There are three things you should know about the Sikorsky CH-53K. It’s big. It’s strong. And it’s smart.
Big, because it’s a CH-53, so of course it is. The K occupies the same footprint as the aircraft it’s replacing, the CH-53E Super Stallion, which is already the largest and heaviest helicopter in the United States military.
But the K will be substantially stronger than the E, thanks to three GE Aviation T408 engines that pack around 7,500 horsepower each (compared to the roughly 4,500-horsepower engines on the CH-53E). Despite retaining the same exterior dimensions, the K will have a maximum gross weight with external load that is 20 percent greater than the E model’s. It will be able to carry up to three times the payload in hot-and-high conditions.
And it has brains as well as brawn. The CH-53K features fly-by-wire flight controls with active inceptors and tactile cueing, allowing pilots to anticipate limits while keeping their eyes outside. When there’s nothing to see outside — as in brownout or whiteout conditions — the K’s advanced software will allow it to essentially fly itself.
Of course, if you’ve been following the CH-53K program in recent years, you probably know most of this. What you may not have heard is how the aircraft is actually performing, now that the program has logged more than 300 flight test hours.
To find out, we went behind the scenes of the CH-53K program at Sikorsky’s Development Flight Test Center in West Palm Beach, Florida. There, we got up close and personal with the K, and spoke with its designers, test pilots, and program managers.
They’re biased, of course. But it’s easy to understand their enthusiasm for what is certainly one of the largest, most technologically advanced rotorcraft ever built.
“It’s just an incredible leap in technology,” said Lt. Col. Foster Carlile, who as lead operational test director for the U.S. Marine Corp’s Marine Operational Test and Evaluation Squadron 1 (VMX-1) has been one of the first Marines to get his hands on the aircraft.
“The flight control laws and how the aircraft maneuvers and the information that’s provided to the pilot is just tenfold what we’re used to,” he said. “It’s really pretty impressive.”
Filling a Need
There’s no question that the Marines — who have ordered 200 of the aircraft –need what the CH-53K has to offer. After years of heavy use in combat and humanitarian operations, the CH-53E fleet has been stressed to the breaking point. Last year, a “Super Stallion Independent Readiness Review” commissioned by the Marines found that the CH-53E fleet suffers from “inadequate inventory; unacceptable availability of the remaining inventory; too many aircraft in maintenance outside the squadrons; and CH-53E aircraft [were] not reset during and after the war.”
The findings prompted the Marines to undertake a complete reset of 147 CH-53Es, a process that is expected to take three years. But that’s really a stopgap measure to keep them flying until the CH-53K achieves full operational capability, which is currently anticipated in 2029 (with initial operational capability expected in 2019). Only then, according to the Marines, will they have an aircraft that can operate “at distances, airspeeds, and gross weights sufficient to support the full range of military operations.”
Really, the Marines needed the CH-53K yesterday, but the program — which was first authorized in 2005 — is now about four years behind its original schedule. In 2011, the U.S. Government Accountability Office (GAO) attributed nearly three years of this delay to early difficulties, including the fact that the program started development before determining how to achieve requirements within program constraints. Since then, early development testing revealed the need for redesigns to the gearbox and other critical components, which have caused the schedule to slip by another year.
As the GAO recently observed, the five-year gap between the CH-53K program’s critical design review and its first flight, in October 2015, “is not consistent with best practices.” But the CH-53K is not an upgraded E model — it’s a brand-new design that just happens to look like a Super Stallion. That has naturally presented some challenges.
“This is a new aircraft,” emphasized Sikorsky’s chief engineer for the CH-53K, Andreas Bernhard. “There’s no common part number between this aircraft and the old aircraft.”
A key performance parameter for the CH-53K is the ability to carry a 27,000-pound (12,245-kilogram) external load over 110 nautical miles at an altitude of 3,000 feet and temperature of 91.5 F (33 C). That’s about three times the lifting ability of the E model in similar conditions. Meeting this ambitious goal required not only the three fuel-efficient GE T408 engines, but also a new split-torque transmission system to handle all that power.
It was during bench testing that engineers discovered a problem with a gear retention rod in the main rotor gearbox — the design issue that was responsible for some of the recent program delays. The retention rod was redesigned, bench tested, then tested further in the full-sized CH-53K ground test vehicle before being incorporated into the program’s four flying prototypes.
Now, according to Col. Hank Vanderborght, U.S. Marine Corps H-53 program manager, “Our gearbox issues are basically largely resolved. We haven’t seen any other problems with the gearbox.” The other good news, he added, “is that we did find these things. Because what you don’t want to do is find them when the aircraft is already fielded.”
