Tag Archives: Robert Stewart Decker

11 March 1959

Sikorsky XHSS-2 Sea King, Bu. No. 147137, made its first flight at Stratford, CT. (U.S. Navy)
Sikorsky XHSS-2 Sea King, Bu. No. 147137, made its first flight at Stratford, CT. (Sikorsky, a Lockheed Martin Company)

11 March 1959: At Stratford, Connecticut, the prototype Sikorsky XHSS-2 Sea King, U.S. Navy Bureau of Aeronautics serial number (Bu. No.) 147137, company serial number 61001, makes its first flight. Sikorsky’s Assistant Chief Test Pilot Robert Stewart Decker is at the controls.

The Sikorsky SH-3A Sea King was the first of the S-61 series of military and civil helicopters, designated as HSS-2 until 1962. It is a large twin-engine helicopter with a single main rotor/tail rotor configuration. The fuselage is designed to allow landing on water. The helicopter was originally used as an anti-submarine helicopter.

HSS-2 mockup, October 1957. (Sikorsky Historical Archives)

The HSS-2 is 72 feet, 6 inches (22.098 meters) long and 16 feet, 10 inches (5.131 meters) high with all rotors turning. The helicopter’s width, across the sponsons, is 16 feet. The main rotors and tail can be folded for more compact storage aboard aircraft carriers, shortening the aircraft to 46 feet, 6 inches (14.173 meters). The empty weight of the HSS-2 is 10,814 pounds (4,905 kilograms). The overload gross weight is 19,000 pounds (8,618 kilograms).

The main rotor has five blades and a diameter of 62 feet, 0 inches (18.898 meters). Each blade has a chord of 1 foot, 6¼ inches (0.464 meters). The rotor blade airfoil was the NACA 0012, which was common for helicopters of that time. The total blade area is 222.5 square feet (20.671 square meters), and the disc area is 3,019 square feet (280.474 square meters). The tail rotor also has five blades and a diameter of 10 feet, 4 inches (3.150 meters). They each have a chord of 7–11/32 inches (0.187 meters). At 100% NR, the main rotor turns 203 r.p.m. and the tail rotor, 1,244 r.p.m.

The first Sea King, prototype XHSS-2 Bu. No. 147137, demonstrates its capability of landing on water. (Sikorsky, a Lockheed Martin Company)

The HSS-2 was powered by two General Electric T58-GE-6 turboshaft engines, which had a Normal Power rating of 900 horsepower, and Military Power rating of 1,050 horsepower; both ratings at 19,555 r.p.m. at Sea Level. The main transmission was rated for 2,000 horsepower, maximum. (Later models were built with more powerful T58-GE-8 engines. Early aircraft were retrofitted.)

The HSS-2 has a cruise speed of 125 knots (144 miles per hour/232 kilometers per hour) at Sea Level, and a maximum speed of 133 knots (153 miles per hour/246 kilometers per hour) at Sea Level. The service ceiling is 12,100 feet (3,688 meters). The hover ceiling at normal gross weight is 5,200 feet (1,585 meters), out of ground effect (HOGE), and 7,250 feet (2,210 meters), in ground effect (HIGE). The HSS-2 had a combat endurance of 4 hours and a maximum range of 500 nautical miles (575 statute miles/926 kilometers).

The Sea King was primarily an anti-submarine aircraft. It could be armed with up to four MK 43 or MK 44 torpedoes and one MK 101 nuclear-armed depth bomb. Other weapons loads included four MK 14 depth charges and four MK 54 air depth bombs.

In 1962, the HSS-2 was redesignated SH-3A Sea King. Many early production aircraft have remained in service and have been upgraded through SH-3D, SH-3G, etc. In addition to the original ASW role, the Sea Kings have been widely used for Combat Search and Rescue operations. Marine One, the call sign for the helicopters assigned to the President of the United States, are VH-3D Sea Kings.

Sikorsky produced the last S-61 helicopter in 1980, having built 794. Production has been licensed to manufacturers in England, Italy, Canada and Japan. They have produced an additional 679 Sea Kings.

