SMA PLT HAS FLUCTUATING PWR; MAKES IT TO THE ARPT.

Narrative

COMS WITH THE SBP TWR HAD ALREADY BEEN ESTABLISHED OVER THE TOWN OF MORRO BAY. A PARTIAL LOSS OF ENG PWR ACCOMPANIED BY FLUCTUATIONS OF THE FUEL FLOW AND RPM WERE ENCOUNTERED. PLT HAD DETERMINED FUEL QUANTITY PRIOR TO TKOF TO HAVE BEEN 18 GALLONS AND CALCULATED APPROX 8 GALLONS REMAINED. GAUGES SHOWED 1/8 IN LEVEL FLT. MIXTURE SETTING WAS INCREASED TO FULL RICH AND AN ATTEMPT TO REESTABLISH NORMAL PWR WAS DONE BY USE AND CHANGING ACFT ATTITUDE AND USE OF AUX PUMP. THE TWR WAS ADVISED BY THE PLT THAT A PARTIAL LOSS OF PWR HAD BEEN ENCOUNTERED BUT THAT FLT COULD BE CONTINUED TO THE SAN LUIS OBISPO ARPT. NORMAL ENG PWR WAS NOT ACHIEVED BY THE TIME THE ACFT WAS 2 MI FROM THE ARPT AT APPROX 3500 FT. THE PLT ELECTED TO DECLARE AN EMER AND ADVISED THE TWR THAT A LNDG WOULD BE MADE ON RWY 11. ON THE FINAL GLIDE FROM 1700 FT MSL AND APPROX 1/2 MI FROM THE APCH END OF RWY 11; THE PLT ELECTED TO SHUT DOWN THE ENG AND STOP THE PROP FROM WINDMILLING TO ASSURE MAX GLIDE; LEAST DRAG ON FINAL FLARE AND PREVENT DAMAGE TO THE CRANKSHAFT AND ENG IN THE EVENT THE LNDG WAS NOT ENTIRELY SUCCESSFUL. THE PLT ADVISED THE TWR OF AN EXPECTED DELAY ON THE RWY AFTER TOUCHDOWN. AFTER TOUCHDOWN; THE PLT ADVISED LNDG WAS SUCCESSFUL; NO DAMAGE HAD OCCURRED TO THE ACFT OR OCCUPANTS AND THAT THE RADIOS WOULD BE TURNED OFF. THE PLT AND PAX PUSHED THE ACFT TO THE DEP END OF THE RWY. THE ACFT WAS TOWED IN BY MAINT PERSONNEL. THE FUEL WAS DRAINED FROM THE SYS AND INSPECTED. THE PLT FOUND 6 GALLONS OF FUEL REMAINED IN THE SYS. THE FUEL WAS VOID OF ANY OBSERVED CONTAMINANTS. THE PLT HAD A MECH INSPECT THE FUEL SCREEN; INJECTORS; ENG DRIVEN PUMP AND AUX FUEL PUMP. A GND TEST AND SUBSEQUENT FLT TEST DEMONSTRATED THE SYS WERE OPERATIONAL. IT IS SUSPECTED THAT AN AIR VAPOR LOCK MAY HAVE DISRUPTED THE CONTINUOUS FUEL FLOW TO THE ENG. THE ACFT MANUFACTURER DOES NOT PROVIDE SPECS FOR RIDDING VAPOR LOCK INFLT OR CONDITIONS WHICH VAPOR LOCK COULD ARISE. RECOMMENDATIONS WOULD BE TO AVOID STEEP TURNS OR SLIPPING THE ACFT WHEN LESS THAN 1/4 TANK FUEL REMAIN IN THE FUEL TANKS. THIS WOULD EQUATE TO 5 GALLONS IN EACH WING TANK PLUS 3 GALLONS FOR THE INVERTED HEADER TANK OR TOTAL OF 13 GALLONS. THIS FUEL QUANTITY WOULD PROVIDE 45-60 MINS OF NORMAL CRUISE FLT. SUGGESTED USE OF THE AUX PUMP FOR CONDITIONS OTHER THAN STARTING THE ENG OR WHEN THE ENG DRIVEN PUMP FAILS COULD BE EXPLAINED IN GREATER DETAIL SO THAT PLTS WOULD BE MORE KNOWLEDGEABLE ABOUT THE PROS AND CONS OF USING THE AUX PUMP TO PURGE AN AIR LOCK INFLT.