Narrative:

En route on a maintenance ferry flight; the oil pressure gauge on the #1 engine dropped down into the yellow caution range. The captain went to the back of the plane to check for an oil leak; where he saw oil leaking from the engine breather. Shortly after the captain returned to the cockpit; the oil pressure dropped below 40 psi causing the warning light to illuminate. We referred to the emergency checklist; which stated to shut the engine down. We shut the engine down and diverted where we did a visual approach and landed without incident. The reason we were ferrying the aircraft was due to an inoperative AC generator on the #1 engine. Maintenance tried to fix the problem by installing a new AC generator; however; that did not fix the problem. Because that did not fix the problem; we were then to ferry the aircraft to a maintenance base to have the problem fixed. My guess is that maintenance did not properly install the new AC generator causing oil to leak from the AC generator. The conditions in ZZZ when they installed the new generator was rainy and cold. The mechanics had just driven from YYY and were soaking wet; which I believe may have contributed to their faulty performance. This is all speculation; and I don't yet know what the actual cause was. Callback conversation with reporter revealed the following information: the reporter stated the corrective action taken by maintenance is unknown. The idea of the damaged or cut oil seals during the installation of the replacement generator is just pure speculation. The left engine did not display any external oil leak during the preflight check and the logbook did not indicate any high oil consumption.

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Original NASA ASRS Text

Title: A DHC-8 AT 12000 FT DIVERTED DUE TO LOSS OF OIL ON THE L ENG. ACFT WAS OPERATING ON A MAINT FERRY TO CORRECT L AC GENERATOR PROB.

Narrative: ENRTE ON A MAINT FERRY FLT; THE OIL PRESSURE GAUGE ON THE #1 ENG DROPPED DOWN INTO THE YELLOW CAUTION RANGE. THE CAPT WENT TO THE BACK OF THE PLANE TO CHK FOR AN OIL LEAK; WHERE HE SAW OIL LEAKING FROM THE ENG BREATHER. SHORTLY AFTER THE CAPT RETURNED TO THE COCKPIT; THE OIL PRESSURE DROPPED BELOW 40 PSI CAUSING THE WARNING LIGHT TO ILLUMINATE. WE REFERRED TO THE EMER CHKLIST; WHICH STATED TO SHUT THE ENG DOWN. WE SHUT THE ENG DOWN AND DIVERTED WHERE WE DID A VISUAL APCH AND LANDED WITHOUT INCIDENT. THE REASON WE WERE FERRYING THE ACFT WAS DUE TO AN INOP AC GENERATOR ON THE #1 ENG. MAINT TRIED TO FIX THE PROB BY INSTALLING A NEW AC GENERATOR; HOWEVER; THAT DID NOT FIX THE PROB. BECAUSE THAT DID NOT FIX THE PROB; WE WERE THEN TO FERRY THE ACFT TO A MAINT BASE TO HAVE THE PROB FIXED. MY GUESS IS THAT MAINT DID NOT PROPERLY INSTALL THE NEW AC GENERATOR CAUSING OIL TO LEAK FROM THE AC GENERATOR. THE CONDITIONS IN ZZZ WHEN THEY INSTALLED THE NEW GENERATOR WAS RAINY AND COLD. THE MECHS HAD JUST DRIVEN FROM YYY AND WERE SOAKING WET; WHICH I BELIEVE MAY HAVE CONTRIBUTED TO THEIR FAULTY PERFORMANCE. THIS IS ALL SPECULATION; AND I DON'T YET KNOW WHAT THE ACTUAL CAUSE WAS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CORRECTIVE ACTION TAKEN BY MAINT IS UNKNOWN. THE IDEA OF THE DAMAGED OR CUT OIL SEALS DURING THE INSTALLATION OF THE REPLACEMENT GENERATOR IS JUST PURE SPECULATION. THE L ENG DID NOT DISPLAY ANY EXTERNAL OIL LEAK DURING THE PREFLT CHK AND THE LOGBOOK DID NOT INDICATE ANY HIGH OIL CONSUMPTION.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.