 31, 1961, and served in units at New River , North Carolina ; Jacksonville ; Santa Ana and El Toro , California ; and New Orleans . On November 25, 1970, it was retired and placed in storage at Davis-Monthan Air Force Base, Arizona , having accumulated 3,416 flying hours. Following the transfer of the helicopter to the Museum, Sikorsky Aircraft Corporation and Marine personnel of HMX-1 restored it at Quantico Marine Base in Virginia . During the restoration, the aircraft was repainted in 1965 Marine markings, with model number YP-13, to represent a significant aircraft assigned to Marine Medium Helicopter Squadron 163. This combat unit operated in the Da Nang area of Vietnam and became one of the most decorated Marine helicopter squadrons of that war.
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