Narrative:

I was on an IFR flight plan from athens, GA, to mc collum airport in marietta, GA. Mc collum is almost due west from athens, and I flew a heading of 276 degrees. I was told to expect the localizer 27 approach into mc collum, which requires radar in order to get to the IAF, which is called hobbo. I was brought down to 3000 ft and turned to a heading of 300 degrees so that I could swing out and then intercept the localizer. I was then told to intercept the localizer, and when the needle started moving, I turned inbound. Shortly thereafter, the controller told me that I was 14 mi from hobbo. Several mins passed before I was contacted again. The next transmission from the controller was misunderstood by me. What I thought he said was 'you're at hobbo, change to advisory approved, contact me on this frequency to cancel IFR either in the air or on the ground.' apparently, what the controller said was 'when you're at hobbo' but I must have missed the word 'when.' I called back and said 'understand at hobbo frequency change approved and will call back to cancel on this frequency.' the controller acknowledged. There are only 2 ways to know that you're at hobbo: by the marker beacon light flashing in the plane and by the controller telling you by looking at his radar. The beacon at hobbo has been known to fail, so even though the marker beacon light wasn't flashing, I thought the controller was calling hobbo for me. I started my descent and my timer, changed to advisory, and announced that I was at hobbo inbound. I leveled off at 1500 ft and started looking for the airport. When it came into sight, I changed back to approach control and said, 'approach has mc collum in sight and I'll cancel IFR at this time.' the controller's reply was 'I've been trying to call you. You descended way before hobbo. You need to be more careful. Your cancellation is received, frequency change approved, and have a good night.' after I changed back to advisory, my marker beacon started flashing. Once on the ground, I telephoned the approach control facility and spoke with the floor manager. I explained to him that I had misunderstood the controller and why I had descended early. He said that 'I had scared them both' and that they thought that I had 'gone in.' he explained that his next job would have been to call the highway patrol to go looking for me and that I need to be more careful. In my opinion, there were 2 factors contributing to this situation: 1) word choice: not only were the words used by the controller misleading and easy to confuse, but mine were as well, because the controller could not tell there was a discrepancy by my readback. This is the reason why we have them in the first place. Also, if I was that far away from hobbo, he should not have been talking about my frequency change already. That led to my further confusion. 2) lack of questioning by pilot: when I thought the controller was telling me I was at hobbo even though my marker beacon was not flashing, I should have double-checked this with the controller.

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Original NASA ASRS Text

Title: SMA PLT ON APCH MISINTERPRETS CLRNC, DSNDS BEFORE FAF.

Narrative: I WAS ON AN IFR FLT PLAN FROM ATHENS, GA, TO MC COLLUM ARPT IN MARIETTA, GA. MC COLLUM IS ALMOST DUE W FROM ATHENS, AND I FLEW A HDG OF 276 DEGS. I WAS TOLD TO EXPECT THE LOC 27 APCH INTO MC COLLUM, WHICH REQUIRES RADAR IN ORDER TO GET TO THE IAF, WHICH IS CALLED HOBBO. I WAS BROUGHT DOWN TO 3000 FT AND TURNED TO A HDG OF 300 DEGS SO THAT I COULD SWING OUT AND THEN INTERCEPT THE LOC. I WAS THEN TOLD TO INTERCEPT THE LOC, AND WHEN THE NEEDLE STARTED MOVING, I TURNED INBOUND. SHORTLY THEREAFTER, THE CTLR TOLD ME THAT I WAS 14 MI FROM HOBBO. SEVERAL MINS PASSED BEFORE I WAS CONTACTED AGAIN. THE NEXT XMISSION FROM THE CTLR WAS MISUNDERSTOOD BY ME. WHAT I THOUGHT HE SAID WAS 'YOU'RE AT HOBBO, CHANGE TO ADVISORY APPROVED, CONTACT ME ON THIS FREQ TO CANCEL IFR EITHER IN THE AIR OR ON THE GND.' APPARENTLY, WHAT THE CTLR SAID WAS 'WHEN YOU'RE AT HOBBO' BUT I MUST HAVE MISSED THE WORD 'WHEN.' I CALLED BACK AND SAID 'UNDERSTAND AT HOBBO FREQ CHANGE APPROVED AND WILL CALL BACK TO CANCEL ON THIS FREQ.' THE CTLR ACKNOWLEDGED. THERE ARE ONLY 2 WAYS TO KNOW THAT YOU'RE AT HOBBO: BY THE MARKER BEACON LIGHT FLASHING IN THE PLANE AND BY THE CTLR TELLING YOU BY LOOKING AT HIS RADAR. THE BEACON AT HOBBO HAS BEEN KNOWN TO FAIL, SO EVEN THOUGH THE MARKER BEACON LIGHT WASN'T FLASHING, I THOUGHT THE CTLR WAS CALLING HOBBO FOR ME. I STARTED MY DSCNT AND MY TIMER, CHANGED TO ADVISORY, AND ANNOUNCED THAT I WAS AT HOBBO INBOUND. I LEVELED OFF AT 1500 FT AND STARTED LOOKING FOR THE ARPT. WHEN IT CAME INTO SIGHT, I CHANGED BACK TO APCH CTL AND SAID, 'APCH HAS MC COLLUM IN SIGHT AND I'LL CANCEL IFR AT THIS TIME.' THE CTLR'S REPLY WAS 'I'VE BEEN TRYING TO CALL YOU. YOU DSNDED WAY BEFORE HOBBO. YOU NEED TO BE MORE CAREFUL. YOUR CANCELLATION IS RECEIVED, FREQ CHANGE APPROVED, AND HAVE A GOOD NIGHT.' AFTER I CHANGED BACK TO ADVISORY, MY MARKER BEACON STARTED FLASHING. ONCE ON THE GND, I TELEPHONED THE APCH CTL FACILITY AND SPOKE WITH THE FLOOR MGR. I EXPLAINED TO HIM THAT I HAD MISUNDERSTOOD THE CTLR AND WHY I HAD DSNDED EARLY. HE SAID THAT 'I HAD SCARED THEM BOTH' AND THAT THEY THOUGHT THAT I HAD 'GONE IN.' HE EXPLAINED THAT HIS NEXT JOB WOULD HAVE BEEN TO CALL THE HWY PATROL TO GO LOOKING FOR ME AND THAT I NEED TO BE MORE CAREFUL. IN MY OPINION, THERE WERE 2 FACTORS CONTRIBUTING TO THIS SIT: 1) WORD CHOICE: NOT ONLY WERE THE WORDS USED BY THE CTLR MISLEADING AND EASY TO CONFUSE, BUT MINE WERE AS WELL, BECAUSE THE CTLR COULD NOT TELL THERE WAS A DISCREPANCY BY MY READBACK. THIS IS THE REASON WHY WE HAVE THEM IN THE FIRST PLACE. ALSO, IF I WAS THAT FAR AWAY FROM HOBBO, HE SHOULD NOT HAVE BEEN TALKING ABOUT MY FREQ CHANGE ALREADY. THAT LED TO MY FURTHER CONFUSION. 2) LACK OF QUESTIONING BY PLT: WHEN I THOUGHT THE CTLR WAS TELLING ME I WAS AT HOBBO EVEN THOUGH MY MARKER BEACON WAS NOT FLASHING, I SHOULD HAVE DOUBLE-CHKED THIS WITH THE CTLR.

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.