An MH-47 Chinook with the 160th Special Operations Aviation Regiment in 2019. US Marine Corps photo by Lance Cpl. Drake Nickels.
The Army grounded its entire fleet of CH-47 Chinooks — about 400 aircraft in all — citing a design flaw that created a potential for engine fires.
The twin-rotor Chinook is the Army's primary heavy-lift helicopter for troops and materiel in virtually every combat zone the Army enters.
A small number of fires were caused by fuel leaks in a few of the helicopters' T55 engines, according to the Army. Army spokesperson Cynthia Smith said an "abundance of caution" led the Army to ground the full fleet.
The Wall Street Journal first reported the grounding.
U.S. Soldiers assigned to Echo Company, 3rd Battalion (General Support), 10th Aviation Regiment, prepare to sling load two 500 gallon fuel containers beneath a CH-47 Chinook helicopter piloted by Soldiers with Bravo Company, 2nd Battalion (General Support), 149th Aviation Regiment, Texas and Oklahoma Army National Guard, during sling load training at Bagram Airfield in Parwan province, Afghanistan, July 30, 2013. (U.S. Army photo by Capt. Peter Smedberg/Released)
Chinooks have been in service with the Army since the 1960s, seeing combat in every conflict since. Their uses in the Army range from workhorse cargo transports as CH-47s to special operations assaults as MH-47s to high-altitude rescues in Alaska.
The T-55 engines are produced by Honeywell, which said in a statement that "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 Army did not provide a timeline for returning the Chinooks to the air.
The grounding comes just a week after the Air Force grounded its fleet of heavy-lift rotor-wing aircraft, the CV-22 Osprey, for an engine issue, though the Marines did not ground their fleet.
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Matt White is a former senior editor for Coffee or Die Magazine. He was a pararescueman in the Air Force and the Alaska Air National Guard for eight years and has more than a decade of experience in daily and magazine journalism.
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