Mitsubishi Aircraft has grounded its MRJ regional jet flight test fleet, following an engine "flameout" on one of its test prototypes on 21 August.
The Japanese manufacturer tells FlightGlobal that there was an "uncommanded shut down" of FTA-2's left Pratt & Whitney PW1200G engine during a test flight.
Mitsubishi would not say what tests the aircraft was conducting when the flameout occurred, but said the incident happened in training airspace over the ocean, about 170km west of Portland. Pilots were alerted to the issue only when the left engine shut down.
The aircraft had taken off from Moses Lake at 14:00 local time and had to make an unscheduled landing at Portland International airport at 17:12 local time.
"After a quick investigation with the borescope, we confirmed that there was partial damage inside the engine. We're still investigating the cause," says the manufacturer, adding that a Pratt & Whitney team is also onsite in Portland, aiding with the investigation.
Mitsubishi has since grounded its flight test fleet. It will only decide when to resume flight tests after the cause of the incident is determined. It was unable to say how this would affect its programme schedule.
Mitsubishi has four flight-test aircraft, and is working to deliver its first MRJ90 to launch customer All Nippon Airways in mid-2020.
Pratt & Whitney has suffered a series of minor crises with the related PW1100G engine (which powers the Airbus A320neo) including bowed rotors, parts shortages, prematurely deteriorating components and an in-flight shutdown.
The PW1000G series powers other types such as the Bombardier CSeries, Embraer E-Jets E2. and Irkut MC21.