14 October 1964: The first prototype Sikorsky YCH-53A Sea Stallion, Bu. No. 151613, made its first flight at the Sikorsky plant at Stratford, Connecticut. (Sikorsky model S-65, serial number 65001.)
The fuselage of the YCH-53A was similar in configuration to the smaller CH-3C (S-61R). It used the dynamic components from the CH-37 Mojave (S-56) and CH-54A Tarhe (S-64).
The Sikorsky CH-53A Sea Stallion is a twin-engine heavy-lift transport helicopter operated by two pilots. It is 88 feet, 2.4 inches (26.883 meters) with rotors turning. The fuselage is 67 feet, 2.4 inches (20.483 meters) long and 8 feet, 10 inches (2.692 meters) wide. The six-blade fully articulated main rotor is 72 feet, 2.7 inches (22.014 meters) in diameter and turns counterclockwise as seen from above. (The advancing blade is on the helicopter’s right.) Main rotor speed is 185 r.pm. The four-blade semi-articulated tail rotor has a diameter of 16 feet (4.877 meters) and is placed on the left side of the tail rotor pylon in a pusher configuration. It turns clockwise as seen from the helicopters left. (The advancing blade is below the axis of rotation.) Overall height (rotors turning) of the Sea Stallion is 24 feet, 10.8 inches (7.599 meters). The tail rotor speed is 792 r.p.m.
The CH-53A is powered by two General Electric T64-GE-6 turboshaft engines rated at 2,850 shaft horsepower, each. Performance of the CH-53D (T64-GE-413, 3,925 s.h.p) has a maximum speed (Vne) of 130 knots (241 kilometers per hour) service ceiling of 16,750 feet (5,105 meters) and range with maximum payload of 540 miles (870 kilometers)
Two YCH-53A prototypes were built, followed by 139 CH-53A Sea Stallion production models.
The CH-53 was developed into the three-engine CH-53E Super Stallion. The current production variant is the CH-53K King Stallion.
12 October 1976: The Sikorsky S-72 Rotor Systems Research Aircraft (RSRA) made its first flight at Stratford, Connecticut. The S-72 was a hybrid aircraft built for the United States Army and the National Aeronautics and Space Administration. Its purpose was to serve as a flight test vehicle for various helicopter rotor configurations.
The S-72 was three-place, four-engine, single main rotor/tail rotor compound helicopter with retractable main landing gear. The flight crew consisted of two test pilots in a side-by-side cockpit, and a flight test engineer in the cabin. The left pilot’s position was equipped with “fly-by-wire” flight controls, while the right seat used conventional mechanical controls as a safety back up. The S-72 had a crew escape system, which blew the main rotor blades off, allowing the crew to land the aircraft in its airplane mode, or to be extracted by rockets.
The aircraft was built with a low-drag fuselage capable of reaching 340 knots (391 miles per hour/630 kilometers per hour) and used the rotors and drive train of the S-61 Sea King. A wing and two turbofan engines allowed the aircraft to fly as an airplane.
The S-72 had an overall length with rotors turning, of 75 feet, 11 inches (23.139 meters). The fuselage had a length of 63 feet, 8 inches (19.406 meters), and maximum width of 8 feet, 4 inches (2.642 meters). The RSRA had an overall height of 15 feet, 6 inches (4.724 meters). The variable incidence wing has a span of 45 feet, 1.2 inches (13.746 meters). The angle of incidence could be varied in flight from +15° to -9°. The span of the horizontal stabilizer is 20 feet, 10 inches (6.350 meters). The S-72 compound helicopter had an empty weight of 20,812 pounds (9,440 kilograms) and gross weight of 26,392 pounds (11,971 kilograms). When stripped to a pure helicopter configuration, the empty weight was reduced to 14,490 pounds (6.573 kilograms).
The S-72 was first flown using the rotors from the S-61. These were later to be replaced with experimental rotor systems. The S-61 main rotor has five blades and a diameter of 62 feet, 0 inches (18.898 meters). Each blade has a chord of 1 foot, 6.25 inches (0.464 meters). The main rotor turns at 203 r.p.m., counter-clockwise, as seen from above. (The advancing blade is on the right.) The S-72’s tail rotor also has five blades and has a diameter of 10 feet, 7.25 inches (3.232 meters). The blades have a chord of 7–11/32 inches (0.187 meters). The tail rotor turns clockwise as seen from the helicopter’s left. (The advancing blade is below the axis of rotation.) The tail rotor turns 1,244 r.p.m.