A U.S. Navy Sikorsky SH-3A Sea King (S-61), Bu. No. 149867, near Oahu, Hawaiian Islands, 5 April 1976. (PH2 (AC) Westhusing, U.S. Navy)

© 2019, Bryan R. Swopes

18 December 1953

Sikorsky XHR2S-1, Bu. No. 133732, the first Model S-56, hovers at Sikorsky Aircraft, Bridgeport, Connecticut. (Sikorsky Historical Archives)

18 December 1953: At Bridgeport, Connecticut, Sikorsky chief test pilot Dimitry D. (“Jimmy”) Viner and co-pilot James Edward Chudars made the first flight of the Sikorsky XHR2S-1 (Sikorsky Model S-56). The XHR2S-1 was a prototype assault and heavy-lift helicopter for the United States Navy and Marine Corps. It was later adopted by the U.S. Army as the H-37 Mohave.

The S-56 was a large twin-engine helicopter, following the single main rotor/tail (anti-torque) rotor configuration pioneered by Sikorsky with the Vought-Sikorsky VS-300 in 1939. The helicopter was designed to be flown by two pilots in a cockpit located above the main cabin. The two engines were placed in nacelles outboard of the stub wings which also housed the helicopter’s retractable main landing gear. Two large clam shell cargo doors and loading ramp were placed in the nose. The HR2S-1 incorporated a stability system and an automatic torque compensating tail rotor.

The S-56 series was the largest and fastest helicopter built up to that time, and remains the largest reciprocating engine helicopter ever built.

U.S. Marine Corps HR2S-1 Bu. No. 138423, the seventh production S-56 helicopter (Sikorsky Historical Archives)

The S-56 was equipped with a five blade articulated main rotor. This allowed increased lift and higher forward air speed before encountering retreating blade stall than earlier three and four blade systems. A six blade rotor system was tested, which showed further improvements, but was not adopted. The main rotor diameter was initially 68 feet (20.726 meters), but later increased to 72 feet (21.946 meters). The main rotor blades had a chord of 1 foot, 9.5 inches (0.546 meters) and used the symmetrical NACA 0012 airfoil, which was standard with American helicopters up to that time. Later in the program, the blades were lengthened and the chord increased to 1 foot, 11.65 inches (0.601 meters). The airfoil was changed to the NACA 0010.9 airfoil. These changes resulted in increased lift and higher speed. The four blade tail rotor had a diameter of 15 feet (4.572 meters). The individual blades had a chord of 1 foot, 1.5 inches (0.343 meters). As is common with American helicopters, the main rotor system turned counter-clockwise as seen from above. (The advancing blade is on the right.) The tail rotor turned counter-clockwise when viewed from the helicopter’s left side. (The advancing blade is above the axis of rotation.)

Sikorsky S-56 three-view illustration with dimensions. (Sikorsky Historical Archives)

With the longer blades installed, the helicopter’s length with rotors turning was 88 feet (26.822 meters). The fuselage had a length of 64 feet, 10.69 inches (19.779 meters), and the height was 17 feet, 2 inches (5.232 meters). The HR2S-1 had an empty weight of 21,502 pounds (9,753 kilograms), and maximum weight (overload) of 31,000 pounds (14,061 kilograms). Its fuel capacity was 1,000 U.S. gallons (3,785 liters) carried in 6 tanks located in the nacelles, wings and fuselage. It could carry 20 fully-equipped troops, or 16 litters. Its maximum cargo capacity was 10,000 pounds (4,536 kilograms).

The HR2S-1 had an automatic main rotor blade folding system, and its tail rotor pylon could be folded alongside the fuselage, reducing the length to 55 feet, 8 inches (16.967 meters) and width to 27 feet, 4 inches (8.331 meters). This allowed the helicopter to use aircraft carrier elevators and reduced storage space on the hangar deck.

