Narrative:

I acknowledged our clearance for descent from FL290 to FL240. We were holding at eni along with a number of other aircraft for sfo. While on the outbnd leg, in the hold, we were cleared to a left turn on a southeast vector and a clearance out of FL290 to FL240. The captain started the turn, but did not begin his descent. I reminded him of the descent after about 1 1/2-2 mins. We received a clearance to FL230 while descending out of FL267 or so. Soon after that we received a clearance to maintain FL270 while we were descending through FL265 at 2000 FPM. Momentum carried the aircraft to 26200' MSL before the newly reassigned altitude of 27000' was reprogrammed into the FMC. Up to this time, there was no mention of conflict from ARTCC. Now at 26200', reprogrammed to FL270, throttles were at climb thrust and altitude began increasing. At that time, ATC asked for an immediate right turn to west and another aircraft in the hold over eni at 26000' was told to begin an immediate turn to an easterly heading and for us to call level at FL270. We called level at FL270. We were never told of a traffic conflict and did not have a visual contact on that other aircraft. We were also at FL262 and climbing in a right turn and he was below and left of us, so it would be difficult to see. Although by the ATC instructions and evasive turns, I guess there must have been. The captain heard the clearance, saw me put the new altitude into the altitude selector. The clearance contained a heading, altitude and speed, and also possibly some other information for leaving the fix. Part of my diversion was, I was heads down after resetting the altitude selector trying to program the FMC to exit the hold, and change the display on the HSI. During this time, I assumed the captain had begun his descent. When I finished programming and saw he was still at FL290 I reminded him of the new altitude. I can only assume the controller thought we were in our descent and at that rate should not have had a conflict alert. Callback conversation with reporter revealed the following: reporter and his captain did not make any inquiry with the center about what really happened and whether or not there was a conflict and loss of separation. To this day, reporter does not know if they lost separation with the aircraft at FL260. As indicated in the report, the controller gave immediate turns to both aircraft and climbed reporter's aircraft. Reporter does not believe that their slowness in leaving FL290 had anything to do with the possible loss of sep at FL260. Rather, he feels that the controller forgot about the aircraft at FL260 and mistakenly descended his aircraft through that altitude.

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Original NASA ASRS Text

Title: ACR MLG GIVEN DESCENT THOUGHT OCCUPIED ALT IN HOLDING PATTERN. CTLR GAVE EVASIVE TURNS AND CLIMB TO PRESERVE SEPARATION.

Narrative: I ACKNOWLEDGED OUR CLRNC FOR DSCNT FROM FL290 TO FL240. WE WERE HOLDING AT ENI ALONG WITH A NUMBER OF OTHER ACFT FOR SFO. WHILE ON THE OUTBND LEG, IN THE HOLD, WE WERE CLRED TO A LEFT TURN ON A SE VECTOR AND A CLRNC OUT OF FL290 TO FL240. THE CAPT STARTED THE TURN, BUT DID NOT BEGIN HIS DSCNT. I REMINDED HIM OF THE DSCNT AFTER ABOUT 1 1/2-2 MINS. WE RECEIVED A CLRNC TO FL230 WHILE DSNDING OUT OF FL267 OR SO. SOON AFTER THAT WE RECEIVED A CLRNC TO MAINTAIN FL270 WHILE WE WERE DSNDING THROUGH FL265 AT 2000 FPM. MOMENTUM CARRIED THE ACFT TO 26200' MSL BEFORE THE NEWLY REASSIGNED ALT OF 27000' WAS REPROGRAMMED INTO THE FMC. UP TO THIS TIME, THERE WAS NO MENTION OF CONFLICT FROM ARTCC. NOW AT 26200', REPROGRAMMED TO FL270, THROTTLES WERE AT CLB THRUST AND ALT BEGAN INCREASING. AT THAT TIME, ATC ASKED FOR AN IMMEDIATE RIGHT TURN TO W AND ANOTHER ACFT IN THE HOLD OVER ENI AT 26000' WAS TOLD TO BEGIN AN IMMEDIATE TURN TO AN EASTERLY HDG AND FOR US TO CALL LEVEL AT FL270. WE CALLED LEVEL AT FL270. WE WERE NEVER TOLD OF A TFC CONFLICT AND DID NOT HAVE A VISUAL CONTACT ON THAT OTHER ACFT. WE WERE ALSO AT FL262 AND CLBING IN A RIGHT TURN AND HE WAS BELOW AND LEFT OF US, SO IT WOULD BE DIFFICULT TO SEE. ALTHOUGH BY THE ATC INSTRUCTIONS AND EVASIVE TURNS, I GUESS THERE MUST HAVE BEEN. THE CAPT HEARD THE CLRNC, SAW ME PUT THE NEW ALT INTO THE ALT SELECTOR. THE CLRNC CONTAINED A HDG, ALT AND SPD, AND ALSO POSSIBLY SOME OTHER INFO FOR LEAVING THE FIX. PART OF MY DIVERSION WAS, I WAS HEADS DOWN AFTER RESETTING THE ALT SELECTOR TRYING TO PROGRAM THE FMC TO EXIT THE HOLD, AND CHANGE THE DISPLAY ON THE HSI. DURING THIS TIME, I ASSUMED THE CAPT HAD BEGUN HIS DSCNT. WHEN I FINISHED PROGRAMMING AND SAW HE WAS STILL AT FL290 I REMINDED HIM OF THE NEW ALT. I CAN ONLY ASSUME THE CTLR THOUGHT WE WERE IN OUR DSCNT AND AT THAT RATE SHOULD NOT HAVE HAD A CONFLICT ALERT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR AND HIS CAPT DID NOT MAKE ANY INQUIRY WITH THE CENTER ABOUT WHAT REALLY HAPPENED AND WHETHER OR NOT THERE WAS A CONFLICT AND LOSS OF SEPARATION. TO THIS DAY, REPORTER DOES NOT KNOW IF THEY LOST SEPARATION WITH THE ACFT AT FL260. AS INDICATED IN THE REPORT, THE CTLR GAVE IMMEDIATE TURNS TO BOTH ACFT AND CLIMBED RPTR'S ACFT. RPTR DOES NOT BELIEVE THAT THEIR SLOWNESS IN LEAVING FL290 HAD ANYTHING TO DO WITH THE POSSIBLE LOSS OF SEP AT FL260. RATHER, HE FEELS THAT THE CTLR FORGOT ABOUT THE ACFT AT FL260 AND MISTAKENLY DSNDED HIS ACFT THROUGH THAT ALT.

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.