NASHVILLE, Tenn. — The U.S. Army has decided to shelve its Advanced Chinook Rotor Blades it was developing as part of the
Boeing-manufactured CH-47F cargo helicopter’s latest upgrades
due to issues that cropped up during testing, according to Brig. Gen. Robert Barrie, the program executive officer for Army aviation.
In 2020, the service was dealing with excessive rotor blade vibrations from the ACRBs as it headed into a limited-user test scheduled for early 2021, so the service decided to cancel that test until it had worked through the issues.
A report from the Pentagon’s chief weapons tester noted vibrations present in ground, hover and forward flight that could pose “safety of flight risk.” Boeing pushed back against the claim it posed a safety risk, but the company did acknowledge vibration issues.
“We’re working closely with the Army on a mitigation system or an adjustment to existing mitigation systems to account for that different vibration frequency,” Andy Builta, Boeing vice president and H-47 program manager, told Defense News a year ago. “It is in no way a safety of flight risk, but it is an issue that needs to be addressed going forward.”
The company may adjust or add dampeners to address the problem, he said. “This is a low-risk, well-known activity that we’ve done across multiple platforms.”The Block II variant
returned to some testing in the spring of 2021 and began to log flight hours. The company said the new rotor blades proved the aircraft can handle an additional 2,500 pounds of lift.
But last fall, the Army decided not to move forward with ACRBs. However, the service is proceeding with the rest of the planned upgrades for the helicopter, Barrie said at the Army Aviation Association of America’s annual conference on April 4.
“As we began developmental flight tests on the blade,” Barrie said, “there were two issues that we had. There was a vibration issue and then there was an aft rotor stall. So as the retreating blade on the aft rotor system swept back, there were stall issues that were created, which increased the stress on the rotor system.”
The two issues combined “and the inability to have an affordable way through — that led the Army to make a decision to stop … and shelve that portion of the development,” he said.