Early S-56 models were powered by two air-cooled, supercharged 2,804.461 cubic inch displacement (45.957 liters) Pratt & Whitney Double Wasp R-2800-50 two-row, 18-cylinder radial engines rated at 1,900 horsepower at 2,500 r.p.m. These were upgraded in later models to R-2800-54s. These were direct drive engines with a compression ratio of 6.75:1. The R-2800-54 was rated at 2,100 horsepower at 2,700 r.p.m. to 5,000 feet (1,524 meters) for takeoff; with a normal power rating of 1,900 horsepower at 2,600 r.p.m. to 7,000 feet (2,134 meters). It required 115/145 octane aviation gasoline. Each engine was supplied with 13.3 gallons (50.35 liters) of lubricating oil. The R-2800-54 was 6 feet, 9.00 inches long (2.057 meters), 4 feet, 5.00 inches (1.346 meters) in diameter, and weighed 2,300 pounds (1,043 kilograms).

The helicopter’s engines were installed at an 80° angle to the aircraft center line, with a 12.5° upward angle to align with the main transmission input. The front of the engines faced inboard. According to Sikorsky, this unusual installation resulted in high oil consumption, and because the engines were operated at continuous high r.p.m., the time interval between engine overhauls was reduced from the normal 2,000 hours to just 350 hours.

Two U.S. Marine Corps HR2S-1 Mohave assault helicopters of Marine Helicopter Transport Squadron (HMR) 462 at Camp Pendelton, California, late 1950s. (Naval History and Heritage Command)

The production HR2S-1 had a cruise speed of 100 knots (115 miles per hour/185 kilometers per hour), and a maximum speed of 121 knots (139 miles per hour/224 kilometers per hour) at Sea Level. The helicopter’s service ceiling was 13,800 feet (4,206 meters), and its absolute hover ceiling was 5,400 feet (1,646 meters). It had a maximum rate of climb of 1,580 feet per minute (8.03 meters per second) at Sea Level, and a vertical rate of climb 950 feet per minute (4.83 meters per second), also at Sea Level. The combat radius of the HR2S-1 was 100 nautical miles (115 statute miles/185 kilometers) at 100 knots (115 miles per hour/185 kilometers per hour.)

55 HR2S-1s were delivered to the U.S. Marine Corps. The U.S. Army purchased 94 S-56s in the H-37A Mohave configuration. 90 of these were later returned to Sikorsky to be upgraded to H-37Bs. This added the automatic stabilization system of the HR2S-1, changed the variable incidence horizontal stabilizers on both side of the fuselage to a single stabilizer on top of the tail rotor pylon. Engine oil capacity was increased to 30 gallons (113.6 liters) per engine.

A total of 154 S-56s were built between 1953 and 1960.

U.S. Marines exit the front cargo doors of a Sikorsky XHR2S-1 helicopter during a demonstration at Bridgeport, Connecticut, circa 1953. The leading Marine is carrying an M1918 .30-caliber Browning Automatic Rifle (commonly known as the “B-A-R”), while those following are armed with the M1 “Garand” .30-caliber semi-automatic rifle. Note the cinematographer behind the starboard cargo door. (National Archives and Records Administration, NAID: 74241875)

From 9 through 11 November 1956, a U.S. Marine Corps HR2S-1 flown by Major Roy Lee Anderson, USMC, and Sikorsky test pilot Robert S. Decker at Windsor Locks, Connecticut,  set three Fédération Aéronautique Internationale (FAI) world records for speed and payload:

On 9 November, the helicopter reached an altitude of 3,722 meters (12,211 feet) with a payload of 5,000 kilograms (11,023 pounds).¹ The following day, 10 November, it set a record for the greatest mass carried to a height of 2,000 meters (6562 feet): 6,010 kilograms (13,250 feet).² Then on 11 November, the HR2S-1 reached a speed of 261.91 kilometers per hour (162.74 mph) over a  3-kilometer (1.86 miles) course.³ For these flights, Major Anderson was awarded a third gold star in lieu of a fourth award of the Distinguished Flying Cross.

