Both the United States Forest Service and the U.S. Army have now lifted the temporarily grounding order which impacted their Boeing CH-47 Chinook fleets in late August.
At the time the Army grounded its fleet of about 400 Chinooks after several engine fires had been traced to faulty O-rings installed on the type’s T55 engines. The Forest Service followed suit days later, grounding its fleet of 12 contracted Chinooks.
The U.S. Army issued a temporary grounding order for its entire fleet due to “a small number” of engine fires according to a according to Army spokeswoman Cynthia O. Smith.
The Army traced the cause of the fires to a fuel leak, which it cited occurring on an “isolated number” of CH-47s. Smith added that the service was taking steps to address the issue and that no injuries or deaths have occurred because of the fuel leaks or engine fires.
The grounding of the entire Chinook fleet was “out of an abundance of caution,” Smith told various media outlets at the time, adding: “The safety of our soldiers is the Army’s top priority, and we will ensure that our aircraft remain safe and airworthy.”
Honeywell, the manufacturer of the T55 engines fitted to the Chinooks, said in a statement that whilst working with the Army it had “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 company added that the “Army and Honeywell were able to validate that none of the questionable O-rings originated or was part of any Honeywell production or Honeywell-overhauled engines.”
The Indian Air Force, which introduced the Chinook into service in 2019, requested additional details from Boeing about the reasons behind the grounding , although it now appears that foreign operators were not impacted by the fault.
“Safety is the highest priority in all USDA Forest Services aviation operations,” Michelle Burnett, U.S. Forest Service national press office, said in a statement at the time. “We grounded 12 contracted CH-47 Chinooks that are part of our national fleet, eight of the 12 CH-47s have completed their inspections and have returned to service. We expect to have the remainder of these necessary inspections completed soon.”
Since the initial statement by the U.S. Army the service has now returned approximately six-in-ten CH-47s to service as of Sept. 14. Army spokesman Jason Waggoner said the service has 59.9 percent of its Chinook fleet available to support ongoing missions and training.
“Though the number could fluctuate day-to-day, this number continues to increase daily with ongoing logbook review and a standard leak-check maintenance procedure outlined in an Aviation Safety Action Message,” cited Waggoner.
