Narrative:

I was flying the cessna 172 rg for currency reasons. It was a sunny; mostly clear afternoon and there were a few aircraft flying in the airport traffic pattern. Because this was a currency flight; I was staying in the traffic pattern as well. As I finished the run-up near the active runway; I completed the before take-off checklist with tower talking in my headset to the other traffic in the pattern. Without verifying; I assumed I was on the tower frequency. It wasn't long before tower cleared me for takeoff for closed traffic. Upon making my second landing; I took-off and made right hand traffic for my last landing. As I called tower for my position on the right downwind; I was informed of landing traffic at my 2 o'clock position; 1;700 ft (MSL) about 1.5 to 2 miles on final approach. What I believe I saw as the landing traffic; at my two o'clock position and on final approach; I called tower and told them I had the traffic in sight. I waited approximately five more seconds until I made my right base turn to give proper separation (after what I thought the traffic was; had past my right wingtip). After turning base I looked one more time at the approach end of the runway; turned my final approach and completed the remaining before landing checklist items. It had not been longer than a few seconds when I saw the other single engine airplane in front of me and below me by a couple hundred feet. As soon as I saw this airplane; I immediately stopped my descent; and rolled into a left 360 degree turn and instructed tower of my actions. It was while I was performing this turn I heard tower tell the other aircraft he wasn't sure of my exact position; but knew I was behind the other airplane; and told the other airplane that I had verified him; as the traffic; 'in sight'. By the time I made my landing; the other aircraft had been taxiing down the taxiway parallel to the runway. He then told tower that I had probably been on the ground frequency; and as I looked at my radio stack; I confirmed my radio was still on the ground frequency. What I believe as the major contributing factor in this case is first; I was communicating with tower on the ground frequency; and second; I must have not been aware of a third landing airplane and mistakenly understood that landing airplane as the landing traffic I was looking for and verified it as. The confusion started; unrealized by me; when I didn't catch the fact that tower was communicating on both the ground frequency and tower frequency; and I should have verified I was operating on the tower frequency. The pilot; when operating with other aircraft in the traffic pattern; should recognize how many planes are in the pattern and where they are at all times; never losing sight; and if traffic is lost; making sure to report that traffic is lost so that ATC can separate aircraft appropriately. Human performance was not an issue at all in this case. Proper self assessments are always made before I personally fly and this was a matter of confusion; misunderstanding of communications between myself and the tower; and an unfortunate circumstance.

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Original NASA ASRS Text

Title: C172RG pilot reports a NMAC with another aircraft in the VFR traffic pattern after misidentifying the aircraft he was assigned to follow by the Tower. The Tower was transmitting on both tower and ground frequencies and the reporter had neglected to switch to Tower frequency prior to the first takeoff; adding to the confusion.

Narrative: I was flying the Cessna 172 RG for currency reasons. It was a sunny; mostly clear afternoon and there were a few aircraft flying in the airport traffic pattern. Because this was a currency flight; I was staying in the traffic pattern as well. As I finished the run-up near the active runway; I completed the Before Take-Off checklist with Tower talking in my headset to the other traffic in the pattern. Without verifying; I assumed I was on the Tower frequency. It wasn't long before Tower cleared me for takeoff for closed traffic. Upon making my second landing; I took-off and made right hand traffic for my last landing. As I called Tower for my position on the right downwind; I was informed of landing traffic at my 2 o'clock position; 1;700 FT (MSL) about 1.5 to 2 miles on final approach. What I believe I saw as the landing traffic; at my two o'clock position and on final approach; I called Tower and told them I had the traffic in sight. I waited approximately five more seconds until I made my right base turn to give proper separation (after what I thought the traffic was; had past my right wingtip). After turning base I looked one more time at the approach end of the runway; turned my final approach and completed the remaining Before Landing checklist items. It had not been longer than a few seconds when I saw the other single engine airplane in front of me and below me by a couple hundred feet. As soon as I saw this airplane; I immediately stopped my descent; and rolled into a left 360 degree turn and instructed Tower of my actions. It was while I was performing this turn I heard Tower tell the other aircraft he wasn't sure of my exact position; but knew I was behind the other airplane; and told the other airplane that I had verified him; as the traffic; 'in sight'. By the time I made my landing; the other aircraft had been taxiing down the taxiway parallel to the runway. He then told Tower that I had probably been on the Ground frequency; and as I looked at my radio stack; I confirmed my radio was still on the Ground frequency. What I believe as the major contributing factor in this case is first; I was communicating with Tower on the Ground frequency; and second; I must have not been aware of a third landing airplane and mistakenly understood that landing airplane as the landing traffic I was looking for and verified it as. The confusion started; unrealized by me; when I didn't catch the fact that Tower was communicating on both the Ground frequency and Tower frequency; and I should have verified I was operating on the Tower frequency. The pilot; when operating with other aircraft in the traffic pattern; should recognize how many planes are in the pattern and where they are at all times; never losing sight; and if traffic is lost; making sure to report that traffic is lost so that ATC can separate aircraft appropriately. Human performance was not an issue at all in this case. Proper self assessments are always made before I personally fly and this was a matter of confusion; misunderstanding of communications between myself and the Tower; and an unfortunate circumstance.

Data retrieved from NASA's ASRS site as of April 2012 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.