Narrative:

IFR aircraft was handed off to me inbound to alx which is a non-towered airport. I instructed the aircraft to expect the GPS runway 36 approach. The pilot asked for vectors to final. I told him to expect the vectors but considered it annoying because it would have been much easier for him to go direct to tatme (straight-in IAF). At about 15 NM sse of the airport; I cleared him '14 mi from billp; maintain 3000 ft until established on the final approach course; cleared GPS runway 36 approach.' a min or two later; just east of tatme; he told me that he had broken out at 2200 ft. I asked him to verify that he was established on the final approach course (since he appeared to be east of tatme) and he replied that he was. I told him that the chart indicated an altitude restr of 2500 ft until the FAF. He replied that his chart indicated 2200 ft. I noticed that the NDB or GPS-a approach had a 2200 ft altitude; so I asked him to verify that he was flying the 'GPS runway 36 approach.' he said; 'affirmative; the GPS-a approach.' I advised him that the GPS 36 and the GPS-a were different approachs and he was not flying the one that he had been cleared for. He apologized and said he was VFR and could cancel his IFR flight plan; which he did. In this particular case; I don't think safety was compromised because he did fly a valid; serviceable approach and no other aircraft were a factor. It could have been a problem if other aircraft were nearby or if I had chosen an approach because the other was notamed as not authority/authorized. Upon reviewing the issue to figure out how I could do better; I came to the realization that an approach named RNAV (GPS) runway 36 should probably be referred to as the RNAV runway 36 approach; even if the pilot is using GPS to fly it. This is a somewhat subtle difference from one labeled NDB 'or' GPS. I will change my technique now to call these RNAV (GPS) approachs 'RNAV' instead of GPS.

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Original NASA ASRS Text

Title: MGM CTLR REPORTED ACFT FLEW WRONG APCH PROC TO ALX WHEN IN FACT CLRNC ISSUED WAS NOT COMPLETE AND/OR ACCURATE.

Narrative: IFR ACFT WAS HANDED OFF TO ME INBOUND TO ALX WHICH IS A NON-TOWERED ARPT. I INSTRUCTED THE ACFT TO EXPECT THE GPS RWY 36 APCH. THE PLT ASKED FOR VECTORS TO FINAL. I TOLD HIM TO EXPECT THE VECTORS BUT CONSIDERED IT ANNOYING BECAUSE IT WOULD HAVE BEEN MUCH EASIER FOR HIM TO GO DIRECT TO TATME (STRAIGHT-IN IAF). AT ABOUT 15 NM SSE OF THE ARPT; I CLRED HIM '14 MI FROM BILLP; MAINTAIN 3000 FT UNTIL ESTABLISHED ON THE FINAL APCH COURSE; CLRED GPS RWY 36 APCH.' A MIN OR TWO LATER; JUST E OF TATME; HE TOLD ME THAT HE HAD BROKEN OUT AT 2200 FT. I ASKED HIM TO VERIFY THAT HE WAS ESTABLISHED ON THE FINAL APCH COURSE (SINCE HE APPEARED TO BE E OF TATME) AND HE REPLIED THAT HE WAS. I TOLD HIM THAT THE CHART INDICATED AN ALT RESTR OF 2500 FT UNTIL THE FAF. HE REPLIED THAT HIS CHART INDICATED 2200 FT. I NOTICED THAT THE NDB OR GPS-A APCH HAD A 2200 FT ALT; SO I ASKED HIM TO VERIFY THAT HE WAS FLYING THE 'GPS RWY 36 APCH.' HE SAID; 'AFFIRMATIVE; THE GPS-A APCH.' I ADVISED HIM THAT THE GPS 36 AND THE GPS-A WERE DIFFERENT APCHS AND HE WAS NOT FLYING THE ONE THAT HE HAD BEEN CLRED FOR. HE APOLOGIZED AND SAID HE WAS VFR AND COULD CANCEL HIS IFR FLT PLAN; WHICH HE DID. IN THIS PARTICULAR CASE; I DON'T THINK SAFETY WAS COMPROMISED BECAUSE HE DID FLY A VALID; SERVICEABLE APCH AND NO OTHER ACFT WERE A FACTOR. IT COULD HAVE BEEN A PROB IF OTHER ACFT WERE NEARBY OR IF I HAD CHOSEN AN APCH BECAUSE THE OTHER WAS NOTAMED AS NOT AUTH. UPON REVIEWING THE ISSUE TO FIGURE OUT HOW I COULD DO BETTER; I CAME TO THE REALIZATION THAT AN APCH NAMED RNAV (GPS) RWY 36 SHOULD PROBABLY BE REFERRED TO AS THE RNAV RWY 36 APCH; EVEN IF THE PLT IS USING GPS TO FLY IT. THIS IS A SOMEWHAT SUBTLE DIFFERENCE FROM ONE LABELED NDB 'OR' GPS. I WILL CHANGE MY TECHNIQUE NOW TO CALL THESE RNAV (GPS) APCHS 'RNAV' INSTEAD OF GPS.

Data retrieved from NASA's ASRS site as of January 2009 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.