Besides the new engines, the CH-53K also gets a performance boost from new composite rotor blades, which as a bonus eliminate the pressurized spar found in earlier CH-53 models. The rotor blades on the CH-53E are a “high maintenance driver” on the CH-53E because they tend to lose pressure from their spars, explained Sikorsky’s chief experimental test pilot for the CH-53K, retired Marine pilot Stephen McCulley. With the K, he said, “that failure mode was removed.”
Yet the most fundamental technology leap in the K is probably its fly-by-wire flight control system, which enables capabilities that simply aren’t possible with the hydro-mechanical flight controls in the CH-53E. According to Bernhard, the CH-53K benefited from Sikorsky’s several generations of fly-by-wire development on aircraft including the CH-148 Cyclone and the UH-60M Upgrade Black Hawk.
“We have leveraged quite a bit of that technology and that learning curve,” said Bernhard. “So we avoided a lot of pitfalls because of that.”
The fly-by-wire system is complemented by active inceptors developed by BAE Systems, including sidearm cyclic controllers that free up the space occupied by a conventional cyclic control. The pilot and co-pilot controls are electronically linked, so that each pilot can feel control inputs made by the other. The collective and cyclic control sticks (inceptors) also provide tactile feedback to the pilots as they approach power or bank limits.
“I can pull up to my 19,000 shaft horsepower, and right before the [rotor rpm starts to drop] I’ll get a little bit of a buzz [in the collective], and I can back off from that,” McCulley explained. “I can pull through it if I need to, but it gives me cues and feedback with my eyes outside.”
Saving Lives, Time, and Money
So what do all of these innovations mean for how the aircraft performs? In his Marine career, McCulley flew CH-53A, D, and E models, in addition to logging time in the MH-53 and CH-53GA (the “German Advanced” variant of the CH-53). “So yes, I’ve flown them all,” he told us. “This so far is my favorite.”
According to McCulley, the CH-53K handles like a smaller helicopter, despite its massive size. “I think that’s because we’ve got such a large rotor disc that enables us to do this heavy-lift mission, this 36,000-pound load, that when you don’t have that load on there, this thing is very maneuverable, very nimble,” he said. “When you’re flying at an internal gross weight of 60,000 pounds, it’s a sports car.”
The full authority fly-by-wire flight control system also enables the aircraft to fly itself very precisely. Pilots can program the aircraft to fly an approach to a specific landing spot, where it will decelerate and roll itself into a hover at 50 feet above the ground. That capability could be life-saving in dusty “brownout” environments like Iraq and Afghanistan (where, as Lt. Col. Carlile put it, every approach into the dust in a CH-53E “would take five years off your life”).
“Now I can go into a brownout without touching the controls and come to a hover,” McCulley explained. After the dust clears, “I can dial myself down to the ground with my [radar altimeter] or I can fly it myself, but I don’t have to go white knuckle on the controls because it will do it for me, and it’s got all of the authority it needs to make those adjustments.”
The automatic flight control system also enables precise control inputs when positioning over or delivering an external load. “With this system, you can come into a point, and if [the crew chief says] ‘left five,’ I click it five times,” McCulley continued. “I hate to say it, but the aircraft flies better than I do.”
In fact, the CH-53K’s control architecture opens the door to remotely piloted or autonomous applications in the future. “If they ever want to go no pilot, no problem,” said McCulley. “It’s not built in; however, because it is fly-by-wire, because it is fully digitally controlled, it’s no different than the autonomous aircraft that we’re currently flying.”
The CH-53K has also been designed to make life easier for cabin and ground crews. Crew chiefs will have wireless intercom systems. The aircraft has a built-in winch, and its interior is wide enough to accommodate 463L master pallets, so pallets won’t have to be broken down before loading. “The time on ground between a 53 Echo and a 53 Kilo, for the same payload that you’re going to carry, is a fraction,” noted Bernhard.
There have also been some safety enhancements in the cabin. The triple hook hell holes have been redesigned to reduce the risk of people falling into them. Integrated rails will allow crew chiefs to move the length of the cabin while remaining tethered to the aircraft, and the troop seats are fully crashworthy. The windows have also been enlarged to permit easier exit in an emergency.
