Sikorsky S-52

S-52

Sikorsky S-52-3
Role	Helicopter
Manufacturer	Sikorsky Aircraft
First flight	12 February 1947
Introduction	April 1951
Primary users	United States Navy United States Army United States Marine Corps United States Coast Guard
Number built	93^[1]
Variants	Sikorsky XH-39 Vertical Hummingbird

The Sikorsky S-52 was a utility helicopter developed by Sikorsky Aircraft in the late 1940s. It was used by the U.S. Navy, Marines, and Coast Guard.^[2] The S-52 was the first US helicopter with all-metal rotor blades. A two-seater, it was developed into the four-seat S-52-2. It was designated HO5S-1 by the U.S. Navy and Marine Corps; HO5S-1G by the Coast Guard; and YH-18A by the Army.

Design and development

Sikorsky Aircraft began designing the S-52 in late 1945.^[3] The prototype S-52, first flown in 1947, was a two-seater and used a 178 hp (133 kW) Franklin air-cooled flat-6 piston engine.^[2]

The two-seat version was modified into the S-52-2, a four-seat helicopter using a 245 hp (183 kW) Franklin O-425-1 air-cooled flat-6. It had a semi-monocoque fuselage of pod-and-boom arrangement with large bubble-like front greenhouse,^[1] three-blade rotor, and quadricycle fixed landing gear. The production S-52-3 (HO5S-1) incorporated a downward sloping (anhedral) v-tail stabilizer.^[4] It also had sliding doors on the right forward and left rear sides, and a vertically split front bubble, allowing the left half to swing open in a clamshell fashion. The engine was placed at the aft end of the cabin and was canted forward 30 degrees to couple with the clutch and transmission.^[5] The pilot in command occupied the right front seat.

The first American helicopter to have all-metal rotor blades,^[1]^[2] the prototype^[2] set several speed and height records in 1948, including 129.6 mph (204.2 km/h) on a 3 km (2 mi) course, 122.75 mph (197.54 km/h) on a 1 km (1,100 yd) circuit, and absolute height 21,220 ft (6,468 m).^[1] It was capable of hover out of ground effect at 5,900 ft (1,798 m) or 9,200 ft (2,804 m) in ground effect.^[1] The S-52 is widely believed to be the first helicopter to be looped, as flown by Harold E. Thompson in 1949.

The S-52 also served as the basis of the turbine-powered S-59, which as the XH-39 competed for and lost the contract that produced the Bell UH-1 Iroquois. This aircraft differed in having a four-bladed rotor (against the S-52's three) and retractable tricycle gear.^[1]

Operational history

The Navy operated the aircraft as a utility type, and it was used by the Marines for observation and scouting in Korea,^[6] where the HO3S proved more popular. Four S-52s were evaluated by the United States Army for utility use in 1950, as the YH-18A, but not purchased in quantity.^[3]

Many of the former military HO5S-1 units were demilitarized, rebuilt, and licensed as civil aircraft by Orlando Helicopters, who acquired the parts inventory from Sikorsky.

Variants

U.S. Army YH-18A in testing

S-52-1: Two seat prototype, first flown in 1948.^[7]

S-52-2: Improved three/four-seat variant.^[7]

S-52-3: Variant of the S-52-2 for the United States Navy and Coast Guard, designated H05S-1 and HO5S-1G.^[8]

YH-18A: Four S-52-2s for evaluation by the United States Army,^[3] two later converted into XH-39s.^[9]

HO5S-1

The Sikorsky S-52 (HO5S-1) at the Smithsonian's Udvar-Hazy center

:Model S-52-3, a United States Navy variant of the four-seat S-52-2, 79 built.^[8]

HO5S-1G: As HO5S-1 for the United States Coast Guard, eight built.^[8]

XH-39: Model S-59 turboprop powered prototype modified from two YH-18As.^[10]

Vertical Hummingbird: Sold by Vertical Aviation Technologies of Sanford, Florida, the Hummingbird 260L is a kit-built design using the basic airframe, blades, main transmission, and tail rotor drive of the Sikorsky S-52 helicopter, but streamlined with a Bell 206 JetRanger nosecone and windshields. The Hummingbird is powered by a Lycoming VO-435—a vertically mounted, opposed six-cylinder 435-cubic-inch engine.^[11]

Operators

A U.S. Marine Corps HO5S-1 evacuating wounded in Korea, 1953.

Honduras

Honduran Air Force^[12]

United States

Specifications

Data from Jane's All The World's Aircraft 1951–52^[14]

General characteristics

Crew: 2
Capacity: 2 passengers or 2 stretchers
Length: 27 ft 5 in (8.36 m) (fuselage length)
Height: 8 ft 8 in (2.64 m)
Empty weight: 1,650 lb (748 kg)
Gross weight: 2,400 lb (1,089 kg)
Max takeoff weight: 2,700 lb (1,225 kg) (overload)
Fuel capacity: 62 US gal (230 l; 52 imp gal)
Powerplant: 1 × Franklin 6V6-245-B16F air-cooled six-cylinder horizintally-opposed piston engine, 245 hp (183 kW)
Main rotor diameter: 33 ft 0 in (10.06 m)
Main rotor area: 855 sq ft (79.4 m²)

Performance

Maximum speed: 110 mph (177 km/h; 96 kn) at sea level
Cruise speed: 96 mph (83 kn; 154 km/h)
Range: 415 mi (361 nmi; 668 km)
Service ceiling: 15,500 ft (4,724 m)
Rate of climb: 1,300 ft/min (6.6 m/s)