The S-72 was powered by two General Electric T58-GE-5 turboshaft engines, driving the rotor system, and two General Electric TF34-GE-2 turbofan engines providing thrust for flight in the airplane or compound helicopter configuration.
The T58-GE-5 turboshaft engines are the same engines that powered the HH-3E Jolly Green Giant combat search and rescue helicopters. They are a free-turbine turboshaft with a 10-stage axial-flow compressor section a 2-stage gas generator turbine (N1) and 1-stage free power turbine (N2). The T58-GE-5 has a Maximum Continuous Power rating of 1,400 shaft horsepower, each, and Military Power rating of 1,500 shaft horsepower. The engine is 59.0 inches (1.499 meters) long, 20.9 inches (0.531 meters) in diameter, and weighs 335 pounds (152 kilograms).
The TF34-GE-2 turbofan was developed for the U.S. Navy’s Lockheed S-3A Viking anti-submarine aircraft. It was a two-spool axial-flow jet engine with a single-stage fan section, 14-stage compressor, and 6-stage turbine section (2 high- and 4 low-pressure stages). The TF34-GE-2 was rated at 9,275 pounds of thrust (41.26 kilonewtons).
The S-72 had a maximum speed in level flight of 300 knots (345 miles per hour/556 kilometers per hour), and 340 knots (391 miles per hour/630 kilometers per hour) in a dive.
Two RSRAs were built. After Sikorsky’s flight test program was completed in 1979, the two RSRA aircraft were delivered to NASA Ames. The Aircraft received civil registrations N740NA (72001) and N741NA (72002).
The stripped airframe of the first Sikorsky S-72, 72001, sits behind a chain link fence at Fort Rucker, Alabama.
1 October 1947: Los Angeles Airways began regularly scheduled air mail service in Los Angeles, using the Sikorsky S-51 helicopter.
“. . . the U.S. Civil Aeronautics Board awarded LAA the route authorities to operate local air mail services in Southern California using the Sikorsky S-51. Before long, LAA was operating a twice-a-day mail service between the main downtown post office and Los Angeles International Airport along with a small package air express service.
“With a fleet of five S-51s, LAA’s first year of operations resulted in 700 tons of mail being carried with approximately 40,000 landings throughout the Los Angeles metropolitan area. The small operation maintained a 95% reliability rate and by the time it began its small package air express service in 1953, it was annually moving nearly 4,000 tons of mail a year.
“In July 1951 the CAB awarded LAA’s reliable helicopter operation the rights for passenger services which started in November 1954 with larger Sikorsky S-55 helicopters while the smaller S-51s continued the mail and small package services. . . .”
The S-51 was a commercial version of the Sikorsky R-5 series of military helicopters. It was a four-place, single-engine helicopter, operated by one pilot. The cabin was built of aluminum with Plexiglas windows. The fuselage was built of plastic-impregnated plywood, and the tail boom was wood monocoque construction. The main rotor consisted of three fully-articulated blades built of metal spars and plywood ribs and covered with two layers of fabric. (All metal blades soon became available.) The three bladed semi-articulated tail rotor was built of laminated wood. The main rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.
The helicopter’s fuselage was 41 feet, 7.5 inches (12.687 meters) long. The main rotor had a diameter of 48 feet (14.630 meters) and tail rotor diameter was 8 feet, 5 inches (2.565 meters), giving the helicopter an overall length of 57 feet, 1 inch (17.399 meters). It was 13 feet, 1.5 inches (4.001 meters) high. The landing gear tread was 12 feet (3.7 meters). The S-51 had an empty weight of 4,050 pounds (1,837 kilograms) and maximum takeoff weight of 5,500 pounds (2,495 kilograms). Fuel capacity was 100 gallons (378.5 liters).
The helicopter was powered by an air-cooled, supercharged, 986.749-cubic-inch-displacement (16.170 liter) Pratt & Whitney Wasp Jr. T1B4 (R-985 AN-5) direct-drive, nine-cylinder radial engine which was placed vertically in the fuselage behind the crew compartment. This engine was rated at 450 horsepower at 2,300 r.p.m., Standard Day at Sea Level. The R-985 AN-5 was 48.00 inches (1.219 meters) long, 46.25 inches (1.175 meters) in diameter and weighed 684 pounds (310.3 kilograms) with a magnesium crankcase.
