Cataloging issue was root cause of Chinook grounding, Army says

The Army will return Chinooks back to service on a case-by-case basis after determining that a cataloging error caused mechanics to install the wrong O-rings on the aircraft during maintenance, creating the fuel leak issue that prompted the service to ground the entire helicopter fleet last week, the Army said.

Those O-rings installed on some aircraft did not meet heat specifications required for the Chinook, causing some to suffer fuel leaks and engine fires, the Army said, adding that the issue did not cause any injuries or deaths.

The service has since corrected the cataloging issue and established a new stock number for the O-ring that meets the heat standard, Army spokeswoman Cynthia Smith said in a statement.

“The Army has provided guidance to the Aviation enterprise that establishes inspection and maintenance procedures for replacing the improper O-rings and returning the fleet to normal flight operations on a case-by-case basis,” Smith said.

The Wall Street Journal first reported the cataloging issue and the Army’s initial decision to ground the fleet.