Narrative:

While level in cruise, 28 NM from the ft pierce airport (destination) on an IFR flight plan in VMC conditions, was given and read back a clearance to descend at pilot's discretion from 6000 ft to 3000 ft. While passing through 3500 ft another controller questioned my last assigned altitude. I repeated the clearance, pilot's discretion down to 3000 ft. He stated the clearance was to 4000 ft, did not ask me to stop and continued to allow my descent. Upon reaching the destination airport, I was advised by tower to phone ZMA. Later after having 2 phone conversations the supervisor stated that she had reviewed the tapes and it appeared that I was only cleared to 4000 ft. I found this hard to believe since I, without doubt, repeated the clearance twice and set the altitude that I was cleared to in my altitude bug. The possibility does exist that I may have made a mistake and deviated from the cleared to altitude, but not intentionally. I later found that another aircraft (unk) was given heading changes to avoid a conflict, but was not advised of any traffic in the area that I was to be aware of, at the time. I believe that if the word 'maintain' had been used with the clearance limit, then I may have been alerted to possible traffic, and if I did deviate from the assigned altitude, then the word 'maintain' would have helped identify the altitude that I was cleared to.

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Original NASA ASRS Text

Title: PLT OF AN SMA SEL OVERSHOT DSCNT ALT.

Narrative: WHILE LEVEL IN CRUISE, 28 NM FROM THE FT PIERCE ARPT (DEST) ON AN IFR FLT PLAN IN VMC CONDITIONS, WAS GIVEN AND READ BACK A CLRNC TO DSND AT PLT'S DISCRETION FROM 6000 FT TO 3000 FT. WHILE PASSING THROUGH 3500 FT ANOTHER CTLR QUESTIONED MY LAST ASSIGNED ALT. I REPEATED THE CLRNC, PLT'S DISCRETION DOWN TO 3000 FT. HE STATED THE CLRNC WAS TO 4000 FT, DID NOT ASK ME TO STOP AND CONTINUED TO ALLOW MY DSCNT. UPON REACHING THE DEST ARPT, I WAS ADVISED BY TWR TO PHONE ZMA. LATER AFTER HAVING 2 PHONE CONVERSATIONS THE SUPVR STATED THAT SHE HAD REVIEWED THE TAPES AND IT APPEARED THAT I WAS ONLY CLRED TO 4000 FT. I FOUND THIS HARD TO BELIEVE SINCE I, WITHOUT DOUBT, REPEATED THE CLRNC TWICE AND SET THE ALT THAT I WAS CLRED TO IN MY ALT BUG. THE POSSIBILITY DOES EXIST THAT I MAY HAVE MADE A MISTAKE AND DEVIATED FROM THE CLRED TO ALT, BUT NOT INTENTIONALLY. I LATER FOUND THAT ANOTHER ACFT (UNK) WAS GIVEN HDG CHANGES TO AVOID A CONFLICT, BUT WAS NOT ADVISED OF ANY TFC IN THE AREA THAT I WAS TO BE AWARE OF, AT THE TIME. I BELIEVE THAT IF THE WORD 'MAINTAIN' HAD BEEN USED WITH THE CLRNC LIMIT, THEN I MAY HAVE BEEN ALERTED TO POSSIBLE TFC, AND IF I DID DEVIATE FROM THE ASSIGNED ALT, THEN THE WORD 'MAINTAIN' WOULD HAVE HELPED IDENT THE ALT THAT I WAS CLRED TO.

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.