A CITABRIA CHAMPION 7EC PLT MISCALCULATED THE ACFT'S FUEL USAGE AND LANDED SAFETY OFF ARPT DUE TO FUEL STARVATION.

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THE FLT ORIGINATED AT ZZZ1. THE PLANNED RTE WAS FROM ZZZ1 TO ZZZ2; EXECUTE A MISSED APCH; THEN TO ZZZ3; EXECUTE A MISSED APCH; THEN RETURN TO ZZZ1 FOR LNDG. THE FLT PROCEEDED AS PLANNED; EXCEPT FOR UNEXPECTED HEADWINDS AND TYPICAL DEVS; UNTIL APPROX 8 MI FROM ZZZ1 INBOUND. AT ABOUT XA25; THE ENG BEGAN TO SURGE ABRUPTLY BTWN OFF AND NORMAL PWR. THE PLT PERFORMED THE NORMAL EMER CHKLIST BUT TO NO AVAIL. THE PLT THEN NOTIFIED ATC THAT THERE WAS AN ENG PROB; THAT HE WOULD LIKELY MAKE AN OFF-ARPT LNDG; AND THAT HE WAS NOT DECLARING AN EMER (THE PLT ANTICIPATED A NORMAL LNDG OFF-ARPT AND THERE WAS NO ASSISTANCE THAT ATC COULD PROVIDE). THE ENG CONTINUED TO SURGE AND THE ACFT WAS LOSING ALT AT 200-300 FPM. THE TOWN OF ABC WAS DIRECTLY BTWN THE ACFT AND THE ARPT SO THE PLT ELECTED TO DEVIATE AROUND THE TOWN TO REMAIN OVER FIELDS SUITABLE FOR LNDG; WHILE CIRCLING TOWARD THE ARPT. AT ABOUT 800 FT AGL; WITH THE ENG STILL SURGING; THE PLT ELECTED NOT TO ATTEMPT TO PROCEED FURTHER BUT TO LAND IN A SUITABLE FIELD AT THAT POINT. A FIELD THAT WAS BENEATH THE ACFT WAS SELECTED. AN UNEVENTFUL LNDG WAS COMPLETED. THE LNDG OCCURRED AT XA30. THERE WAS NO DAMAGE TO THE ACFT OR TO ANY PROPERTY; AND THERE WERE NO INJURIES. THE PLANNED FLT TIME WAS 3.2 HRS. THERE WERE 24 GALLONS OF USABLE FUEL ON BOARD. EXPECTED FUEL BURN WAS 4.8 GPH. THERE SHOULD HAVE BEEN ENOUGH FUEL FOR 5 HRS. THE FUEL WAS EXHAUSTED AFTER 3.7 HRS. THERE WERE SEVERAL SMALL FACTORS WHICH CONTRIBUTED TO THE UNEXPECTED FUEL SHORTAGE. FUEL BURN DATA WAS ESTABLISHED 1 1 1/2 YRS PREVIOUSLY WHEN USING AGGRESSIVE LEANING AT ALL TIMES; AND AT RELATIVELY LOW PWR SETTINGS. 3 WKS PRIOR TO THE FLT IN QUESTION; THE A&P MECH PERFORMING THE ANNUAL INSPECTION ADVISED THE PLT THAT EXCESSIVE LEANING WAS HARMFUL TO THE ENG AND SUGGESTED THAT IT SHOULD NOT BE LEANED UNLESS ABOVE 5000 FT MSL. THE FLT IN QUESTION WAS CONDUCTED AT 5000 FT MSL. IN ADDITION; THE PLT BEGAN USING HIGHER PWR SETTINGS; BELIEVING THIS WAS DESIRABLE FOR THIS ENG. ANOTHER FACTOR THAT MAY HAVE CONTRIBUTED IN A SMALL WAY TO HIGHER-THAN-EXPECTED FUEL USE WAS NOT INCLUDING GND RUN TIMES. BUT THE MAIN FACTOR WAS NOT RECALCULATING FUEL BURN DATA AFTER CHANGING OPERATING PROCS. THIS EXPERIENCE DEMONSTRATES HOW SMALL FACTORS THAT INDIVIDUALLY MAY SEEM UNIMPORTANT INDIVIDUALLY CAN ACCUMULATE INTO LARGE PROBS. IT ALSO DEMONSTRATES THE IMPORTANCE OF ENSURING THAT THE DATA USED FOR PLANNING; IN THIS CASE FUEL BURN DATA BASED ON SPECIFIC LEANING AND PWR SETTINGS; APPLIES TO THE OP BEING UNDERTAKEN. ALSO; THE TRAINING THE PLT RECEIVED OVER AND OVER AGAIN IN EMER PROCS; INCLUDING DECISION-MAKING; SELECTION OF A SUITABLE LNDG SITE; AND IN NO-PWR LNDGS PAID OFF. THE DECISION TO AVOID A FLT PATH OVER AREAS WITH NO SUITABLE LNDG SITES; EG; DIRECTLY TO THE ARPT OVER DOWNTOWN ABC; AND THE DECISION TO LAND WHEN A SAFE LNDG COULD BE ASSURED RATHER THAN TO POSTPONE LNDG UNTIL NO SAFE OPTIONS REMAINED; MADE THE DIFFERENCE BTWN AN UNEVENTFUL LNDG AND AN INCIDENT OR AN ACCIDENT. ALTHOUGH THERE IS ALWAYS RISK WHEN AN ENG STOPS INFLT; AT NO POINT WAS THE SAFE OUTCOME OF THIS FLT IN DOUBT. THE IMPORTANCE OF EMER DECISION-MAKING AND PROCS IS PROPERLY EMPHASIZED IN PRIMARY TRAINING AND FLT REVIEWS. THERE IS NOTHING LIKE EXPERIENCING IT TO MAKE REAL AND IMMEDIATE THE EVER-PRESENT POSSIBILITY OF AN UNPLANNED LNDG AND THE VALUE OF PREPARATION AND PRACTICE; FOR EXPERIENCED PLTS AS WELL AS STUDENTS.