Major Roy Lee Anderson, USMC, (left) and Sikorsky test pilot Robert Stewart Decker. (Fédération Aéronautique Internationale)
The world-record-setting Sikorsky HR2S-1. Note the dorsal filet. (Fédération Aéronautique Internationale)

¹ FAI Record File Number 13129

² FAI Record File Number 13124

³ FAI Record File Number 13098

© 2023, Bryan R. Swopes

9–11 November 1956

Major Roy Lee Anderson, USMC (left), and Sikorsky test pilot Robert Stewart Decker. (FAI)

9–11 November 1956: Over a three-day period at Windsor Locks, Connecticut, a Sikorsky HR2S-1 heavy-lift helicopter, flown by Major Roy Lee Anderson, United States Marine Corps, and Sikorsky test pilot Robert Stewart Decker, set three Fédération Aéronautique Internationale (FAI) world records for payload and speed.

On 9 November 1956, the HR2S-1 carried a payload of  5,000 kilograms (11,023 pounds) payload to an altitude of 3,722 meters (12,211 feet). ¹

The following day, 10 November, it set a record for the Greatest Mass Carried to a Height of 2,000 Meters (6562 feet), with a payload of 6,010 kilograms (13,250 pounds). ²

On 11 November, the third day, Anderson and Decker flew the helicopter to a speed of 261,91 kilometers per hour (162.74 miles per hour) over a  3-kilometer (1.86 statute miles) course .³

For these flights, Major Anderson was awarded a third gold star in lieu of a fourth award of the Distinguished Flying Cross.

The world-record-setting Sikorsky HR2S-1. (Fédération Aéronautique Internationale)

United Press reported:

US Helicopter Sets Altitude, Speed Records

     STRATFORD, Conn.—UP—A twin-engine Marine helicopter has established two international records for speed and altitude.

     The Sikorsky division of United Aircraft Corporation said one of its S56 helicopters reached 162.7 miles per hour during a recent trial. The old record, set two years ago by another Sikorsky model, was 156 miles per hour.

Tops Russian Craft

     The S56 flew more than 12,000 feet high while carrying 11,050 pounds. With the payload increased to 13,250 pounds it reached 7,000 feet, far outstripping the previous mark set by a Russian craft of 8,820 pounds to 6,560 feet.

     The altitude trials were conducted from Sikorsky’s field in Stratford. Major Roy L. Anderson was pilot and Robert S. Decker copilot.

     The records are subject to confirmation by the Federation Aeronautique Internationale. The trials were conducted under the auspices of the National Aeronautics [sic] Association.

The Modesto Bee, Vol 79, No. 272, Tuesday, 13 November 1956, Page 12, Column 2

The Sikorsky HR2S-1 was an assault and heavy-lift helicopter produced for the United States Navy and Marine Corps. It was later adopted by the U.S. Army as the H-37 Mohave.

The S-56 was a large twin-engine helicopter, following the single main rotor/tail (anti-torque) rotor configuration pioneered by Sikorsky with the Vought-Sikorsky VS-300 in 1939. The helicopter was designed to be flown by two pilots in a cockpit located above the main cabin. The two engines were placed in nacelles outboard of the stub wings which also housed the helicopter’s retractable main landing gear. Two large clam shell cargo doors and loading ramp were placed in the nose. The HR2S-1 incorporated a stability system and an automatic torque compensating tail rotor.

The S-56 series was the largest and fastest helicopter built up to that time, and remains the largest reciprocating engine helicopter ever built.

The S-56 was equipped with a five blade articulated main rotor. This allowed increased lift and higher forward air speed before encountering retreating blade stall than earlier three and four blade systems. A six blade rotor system was tested, which showed further improvements, but was not adopted. The main rotor diameter was initially 68 feet (20.726 meters), but later increased to 72 feet (21.946 meters). The main rotor blades had a chord of 1 foot, 9.5 inches (0.546 meters) and used the symmetrical NACA 0012 airfoil, which was standard with American helicopters up to that time. Later in the program, the blades were lengthened and the chord increased to 1 foot, 11.65 inches (0.601 meters). The airfoil was changed to the NACA 0010.9 airfoil. These changes resulted in increased lift and higher speed. The four blade tail rotor had a diameter of 15 feet (4.572 meters). The individual blades had a chord of 1 foot, 1.5 inches (0.343 meters). As is common with American helicopters, the main rotor system turned counter-clockwise as seen from above. (The advancing blade is on the right.) The tail rotor turned counter-clockwise when viewed from the helicopter’s left side. (The advancing blade is above the axis of rotation.)

