A PA30 ON A POST MAINT TEST FLT DEVELOPED A STREAMING FUEL CAP LEAK REQUIRING AN ENG SHUTDOWN FOLLOWED BY A NORMAL GEAR EXTENSION FAILURE.

Narrative

DURING A MAINT RETURN TO SVC FLT; WHEN APPROX 15 NM SE OF ARPT; WHILE CRUISING AT 4000 FT; I NOTICED A STREAM OF FUEL LEAVING THE L WING. NOT KNOWING EXACTLY WHERE IT WAS COMING FROM; I SHUT DOWN AND FEATHERED THE L ENG. WE TURNED BACK TOWARDS THE ARPT. WHILE LINING UP FOR FINAL APCH ON RWY 23; THE LNDG GEAR WOULD NOT EXTEND. WE LEVELED OFF AND PROCEEDED TO CIRCLE TO THE NE AT 1 MI OF THE LNDG RWY THRESHOLD. WE PROCEEDED TO RUN THE MANUAL EXTENSION PROC. AS I FLEW THE ACFT; THE SECOND PLT/OBSERVER WAS ABLE TO CARRY OUT THE PROC/CHKLIST. AFTER WE VERIFIED THE GEAR DOWN; WE PROCEEDED TO LAND WITHOUT INCIDENT. WE FOUND A FAULTY MAIN GAS TANK CAP SEAL CAUSED SIPHONING OF THE FUEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT TYPE WAS A PA30. HE SAID THAT UNTIL AFTER LNDG THEY DID NOT KNOW THAT THE FUEL WAS STREAMING FROM THE FUEL CAP BECAUSE THEY COULD NOT CLEARLY SEE WHERE IT WAS STREAMING FROM. HE WAS VERY CONCERNED ABOUT THE FUEL ESPECIALLY IF THE GEAR COULD NOT BE EXTENDED. THE PLT IN THE R SEAT WAS A VOLUNTEER WHO DID NOT FULLY COMPREHEND THE POTENTIAL DANGER THE ACFT WAS EXPERIENCING.