Primary finding
Probable cause
Hydraulic fluid exhaustion due to the chafed 'a' system hydraulic line and the improper installation by unknown maintenance personnel of the 'b' system line.
Investigator assessment
Analysis narrative
The airplane experienced a dual hydraulic system failure during final approach. The captain elected to go around and land at a nearby military airport that had longer runways. The landing was uneventful. Investigation revealed that a hole had been chafed through a return line in the 'a' hydraulic system at a bracket in the left wheel well area. It was also determined that an 'a' system and a 'b' system return line had been cross connected in the area of the no. 1 pylon. The cross connected lines allowed the 'b' system fluid to transfer into the 'a' system and vent overboard. Both hydraulic systems, indications and readings, and tests were normal until the hole was chafed through the 'a' system line. A maintenance record review could not determine at what point in time the lines had been reversed.
Source record
Factual narrative
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