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
Variants	Sikorsky XH-39; Vertical Hummingbird

The Sikorsky S-52 is 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-six 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-six. It had a semi-monocoque fuselage of pod-and-boom arrangement with a large bubble-like front greenhouse,^[1] a 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 an absolute height of 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 was the first helicopter to be flown in a loop, as flown by Harold E. Thompson on 19 May 1949.^[6]

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,^[7] 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.^{[citation needed]}

Variants[]

U.S. Army YH-18A in testing

S-52-1: Two-seat prototype, first flown in 1948.^[8]

S-52-2: Improved three/four-seat variant.^[8]

S-52-3: Variant of the S-52-2 for the United States Navy and Coast Guard, designated HO5S-1 and HO5S-1G.^[9]

YH-18A: Four S-52-2s for evaluation by the United States Army,^[3] two later converted into XH-39s.^[10]

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.^[9]

HO5S-1G: As HO5S-1 for the United States Coast Guard, eight built.^[9]

XH-39: Model S-59 turboprop-powered prototype modified from two YH-18As.^[11]

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.^[12]

Operators[]

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

Honduras

Honduran Air Force^[13]

United States

United States Army^[3]
United States Coast Guard^[14]
United States Marine Corps^{[citation needed]}
United States Navy^{[citation needed]}

Specifications[]

Data from Jane's All The World's Aircraft 1951–52.^[15]

General characteristics

Crew: two
Capacity: two passengers or two 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 horizontally-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 (180 km/h, 96 kn) at sea level
Cruise speed: 96 mph (154 km/h, 83 kn)
Range: 415 mi (668 km, 361 nmi)
Service ceiling: 15,500 ft (4,700 m)
Rate of climb: 1,300 ft/min (6.6 m/s)

References[]

Notes[]

^ Jump up to: ^a ^b ^c ^d ^e ^f Polmar and Kennedy, p. 288.
^ Jump up to: ^a ^b ^c ^d Donald 1997, p. 840.
^ Jump up to: ^a ^b ^c ^d Harding 1990, p. 228.
^ FAA type certificate
^ Flight manual, page 5
^ Guinness World Records 2019. Portable Press, 2019. p. 164. ISBN 9781684127184.
^ Polmar and Kennedy, p. 289 caption.
^ Jump up to: ^a ^b "Sikorsky S-52 Series – A Successful Little Helicopter and its Background". Flight International. 7 August 1953. p. 178.
^ Jump up to: ^a ^b ^c Andrade 1979, p. 195
^ Andrade 1979, p. 119
^ Andrade 1979, p. 122
^ Hummingbird Helicopter Archived 23 November 2009 at the Wayback Machine. 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[]

[Polmar_Kennedy_p288-1] Jump up to: ^a ^b ^c ^d ^e ^f Polmar and Kennedy, p. 288.

[Donald_p840-2] Jump up to: ^a ^b ^c ^d Donald 1997, p. 840.

[Harding_p228-3] Jump up to: ^a ^b ^c ^d Harding 1990, p. 228.

[4] FAA type certificate

[5] Flight manual, page 5

[6] Guinness World Records 2019. Portable Press, 2019. p. 164. ISBN 9781684127184.

[7] Polmar and Kennedy, p. 289 caption.

[flight-8] Jump up to: ^a ^b "Sikorsky S-52 Series – A Successful Little Helicopter and its Background". Flight International. 7 August 1953. p. 178.

[us195-9] Jump up to: ^a ^b ^c Andrade 1979, p. 195

[us119-10] Andrade 1979, p. 119

[us122-11] Andrade 1979, p. 122

[12] Hummingbird Helicopter Archived 23 November 2009 at the Wayback Machine. vertical-aviation.com.

[13] Hagedorn 1986, p. 63.

[Pearcy_p292-3-14] Pearcy 1991, pp. 292–293.

[jawa51_p289-0c-15] Bridgman 1951, pp. 289c–290c.

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