28th Annual Toy Run
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2007 ABATE of Tulsa's 28th Annual Toy Run |
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Helicopter Information
on the
Sikorsky UH-34D
The H-34 started out 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 of 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 Este 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 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, 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 H-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. From the late
1950s until the CH-46 entered service in 1965, the UH-34 operated as the
mainstay of Marine Corps helicopter units.
Pilots of H-34s flying in Vietnam discovered that
some of the design’s innovative features carried penalties in the combat
zone. 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 haggard, but reliable H-34 remained in service until
resolution of 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 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.”
In the late 1950s, Air America, a CIA-created airline,
began flying UH-34Ds, manned by crews on leave from the Marine Corps, in
Laos. 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 of the war zone. Beginning in late 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 replaced the UH-13Js,
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/UH-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 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 easily.
It is remarkable that an aircraft, initially rejected by all
of the services, ultimately served for so long and in such numbers. Even more
remarkable is the genuine affection with which the aircrews who flew it in
combat recall their service. Every year literally 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 an UH-34D, bureau number
148768, to the National Air and Space Museum as a representative medium-size
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, it was restored by the Sikorsky Aircraft Corporation and Marine
personnel of HMX-1 at Quantico Marine Base 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.
Rotor
Diameter: 17.7 m (56 ft)
Length: 14.7m (46 ft 9 in)
Height: 4.8m (15 ft 11 in)
Weights: Empty 3,590 kg (7,900 lb)
Gross 5,897 kg (13,000 lb)
Engine: Wright R-1820-84, 1,525 hp
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