The S-51 had a maximum speed (Vne) of 107 knots (123.1 miles per hour/198.2 kilometers per hour). Range was 275 miles (442.6 kilometers). The service ceiling was 14,800 feet (4,511 meters). The absolute hover ceiling was 3,000 feet (914.4 meters).
Of 220 helicopters in the S-51 series built by Sikorsky, 55 were commercial models.
27 September 2008: A United States Air Force Sikorsky MH-53M Pave Low IV special operations helicopter, serial number 68-8284, assigned to the 20th Expeditionary Special Operations Squadron, flew its final combat mission before being withdrawn from service and retired after 40 years and 12,066.6 flight hours.
“Cowboy 26” was flown by Major Philip Cooper, Captain Peter Hettinger, and Colonel Scott Howell, with Technical Sergeant Henry Woodie, Staff Sergeant Shawn Lewis, Senior Airman Eric Harp, and Airman 1st Class Joshua Lucas.
68-8284 was built by the Sikorsky Aircraft Corporation at Bloomfield, Connecticut, as one of 40 HH-53C Super Jolly Green Giants for Combat Search and Rescue (CSAR). It was delivered to the Air Force in August 1968. 68-8284 was assigned to the 40th Air Rescue and Recovery Squadron at Nakhon Phanom Royal Thai Air Force Base, 1971–1972. It operated as “Jolly Green 55.”
On 5 September 1971, with flight crew Major Jerry R. Thompson, Gary L. Gamble (CP), FE Raymond Duarte and PJs William D. Brinson and Michael D Vogele, it rescued the survivors of “Knife 33,” a 21st SOS CH-3E that went down in Laos. On 19 December 1971 (Capt Harold O. Jones (P), David G. Daus (CP), FE Jerrold T. Dearmans, with PJs Leon Fullwood and William D. Brinson, the crew of Falcon 74, a 13th TFS/432 TFW F-4D Phantom II which had gone down shot down 17 December by a SAM near Ban Poung Ban in northeastern Laos. Maj. William T. Stanley, Capt. Lester O’Brien were safely recovered.
8284 was later assigned to the 67th Aerospace Rescue and Recovery Squadron (39th Aerospace Rescue and Recovery Wing) at RAF Woodbridge, Suffolk, England. 68-8284 has been constantly modernized and upgraded. It was initially converted to the MH-53J Pave Low III/Enhanced configuration by the Naval Air Rework Facility, NAS Pensacola, Florida, in the late 1980s. The helicopter was further modified to the MH-53M Pave Low IV configuration at the Naval Air Depot, MCAS Cherry Point, North Carolina.
The MH-53M Pave Low IV is a variant of Sikorsky’s S-65 heavy-lift military transport helicopter series. The MH-53M is a single main rotor, single tail rotor, twin-engine helicopter. It has a crew of six: 2 pilots, 2 flight engineers and 2 gunners. The Pave Low IV is equipped with Terrain-Following Radar and Forward Looking Infrared (FLIR) for low-level operations in darkness and low visibility.
The MH-53M fuselage is 67 feet, 2.4 inches (20.483 meters) long, and the helicopter has a maximum length of 91 feet, 11.34 inches (28.025 meters) with rotors turning and the refueling boom extended. The height to the top of the main rotor pylon is 17 feet, 1.68 inches (5.224 meters). The maximum height (rotors turning) is 24 feet, 10.88 inches (7.592 meters).
The fully-articulated 6-blade main rotor has a diameter of 72 feet, 2.7 inches (22.014 meters). The main rotor turns counter-clockwise at 185 r.p.m. (100% Nr), as seen from above. (The advancing blade is on the helicopter’s right.) The main rotor blades are built with titanium spars and have -16° of twist. The semi-articulated four-blade tail rotor has a diameter of 16 feet, 0 inches (4.877 meters) and is positioned on the left side of the tail pylon. It turns clockwise at 792 r.p.m., as seen from the helicopter’s left side. (The advancing blade is below the axis of rotation.) The gap between rotor arcs is just 4.437 inches (11.270 centimeters).
