US Marines, NAVAIR declare CH-53K Heavy-Lift King Stalion engine problems resolved.

The U.S. Marine Corps and Sikorsky have resolved the engine integration issues that slowed down the CH-53K King Stallion heavy-lift helicopter program, the service announced. Megan Eckstein reports on USNI News.

A Sikorsky CH-53 King Stallion flies at the ILA Berlin Air Show on April 25, 2018, in Schoenefeld, Germany (Picture source: Sean Gallup/Getty Images)

The helicopter’s test program was overhauled in the spring after falling behind due to testing inefficiencies and challenges with the engine, including exhaust gas re-ingestion (EGR). In April, the Marine Corps signed a $1.13-billion contract with Sikorsky for Lots 2 and 3, though the contract was somewhat scaled back compared to previous plans due to cost growth and testing delays. The announcement made on Dec.17 that the engine problems have been resolved makes more realistic the government/industry team’s plans to take the helicopter on sea trials in the spring and ultimately conduct a first deployment by 2023 or 2024.

The helicopters are powered by three new General Electric T-408 engines that allow them to carry 27,000 pounds for 110 nautical miles, or up to 36,000 pounds in shorter flights – allowing the helicopter to lift a pair of Joint Light Tactical Vehicles (JLTVs).

However, during testing, it was discovered that the engines were sucking in exhaust instead of clean air, leading to a major effort to address the EGR issue.

Sikorsky CH-53K King Stalion lifting a JLTV (Picture source: Sikorsky)

Steve Schmidt, Sikorsky’s CH-53K Chief Engineer, told USNI News that the problem actually wasn’t quite what the team thought originally, and that the all-digital design of the helicopter allowed the team to diagnose the problem, model it and engineer a fix much faster than would have been possible with traditional paper drawings.

NAVAIR spokeswoman Megan Wasel said the effort to get at the root cause of this problem and to prevent it going forward was significant. Schmidt said the data from flight tests and modeling showed the problem wasn’t quite what they initially thought. Therefore, the change made to the helicopter includes elongating the exhaust pipe and adding support for the longer and heavier piece. Sikorsky, NAVAIR and the Marine Corps are set up to keep the remainder of their test and fielding plan on track.

Schmidt said four test helicopters would be outfitted with the change by the end of 2020, allowing the Marines to use these improved helicopters for initial operational test and evaluation. He could not comment on whether the improvements would be used in upcoming sea trials in 2020, but he simply said that the government understood the situation and would decide how to move forward to keep the program on track. Sikorsky spokeswoman Melissa Chadwick told USNI News that, by engineering the change by the end of this year and beginning to backfit it and insert it into the production line for new helicopters, the planned schedule would see no impact.

The helicopter already demonstrated or exceeded all requirements for speed, range, altitude, lift capacity and more, and the test team put the aircraft through its paces in extreme weather and other conditions. The test team plans to bring a helo to a Navy amphibious warship sometime between February and May 2020 for sea trials, where the helicopter will prove it can take off from and land on a flight deck at sea and can be maintained underway.

Initial operational test and evaluation is set to begin in early 2021, which would allow the Marine Corps to declare initial operational capability in time for the first deployment in 2023 or 2024.