Narrative:

I was delivering the plane [for] maintenance. During preflight I noticed the left fuel tank was 1/4 full and the right fuel tank 1/2 full indicating 20 gallons of fuel or 2.7 hours according to the gauges and a look into the tanks. This should be plenty of fuel for a less than 22 hour flight. For maintenance purposes; I wanted the left tank empty. I departed with the fuel selector on 'both;' switching to the left tank at 3;500 ft over the reservoir. I switched the fuel selector to the right tank about 10 miles from the flights midpoint thinking I had about 2 hours fuel left for the additional 43 minutes to my destination. When I switched from left to right tank the gauge indicated 1/2 full. I checked 1 minute later and again in 1 more minute and the gauge still indicated 1/2 full. I checked the gauge again in 2 minutes and it indicated empty. The right gauge sender was overhauled one month earlier and this was the first tank of fuel since repair. This new reading caused some concern so I pushed 'nearest' on my GPS. It informed me a suitable airport was 7.5 miles to my 7 o'clock. I immediately turned toward it and looked on my chart for the frequency. The airport I selected was a class east airport and not sensing an error I dialed in 122.8 and announced my intentions to that airport CTAF traffic. I could see the airport runway and saw no traffic and hearing nothing; I said I would land down wind on runway 14. I did just that noticing an aircraft several hundred feet above me and climbing. The reason I was looking for traffic was because I was landing down wind and if I saw traffic I could have used the taxiway; grass or ramp for that matter; if necessary. I landed; taxied off to the ramp area and shut down. A fellow in an airport truck drove up to me and said I did not contact the tower. He was correct as I contacted the wrong airport. When I saw this airport on my GPS and on my chart I did not realize there were two airports with same name. The gentlemen gave me the tower phone number which I called immediately to explain what happened. He was very nice and handed me off to his boss. I explained to them as well; adding that I thought it was safer to do what I did instead of taking a chance the gauge was correct on last reading and try to continue; run out of fuel and land in hostile terrain. Landing at an airport and purchase fuel seemed to be my best option; so that is what I did. The supervisor informed me that their supervisor would like to call me the next day or week so I provided both my home and cell numbers. I then filled the right tank with 20 gallons telling me there were 6 gallons left. I then followed proper procedures and departed for my destination. The most egregious error made by me was landing at a towered airport using the wrong frequency. I did not actually see the tower until I shut down and was told where to look. I was far more focused on flying the aircraft and a safe landing than anything else due to a perceived) low fuel problem. I now know there are at least two same name airports. I discovered the airport I used has several names. This is a bit confusing to a tourist. In the future I shall be more careful in selecting the proper frequency for the airport I intend to use as this has never happened to me before. I shall get the gauge problem resolved.

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Original NASA ASRS Text

Title: A C-170 pilot became concerned that his fuel system was malfunctioning and so landed at the nearest suitable airport which turned out to be towered but he confused it with a similarly named nearby CTAF airport.

Narrative: I was delivering the plane [for] maintenance. During preflight I noticed the left fuel tank was 1/4 full and the right fuel tank 1/2 full indicating 20 gallons of fuel or 2.7 hours according to the gauges and a look into the tanks. This should be plenty of fuel for a less than 22 hour flight. For maintenance purposes; I wanted the left tank empty. I departed with the fuel selector on 'both;' switching to the left tank at 3;500 FT over the Reservoir. I switched the fuel selector to the right tank about 10 miles from the flights midpoint thinking I had about 2 hours fuel left for the additional 43 minutes to my destination. When I switched from left to right tank the gauge indicated 1/2 full. I checked 1 minute later and again in 1 more minute and the gauge still indicated 1/2 full. I checked the gauge again in 2 minutes and it indicated empty. The right gauge sender was overhauled one month earlier and this was the first tank of fuel since repair. This new reading caused some concern so I pushed 'nearest' on my GPS. It informed me a suitable airport was 7.5 miles to my 7 o'clock. I immediately turned toward it and looked on my chart for the frequency. The airport I selected was a Class E airport and not sensing an error I dialed in 122.8 and announced my intentions to that airport CTAF traffic. I could see the airport runway and saw no traffic and hearing nothing; I said I would land down wind on Runway 14. I did just that noticing an aircraft several hundred feet above me and climbing. The reason I was looking for traffic was because I was landing down wind and if I saw traffic I could have used the taxiway; grass or ramp for that matter; if necessary. I landed; taxied off to the ramp area and shut down. A fellow in an airport truck drove up to me and said I did not contact the Tower. He was correct as I contacted the wrong airport. When I saw this airport on my GPS and on my chart I did not realize there were two airports with same name. The gentlemen gave me the Tower phone number which I called immediately to explain what happened. He was very nice and handed me off to his boss. I explained to them as well; adding that I thought it was safer to do what I did instead of taking a chance the gauge was correct on last reading and try to continue; run out of fuel and land in hostile terrain. Landing at an airport and purchase fuel seemed to be my best option; so that is what I did. The Supervisor informed me that their Supervisor would like to call me the next day or week so I provided both my home and cell numbers. I then filled the right tank with 20 gallons telling me there were 6 gallons left. I then followed proper procedures and departed for my destination. The most egregious error made by me was landing at a towered airport using the wrong frequency. I did not actually see the Tower until I shut down and was told where to look. I was far more focused on flying the aircraft and a safe landing than anything else due to a perceived) low fuel problem. I now know there are at least two same name airports. I discovered the airport I used has several names. This is a bit confusing to a tourist. In the future I shall be more careful in selecting the proper frequency for the airport I intend to use as this has never happened to me before. I shall get the gauge problem resolved.

Data retrieved from NASA's ASRS site as of July 2013 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.