The CH-53 Sea Stallion (Sikorsky S-65) is a family of American heavy-lift transport helicopters designed and built by the American manufacturer Sikorsky Aircraft. The Sea Stallion was developed in response to a March 1962 request from the United States Navy's Bureau of Naval Weapons for a replacement for the Sikorsky CH-37 Mojave helicopters flown by the United States Marine Corps (USMC).
In July 1962, Sikorsky's proposal, which was essentially a scaled-up S-61R fitted with twin General Electric T64 turboshaft engines and the dynamic systems of the S-64/CH-54, was selected. On 14 October 1964, the YCH-53A performed its maiden flight; the first deliveries of production CH-53s to operational units commenced on 12 September 1966. In 1967, it first saw combat when it was deployed to the Vietnamese theater. The CH-53 quickly proved its value for moving heavy payloads, particularly in the recovery of damaged aircraft.
Several variants of the type were promptly introduced. The United States Air Force introduced the HH-53 "Super Jolly Green Giant", configured for special operations and combat search and rescue (CSAR) missions, during the latter part of the Vietnam War. The majority of these were rebuilt into the MH-53 Pave Low. The visually similar CH-53E Super Stallion is a heavier-lifting improved version of the rotorcraft, designated S-80E by Sikorsky. Its third engine makes it more powerful than the Sea Stallion and thus displaced it for the heavy-lift mission. Many early-build CH-53s were refitted with more powerful engines, while others were reconfigured for different mission roles, such as US presidential flights, training, and airborne mine countermeasures (AMCM) operations.
Several export deals for the CH-53 were made, leading to several international operators, including Germany, Iran, and Israel. Several unusual or high-profile operations have been undertaken, such as the capture and transportation of a Soviet advanced radar system to Israel under Operation Rooster 53 in 1969, and Iran's capture of five American CH-53s as a result of Operation Eagle Claw in 1980. Various operators deployed their CH-53s during international missions, often under the auspices of NATO or the United Nations, such as for UNSCOM in Iraq, in Kosovo with Kosovo Force (KFOR), Implementation Force (IFOR) in Bosnia and Herzegovina, and the International Security Assistance Force (ISAF) in Afghanistan. While several operators have opted to retain the type into the twenty-first century, many others have opted to supplement or withdraw their Sea Stallions in favor of other platforms, sometimes with the more powerful CH-53E. The CH-53 remains in service with German and Israeli forces, and is one of the largest military helicopters in service. Germany is planning to replace its fleet, as of the 2020s, with the latest version of the twin-rotor CH-47 Chinook. In US service, the CH-53 was replaced in some roles by the V-22 Osprey tilt rotor.
Development
Origins In 1960, the United States Marine Corps (USMC) began to seek a replacement for their HR2S piston-powered helicopters. In January 1961, the USMC began working with the U.S. Army, Navy, and Air Force on the "Tri-Service VTOL transport", which would eventually emerge as the LTV XC-142 tiltwing. The design became more elaborate and the program stretched out, causing the USMC to drop out when they decided they would not receive a working machine in a satisfactory timeframe. In particular, there were concerns that the high levels of downwash produced by the XC-142A would render shipborne operations impractical. In the end, the XC-142A, although a very innovative and capable machine, never entered production."S-65 Origins / US Marine CH-53A & CH-53D Sea Stallion". Airvectors.net, 1 January 2016.
In March 1962, the United States Navy's Bureau of Naval Weapons, acting on behalf of the USMC, issued a request for a "Heavy Helicopter Experimental / ". The specifications dictated a load capability of with an operational radius of at a speed of . It was also specified to possess a higher top speed and greater lifting capacity than existing helicopters, while having a lower empty weight than preceding designs. The was to be used in the assault transport, aircraft recovery, personnel transport, and medical evacuation roles. In the assault transport role, it was to be mostly used to haul heavy equipment instead of troops.
In response, Boeing Vertol offered a modified version of the CH-47 Chinook. Kaman Aircraft offered a development of the British Fairey Rotodyne compound helicopter, and Sikorsky offered what amounted to a scaled-up version of the S-61R, with twin General Electric T64 turboshaft engines and the dynamic system of the S-64/CH-54, to be designated the S-65. Kaman's proposal quickly died when the British government dropped its backing of the Rotodyne program.
Competition between Boeing Vertol and Sikorsky was intense, with the Chinook having an advantage because it was being acquired by the United States Army. In July 1962, Sikorsky's bid was selected as the winner on account of various considerations, including cost, technical factors, and production capability. A contract was not immediately forthcoming due to budgetary limitations.
The USMC had originally sought to procure four prototypes. In light of funding shortfalls, Sikorsky, determined to keep the deal, reduced their estimate for the program's development costs by proposing that development could be performed with only two prototypes. Military officials favorably received the company's proposed reduction. In September 1962, Sikorsky was awarded a $9,965,635 (~$ in ) contract for the production of a pair of YCH-53A prototypes, as well as a mockup and a ground-test airframe.
