U.S. Army Grounds Fleet of CH-47 Chinooks Because of Engine Fire Risk

Honeywell said O-rings not meeting design specifications had been installed in Honeywell T55 engines aboard CH-47 Chinooks. [Courtesy: U.S. Army/Master Sgt. Ryan C. Matson]

The U.S. Army has temporarily grounded its entire fleet of Boeing (NYSE: BA) CH-47 Chinook heavy-lift helicopters "out of an abundance of caution" after discovering the installation of a faulty part has caused fuel leaks that led to engine fires.

The issue was caused by the installation of a part that did not meet design specifications in some Honeywell (NASDAQ: HON) T55 Turboshaft engines during routine maintenance, the OEM said Tuesday evening.

The move affects an estimated 400 CH-47 aircraft.

"The Army has identified the root cause of fuel leaks that caused a small number of engine fires among an isolated number of H-47 helicopters and is implementing corrective measures to resolve this issue," an Army spokesperson told FLYING in a statement.

"While no deaths or injuries occurred, the Army temporarily grounded the H-47 fleet out of an abundance of caution, until those corrective actions are complete," the service spokesperson said.

News of the grounding comes following a report that engine fires have occurred in "recent days," the Wall Street Journal reported Tuesday evening. The potentially faulty part was installed in more than 70 aircraft, according to the newspaper.

Honeywell said it was working with the Army to investigate the issue surrounding the T55 engines, which also provide powerplants for the special forces MH-47 variant.

"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," a Honeywell spokesperson said in a statement. "It is believed these suspect O-Rings have been identified and isolated."

None of the questionable O-rings originated or were part of Honeywell's production or Honeywell-overhauled engines, the company said.

"Joint U.S. Army and Honeywell engineers identified the issue and are now working with the Army to provide replacement O-rings on all affected Chinooks," the company spokesperson added.

READ MORE: Military Training Aircraft Grounded Over Ejection Seat Concerns

The CH-47 tandem rotor heavy-lift helicopter, which has been in service for more than 60 years, is the latest military aircraft to be temporarily grounded recently over mechanical concerns.

Earlier this summer, a potential defect in cartridge actuated devices (CAD) used to initiate ejection seats prompted the Air Force to ground hundreds of military aircraft, including U.S. Air Force F-35A Lightning II fighters, T-38 Talons, and T-6 Texan IIs.