Narrative:

First officer flying with autoplt off due to turbulence. We requested FL280 and were told we had traffic at 12 O'clock at FL290 and we would be cleared to FL280 when clear of traffic. Shortly after this transmission, the aircraft descended approximately 300 ft. The first officer corrected back to FL310 and was there when center asked us if we were at FL310 and that we should maintain FL310. Traffic passed underneath us. A call to ARTCC after we landed, talked to an ATC controller X at ZME, revealed no traffic conflict occurred and, according to him, there was no problem.

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Original NASA ASRS Text

Title: CREW HAD AN ALTDEV.

Narrative: FO FLYING WITH AUTOPLT OFF DUE TO TURB. WE REQUESTED FL280 AND WERE TOLD WE HAD TFC AT 12 O'CLOCK AT FL290 AND WE WOULD BE CLRED TO FL280 WHEN CLR OF TFC. SHORTLY AFTER THIS XMISSION, THE ACFT DSNDED APPROX 300 FT. THE FO CORRECTED BACK TO FL310 AND WAS THERE WHEN CTR ASKED US IF WE WERE AT FL310 AND THAT WE SHOULD MAINTAIN FL310. TFC PASSED UNDERNEATH US. A CALL TO ARTCC AFTER WE LANDED, TALKED TO AN ATC CTLR X AT ZME, REVEALED NO TFC CONFLICT OCCURRED AND, ACCORDING TO HIM, THERE WAS NO PROB.

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.