Incident Overview
A regularly scheduled air carrier flight was climbing to altitude when the oil pressure and quantity on the #3 engine dropped to zero. The crew shut down the engine. Shortly thereafter, the #1 engine oil pressure also dropped to zero, and the crew reduced it to idle. The flight diverted and executed a normal landing.
Technical Details
Investigation revealed that the #3 engine lost its oil due to a failed oil pressure tube connected to the #6 bearing. This tube was subsequently lost in transit by American Airlines (AAL) freight personnel, preventing a detailed examination.
The #1 engine lost oil due to contamination of its oil system with hydraulic fluid. Interviews with American Airlines and contract maintenance personnel who had serviced the aircraft within the previous 30 days found no discrepancies that would have allowed hydraulic fluid to enter the oil system.
Investigation Findings
The probable cause for the #3 engine oil loss was the failure of the oil pressure tube to the #6 bearing. For the #1 engine, the oil loss was caused by hydraulic fluid contamination, but the source of the contamination could not be determined from the available evidence.