SMA MAKES FORCED LNDG ON PIT ARPT DUE FUEL EXHAUSTION.

Narrative

ACFT IS HIGHLY MODIFIED WITH TAILWHEEL CONVERSION AND 150 HP ENG FUEL BURN ABOUT 7.5 GPH. DEPARTED 6PA4 AT XA45 AM; LORAN DIRECT TO PIT ARRIVING OVER PHOTO TARGET AT XB35. CRUISE AT 6500 FT ENRTE; DIVERSION OVER JOHNSTOWN AREA DUE TO CLOUDS/CEILINGS; TO 3200 FT; ALTER COURSE; CLB BACK TO 6500 FT WITH ZOB. CIRCLING OVER 2ND TARGET; NNE OF PIT; WHEN ENG MISSED A BEAT (XA54 AM). ASKED TWR FOR LNDG INSTRUCTIONS (IMMEDIATE; DUE TO CRITICAL FUEL). THEY ASKED IF I WISHED TO DECLARE AN EMER. REPLY: 'NEGATIVE AT THIS TIME; CRITICAL FUEL SIT ONLY.' I WAS CLRED TO LAND ON RWY 28R; SET UP FOR FINAL AND PROCEEDED THROUGH ENG OUT CHKLIST. ENG STILL RUNNING UNTIL FINAL 500 FT BEFORE NUMBERS. MADE UNEVENTFUL LNDG; AND ROLLED CLR OF RWY; APPROX 125 FT N OF CTRLINE. EMER EQUIP DISPATCHED; NOT REQUIRED. ACFT HOLDS 26 GALLONS 22.5 USABLE. CONDITIONS WERE WIND 270 AT 6000 (24 KTS). POSSIBLE ADDITIONAL CAUSE OF PREMATURE STARVATION IS: ACFT SET UP FOR PHOTOGRAPHY: 1750 RPM; 10 DEGS FLAPS; TRIM NOSE HIGH. AT APPROX 50 MPH IN L BANK OF 10 DEG OR GREATER; SIPHONING EFFECT SOMETIMES TAKES PLACE THROUGH UNDER L WING VENT TUBE; DEPENDING ON ANGLE OF APCH AND WIND. I BELIEVE; BASED ON GAUGES AND YOKE-MOUNTED STOP WATCH; THAT I WAS NOT FUEL CRITICAL UNTIL AFTER 6500 FT CRUISE RESUMED; W OF JOHNSTOWN. HIGH WIND STRONGER THAN ANTICIPATED. I CAME INBOUND TO PIT ON 119.35 AND ANNOUNCED MY INTENT TO SHOOT BOTH TARGETS WITHIN 15-20 MINS; THEN PROCEED FOR FUEL. BY MY CALCULATIONS; I WAS ON SCHEDULE. CONCLUSION: FUEL BURN HIGHER DUE TO INCREASED HIGH WIND; SOME LOSS DUE TO SIPHONING EFFECT AND SLOW FLT. COURSE OF ACTION: UNDER SIMILAR CONDITIONS; PLAN FUEL STOP 30 MINS EARLIER. CONTACTED FAA BY REQUEST.