Mitsubishi Aircraft has returned one of its MRJ regional jet prototypes to flight testing, as the investigation into an engine flameout last month continues.

The Japanese manufacturer tells FlightGlobal that it "reviewed and re-inspected" the Pratt & Whitney PW1200G powerplants on FTA-4 with the engine maker and determined that the aircraft was able to resume flight tests. The aircraft hence completed two test flights on 6 September without incident.

FTA-4 is responsible for trialing various functions, including testing the MRJ's powerplant and air systems, as well as natural icing and fire protection.

Mitsubishi grounded its test fleet last month after an "uncommanded shut down" of FTA-2's left engine during a test flight on 21 August. The troubled engine had to be replaced before the jet could return to the manufacturer's test base at Moses Lake.

"We are still in the process of determining the cause of the malfunction in the engine on FTA-2," says Mitsubishi.

It adds that it will resume flight tests with the rest of its test fleet "in a phased manner", after inspection and verification of the engines, and with approval from the Japan Civil Aviation Bureau.

Neither the manufacturer nor the engine maker has provided more details of the engine damage or the cause of the flameout since the 21 August incident.

Source: Cirium Dashboard