Narrative:

On approach to lex, radar vectors to ILS runway 22 final, both my first officer and I understood a clearance to descend to 2300'. I read it back, it was acknowledged, and I set it in the altitude alerter. My first officer said later that he knew that was below guide slope intercept altitude but we were VMC, and the intercept altitude for runway 4 is 2000' so he assumed, as did I, that 2300' was a minimum vectoring altitude. After leveling at 2300' and approximately 1 1/2 minutes, the controller called and said, '...maintain 3200'.' I answered back that we were already at 2300' but were climbing to 3200'. After about 30 seconds hesitation, the controller asked our flight conditions, to which I said, 'VFR'. I told him that I understood we were cleared to 2300'. Nothing else was said about it. At that time I noticed the intercept altitude to be 3200'. Upon landing I phoned the tower. The controller was not upset, (nor was I since we were in VMC), but in the conversation, we both realized that each one had been confident that the other had erred. I feel that had I reviewed the approach better, I would have been more alert to the difference between the 'cleared to' altitude and published intercept altitude. Then I would have queried the controller. If indeed we were issued 3200', the controller simply missed my readback. If it was 2300', then he erred.

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Original NASA ASRS Text

Title: ACR MLG ALT DEVIATION DURING RADAR VECTORS FOR ILS APCH.

Narrative: ON APCH TO LEX, RADAR VECTORS TO ILS RWY 22 FINAL, BOTH MY F/O AND I UNDERSTOOD A CLRNC TO DSND TO 2300'. I READ IT BACK, IT WAS ACKNOWLEDGED, AND I SET IT IN THE ALT ALERTER. MY F/O SAID LATER THAT HE KNEW THAT WAS BELOW GUIDE SLOPE INTERCEPT ALT BUT WE WERE VMC, AND THE INTERCEPT ALT FOR RWY 4 IS 2000' SO HE ASSUMED, AS DID I, THAT 2300' WAS A MINIMUM VECTORING ALT. AFTER LEVELING AT 2300' AND APPROX 1 1/2 MINUTES, THE CTLR CALLED AND SAID, '...MAINTAIN 3200'.' I ANSWERED BACK THAT WE WERE ALREADY AT 2300' BUT WERE CLIMBING TO 3200'. AFTER ABOUT 30 SECONDS HESITATION, THE CTLR ASKED OUR FLT CONDITIONS, TO WHICH I SAID, 'VFR'. I TOLD HIM THAT I UNDERSTOOD WE WERE CLRED TO 2300'. NOTHING ELSE WAS SAID ABOUT IT. AT THAT TIME I NOTICED THE INTERCEPT ALT TO BE 3200'. UPON LNDG I PHONED THE TWR. THE CTLR WAS NOT UPSET, (NOR WAS I SINCE WE WERE IN VMC), BUT IN THE CONVERSATION, WE BOTH REALIZED THAT EACH ONE HAD BEEN CONFIDENT THAT THE OTHER HAD ERRED. I FEEL THAT HAD I REVIEWED THE APCH BETTER, I WOULD HAVE BEEN MORE ALERT TO THE DIFFERENCE BETWEEN THE 'CLRED TO' ALT AND PUBLISHED INTERCEPT ALT. THEN I WOULD HAVE QUERIED THE CTLR. IF INDEED WE WERE ISSUED 3200', THE CTLR SIMPLY MISSED MY READBACK. IF IT WAS 2300', THEN HE ERRED.

Data retrieved from NASA's ASRS site as of August 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.