Narrative:

In moderate turbulence a requested des to FL310. Clearance denied due to air carrier Y 1.5 mi to left at FL310. Other aircraft was visually in sight. First officer was off radio using P/a to alert F/a's to be seated. I requested immediate vector and des to FL310 or FL280. Received turn of 35 degrees to right away from air carrier Y and des. I mentally accepted clearance to FL310 and believe I read back same. At approximately FL320 den ARTCC said we busted altitude. Air carrier Y was in sight, 5-6 NM diverging. The possibility exists that I erred in clearance. The safety situation is twofold. 1) I was alone in communication loop with first officer necessarily on P/a. Aircraft was very difficult to maintain radial and in moderate turbulence. Autoplt was in turbulence mode. 2) flight plan was oma to slc via lnk-hct-gil-che-ffu-slo. Den ARTCC changed it en route to dir den-J116-ffu-slc, resulting in flow concentration over den that prevented altitude flexibility on a day of exceptional turbulence. Original routing was more logical but ATC likes everyone to line up for flow control concentrating aircraft aloft. Supplemental information from acn 80645: we had turned 35 degrees to the right and were descending through FL320. Den called to ask to what altitude we were descending and I responded, after checking with captain, FL310. Den said our limit was FL330 and to immediately climb to FL330 with a further turn to right.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 ACR AFTER ACR X DESCENDED BELOW ASSIGNED ALT.

Narrative: IN MODERATE TURBULENCE A REQUESTED DES TO FL310. CLRNC DENIED DUE TO ACR Y 1.5 MI TO LEFT AT FL310. OTHER ACFT WAS VISUALLY IN SIGHT. F/O WAS OFF RADIO USING P/A TO ALERT F/A'S TO BE SEATED. I REQUESTED IMMEDIATE VECTOR AND DES TO FL310 OR FL280. RECEIVED TURN OF 35 DEGS TO RIGHT AWAY FROM ACR Y AND DES. I MENTALLY ACCEPTED CLRNC TO FL310 AND BELIEVE I READ BACK SAME. AT APPROX FL320 DEN ARTCC SAID WE BUSTED ALT. ACR Y WAS IN SIGHT, 5-6 NM DIVERGING. THE POSSIBILITY EXISTS THAT I ERRED IN CLRNC. THE SAFETY SITUATION IS TWOFOLD. 1) I WAS ALONE IN COM LOOP WITH F/O NECESSARILY ON P/A. ACFT WAS VERY DIFFICULT TO MAINTAIN RADIAL AND IN MODERATE TURBULENCE. AUTOPLT WAS IN TURBULENCE MODE. 2) FLT PLAN WAS OMA TO SLC VIA LNK-HCT-GIL-CHE-FFU-SLO. DEN ARTCC CHANGED IT ENRTE TO DIR DEN-J116-FFU-SLC, RESULTING IN FLOW CONCENTRATION OVER DEN THAT PREVENTED ALT FLEXIBILITY ON A DAY OF EXCEPTIONAL TURBULENCE. ORIGINAL ROUTING WAS MORE LOGICAL BUT ATC LIKES EVERYONE TO LINE UP FOR FLOW CTL CONCENTRATING ACFT ALOFT. SUPPLEMENTAL INFORMATION FROM ACN 80645: WE HAD TURNED 35 DEGS TO THE RIGHT AND WERE DSNDING THROUGH FL320. DEN CALLED TO ASK TO WHAT ALT WE WERE DSNDING AND I RESPONDED, AFTER CHKING WITH CAPT, FL310. DEN SAID OUR LIMIT WAS FL330 AND TO IMMEDIATELY CLB TO FL330 WITH A FURTHER TURN TO RIGHT.

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.