Narrative:

The article in the july bulletin about silicone sagas really struck home. My partners and I purchased a 1964 small aircraft in dec/90. The plane was low time, in good shape and flew like a dream. One day I was flying at about 11000 ft over the mountains northeast of burbank headed for lancaster. The engine was leaned with a single probe egt and I was flying on the right tank. My first indication something was wrong was when the engine started running like it was about to quit. It seemed to be starving for fuel. I noted the egt had risen significantly and I thought the engine was going to quit. I immediately began carburetor heat and efforts to make the mixture richer. However there was no response. After pushing, pulling and twisting several knobs with little success, I changed to the left tank and noted an immediate drop in the egt as the engine returned to normal. When I returned to home base we checked everything thoroughly. It seemed that I, as the only one having the problem, at first we were not sure that it was not ice the first time. But as repeat occurrences happened, it became obvious that it was a mechanical fuel flow problem with the right tank. As soon as the tank was switched to the left or both position, it cleared up. Our efforts were all unsuccessful. We drained tanks, pulled valves, checked fuel flows, checked screens and filters and had the carburetor checked. We discovered one of the float bulbs was broken but failed to really identify the culprit. We went to several mechanics and talked to anyone that would listen and our efforts to find the problem were unsuccessful. One day my partner was doing a preflight when he noted the right fuel drain did not drain when he inserted the fuel tester. We again started to pull things apart, drain tanks and check fuel flows. This time we discovered in the right tank a glob of silicone about 1/2 the size of an egg. The records revealed that the airworthiness directive on the fuel tank filler caps a few yrs before, prior to us purchasing the plane. Apparently the mechanic used an excessive amount of silicone sealer which ended up in the tank. It appears that, as we flew, the silicone ball would float about until the glob was caught in the suction created when the right tank was selected. This did not always occur. Things had to be just right. If the tank was switched, the suction was relieved and the glob would float away. When flows were checked by opening lines, there was no suction so the opening would not clog. It seems that the day my partner did the preflight and the fuel would not flow, the right tank was low on fuel. The ball had settled right on the valve and it plugged the line.

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Original NASA ASRS Text

Title: ONE OF THE OWNER PARTNERS IN AN SMA RESPONDED TO AN ARTICLE IN CALLBACK ABOUT THE PROBLEMS OF SILICONE IN ACFT USE. HE STATED THAT HIS ACFT HAD A GLOB OF SILICONE IN ONE OF ITS GAS TANKS THAT SERIOUSLY RESTRICTED THE FUEL FLOW.

Narrative: THE ARTICLE IN THE JULY BULLETIN ABOUT SILICONE SAGAS REALLY STRUCK HOME. MY PARTNERS AND I PURCHASED A 1964 SMA IN DEC/90. THE PLANE WAS LOW TIME, IN GOOD SHAPE AND FLEW LIKE A DREAM. ONE DAY I WAS FLYING AT ABOUT 11000 FT OVER THE MOUNTAINS NE OF BURBANK HEADED FOR LANCASTER. THE ENG WAS LEANED WITH A SINGLE PROBE EGT AND I WAS FLYING ON THE R TANK. MY FIRST INDICATION SOMETHING WAS WRONG WAS WHEN THE ENG STARTED RUNNING LIKE IT WAS ABOUT TO QUIT. IT SEEMED TO BE STARVING FOR FUEL. I NOTED THE EGT HAD RISEN SIGNIFICANTLY AND I THOUGHT THE ENG WAS GOING TO QUIT. I IMMEDIATELY BEGAN CARB HEAT AND EFFORTS TO MAKE THE MIXTURE RICHER. HOWEVER THERE WAS NO RESPONSE. AFTER PUSHING, PULLING AND TWISTING SEVERAL KNOBS WITH LITTLE SUCCESS, I CHANGED TO THE L TANK AND NOTED AN IMMEDIATE DROP IN THE EGT AS THE ENG RETURNED TO NORMAL. WHEN I RETURNED TO HOME BASE WE CHKED EVERYTHING THOROUGHLY. IT SEEMED THAT I, AS THE ONLY ONE HAVING THE PROBLEM, AT FIRST WE WERE NOT SURE THAT IT WAS NOT ICE THE FIRST TIME. BUT AS REPEAT OCCURRENCES HAPPENED, IT BECAME OBVIOUS THAT IT WAS A MECHANICAL FUEL FLOW PROBLEM WITH THE R TANK. AS SOON AS THE TANK WAS SWITCHED TO THE L OR BOTH POS, IT CLRED UP. OUR EFFORTS WERE ALL UNSUCCESSFUL. WE DRAINED TANKS, PULLED VALVES, CHKED FUEL FLOWS, CHKED SCREENS AND FILTERS AND HAD THE CARB CHKED. WE DISCOVERED ONE OF THE FLOAT BULBS WAS BROKEN BUT FAILED TO REALLY IDENT THE CULPRIT. WE WENT TO SEVERAL MECHS AND TALKED TO ANYONE THAT WOULD LISTEN AND OUR EFFORTS TO FIND THE PROBLEM WERE UNSUCCESSFUL. ONE DAY MY PARTNER WAS DOING A PREFLT WHEN HE NOTED THE R FUEL DRAIN DID NOT DRAIN WHEN HE INSERTED THE FUEL TESTER. WE AGAIN STARTED TO PULL THINGS APART, DRAIN TANKS AND CHK FUEL FLOWS. THIS TIME WE DISCOVERED IN THE R TANK A GLOB OF SILICONE ABOUT 1/2 THE SIZE OF AN EGG. THE RECORDS REVEALED THAT THE AIRWORTHINESS DIRECTIVE ON THE FUEL TANK FILLER CAPS A FEW YRS BEFORE, PRIOR TO US PURCHASING THE PLANE. APPARENTLY THE MECH USED AN EXCESSIVE AMOUNT OF SILICONE SEALER WHICH ENDED UP IN THE TANK. IT APPEARS THAT, AS WE FLEW, THE SILICONE BALL WOULD FLOAT ABOUT UNTIL THE GLOB WAS CAUGHT IN THE SUCTION CREATED WHEN THE R TANK WAS SELECTED. THIS DID NOT ALWAYS OCCUR. THINGS HAD TO BE JUST RIGHT. IF THE TANK WAS SWITCHED, THE SUCTION WAS RELIEVED AND THE GLOB WOULD FLOAT AWAY. WHEN FLOWS WERE CHKED BY OPENING LINES, THERE WAS NO SUCTION SO THE OPENING WOULD NOT CLOG. IT SEEMS THAT THE DAY MY PARTNER DID THE PREFLT AND THE FUEL WOULD NOT FLOW, THE R TANK WAS LOW ON FUEL. THE BALL HAD SETTLED RIGHT ON THE VALVE AND IT PLUGGED THE LINE.

Data retrieved from NASA's ASRS site as of July 2007 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.