US Army replaces problematic engine part on Chinook helicopters

The US Army has nearly finished swapping out a leaky part in CH-47 Chinook helicopter engines that led to a number of engine fires, according to the Army Aviation and Missile Command Aviation Branch maintenance officer.

The Army expects to have fixed all affected Chinook helicopters in the fleet by the end of February, Chief Warrant Officer 5 Patrick O’Neill told Defense News in a recent statement, Defense News reports.

At the end of August 2022, the Army grounded the entire fleet of CH-47s while it fixed the fuel leaks. Honeywell provides the T-55 engine for the Boeing-manufactured Chinook.

The service discovered that, during routine depot maintenance, Army maintainers had installed O-rings — meant to prevent leaks between engine parts — that did not meet “Honeywell design specifications” and were not supplied by the company, according to a statement from Honeywell issued at the time of the fleet grounding.

The o-ring was not “defective,” but was “an incorrect part not designed for that manifold,” the Defense Logistics Agency said in a statement.

Honeywell provided the spare parts for the T55 engine maintenance until February 2019; since then, the Army has taken over sustaining the engine within its own depots.

As part of this transition, DLA said the military used an incorrect o-ring. The agency is now on contract to buy 200 of the correct o-rings from residual stock and is working with Honeywell and its sole-source vendor CE Conover to buy additional o-rings.

The Army doesn’t know how many engines received the incorrect part because o-rings do not have a serial number and are not tracked by tail numbers, O’Neill said, so every helicopter engine in the inventory is receiving a new part.

According to O’Neill, partner nations with Chinook fleets were informed of the issue and conducted inspections. “As a result of these inspections, the Army security assistance enterprise is currently working with our partner nations to address the identified requirement,” he said.

With the deadline looming to swap out the part, O’Neill said “nearly the entire CH-47 fleet has replaced their O-rings in the T-55 engines” and no Chinooks “at the moment” are grounded due to the issue.