Narrative:

I was 15 mi northwest of gallatin field inbound for landing when I tuned in the advisory frequency of 123.6. This is mistake #1. I had two montana airport directories with me and I inadvertently used the older issue which listed that frequency. The correct frequency was 123.65. At 10 mi northwest, I reported my position, altitude, and intentions to land straight in on runway 12. I thought it odd that there was no response but continued on, thinking that it was just an advisory service and since I didn't ask for any information, they didn't give me any. I scanned the area, saw nothing in sight, and decided to see what an ILS approach would be like into this airport since I am starting instrument training. Mistake #2. I should have verified contact with the controling agency before lining up on an instrument approach path. At 5 mi northwest, I announced my position, altitude, nd intention to land straight in on runway 12, again. I was beginning to worry about this lack of communication when I reported again at 3 mi northwest, got no response, and saw an aircraft just taking off on runway 12. At this same moment I saw an air carrier mg above and to the side of my flight path approximately 200' vertical and 1000' horizontal. I could see he was in an apparent go around and I elected to land. When stopped on the ramp I searched for what I thought was a bad connection in the headset plugins or a radio problem. I discovered my error in frequency selection just in time to see an airline captain coming to greet me after a 1/2 mi walk from the main terminal where he parked the medium large transport. He informed me that we would have missed by as little as 100' when he overtook me from above on the ILS runway 12 approach. To correct this problem I will work with an instructor on proper radio procedures, and keep only current flight information, and spend more time on flight planning. I feel very fortunate that no person was harmed by my negligent actions on this day.

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Original NASA ASRS Text

Title: NON TWR ARPT. TUNED WRONG CTAF FREQ RESULTING IN NMAC WITH ACR ON STRAIGHT IN APCH.

Narrative: I WAS 15 MI NW OF GALLATIN FIELD INBND FOR LNDG WHEN I TUNED IN THE ADVISORY FREQ OF 123.6. THIS IS MISTAKE #1. I HAD TWO MONTANA ARPT DIRECTORIES WITH ME AND I INADVERTENTLY USED THE OLDER ISSUE WHICH LISTED THAT FREQ. THE CORRECT FREQ WAS 123.65. AT 10 MI NW, I RPTED MY POS, ALT, AND INTENTIONS TO LAND STRAIGHT IN ON RWY 12. I THOUGHT IT ODD THAT THERE WAS NO RESPONSE BUT CONTINUED ON, THINKING THAT IT WAS JUST AN ADVISORY SVC AND SINCE I DIDN'T ASK FOR ANY INFO, THEY DIDN'T GIVE ME ANY. I SCANNED THE AREA, SAW NOTHING IN SIGHT, AND DECIDED TO SEE WHAT AN ILS APCH WOULD BE LIKE INTO THIS ARPT SINCE I AM STARTING INSTRUMENT TRNING. MISTAKE #2. I SHOULD HAVE VERIFIED CONTACT WITH THE CTLING AGENCY BEFORE LINING UP ON AN INSTRUMENT APCH PATH. AT 5 MI NW, I ANNOUNCED MY POS, ALT, ND INTENTION TO LAND STRAIGHT IN ON RWY 12, AGAIN. I WAS BEGINNING TO WORRY ABOUT THIS LACK OF COM WHEN I RPTED AGAIN AT 3 MI NW, GOT NO RESPONSE, AND SAW AN ACFT JUST TAKING OFF ON RWY 12. AT THIS SAME MOMENT I SAW AN ACR MG ABOVE AND TO THE SIDE OF MY FLT PATH APPROX 200' VERT AND 1000' HORIZ. I COULD SEE HE WAS IN AN APPARENT GO AROUND AND I ELECTED TO LAND. WHEN STOPPED ON THE RAMP I SEARCHED FOR WHAT I THOUGHT WAS A BAD CONNECTION IN THE HEADSET PLUGINS OR A RADIO PROB. I DISCOVERED MY ERROR IN FREQ SELECTION JUST IN TIME TO SEE AN AIRLINE CAPT COMING TO GREET ME AFTER A 1/2 MI WALK FROM THE MAIN TERMINAL WHERE HE PARKED THE MLG. HE INFORMED ME THAT WE WOULD HAVE MISSED BY AS LITTLE AS 100' WHEN HE OVERTOOK ME FROM ABOVE ON THE ILS RWY 12 APCH. TO CORRECT THIS PROB I WILL WORK WITH AN INSTRUCTOR ON PROPER RADIO PROCS, AND KEEP ONLY CURRENT FLT INFO, AND SPEND MORE TIME ON FLT PLANNING. I FEEL VERY FORTUNATE THAT NO PERSON WAS HARMED BY MY NEGLIGENT ACTIONS ON THIS DAY.

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.