Sikorsky CH-53K King Stallion

The massive elastomerically-articulated titanium rotor head uses fewer fastenings and connections than legacy helicopters, reducing weight, maintenance time and e­ffort.

The USMC’s heavy-lift replacement program, the CH-53K, conducted its first flight on October 27, 2015. The CH-53K will replace the Corps’ CH-53E, which is now 28 years old. Although “unexpected redesigns to critical components” delayed a low-rate initial production decision, the program achieved Milestone C in April 2017, and the President’s FY 2019 budget requests $1,601.8 million for the procurement of eight aircraft in its second year of low-rate initial production. The helicopter is predicted to reach IOC in 2019, almost four years later than initially anticipated. This is of increasing concern as the Marine Corps maintains only 139 CH-53Es and will not have enough helicopters to meet its heavy-lift requirement of 200 aircraft without the transition to the CH-53K.

The Sikorsky CH-53K King Stallion is a new development for the US Marine Corps and has nothing in common with the CH-53 of the Bundeswehr. The development-goal was ,more cargo space, more payload and better performance (especially at high altitudes and in hot weather conditions). The cornering point is the ability to fly an external sling load of 12.2 tons over a distance of 200 kilometers and return to the starting point afterwards.

For the internal transport of vehicles and material, the cabin cross-section was increased to 2.74 x 2 meters. According to Sikorsky, two 4.500 kilograms of heavy-duty 463L pallets fit – allowing direct reloading from a C-5 or C-17 airplane into a CH-53K. The delays occurring in new developments is not unusual even with a “3-D virtual-reality digital designed” helicopter. Problems arose with the main transmission and the first flight was delayed until October 2015. At the moment, four prototypes are flying, which have completed more than 450 flying hours at this time.

New features

The CH-53K has been designed from the outset to be easily maintained. Its design was predicated on using tried and tested modern systems rather than developing new concepts. In accordance with that, Sikorsky drew on its experience with its S.92 and adapted the health and usage monitoring system (HUMS) from that helicopter for the King Stallion. Used for fleet management, it provides significant information about the operational performance of the aircraft and its parts and reliability and overall real-time data about the aircraft – it provides a picture of what `normal’ is. This means that problems can be identified before they get out of hand. The aircraft’s new GE Aviation GE38/T-408 engines are lighter than the legacy engine but develop 57% more power, 7,500shp, have up to 63% fewer parts and use 18% less fuel. Fourth-generation rotor blades, which provide a rotor span of 39ft 6in (12.04m), have 12% more surface area than on the CH-53E. Fitted with anhedral tips they are coupled with a composite cu attachment that attaches the main blades directly to an elastomerically-articulated titanium rotor head, itself 9ft (2.74m) across, doing away with conventional fasteners. As would be expected in such an advanced machine, it benefits from a modern glass cockpit and fly-by-wire flight controls. This reliance on existing technologies is not without hazard and in mid-2018 Bloomberg reported that a significant number of components require redesign and requalification. Instead of the availability rate of 75% to 90% required to keep the programme on track, only 65% was being achieved, meaning IOC is likely to be further delayed.

Facts and figures

Military vehicles are getting bigger and heavier. The Marine Corps uses its fleet of 142 surviving CH-53Es for transportation of heavy equipment and supplies during the ship-to-shore movement of an amphibious assault and during subsequent operations ashore. The CH-53K will do the same and more. The CH-53E, the backbone of the US Marine Corps’ heavy-lift helicopter fleet is an impressive machine, but it is wearing out and is labour-intensive – the maintenance hours to flight hours ratio is 44 to 1. The fleet was subject to an independent readiness review in 2015 that mandated it be brought back to full capability by 2020, with the aim of sustaining it until it is replaced by the King Stallion in 2029. This programme itself is falling behind target because of a shortage of parts and inefficiencies in the maintenance system. The E-model is capable of lifting a total of 30,000lb (13,600kg) internally or 36,000lb (14,500kg) as an external load for a maximum takeoff weight (MTOW) of 73,500lb (33,300kg). Operationally it is said to be capable of carrying a load of 31,967lb (14,500kg) for 50 nautical miles (92.6km) and returning to the ship. A typical load might be a 16,000lb (7,264kg) M198 howitzer or a 26,000lb (11,804kg) LAV- 25 light armoured vehicle. As a troop transport it can carry up to 55 fully equipped Marines.

The CH-53K’s maximum design gross weight (MDGW) is 88,000lb (39,900kg) and its MTOW will be 84,700lb (38,400kg). In service it is expected to be capable of carrying 27,000lb (12,200kg) over a radius of action of 110 nautical miles (204km), more than double that of the CH-53E. In the external lift mission loads can be carried on three hooks. The forward and aft hooks are rated to carry 25,600lb (11,400kg) between them while the centre single point hook is rated up to 36,000lb (16,300kg). That is a phenomenal amount for a helicopter; a C-130H Hercules tactical airlifter is usually quoted as having a useful payload of 45,000lb (20,400kg). This lifting ability is what has made the CH-53 the platform of choice for recovering downed aircraft, but even with the added power the CH-53K will not be able to recover an entire C-130 Hercules. However, it will be able to bring back every other aircraft in the Marine Corps’ inventory, including other CH-53s.

