NTSB Identification: LAX97FA189.
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Scheduled 14 CFR (D.B.A. SKYWEST AIRLINES )
Accident occurred Wednesday, May 21, 1997 in SAN DIEGO, CA
Probable Cause Approval Date: 07/17/2001
Aircraft: Embraer EMB-120, registration: N198SW
Injuries: 17 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

After suffering a total loss of power and subsequent fire of the number 2 engine, the Skywest crew made a successful emergency landing. The airplane overran the end of the runway by 1,300 feet, but no additional damage occurred and there were no injuries to the passengers or crew. Immediately prior to the accident flight, a maintenance person added 2.5 quarts of oil to the number 2 engine, when he could not determine the engine's oil level. No evidence was found of any assembly anomalies during the engine hot section inspection, which was performed about 2.3 hours prior to the accident flight. The engine fire resulted from ignition of oil that had leaked across bearing seals. Oil will back flow into the engine rather than drain overboard from the filler neck under overfull operating conditions. The elapsed time between engine shutdown and oil level determination provided by Embraer in its Maintenance Manual are inconsistent with the instructions provided by Pratt & Whitney. The Skywest mechanic may not have allowed adequate elapsed time to permit the oil to drain back into the engine reservoir prior to adding additional oil, thereby overfilling the tank. The clear color of the oil, particularly in a new engine, is difficult to see when determining oil quantity.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The failure of maintenance personnel to allow adequate time for the engine oil to drain back into the engine oil reservoir prior to adding additional oil, thereby overfilling the reservoir, which resulted in an engine fire and subsequent damage to hydraulic lines and components, including the brakes, which precluded stopping the airplane prior to overrunning the runway end. An additional factor was the confusing and insufficiently defined procedures for servicing the engine oil.

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