US Army grounds entire Chinook fleet over engine woes

After suffering an undisclosed number of recent engine fires, the US Army confirmed that it has grounded its entire fleet of Boeing CH-47 Chinook heavy-lift tactical transport helicopters as a precautionary measure on August 30.

While the Chinook fleet has suffered from these recent engine fires, US Army officials have confirmed that such incidents have not resulted in any deaths or injuries. In a statement issued to Key.Aero, US Army spokesperson Cynthia Smith explained that fuel leaks had been identified as the cause of the recent engine fires, citing that it only affected an “isolated number of H-47 helicopters.” Smith added that the service is now “implementing corrective measures to resolve this issue.”

Three Boeing CH-47F Chinook heavy-lift tactical transport helicopters from the Georgia Army National Guard's (ARNG's) Detachment 1, Bravo Company, 1-169th General Support Aviation Battalion conduct a multi-ship training flight near Savannah, Georgia, on November 12, 2013, in preparation for a deployment to Afghanistan.
Three Boeing CH-47F Chinook heavy-lift tactical transport helicopters from the Georgia Army National Guard's (ARNG's) Detachment 1, Bravo Company, 1-169th General Support Aviation Battalion conduct a multi-ship training flight near Savannah, Georgia, on November 12, 2013, in preparation for a deployment to Afghanistan. Georgia ARNG/Maj Will Cox

The grounding order took effect within 24 hours of its issuing, but it remains unclear how long the fleet will remain unavailable for. A workhorse for the US and its allies since it made its combat debut during the Vietnam War, the Chinook is one of the US Army’s primary airlift assets and is vital to supporting a variety of ongoing domestic and international training/combat missions, which means that the safe return of regular CH-47 operations will be of upmost priority for the US Army.

“Based on the results of our investigation, some aircraft may not require corrective measures and may soon return to normal flight operations,” Smith continued. “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 safety of our soldiers is the Army’s top priority, and we will ensure our aircraft remain safe and airworthy.”

The US Army’s decision to ground its roughly 400-strong CH-47 Chinook fleet was first reported by the Wall Street Journal, which stated that service officials had identified at least 70 aircraft with faulty aftermarket O-rings – a sealing solution which is used in aviation to seal moisture and environmental contaminants out, separate surfaces to mitigate friction and keep essential fluids (such as fuel) in. These faulty components had been fitted in some of the Honeywell International T55 turboshaft engines that are used to power the CH-47 fleet.

A spokesperson from Honeywell has stated that the US-based engine manufacturer worked with the US Army to identify the issue that led to the fleet-wide grounding order. It is believed that the faulty O-rings – which were not produced by Honeywell – were installed during routine maintenance and the firm is now working to supply the US Army with appropriate replacements. At present, the US Army appears to be the only global Chinook operator to be suffering from such issues.