Meanwhile, maintainers should appreciate the CH-53K’s health and usage monitoring systems (HUMS) and built-in diagnostics capabilities. “From the ground up, we’ve designed the diagnostic system to be self-reporting, so our intent there is to make it easy for the [maintainers] working on this aircraft,” said McCulley. “They can come in and download, and it will tell them everything that’s broken, down to a line replaceable unit, so they know what to pull out and repair.”
The CH-53K has built-in diagnostics for shaft balancing, rotor balancing, rotor track and balance, and tail balance. Automatic engine health monitoring is also built in. “The other beautiful thing here is [the CH-53K] will do its entire mission spectrum, all the way down to the engines being at zero margin,” added McCulley. “It’s going to be a change for the Marines because they’re used to engines that don’t have that capability.”
And when the engines are changed out, the aircraft will no longer require a full flight control rig, thanks to the full authority digital engine control and fly-by-wire control system. With the CH-53E, McCulley recalled, “that was a full-day effort, to do that rig. [In the CH-53K] an engine change, if I have to make an engine change, becomes half a shift.”
While the technology in the K should make routine maintenance tasks easier, the real aim is to dramatically reduce the overall maintenance burden compared to the CH-53E, which requires more than 40 maintenance hours per flight hour. Improved components — such as engines with 64 percent fewer parts than the engines on the E model — should help with this goal.
More fundamentally, the CH-53K’s integrated vehicle health monitoring system will allow the Marines to track trends across the fleet in order to anticipate and prevent component failures.
“The real power of HUMS is the fleet management capability,” said Bernhard. “We can give the fleet user a much better ability to take what used to be reactive maintenance . . . and turn that into preventative, pre-planned maintenance.”
Looking to the Future
The CH-53K program has made strong progress since first flight in October 2015. All four flight test vehicles are now flying and gradually expanding the aircraft’s envelope. Already, the CH-53K has flown at an altitude of 10,000 feet, reached an airspeed of 185 knots, and lifted loads up to 27,000 pounds.
In October 2016, the aircraft successfully completed initial operational testing by the Marine Corps, a key step in the transition from development to production. The week-long operational assessment included lifting 27,000 pounds in a hover, and carrying a 12,000-pound load on a 110-nautical-mile mission. Ground evaluations included the embarkation and debarkation of combat-equipped troops, internal and external cargo rigging, tactical bulk fuel delivery system operation, and medevac litter configuration.
“The operational assessment was really the first time where we had a Marine Corps crew fly the aircraft and perform operationally representative mission profiles,” said Col. Vanderborght.
Now the program is rapidly approaching the “Milestone C” decision for low-rate initial production, which is anticipated in the second quarter of 2017. In addition to securing the necessary contractual agreements, successful completion of Milestone C requires the program to have reached 400 flight test hours. By mid-December 2016, the program had reached 314 flight test hours and was logging them at the rate of 50 to 60 hours per month.
“We’re on a really good path to achieving Milestone C,” Vanderborght said at the time.
After low-rate initial production is approved, the flight testing program will continue in parallel. Dr. Michael Torok, Sikorsky’s vice president of the CH-53K program, said he expects the baseline flight testing program to last another two-and-a-half years.
“In general, we’ll hit most of the envelope expansion probably by next summer, toward the fall,” he said. “Beyond that, the rest of the back end of the testing, is filling out the specific details of all the points, of all the conditions, so that we have a really comprehensive set of data, which will support the aircraft for the next 40 years.”
Four CH-53K engineering demonstration models will be used for developmental testing by Air Test and Evaluation Squadron 21 (HX-21) at Naval Air Station Patuxent River, Maryland. Two of these will later be converted into practical job trainers for initial accession training in New River, North Carolina, which is also where the Marine’s first CH-53K fleet squadron will be stood up. If all goes according to plan, that should happen sometime in 2019.
The Marines can hardly wait. “One of the primary, if not the primary element to victory in warfare is logistics. And the K is right in the middle of that, it’s a key logistical enabler,” said Vanderborght. “It’s really going to enable the Marine Corps to project power ashore from the sea, and really mechanize those future warfighting concepts that our nation is looking to be able to do in the future.”
For the pilots who will be flying the CH-53K in theater, the aircraft’s promise is more personal.
“Marines, our whole mission in life is to support the infantry, support the ground units, whatever they need,” said Lt. Col. Jonathan Morel of HX-21, who is the chief government test pilot for the CH-53K. “And so if they say, ‘We need this,’ and you crunch the numbers and you say, ‘I can’t do it,’ that hurts. . . . All of the things [on the CH-53K] are going to let our community be able to say ‘yes’ much more often to whatever the request is.”