As a `trash hauler’ the King Stallion excels. The strengthened floor has a floor loading of 300lb/ft2 (1,470kg/m2) allowing for the carriage of very heavy cargo. With an eye to export orders, Lockheed’s publicity material stresses the aircraft’s ability to carry Germany’s Fennek Leichter Gepanzerter Spähwagen (Light Armoured Reconnaissance Vehicle), although the blurb refers to it as a tank. Although the new helicopter is roughly the same size as the E-model it is replacing, it is importantly a little bit bigger. A CH-53K, ready to fl y with its rotors and tail unfolded, is 99ft (30.2m) long, 17.5ft (5.3m) wide and stands 28.3ft (8.6m) tall. Internally the cabin is 29.85ft (9.1m) long, 8.85ft (2.7m) wide and 6.56ft (2m) tall. By contrast, although the CH-53E’s cabin at 29.91ft long (9.91m) is almost the same, at 7.51ft (2.29m) wide it is more than 18 inches narrower. Because the CH-53K is almost the same size as the Super Stallion it will still be able to land on the Marine Corps’ amphibious warfare ships. However, the wider cabin enables it to carry the ubiquitous Humvee internally, something the CH-53E cannot do. The armoured version of the High Mobility Multipurpose Wheeled Vehicle (HMMWV), to give the Humvee its proper designation, weighs in at up to 24,250lb (11,000kg). In its original form, before the addition of armour to resist the impact of improvised explosive devices, the vehicle weighed less than a quarter of that, emphasizing the need for increased lift capacity on the future battlefield. On January 18, 2018, YCH-53K BuNo 168781 lifted the Humvee’s replacement, the Joint Light Tactical Vehicle (JLTV) that weighs 14,000lb (6,400kg) and more. A CH-53K became the heaviest Sikorsky helicopter to fl y in March 2018 when it took o at a gross weight of more than 91,000lb (41,277kg) carrying an external load of 27,000lb (12,200kg) during trials at Sikorsky’s Development Flight Center in Florida. The wider cabin also allows for the carriage of 34 troops sitting in crashworthy seats as well as palleted or other cargo. In the medevac role it can be fitted with 24 litters.

The King Stallion has a service ceiling of 16,000ft at the International Standard Atmosphere with an outside air temperature of 15°C. At 24°C this drops to 13,200ft but such a temperature at that height is very rare. These figures confirm the aircraft’s suitability for operation at `hot and high’ locations. A time-consuming feature of the CH-53E when it comes to operating from a hubbase is the need to break down cargos into standard US Marine Corps 40 x 48-inch (1.01 x 1.21m) wooden pallets when they are transferred from an incoming transport aircraft for transportation further into the Marines’ area of operations. The CH-53K can carry six of those pallets, each weighing 2,500lb (1,100kg). However, because of the slightly wider fuselage, it can carry two fullsize NATO standard 463L pallets of 10,000lb (4,536kg) each or five of the smaller 463L half-pallets of 5,000lb (2,268kg). This is of enormous importance when supplies are urgently needed on the battlefield. The cargo is loaded via an automated rolling lockable flooring system.

In addition to its own fuel load of 2,286 US gallons (8,653 litres), which itself weighs 15,545lb (7,095kg) and is carried in two external sponsons with two fuel cells in each, when acting as a flying petrol bowser its tactical bulk fuel delivery system comprises three 800 US gallon (3,030 litre) tanks.

History has a habit of repeating itself and when it became apparent in the mid-2000s that the Marines were chewing up Super Stallions at a much faster rate than planned and budgeted for, a remedy was sought. Various plans were put forward to fulfil the Heavy Lift Replacement (HLR) programme. Instead of performing expensive upgrades that would only temporarily delay the type’s retirement, a decision was made to build new aircraft. Sikorsky (then a subsidiary of United Technologies Corporation (UTC, but since 2015 a part of Lockheed Martin) proposed an upgraded new-build Super Stallion, using the latest construction techniques and technology, the CH-53X. As early as 2006 the Pentagon signed a $18.8 billion deal for 156 of the new helicopters. The project was seen as high priority because of the rapid deterioration of the CH-53E fleet and early plans called for an initial operating capability (IOC), defined as a detachment of four aircraft with combat ready crews capable of deploying with all required equipment and spares, in the 2014 – 2015 timeframe. The last of the 156 machines was to be delivered in 2021. This programme has repeatedly slipped. The most obvious change in the program of record was the addition, in 2010, of 44 aircraft to the Marines’ requirement, raising the figure from 156 to the present 200. As this is written, IOC is planned for January 2019, four years later than originally expected.

The Corps intends to equip eight active duty squadrons one training squadron and one reserve squadron with the new CH-53K King Stallion.

Three of six production helicopters intended to serve as system development and demonstration (SDD) aircraft, have been delivered to the Marine Corps at MCAS New River, North Carolina. One of these, BuNo 169019, made the type’s first trip outside the United States in April 2018 when it visited the ILA Airshow in Berlin and was demonstrated to the German Bundeswehr. The type, along with Boeing’s CH-47F Chinook, is in the running to replace Germany’s 64 CH-53s that have been in service for decades. The remaining three SDD machines are expected to be delivered in 2019.

Plans call for low-rate initial production (LRIP) of 26 helicopters in four lots to the fourth quarter of 2023. Lot 1 comprises two aircraft, Lot 2 four and Lot 3 seven. Full-rate production of 168 helicopters will begin with the awarding of Lot 5 in the fourth quarter of 2019 and run through to Lot 12 at the end of 2031.

As well as Germany, Israel and Japan, both existing operators of the H-53, have expressed an interest in the King Stallion. The US Navy also operates a variant of the legacy platform in the shape of the MH-53E Sea Dragon, which it uses for countering sea mines. The German acquisition is by no means a done deal, neighbours the Netherlands, Italy, Spain and the UK all use Chinook, but it is likely there will be small numbers of machines sold overseas

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