Pilot of small aircraft miscalculates fuel needs for his trip by 1 hour. Re-examines fuel use in-fli...

Attributes
ACN	371687
Time
Date	199706
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bil
State Reference	MT
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other descent other other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 50 flight time total : 3200 flight time type : 1100
ASRS Report	371687
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : provided flight assist other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Was en route sgf (home base) to alaska. Departed SD01 VFR. Encountered lowering clouds vicinity gillette, wy, and filed IFR direct lewistown, mt, for fuel stop. While passing north of bil, became aware of fuel gauges showing lower than expected. Have flown this plane for 10 yrs and know fuel gauges are fairly accurate below 3/4 level. Had planned for flight to lewistown plus 1 hour reserve. Deduced from fuel gauges would have little or no reserve upon reaching lewistown. Immediately called ATC and diverted to bil. Due to fuel uncertainty, asked bil approach to vector us directly to airport, rather than out for normal ILS approach. Controller brought us directly in to runway 16. Controller was very helpful, reassuring, professional. Broke out of broken layer at approximately 600 ft AGL, on centerline of runway 16. Landed normally and taxied to ramp. Tried to inspect fuel remaining but new, restr fuel port would not allow entry of inspection mirror. Have reviewed flight planning, flight time, estimated fuel on board (use dipstick to measure), believe I simply miscalculated fuel by 1 hour. Been flying 31 yrs, no excuse, but first time to happen to me.

Original NASA ASRS Text

Title: PLT OF SMA MISCALCULATES FUEL NEEDS FOR HIS TRIP BY 1 HR. RE-EXAMINES FUEL USE INFLT AND DECIDES TO DIVERT TO REFUEL.

Narrative: WAS ENRTE SGF (HOME BASE) TO ALASKA. DEPARTED SD01 VFR. ENCOUNTERED LOWERING CLOUDS VICINITY GILLETTE, WY, AND FILED IFR DIRECT LEWISTOWN, MT, FOR FUEL STOP. WHILE PASSING N OF BIL, BECAME AWARE OF FUEL GAUGES SHOWING LOWER THAN EXPECTED. HAVE FLOWN THIS PLANE FOR 10 YRS AND KNOW FUEL GAUGES ARE FAIRLY ACCURATE BELOW 3/4 LEVEL. HAD PLANNED FOR FLT TO LEWISTOWN PLUS 1 HR RESERVE. DEDUCED FROM FUEL GAUGES WOULD HAVE LITTLE OR NO RESERVE UPON REACHING LEWISTOWN. IMMEDIATELY CALLED ATC AND DIVERTED TO BIL. DUE TO FUEL UNCERTAINTY, ASKED BIL APCH TO VECTOR US DIRECTLY TO ARPT, RATHER THAN OUT FOR NORMAL ILS APCH. CTLR BROUGHT US DIRECTLY IN TO RWY 16. CTLR WAS VERY HELPFUL, REASSURING, PROFESSIONAL. BROKE OUT OF BROKEN LAYER AT APPROX 600 FT AGL, ON CTRLINE OF RWY 16. LANDED NORMALLY AND TAXIED TO RAMP. TRIED TO INSPECT FUEL REMAINING BUT NEW, RESTR FUEL PORT WOULD NOT ALLOW ENTRY OF INSPECTION MIRROR. HAVE REVIEWED FLT PLANNING, FLT TIME, ESTIMATED FUEL ON BOARD (USE DIPSTICK TO MEASURE), BELIEVE I SIMPLY MISCALCULATED FUEL BY 1 HR. BEEN FLYING 31 YRS, NO EXCUSE, BUT FIRST TIME TO HAPPEN TO ME.

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.

Pilot of small aircraft miscalculates fuel needs for his trip by 1 hour. Re-examines fuel use in-flight and decides to divert to refuel.