The development program did not go entirely smoothly, due to a shortage of engineering resources plus various failures of subcontractors and the government, but these problems were gradually overcome. There was also pressure against the program from U.S. Secretary of Defense Robert S. McNamara, who promoted the concept of "commonality" between the armed services by adopting the Chinook instead. The USMC managed to convince McNamara's staff that the Chinook could not meet their requirements without numerous expensive changes.
The first YCH-53A performed its initial flight at the Sikorsky plant in Stratford, Connecticut, on 14 October 1964, about four months behind schedule. In September, the USMC had already placed an initial production contract for 16 helicopters. Flight trials went more smoothly than expected, helping make up for the time lost in development. In November 1964, the type was formally introduced to the general public. Around this time, it received the military designation and name CH-53A Sea Stallion. In September 1966, the first deliveries of the CH-53 to an operational unit occurred.Frawley 2002, p. 148.
Further development
In January 1967, the CH-53A arrived in Vietnam and proved useful, eventually recovering more downed aircraft than the CH-54. 141 CH-53As were built, including the two prototypes. The U.S. Navy acquired 15 CH-53As from the USMC in 1971 for airborne mine countermeasures (AMCM) activities. The helicopters had more powerful T64-GE-413 turboshafts installed and received the designation RH-53A.
The United States Air Force ordered the HH-53B in September 1966 and it first flew in March 1967. It added a refueling probe, drop fuel tanks, a rescue hoist, and featured upgraded T64-GE-3 engines. The Air Force used the HH-53B for combat search and rescue (CSAR).Donald, David, ed. "Sikorsky S-65". The Complete Encyclopedia of World Aircraft. Barnes & Noble Books, 1997. . HH-53C was an improved CSAR variant with a smaller fuel tank in exchange for more armor and better communication systems. The CH-53C was similar except it lacked a refueling probe. It was used by the USAF for more general transport work., Vectorsite.net, 1 May 2006.
Heavy lifting in tropical climates demanded more power, so the USMC decided to acquire an improved variant, the CH-53D, with uprated engines, originally the T64-GE-412, then later the T64-GE-413. The CH-53D included an uprated transmission to go with the more powerful engines, and a revised interior to permit a load of 55 troops.
The initial flight of the CH-53D was in January 1969. The CH-53D served alongside the CH-53A through the rest of the Vietnam War. A VIP transport version designated VH-53D with plush accommodations was used by the USMC for US presidential flights. The US Navy also acquired CH-53D-based helicopters for minesweeping. These were designated RH-53D and included mine sweeping gear such as a pair of 0.50 BMG (12.7 mm) Browning machine guns for detonating mines. The Navy received 30 RH-53Ds, beginning in 1973. After the RH-53Ds were in service, the RH-53As were handed back to the USMC and restored to CH-53A configuration.
In the 1980s, Israeli Air Force's CH-53 Yas'ur fleet was upgraded by Israel Aircraft Industries and Elbit Systems. The project – which ended in 1997 – improved the CH-53 avionics, robustness and extended its life span by at least two decades.
In 1989, some of the CH-53As being retired by the USMC were passed on to the U.S. Air Force for training, with these helicopters redesignated TH-53As. The TH-53As were stripped of most operational equipment and painted in USAF camouflage colors.
Design
The Sikorsky CH-53 Sea Stallion is a heavy lift military transport helicopter. The CH-53A carries a crew of four; pilot, copilot, crew chief, and an aerial observer. It can carry various payloads, including up to 38 fully-equipped troops, 24 litters with medical attendants, an internal cargo load of , or an external load of on the single-point sling hook. Access to the main cabin is via the large passenger door on the right side of the fuselage behind the cockpit, as well as by a power-operated loading ramp to the rear. This loading ramp was capable of facilitating drive-on loading operations, enabling quicker cargo movements. The CH-53A was designed to have a useful payload capacity, in terms of weight, of almost half of the rotorcraft's empty weight.
It is provisioned with mechanical flight controls, which are backed by three independent hydraulic systems. As noted by Sikorsky engineer Edward S Carter Junior, the rotorcraft could be equipped to facilitate all-weather operations. It shares a somewhat similar fuselage design, albeit on a substantially larger scale, with the Sikorsky S-61R series. While the Sea Stallion's fuselage is watertight, the helicopter is not intended for amphibious use and its ability to land on water is meant to only be used in emergency situations.
To save space, which is normally at a premium on board most naval vessels, both the tail boom and the rotors can be folded while the helicopter is stowed; to reduce the workload involved in this process, an automated folding system was developed by Sikorsky. Both the crew and vital systems are protected by armoring across key areas. All of the fuel was housed within sponsons on either side of the fuselage. The CH-53A was typically equipped with a pair of 7.62×51mm NATO M60 machine guns that point out to each side of the fuselage.