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Army grounds entire CH-47 Chinook helicopter fleet over engine fires

The Army has grounded the entirety of its CH-47 Chinook helicopter fleet “out of an abundance of caution” after an undisclosed number of recent engine fires, the service confirmed Tuesday evening.

The Wall Street Journal first reported the move to shut down the Boeing-made fleet. No deaths or injuries occurred due to the fires.

In a statement emailed to Army Times, Army spokesperson Cynthia Smith attributed the issue to fuel leaks. She indicated that the service has “identified the root cause” of the leaks and “is implementing corrective measures to resolve this issue.”

Engine manufacturer Honeywell International told Army Times in a statement that the leaks were due to faulty aftermarket O-rings that weren’t produced by the company.

“In full coordination with the U.S. Army, Honeywell helped discover that O-rings not meeting Honeywell design specifications had been installed in some T55 engines during routine and scheduled maintenance at an Army Depot,” the statement said. “It is believed these suspect O-Rings have been identified and isolated.”

Smith’s statement tried to downplay the scope of the problem, declaring that “some aircraft may not require corrective measures and may soon return to normal flight operations.” Army officials did not respond to questions from Army Times about the repair timeline or its potential impact on training and operations.

The Army spokesperson did not specify how many aircraft had caught fire and how many required corrective maintenance. According to the Wall Street Journal, service officials have identified at least 70 aircraft with the faulty part out of the Army’s approximately 400 Chinooks.

While a joint team of Honeywell and Army engineers identified the engine problem, it’s not clear when they realized they needed to look for it.

A July aviation safety bulletin published by the service’s Combat Readiness Center highlighted an incident where a hovering Chinook had to land and use its fire suppression system to address “a small active fire near the aft portion of the No. 2 engine.” Army Times previously covered CRC officials’ efforts and process for reconstructing accidents.

Smith added that the grounding was meant to “ensure our aircraft remain safe and airworthy.”