Narrative:

This event arose from a failure to identify the ATC communication frequency to obtain clearance into glh control zone at greenville, ms. Contributing factors: 1) in-flight loss of left fuel tank filler cap resulting in siphoning fuel. 2) possible fuel exhaustion -- pilot workload in approach/descent landing phase. 3) partial obscuring of facility frequency on chart. 4) failure to follow my normal procedure of listing ATC frequencys anticipated first officer the flight on my trip log sheet during flight planning 5) failure to contact FSS to advise of fuel concerns, request information, assistance and/or declare emergency. Fuel gauges were behaving abnormally. I initially discounted it, attributing it to 'those unreliable cessna fuel gauges.' I did check that the fuel selector valve was physically in the 'both' tanks detent. Some few mins later, I observed that the right tank gauge was indicating 'full' and the left tank gauge was indicating 'empty.' I had personally visually checked and dipsticked both tanks during preflight inspection, confirming that I had 69 gallons aboard (over 5 hours to fuel exhaustion) for a planned flight of 2 hours. I replaced and secured the fuel caps. I now felt forced to conclude that a fuel cap must be missing, siphoning fuel from one (or both!) tanks(south). About 20 NM from my intended destination (glh), I reduced power, slowed the aircraft to approach speed, and began a gentle descent towards glh, hoping to conserve the fuel remaining to touchdown. I looked at the sectional chart for the facility's communication frequency and saw only unicom 122.95 which I called twice without response. As I neared the airport vicinity, assuming the control zone was not active, I searched for any aircraft in the pattern or taxiing -- seeing none. I monitored unicom for traffic announcements. Not seeing or hearing any traffic, I chose runway 36R since it was closest. I landed on runway 36R, taxied in and parked at the FBO. I inspected the aircraft and discovered that the left fuel tank filler cap was missing. Dipsticking the tanks, I found less than 5 gallons in the left tank and approximately 12 gallons in the right tank. After discussing the incident by telephone with control tower personnel, I mentally reviewed the events of the flight and now know that the control tower was in operation. I found that in planning the trip I had drawn my next leg course directly over the control tower frequency, partially obscuring it. I have resolved to: 1) pay extra attention to assuring fuel and oil cap security prior to any flight. 2) always prepare a list of communication frequencys. 3) notify FSS immediately upon discovering any in-flight aircraft discrepancy or problems. 4) never draw course lines through/over airport, navigation or communications frequency information. 5) relate this experience publicly at the next flight safety meetings that I attend.

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Original NASA ASRS Text

Title: UNEXPLAINED FUEL QUANTITY INDICATION PROBS ARE THE RESULT OF A MISSING FUEL CAP. ENTRY INTO A CLASS D AIRSPACE AND LNDG WITHOUT CONTACT WITH TWR ARE INCLUDED IN THE DAY'S PROBS.

Narrative: THIS EVENT AROSE FROM A FAILURE TO IDENT THE ATC COM FREQ TO OBTAIN CLRNC INTO GLH CTL ZONE AT GREENVILLE, MS. CONTRIBUTING FACTORS: 1) INFLT LOSS OF L FUEL TANK FILLER CAP RESULTING IN SIPHONING FUEL. 2) POSSIBLE FUEL EXHAUSTION -- PLT WORKLOAD IN APCH/DSCNT LNDG PHASE. 3) PARTIAL OBSCURING OF FACILITY FREQ ON CHART. 4) FAILURE TO FOLLOW MY NORMAL PROC OF LISTING ATC FREQS ANTICIPATED FO THE FLT ON MY TRIP LOG SHEET DURING FLT PLANNING 5) FAILURE TO CONTACT FSS TO ADVISE OF FUEL CONCERNS, REQUEST INFO, ASSISTANCE AND/OR DECLARE EMER. FUEL GAUGES WERE BEHAVING ABNORMALLY. I INITIALLY DISCOUNTED IT, ATTRIBUTING IT TO 'THOSE UNRELIABLE CESSNA FUEL GAUGES.' I DID CHK THAT THE FUEL SELECTOR VALVE WAS PHYSICALLY IN THE 'BOTH' TANKS DETENT. SOME FEW MINS LATER, I OBSERVED THAT THE R TANK GAUGE WAS INDICATING 'FULL' AND THE L TANK GAUGE WAS INDICATING 'EMPTY.' I HAD PERSONALLY VISUALLY CHKED AND DIPSTICKED BOTH TANKS DURING PREFLT INSPECTION, CONFIRMING THAT I HAD 69 GALLONS ABOARD (OVER 5 HRS TO FUEL EXHAUSTION) FOR A PLANNED FLT OF 2 HRS. I REPLACED AND SECURED THE FUEL CAPS. I NOW FELT FORCED TO CONCLUDE THAT A FUEL CAP MUST BE MISSING, SIPHONING FUEL FROM ONE (OR BOTH!) TANKS(S). ABOUT 20 NM FROM MY INTENDED DEST (GLH), I REDUCED PWR, SLOWED THE ACFT TO APCH SPD, AND BEGAN A GENTLE DSCNT TOWARDS GLH, HOPING TO CONSERVE THE FUEL REMAINING TO TOUCHDOWN. I LOOKED AT THE SECTIONAL CHART FOR THE FACILITY'S COM FREQ AND SAW ONLY UNICOM 122.95 WHICH I CALLED TWICE WITHOUT RESPONSE. AS I NEARED THE ARPT VICINITY, ASSUMING THE CTL ZONE WAS NOT ACTIVE, I SEARCHED FOR ANY ACFT IN THE PATTERN OR TAXIING -- SEEING NONE. I MONITORED UNICOM FOR TFC ANNOUNCEMENTS. NOT SEEING OR HEARING ANY TFC, I CHOSE RWY 36R SINCE IT WAS CLOSEST. I LANDED ON RWY 36R, TAXIED IN AND PARKED AT THE FBO. I INSPECTED THE ACFT AND DISCOVERED THAT THE L FUEL TANK FILLER CAP WAS MISSING. DIPSTICKING THE TANKS, I FOUND LESS THAN 5 GALLONS IN THE L TANK AND APPROX 12 GALLONS IN THE R TANK. AFTER DISCUSSING THE INCIDENT BY TELEPHONE WITH CTL TWR PERSONNEL, I MENTALLY REVIEWED THE EVENTS OF THE FLT AND NOW KNOW THAT THE CTL TWR WAS IN OP. I FOUND THAT IN PLANNING THE TRIP I HAD DRAWN MY NEXT LEG COURSE DIRECTLY OVER THE CTL TWR FREQ, PARTIALLY OBSCURING IT. I HAVE RESOLVED TO: 1) PAY EXTRA ATTN TO ASSURING FUEL AND OIL CAP SECURITY PRIOR TO ANY FLT. 2) ALWAYS PREPARE A LIST OF COM FREQS. 3) NOTIFY FSS IMMEDIATELY UPON DISCOVERING ANY INFLT ACFT DISCREPANCY OR PROBS. 4) NEVER DRAW COURSE LINES THROUGH/OVER ARPT, NAV OR COMS FREQ INFO. 5) RELATE THIS EXPERIENCE PUBLICLY AT THE NEXT FLT SAFETY MEETINGS THAT I ATTEND.

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.