Empty, the MH-53M weighs 32,000 pounds (14,515 kilograms). Its maximum takeoff weight is 46,000 pounds (20,865 kilograms).
Its two General Electric T64-GE-100 axial-flow turboshaft engines have a Normal Continuous Power rating of 3,810 shaft horsepower at 85 °F. (30 °C.), Military Power rating of 4,090 shaft horsepower, and a Maximum Power rating of 4,330 shaft horsepower. The T64-GE-100 is 79 inches (2.007 meters) long, 20 inches (0.508 meters) in diameter and weighs 720 pounds (327 kilograms). Output (100% N2) is 13,600 r.p.m.
The MH-53M has a maximum speed of 196 miles per hour (315 kilometers per hour) and a service ceiling of 16,000 feet (4877 meters). It carries two 450-gallon (1,703 liter) jettisonable fuel tanks under each sponson.
The MH-53M is armed with two M134 7.62mm miniguns and a GAU-18/A .50 caliber machine gun.
At the time they were retired, the MH-53Ms were the fastest, heaviest, most powerful helicopters in the United States Air Force inventory.
After leaving Iraq, 68-8284 was transported by C-17 Globemaster III to England. It was loaned to the Royal Air Force Museum Cosford, where it is on display.
Recommended:On a Steel Horse I Ride: A History of the MH-53 Pave Low Helicopters in War and Peace, by Darrel D. Whitcomb. Air University Press, Air Force Research Institute, Maxwell Air Force Base, Alabama, September 2012.
1 September 1953: The Societé Anonyme Belge d’Exploitation de la Navigation Aérienne (SABENA) began scheduled international passenger service flying the Sikorsky S-55, a commercial variant of the military H-19 Chickasaw. It carried 8 passengers.
For just over three years, since 21 August 1950, SABENA flew mail from Brussels to Antwerp, Liege, and Turnhout using the Bell Model 47D-1.
The Sikorsky Aircraft Corporation S-55 was flown by two pilots in a cockpit placed above the passenger/cargo compartment. The most significant design feature was moving the engine from directly under the main rotor mast to a position at the front of the helicopter. Installed at an angle, the engine turned a drive shaft to the main transmission. The engine placement provided space for a large passenger/cargo compartment. The aircraft was constructed primarily of aluminum and magnesium, with all-metal main and tail rotor blades.
The main rotor consisted of three fully-articulated blades built of hollow aluminum spars, with aluminum ribs. Spaces within the blade were filled with an aluminum honeycomb. The blades were covered with aluminum sheet. The hollow spars were filled with nitrogen pressurized to 10 p.s.i. An indicator at the blade root would change color if nitrogen was released, giving pilots and mechanics an indication that the spar had developed a crack or was otherwise compromised. The main rotor turned counter-clockwise as seen from above. (The advancing blade is on the helicopter’s right.) Flapping hinges were offset from the main rotor axis, giving greater control response and effectiveness. The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.
The helicopter’s fuselage was 42 feet, 2 inches (12.852 meters). The main rotor had a diameter of 53 feet (16.154 meters) and tail rotor diameter was 8 feet, 8 inches (2.642 meters), giving the helicopter an overall length with all blades turning of 62 feet, 2 inches (18.948 meters). It was 13 feet, 4 inches (4.064 meters) high. The landing gear tread was 11 feet (3.353 meters). The S-55 had an empty weight of 4,785 pounds (2,173 kilograms) and maximum takeoff weight of 7,200 pounds (3,271 kilograms). Fuel capacity was 185 gallons (698 liters).
The S-55 commercial helicopter and H-19/HO4S and HRS military variants used an air-cooled, supercharged 1,301.868-cubic-inch (21.334 liter) Wright Aeronautical Division 871C7BA1 Cyclone 7 (R-1300-3) 7-cylinder radial engine with a compression ratio of 6.2:1. The R-1300-3 was also a direct-drive engine, but was rated at 700 horsepower at 2,400 r.p.m., Normal Power, and 800 horsepower at 2,600 r.p.m. for Take-Off. The engine incorporated a large cooling fan to circulate air around the cylinders. The R-1300-3 was 49.68 inches (1.261 meters) long, 50.45 inches (1.281 meters) in diameter, and weighed 1,080 pounds (490 kilograms).