Maintenance and Modifications
Engine Fires Prompt Army To Ground Entire Chinook Fleet
CH-47 engine fires are linked to use of nonstandard engine O-rings.

The U.S. Army has grounded its entire fleet of 442 Boeing CH-47 Chinook tandem rotor helicopters fitted with dual Honeywell T55 engines after a “handful” of fuel leak-induced engine fires. They are believed to be linked to the installation of non-Honeywell, nonstandard O-rings in approximately 70 aircraft.