Narrative:

While talking to operations, the captain received a clearance to FL240. I did not hear the clearance myself, but observed the captain dialing in the newly assigned altitude (FL240). Per company policy, he pointed at the new altitude until I acknowledged it (by also pointing to it with my finger). Since the captain did not start the descent, I assumed it was issued as a pilot's discretion descent. I finished talking with operations and then assumed control of VHF #1, the primary ATC radio. Shortly after taking control of it, the controller asked us to verify our altitude. I responded 'FL310.' he then directed us to descend and maintain FL240 and said 'I told you to start your descent.' I acknowledged and we immediately began our descent. There were no TCASII RA's or other verbal indications that our short delay in complying with the ATC clearance resulted in any procedural problems (ie, loss of separation, etc.)

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Original NASA ASRS Text

Title: A B737-400 FO OBSERVED THE CAPT PERFORM THE PROPER ALT CHANGING PROC, BUT HE DID NOT INSURE THAT THE CAPT ACTUALLY EXECUTED THE DSCNT REQUESTED BY ZOA.

Narrative: WHILE TALKING TO OPS, THE CAPT RECEIVED A CLRNC TO FL240. I DID NOT HEAR THE CLRNC MYSELF, BUT OBSERVED THE CAPT DIALING IN THE NEWLY ASSIGNED ALT (FL240). PER COMPANY POLICY, HE POINTED AT THE NEW ALT UNTIL I ACKNOWLEDGED IT (BY ALSO POINTING TO IT WITH MY FINGER). SINCE THE CAPT DID NOT START THE DSCNT, I ASSUMED IT WAS ISSUED AS A PLT'S DISCRETION DSCNT. I FINISHED TALKING WITH OPS AND THEN ASSUMED CTL OF VHF #1, THE PRIMARY ATC RADIO. SHORTLY AFTER TAKING CTL OF IT, THE CTLR ASKED US TO VERIFY OUR ALT. I RESPONDED 'FL310.' HE THEN DIRECTED US TO DSND AND MAINTAIN FL240 AND SAID 'I TOLD YOU TO START YOUR DSCNT.' I ACKNOWLEDGED AND WE IMMEDIATELY BEGAN OUR DSCNT. THERE WERE NO TCASII RA'S OR OTHER VERBAL INDICATIONS THAT OUR SHORT DELAY IN COMPLYING WITH THE ATC CLRNC RESULTED IN ANY PROCEDURAL PROBS (IE, LOSS OF SEPARATION, ETC.)

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.