What happened
During flight, the number 2 engine of the aircraft experienced a total loss of power followed by an engine fire. The Skywest crew executed a successful emergency landing; however, the airplane overran the end of the runway by 1,300 feet. There were no injuries to the passengers or the crew, and no additional damage occurred to the aircraft beyond the initial engine fire.
The investigation
The investigation focused on maintenance actions performed immediately prior to the accident flight. A maintenance technician had added 2.5 quarts of oil to the number 2 engine because they were unable to determine the existing oil level. An inspection of the engine's hot section, which had been completed approximately 2.3 hours before the flight, revealed no assembly anomalies.
Investigators determined that the engine fire was caused by the ignition of oil that had leaked across bearing seals. It was noted that under overfull operating conditions, oil can backflow into the engine instead of draining overboard from the filler neck.
Findings
The investigation identified inconsistencies between the elapsed time requirements for oil level determination found in the Embraer Maintenance Manual and the instructions provided by Pratt & Whitney. The mechanic may not have allowed enough time for the oil to drain back into the engine reservoir before adding more, resulting in an overfilled oil tank. Additionally, the clear color of the oil, especially in a new engine, makes it difficult to visually determine the quantity during inspection.