AT75, en-route, north of Visby Sweden, 2014

AT75, en-route, north of Visby Sweden, 2014

Summary

On 30 November 2014, an ATR 72-500 suddenly experienced severe propeller vibrations whilst descending through approximately 7,000 feet with the power levers at flight idle. The vibrations subsided after the crew feathered the right engine propeller and then shut the right engine down. The flight was completed without further event. Severe damage to the right propeller mechanism was found with significant consequential damage to the engine. Several other similar events were found to have occurred to other ATR72 aircraft and, since the Investigation could not determine the cause, the EASA was recommended to impose temporary operating limitations pending OEM resolution.

Description

On 30 November 2014, an ATR 72-500 (SE-MBD) being operated by Braathens Regional on a scheduled domestic passenger flight from Stockholm Bromma to Visby as DC 929 was descending through 7,000 feet in day VMC when severe vibrations of apparent propeller origin suddenly began. The crew concluded that the source of these was the right engine and after feathering the propeller, that engine was shut down and the vibrations ceased. An emergency was declared to ATC and the flight to destination was completed without further event.

Investigation

An Investigation was carried out by the Swedish Accident Investigation Authority (SHK). FDR and CVR data relevant to the event were successfully downloaded.

It was noted that the 50 year-old Captain had accumulated 7,074 total flying hours which included 2,920 hours on type and was acting as PF for the flight during which the incident occurred. The 36 year-old First Officer had accumulated 2,381 flying hours which included 2,162 hours on type.

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