References

Notes

1 2 3 4 5 6 Polmar and Kennedy, p. 288.
1 2 3 4 Donald 1997, p. 840.
1 2 3 4 Harding 1990, p. 228.
↑ FAA type certificate
↑ Flight manual, page 5
↑ Polmar and Kennedy, p. 289 caption.
1 2 "Sikorsky S-52 Series - A Successful Little Helicopter and its Background". Flight International. 7 August 1953. p. 178.
1 2 3 Andrade 1979, p.195
↑ Andrade 1979, p.119
↑ Andrade 1979, p.122
↑ Hummingbird Helicopter. vertical-aviation.com.
↑ Hagedorn 1986, p. 63.
↑ Pearcy 1991, pp. 292–293.
↑ Bridgman 1951, pp. 289c–290c.

Sources

FAA Type Data Certificate, Helicopter Specification No. 1H2, rev. 3; 7 July 1961.
GAA Rotorcraft Flight Manual for Model S-52-3 Helicopter, Publication No. SA4045-10 Register 2, Sikorsky Aircraft Division of United Aircraft, 1952.
Bridgman, Leonard. Jane's All The World's Aircraft 1951–52. London: Sampson Low, Marston & Company, Ltd, 1951.
Donald, David, ed. "Sikorsky S-52". Encyclopedia of World Aircraft. Etobicoke, Ontario: Prospero Books, 1997. ISBN 1-85605-375-X.
Hagedorn, Daniel P. "From Caudillos to COIN" Air Enthusiast, Thirty-one, July–November 1986. pp. 55–70.
Harding, Stephen. "Sikorsky H-28". U.S. Army Aircraft Since 1947. Shrewsbury, England: Airlife, 1990. ISBN 1-85310-102-8.
Pearcy, Arthur. U.S. Coast Guard Aircraft Since 1916. Shrewsbury, England: Airlife, 1991. ISBN 1-85310-118-4.
Polmar, Norman, and Floyd D. Kennedy, Jr. Military Helicopters of the World. Annapolis, MD: Naval Institute Press, 1981. ISBN 0870213830.

External links

Wikimedia Commons has media related to Sikorsky S-52.

Sikorsky aircraft

Fixed-wing aircraft (company designations)	S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 S-10 S-11 S-12 S-13 S-14 S-15 S-16 S-17 S-18 S-19 S-20 S-21 S-22 S-23 S-24 S-25 S-26 S-27 S-28 S-29-A S-30 S-31 S-32 S-33 S-34 S-35 S-36 S-37 S-38 S-39 S-40 S-41 S-42 S-43 VS-44 S-45

Fixed-wing aircraft (military designations)	C-6 C-28 JRS JR2S PS RS XBLR-3 XPBS XSS XV-2

Helicopters (company designations)	VS-300 (S-46) S-47 S-48 S-49 S-51 S-52 S-53 S-54 S-55 S-56 S-57 S-58 S-59 S-60 S-61 S-61L/N S-61R S-62 S-63 S-64 S-65 S-66 S-67 S-68 S-69 S-70 S-71 S-72 S-73 S-74 S-75 S-76 S-80 S-92/H-92 S-97 S-300 S-333 S-434

Helicopters (military designations)	SH-3 HH-3E/F R-4 H-5 H-6 H-18 H-19 H-34 CH-37 XH-39 HH-52A CH-53 CH-53E CH-53K CH-54 HH-60G HH-60J MH-60R/S SH-60B/F SH-60J/K UH-60 VH-60 RAH-66 CH-124 CH-148

Experimental aircraft	Cypher Cypher II Firefly X2 XBLR-3 XV-2

United States helicopter designations, Army/Air Force and Tri-Service systems

Numerical sequence used by USAAC/USAAF/USAF 1941–present; US Army 1948–1956 and 1962–present; US Navy 1962–present

Main sequence
(1941–1962)

Prefix R-, 1941–1948	R-1 R-2 R-3 R-4 R-5 R-6 R-7 R-8 R-9 R-10 R-11 R-12 R-13 R-14 R-15 R-16

Prefix H-, 1948–1962	H-5 H-6 H-9 H-10 H-11 H-12 H-13/J H-15 H-16 H-17 H-18 H-19 H-20 H-21 H-22 H-23 H-24 H-25 H-26 H-27 H-28 H-29 H-30 H-31 H-32 H-33 H-34 H-35 H-36¹ H-37 H-38¹ H-39 H-40 H-41 H-42 H-43 H-44¹ H-45¹

Main joint sequence
(1962–present)

1962 redesignations	OH-13/UH-13J UH-19 CH-21 OH-23 UH-25 CH-34 CH-37 HH-43

New designations	CH-46/HH-46/UH-46 CH-47 UH-48 XH-49 QH-50 XH-51 HH-52 CH-53/HH-53/MH-53/CH-53E/CH-53K CH-54 TH-55 AH-56 TH-57 OH-58 XH-59 UH-60/SH-60/HH-60/HH-60J YUH-61 XCH-62 YAH-63 AH-64 HH-65 RAH-66 TH-67 MH-68 H-69¹ ARH-70 VH-71 UH-72 H-73 to H-89¹ MH-90 H-91¹ VH-92

1962 redesignations
reusing old numbers

¹ Not assigned

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