Sikorsky S-56 three-view illustration with dimensions. (Sikorsky Historical Archives)

With the longer blades installed, the helicopter’s length with rotors turning was 88 feet (26.822 meters). The fuselage had a length of 64 feet, 10.69 inches (19.779 meters), and the height was 17 feet, 2 inches (5.232 meters). The HR2S-1 had an empty weight of 21,502 pounds (9,753 kilograms), and maximum weight (overload) of 31,000 pounds (14,061 kilograms). Its fuel capacity was 1,000 U.S. gallons (3,785 liters) carried in 6 tanks located in the nacelles, wings and fuselage. It could carry 20 fully-equipped troops, or 16 litters. Its maximum cargo capacity was 10,000 pounds (4,536 kilograms).

The HR2S-1 had an automatic main rotor blade folding system, and its tail rotor pylon could be folded alongside the fuselage, reducing the length to 55 feet, 8 inches (16.967 meters) and width to 27 feet, 4 inches (8.331 meters). This allowed the helicopter to use aircraft carrier elevators and reduced storage space on the hangar deck.

Early S-56 models were powered by two air-cooled, supercharged 2,804.461 cubic inch displacement (45.957 liters) Pratt & Whitney Double Wasp R-2800-50 two-row, 18-cylinder radial engines rated at 1,900 horsepower at 2,500 r.p.m. These were upgraded in later models to R-2800-54s. These were direct drive engines with a compression ratio of 6.75:1. The R-2800-54 was rated at 2,100 horsepower at 2,700 r.p.m. to 5,000 feet (1,524 meters) for takeoff; with a normal power rating of 1,900 horsepower at 2,600 r.p.m. to 7,000 feet (2,134 meters). It required 115/145 octane aviation gasoline. Each engine was supplied with 13.3 gallons (50.35 liters) of lubricating oil. The R-2800-54 was 6 feet, 9.00 inches long (2.057 meters), 4 feet, 5.00 inches (1.346 meters) in diameter, and weighed 2,300 pounds (1,043 kilograms).

The helicopter’s engines were installed at an 80° angle to the aircraft center line, with a 12.5° upward angle to align with the main transmission input. The front of the engines faced inboard. According to Sikorsky, this unusual installation resulted in high oil consumption, and because the engines were operated at continuous high r.p.m., the time interval between engine overhauls was reduced from the normal 2,000 hours to just 350 hours.

Two U.S. Marine Corps HR2S-1 Mohave assault helicopters of Marine Helicopter Transport Squadron (HMR) 462 at Camp Pendelton, California, late 1950s. (Naval History and Heritage Command)

The production HR2S-1 had a cruise speed of 100 knots (115 miles per hour/185 kilometers per hour), and a maximum speed of 121 knots (139 miles per hour/224 kilometers per hour) at Sea Level. The helicopter’s service ceiling was 13,800 feet (4,206 meters), and its absolute hover ceiling was 5,400 feet (1,646 meters). It had a maximum rate of climb of 1,580 feet per minute (8.03 meters per second) at Sea Level, and a vertical rate of climb 950 feet per minute (4.83 meters per second), also at Sea Level. The combat radius of the HR2S-1 was 100 nautical miles (115 statute miles/185 kilometers) at 100 knots (115 miles per hour/185 kilometers per hour.)

55 HR2S-1s were delivered to the U.S. Marine Corps. The U.S. Army purchased 94 S-56s in the H-37A Mohave configuration. 90 of these were later returned to Sikorsky to be upgraded to H-37Bs. This added the automatic stabilization system of the HR2S-1, changed the variable incidence horizontal stabilizers on both side of the fuselage to a single stabilizer on top of the tail rotor pylon. Engine oil capacity was increased to 30 gallons (113.6 liters) per engine.

A total of 154 S-56s were built between 1953 and 1960.

U.S. Marines exit the front cargo doors of a Sikorsky XHR2S-1 helicopter during a training exercise. (NAID 74241875

¹ FAI Record File Number 13129

² FAI Record File Number 13124

³ FAI Record File Number 13098

© 2023, Bryan R. Swopes