With the first CH-53K test article—a ground-test vehicle (GTV)—more than halfway complete, a longtime U.S. Marine Corps plan to overhaul its heavy-lift fleet is nearing developmental testing and production.

The technical hurdles in developing a new rotorcraft in the same footprint as the CH-53E it replaces, while more than doubling its load, appear to have been retired, says Col. Robert Pridgen, the Marines' CH-53K program manager. “There is nothing in front of us that is going to slow me down,” he tells Aviation Week. He acknowledges that flight-testing discoveries are possible.

One of the main challenges—developing a new split-torque gearbox—has already been overcome, and “that was no small mountain to climb,” he declares. With this design, three GE38-1B engines separately feed into the gearbox, allowing for a lighter design than the helicopter's predecessor, says Dave Zack, Sikorsky's CH-53K program manager.

The introduction of high-efficiency, composite main rotor blades, each with a swept anhedral tip, are also key to the CH-53K's improved performance. Zack says these massive structures are a generational advancement over the upgrades that Sikorsky added to the UH-60M's main blades. Moreover, these changes are integral to a design that will enable the Marines to carry far more cargo and operate off of amphibious ships.

Sikorsky won the $3 billion CH-53K development contract in April 2006 after submitting an unsolicited proposal; the Marine Corps was looking at options to upgrade its heavy-lift fleet comprised of CH-53D and E models. Technology maturation early in the program for the main rotor blades and gearbox was critical, as both were at a technology readiness level of 4 instead of 6, which is typically when the Pentagon moves forward with a design.

Sikorsky's development contract stands out among many Pentagon aircraft deals in that it is a cost-plus, incentive-fee arrangement. This means the Pentagon pays the cost of the work rather than capping the price—a strategy adopted to accommodate the immature technology early in the program. The Pentagon estimates it will cost $25.7 billion to buy 200 CH-53Ks. The figure includes roughly $6.8 billion in growth due largely to a quantity increase; the Marines originally expected to buy 156 rotorcraft.

With the design sound and fabrication of the first test articles underway, Sikorsky is gearing up its manufacturing and testing base. Together with its top industry partners, the team has invested $340 million in various facilities. Among them is a massive durability test center here at Sikorsky's plant as well as a systems integration laboratory (SIL) that incorporates production-representative hardware and software. Roughly 95% of the K's software has been loaded into the SIL.

Zack says the development approach for the CH-53K team is “all about early discovery.” The use of the SIL and GTV early in the program is thought to enhance the chances of discovering design issues earlier in the test program. In addition to the GTV, there will be separate fatigue and static test articles and four flight-test aircraft. The first two flight-test aircraft are now being assembled at the company's West Palm Beach, Fla., facility.

The development phase is 62% complete, with about one-quarter of the remainder of the work focused on flight and ground testing, says Zack.

The CH-53K is the first all-digital “design-in-context” capability used by Sikorsky on any of its aircraft, Zack notes. This means that there are no drawings; the design is entirely digital and accessible by each of the major subcontractors in an integrated fashion. He says the team initially estimated that using this design concept would reduce assembly time by 30%; in some cases—such as work on the main gearbox—a 70% reduction is expected. “The limiting factor was how quickly the guy could get a fastener out of his pocket,” says Zack, noting the precision of the digital design. Sponson installation time is estimated to be 50% shorter than expected.

To fabricate the CH-53K, the company used an approach similar to Boeing's for the 787. However, as Boeing experienced problems mating parts and managing its supplier network, Sikorsky gathered lessons. Spirit AeroSystems, a key subcontractor that builds the helicopter's fuselage, is also on the 787 team and was able to provide insight on how to improve processes for the CH-53K team, says Zack.

The first four production CH-53Ks, dubbed system demonstration test articles, will be built at the West Palm Beach facility and will be used for the Marine Corps' operational evaluation. These articles, as well as manuals and spares, will also be needed to declare initial operational capability in 2018. The company has not yet announced where full-rate production will take place, but a new facility in Florida is being sized to handle the K.

As with all current military programs, affordability is essential. Zack says Sikorsky is exploring ways to reduce the price of both testing and production.

The Marines renegotiated the Sikorsky development contract last year; it originally included an award-fee schedule. The shift to an incentive-fee plan is spurring the company to deliver as much as six months early on key milestones, an achievable task, says Zack. “We wanted to incentivize them to meet some cost targets and some schedule targets,” says Pridgen.

First flight is slated for the first quarter of 2014 based on the accelerated plan.

CH-53E and CH-53K Performance Comparison
CH-53E (T64-GE-419) CH-53K Delta %
Maximum External Gross Weight (lb.) 73,500 88,000 20%
Maximum Internal Gross Weight (lb.) 13,224 27,764 110
USMC Standard Ship-to-Shore Mission External Payload (110-nm radius-of-action, Navy Hot Day, 56-sq.-ft. Delta Drag) (lb.) 13,224 27,764 110
USMC Standard Ship-to-Shore Mission External Payload (maximum radius-of-action carrying 12,000-lb. external load) 130 210 62
Hover Pressure Altitude Ceiling at Maximum Internal Gross Weight (no-power margin, standard-day, hover OGE) 4,111 10,951 166
Cabin Width Accommodation of NATO L-size Pallet No Yes Improved
Air Transportability Same
Aircraft Footprint & Ship Operations Same
Logistics Footprint (weight and volume) ~25% Reduction ~25
Material Maintenance Cost ($ per flight hour) ~40% Reduction ~40
Interoperability Improved Improved
Source: Sikorsky Aircraft