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.