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The U.S. Army’s Yuma Proving Ground in southern Arizona sees its fair share of dust clouds. But there are dust clouds, and then there are dust clouds.
Late last summer, the Sikorsky CH-53K experimental flight test team stirred up some record-setting dust clouds when they visited Yuma for degraded visual environment (DVE) and hot weather testing. According to Sikorsky senior experimental test pilot John Rucci, Yuma is a popular location for DVE testing because the particulate matter there “represents about the worst you can find on the planet. And then you actually prepare the LZ with a tractor that essentially discs the sand up into a fine talcum powder, which makes it even worse.”
As seen in video footage of the testing, the CH-53K — which will have a maximum gross weight of 88,000 pounds (39,900 kilograms) — churned up massive, billowing, persistent clouds of dust as it practiced reduced visibility landings (RVLs), an essential capability for its U.S. Marine Corps customer.
“In a daytime environment, it was about the worst dust cloud I’ve ever seen, in terms of just the consistency, how it prevailed, how it just sat there,” recalled Rucci, a former Marine Corps CH-53E pilot who experienced brownout landings while on deployment in the Middle East in the early 2000s. “But because the aircraft was that much more stable, it made my job much easier.”
Rucci spoke with Vertical in advance of last week’s Sea-Air-Space exposition in National Harbor, Maryland, where Sikorsky and parent company Lockheed Martin were promoting the CH-53K’s progress. The roughly $31 billion development program has received some critical press coverage recently, with the revelation of technical issues that will cause it to miss its target for initial combat capability by the end of this year.
According to Rucci, however, the program has been racking up some significant milestones — the successful DVE testing among them.
“I’m always eager to tell success stories because I know there’s been a lot of negative angles out there on the aircraft, just in terms of its development efficiency and process,” he said. “I would say that in terms of track records of development aircraft we’re doing very well, and to give a functionality like this [DVE capability] . . . I know it’s going to do the job.”
According to Lockheed Martin, the CH-53K program has now logged more than 1,400 flight test hours across four experimental developmental models and two system demonstration test articles. Rucci said that last year’s testing in Yuma accounted for roughly 25 of those hours, including the evaluation of critical components in temperatures of up to 108 F (42 C).
The DVE portion of the testing encompassed a series of maneuvers, from landings on the ground — simulating troop insertions and extractions — to approaches to a high hover, as would be required to pick up external loads. This round of testing was performed at an aircraft operating weight of approximately 60,000 lb. (27,215 kg). Sikorsky intends to return to Yuma in the summer of 2020 for testing at the maximum internal gross weight of 74,000 lb. (33,565 kg) and with external loads up to the absolute max gross weight of 88,000 lb.
“It was a build-up process, like everything is in flight tests, because we were at the same time testing the reliability of our engine air particle separator system . . . and our engines themselves and how they reacted to the fine talcum dust,” Rucci explained. “We were really pleased with the results we saw there that allowed us to extend our period of dust ingestion over time.”
Reduced visibility landings are among the most challenging maneuvers that helicopter pilots perform, because pilots typically rely heavily on visual cues to maintain stability while close to the ground. As Rucci explained, the Marine Corps over the years has doctrinally perfected an RVL technique that brings the aircraft to the ground on a glide path that is not too shallow, and not too steep.
“If you perform either one of those types of approaches [very shallow or very steep] into the dust, you’re going to incur the dust cloud at a different part of the descent profile than you desired to, and you may lose sight of the ground before you’re completely stabilized,” he said.
As part of the testing in Yuma, the CH-53K team confirmed that the RVL descent profile that works for the CH-53E works for the newer generation aircraft, too. Then, they worked to tune the software in the fly-by-wire K model to automate that desired approach.
“So that was part of the effort, to get the computer to fly the approach to the same numbers that a pilot would fly it,” Rucci said. That, he explained, allows the pilot to “back out of the loop and monitor the approach . . . then all they have to do is maybe tweak to go a little further or a little short depending on where the intended point of landing is.”
According to Rucci, the pilot can make those adjustments by simply manipulating the sidearm controller — the active inceptor that replaces a conventional helicopter cyclic in the CH-53K. Pilots also have the option of making adjustments through a beeper trim, but Rucci said that rudimentary kind of input “isn’t agile enough in the real world to make an input that a crew chief might be calling for in real time. . . . It’s actually much better for the pilot just to get on the stick and displace it.”
Once the pilot has made the desired correction, the automatic flight control system will resume the planned deceleration profile. “It responds in the manner that you would expect it to respond if you were flying yourself,” Rucci said. “It’s been tuned to not be overly aggressive, so when you put an input in to correct it, it then doesn’t pop the nose up or do anything that would be disorienting in the dust environment.”
Should the pilots lose all visual references, the aircraft can maintain a stable low hover with no uncommanded drift, Rucci said. In fact, he said, the stability of the CH-53K in an auto-hover is “astonishing” when compared to helicopters with conventional mechanical flight controls.
“[In the CH-53K], because of the fly-by-wire, the full authority, the rate that it has, it is making the corrections at a rate [that] you really don’t even feel them, as the pilot,” he said. “I call it ‘pilot nirvana.’ . . . It’s really incredible.”
Rucci predicted that the K’s workload-reducing automation will enhance both safety and efficiency for the Marines. Today, CH-53E pilots require frequent, intensive training in RVLs to stay proficient, “which translates into a lot of hours spent doing a task to be able to do that consistently [when] you have to do it for real,” he said.
“Whereas I feel the K, because of the workload reductions, because of the way the aircraft flies, you won’t need to have that level of intense training in order to be able to pull off that mission.”