Narrative:

On a wbound course to asn (talladega) from the ZTL controled area, I was told by ZTL to report field in sight and descend from cruise altitude of 6000 ft MSL to 5000 ft MSL and hold. I was told there was a B737 inbound to anniston which would cross my path. I was then told to switch to bhm approach. I reported in who I was and that I was descending to 5000 ft MSL as instructed by ZTL. Bhm approach came back and told me to descend to 4000 ft MSL and hold because there was a B737 en route. I called back that I would be descending to 4000 ft MSL as instructed and that I had the B737 in sight. After a few moments I noticed as I was descending through 4500 ft MSL to 4000 ft MSL as instructed that I was heading straight for the path of the B737. I called in and requested what altitude the B737 was at, and was told he was descending through to anniston and was already with anniston radio. I asked for immediate deviation left to avoid and began turning as the controller from bhm approach approved. He then asked me what my altitude was and I called back 4300 ft MSL descending to 4000 ft MSL as that was what I had been given as my assigned altitude. He then, angrily, came back to tell me that I was supposed to be at 5000 ft MSL and was not cleared for 4000 ft MSL. He told me to return to 5000 ft MSL immediately. I returned to 5000 ft MSL as requested at best climb I could manage. By this time the B737 as well as anniston airport were behind me and I was over my destination asn (talladega) at 5000 ft MSL. I called for further instructions and was told to hold visually over asn. I called back for an 'expect further clearance' time estimate and was not given any kind of concrete timeframe. I feel that the bhm controller either mistakenly gave me 4000 ft MSL as an assigned altitude or he did not hear my reply to what I thought was a clearance to 4000 ft MSL. He then became vindictive towards me till I canceled IFR over asn (talladega).

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Original NASA ASRS Text

Title: PA28 PLT IFR LNDG ASN HAS AN NMAC WITH A B737 RESULTING FROM CONFUSION OF ASSIGNED ALT.

Narrative: ON A WBOUND COURSE TO ASN (TALLADEGA) FROM THE ZTL CTLED AREA, I WAS TOLD BY ZTL TO RPT FIELD IN SIGHT AND DSND FROM CRUISE ALT OF 6000 FT MSL TO 5000 FT MSL AND HOLD. I WAS TOLD THERE WAS A B737 INBOUND TO ANNISTON WHICH WOULD CROSS MY PATH. I WAS THEN TOLD TO SWITCH TO BHM APCH. I RPTED IN WHO I WAS AND THAT I WAS DSNDING TO 5000 FT MSL AS INSTRUCTED BY ZTL. BHM APCH CAME BACK AND TOLD ME TO DSND TO 4000 FT MSL AND HOLD BECAUSE THERE WAS A B737 ENRTE. I CALLED BACK THAT I WOULD BE DSNDING TO 4000 FT MSL AS INSTRUCTED AND THAT I HAD THE B737 IN SIGHT. AFTER A FEW MOMENTS I NOTICED AS I WAS DSNDING THROUGH 4500 FT MSL TO 4000 FT MSL AS INSTRUCTED THAT I WAS HEADING STRAIGHT FOR THE PATH OF THE B737. I CALLED IN AND REQUESTED WHAT ALT THE B737 WAS AT, AND WAS TOLD HE WAS DSNDING THROUGH TO ANNISTON AND WAS ALREADY WITH ANNISTON RADIO. I ASKED FOR IMMEDIATE DEV L TO AVOID AND BEGAN TURNING AS THE CTLR FROM BHM APCH APPROVED. HE THEN ASKED ME WHAT MY ALT WAS AND I CALLED BACK 4300 FT MSL DSNDING TO 4000 FT MSL AS THAT WAS WHAT I HAD BEEN GIVEN AS MY ASSIGNED ALT. HE THEN, ANGRILY, CAME BACK TO TELL ME THAT I WAS SUPPOSED TO BE AT 5000 FT MSL AND WAS NOT CLRED FOR 4000 FT MSL. HE TOLD ME TO RETURN TO 5000 FT MSL IMMEDIATELY. I RETURNED TO 5000 FT MSL AS REQUESTED AT BEST CLB I COULD MANAGE. BY THIS TIME THE B737 AS WELL AS ANNISTON ARPT WERE BEHIND ME AND I WAS OVER MY DEST ASN (TALLADEGA) AT 5000 FT MSL. I CALLED FOR FURTHER INSTRUCTIONS AND WAS TOLD TO HOLD VISUALLY OVER ASN. I CALLED BACK FOR AN 'EXPECT FURTHER CLRNC' TIME ESTIMATE AND WAS NOT GIVEN ANY KIND OF CONCRETE TIMEFRAME. I FEEL THAT THE BHM CTLR EITHER MISTAKENLY GAVE ME 4000 FT MSL AS AN ASSIGNED ALT OR HE DID NOT HEAR MY REPLY TO WHAT I THOUGHT WAS A CLRNC TO 4000 FT MSL. HE THEN BECAME VINDICTIVE TOWARDS ME TILL I CANCELED IFR OVER ASN (TALLADEGA).

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.