Narrative:

I departed on an IFR trip. On climbout tower advised me to turn to 100 degrees and contact departure. As I was turning to 100 degrees and contacting departure oil suddenly gushed from my right engine. I was approximately 900 ft AGL. I continued my turn to north planning to enter a left downwind for runway 17R. I advised departure that I needed to return for landing. He asked if I needed to declare an emergency and suggested runway 26. I declined the emergency and stated that I was too high for runway 26 or for a left downwind for runway 17R and that I would like to continue my turn and head west and then enter a right downwind for runway 17R. This would give me more time to lose altitude and not super-cool my left good engine on a sudden descent. I was handed off to the tower. The tower controller also asked if I wanted an emergency. I declined again because the malfunctioning right engine continued to operate normally and with the reduced power although there was still a stream of oil. The engine temperature and oil pressure continued to stay within normal range. I did not shut down the right engine but if I had to do so I would have declared an emergency. The landing was uneventful. After landing I called the tower and discussed the incident with the tower chief. He did not express to me that my initial turn to 350 degrees had caused a problem. He said that he would review the tapes and advise me later if there was a problem. Upon examination of the engine oil filler cap was found to be loose. Oil had been put in both engines prior to takeoff. The line guy and I both felt the caps to be sure they were tight. Apparently the right one was cross-threaded and we did not catch this fact. When the engine pressurized it popped the cap. There was oil remaining in the engine. After maintenance washed down the engine and added more oil I continued with the trip. There was no further incident. Maintenance is going to examine the caps for each engine to be sure that the threading is not wearing. It is an old airplane.

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Original NASA ASRS Text

Title: A C421 pilot returned to the departure airport when an improperly secured oil filler cap opened permitting oil to be drawn from the tank.

Narrative: I departed on an IFR trip. On climbout Tower advised me to turn to 100 degrees and contact departure. As I was turning to 100 degrees and contacting departure oil suddenly gushed from my right engine. I was approximately 900 FT AGL. I continued my turn to north planning to enter a left downwind for Runway 17R. I advised departure that I needed to return for landing. He asked if I needed to declare an emergency and suggested Runway 26. I declined the emergency and stated that I was too high for Runway 26 or for a left downwind for Runway 17R and that I would like to continue my turn and head west and then enter a right downwind for Runway 17R. This would give me more time to lose altitude and not super-cool my left good engine on a sudden descent. I was handed off to the Tower. The Tower Controller also asked if I wanted an emergency. I declined again because the malfunctioning right engine continued to operate normally and with the reduced power although there was still a stream of oil. The engine temperature and oil pressure continued to stay within normal range. I did not shut down the right engine but if I had to do so I would have declared an emergency. The landing was uneventful. After landing I called the Tower and discussed the incident with the Tower Chief. He did not express to me that my initial turn to 350 degrees had caused a problem. He said that he would review the tapes and advise me later if there was a problem. Upon examination of the engine oil filler cap was found to be loose. Oil had been put in both engines prior to takeoff. The line guy and I both felt the caps to be sure they were tight. Apparently the right one was cross-threaded and we did not catch this fact. When the engine pressurized it popped the cap. There was oil remaining in the engine. After maintenance washed down the engine and added more oil I continued with the trip. There was no further incident. Maintenance is going to examine the caps for each engine to be sure that the threading is not wearing. It is an old airplane.

Data retrieved from NASA's ASRS site as of April 2012 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.