Narrative:

I was PIC (and only person on board) of C150, departing pope field (gfd). I experienced a severe power loss at full throttle while crossing the north threshold of runway 36. My altitude was approximately 250 ft AGL. I reduced power setting and engine seemed to run normally, but producing less than full power. I increased power setting, but engine only increased slightly in power. Highest power setting was not sufficient to sustain level flight and engine power was continuing to decrease at full throttle. I established best glide speed of 70 mph and picked a field of sufficient length for safe landing to my left (west). I performed a 90 degree left turn and began a final approach for landing immediately straight ahead. I reduced power to idle and applied full flaps, descended, flared, and landed as I normally would, applied brakes until stopped. I observed that engine was still running at a normal idle speed, and followed normal shut down procedure. I then exited the aircraft and proceeded to check fuel levels by visual inspection. Upon opening the left tank cap, a rushing air sound was observed until the cap was completely removed. It felt as though a suction force was retaining the cap at first. No such sound or observation was noticed upon removal of the right cap. Fuel quantity in both tanks was visually observed to be approximately 1.5 - 2.0 inches (3-4 gallons per tank, 6-8 gallons total). Pilot and aircraft were undamaged. Pilot's conclusion: the fuel venting system was probably blocked (possible insect infestation). Owner/pilot will have fuel vent system inspected prior to further operation of aircraft. This aircraft has been flown by same pilot for 40 hours on a regular basis since purchase date, 45 days from the date of this incident. No problems have ever been observed with this aircraft during any operation the previous 40 hours of flight by this owner/pilot. Preventive measures: none. Fuel vent was inspected during preflight with no abnormalities observed. If insect infestation (or other blockage) is beyond a point of visual detection, then there is no way to determine this problem exists prior to flight, during a normal preflight inspection. Blowing on the vent tube is probably undesirable as this would either force the obstruction further into the vent or all the way into the tank, where it could cause the same or other problems later. Solution: have a licensed a&P mechanic inspect and test system in order to determine exact cause of this problem.

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Original NASA ASRS Text

Title: PLT OF C150 HAS LOSS OF ENG PWR JUST AFTER TKOF AND MAKES AN OFF ARPT LNDG WITH NO DAMAGE.

Narrative: I WAS PIC (AND ONLY PERSON ON BOARD) OF C150, DEPARTING POPE FIELD (GFD). I EXPERIENCED A SEVERE PWR LOSS AT FULL THROTTLE WHILE XING THE N THRESHOLD OF RWY 36. MY ALT WAS APPROX 250 FT AGL. I REDUCED PWR SETTING AND ENG SEEMED TO RUN NORMALLY, BUT PRODUCING LESS THAN FULL PWR. I INCREASED PWR SETTING, BUT ENG ONLY INCREASED SLIGHTLY IN PWR. HIGHEST PWR SETTING WAS NOT SUFFICIENT TO SUSTAIN LEVEL FLT AND ENG PWR WAS CONTINUING TO DECREASE AT FULL THROTTLE. I ESTABLISHED BEST GLIDE SPD OF 70 MPH AND PICKED A FIELD OF SUFFICIENT LENGTH FOR SAFE LNDG TO MY L (W). I PERFORMED A 90 DEG L TURN AND BEGAN A FINAL APCH FOR LNDG IMMEDIATELY STRAIGHT AHEAD. I REDUCED PWR TO IDLE AND APPLIED FULL FLAPS, DSNDED, FLARED, AND LANDED AS I NORMALLY WOULD, APPLIED BRAKES UNTIL STOPPED. I OBSERVED THAT ENG WAS STILL RUNNING AT A NORMAL IDLE SPD, AND FOLLOWED NORMAL SHUT DOWN PROC. I THEN EXITED THE ACFT AND PROCEEDED TO CHK FUEL LEVELS BY VISUAL INSPECTION. UPON OPENING THE L TANK CAP, A RUSHING AIR SOUND WAS OBSERVED UNTIL THE CAP WAS COMPLETELY REMOVED. IT FELT AS THOUGH A SUCTION FORCE WAS RETAINING THE CAP AT FIRST. NO SUCH SOUND OR OBSERVATION WAS NOTICED UPON REMOVAL OF THE R CAP. FUEL QUANTITY IN BOTH TANKS WAS VISUALLY OBSERVED TO BE APPROX 1.5 - 2.0 INCHES (3-4 GALLONS PER TANK, 6-8 GALLONS TOTAL). PLT AND ACFT WERE UNDAMAGED. PLT'S CONCLUSION: THE FUEL VENTING SYS WAS PROBABLY BLOCKED (POSSIBLE INSECT INFESTATION). OWNER/PLT WILL HAVE FUEL VENT SYS INSPECTED PRIOR TO FURTHER OP OF ACFT. THIS ACFT HAS BEEN FLOWN BY SAME PLT FOR 40 HRS ON A REGULAR BASIS SINCE PURCHASE DATE, 45 DAYS FROM THE DATE OF THIS INCIDENT. NO PROBS HAVE EVER BEEN OBSERVED WITH THIS ACFT DURING ANY OP THE PREVIOUS 40 HRS OF FLT BY THIS OWNER/PLT. PREVENTIVE MEASURES: NONE. FUEL VENT WAS INSPECTED DURING PREFLT WITH NO ABNORMALITIES OBSERVED. IF INSECT INFESTATION (OR OTHER BLOCKAGE) IS BEYOND A POINT OF VISUAL DETECTION, THEN THERE IS NO WAY TO DETERMINE THIS PROB EXISTS PRIOR TO FLT, DURING A NORMAL PREFLT INSPECTION. BLOWING ON THE VENT TUBE IS PROBABLY UNDESIRABLE AS THIS WOULD EITHER FORCE THE OBSTRUCTION FURTHER INTO THE VENT OR ALL THE WAY INTO THE TANK, WHERE IT COULD CAUSE THE SAME OR OTHER PROBS LATER. SOLUTION: HAVE A LICENSED A&P MECH INSPECT AND TEST SYS IN ORDER TO DETERMINE EXACT CAUSE OF THIS PROB.

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.