Narrative:

ZDC cleared us to FL350 and shortly after cleared us to FL330. Before leveling FL330, we were given another descent to FL290. Shortly after the clearance to FL290, ZDC directed us to increase our rate of descent. While descending at 2000 FPM, ZDC directed us to use best rate, and once through FL290 turn left heading 050 degrees. Our instructions were confusing because we were asked to use best rate of descent and we only had to lose 3000-4000 ft. Because of the urgency with which ZDC was taking us down, I recall noting there must be a traffic conflict, so we needed to comply with the instructions and increase our descent rate. At approximately FL290, I spotted an aircraft Y, DC9, in our 10 O'clock position moving to 12 O'clock position. As we were never instructed to look for traffic, my copilot and I were shocked. Assuming our previous instructions to increase rate of descent were needed to resolve a conflict with the DC9, I took evasive measures and descended below the traffic. Once clear of the traffic, I queried my copilot about our assigned altitude, which he thought was FL290. We were between FL260 and FL270 so I climbed without delay to FL290. Supplemental information from acn 477180: it is my opinion that had we seen the DC9 earlier, we might not have had to resort to such extreme maneuvers to avoid the aircraft. (We possibly could have reduced our rate of descent or changed heading.) we did not see the DC9 until it emerged from behind clouds that were between us the DC9. If we were advised about possible traffic by ATC, this could have also helped the situation. Supplemental information from acn 478316: I was working a high altitude en route sector with WX affecting about 20% of the sector and aircraft deviating off their assigned rtes. A lear 23 (aircraft X) was above other traffic and needed to be descended since his destination was nearby. I placed the lear on a heading and assigned him an altitude of FL290 and asked him for his best rate of descent. He acknowledged for the heading and the correct altitude. He was descending in the vicinity of a DC9 at FL280. The DC9 reported a learjet descending through his altitude and asked if we were working that aircraft. I replied that he should be at FL290 and asked the lear to say his altitude. The lear said he was at FL290. The lear also said the proximity of the aircraft seemed close. The DC9 later reiterated that the learjet was below his altitude.

Google
 

Original NASA ASRS Text

Title: LOSS OF TFC SEPARATION N OF GSO, NC.

Narrative: ZDC CLRED US TO FL350 AND SHORTLY AFTER CLRED US TO FL330. BEFORE LEVELING FL330, WE WERE GIVEN ANOTHER DSCNT TO FL290. SHORTLY AFTER THE CLRNC TO FL290, ZDC DIRECTED US TO INCREASE OUR RATE OF DSCNT. WHILE DSNDING AT 2000 FPM, ZDC DIRECTED US TO USE BEST RATE, AND ONCE THROUGH FL290 TURN L HDG 050 DEGS. OUR INSTRUCTIONS WERE CONFUSING BECAUSE WE WERE ASKED TO USE BEST RATE OF DSCNT AND WE ONLY HAD TO LOSE 3000-4000 FT. BECAUSE OF THE URGENCY WITH WHICH ZDC WAS TAKING US DOWN, I RECALL NOTING THERE MUST BE A TFC CONFLICT, SO WE NEEDED TO COMPLY WITH THE INSTRUCTIONS AND INCREASE OUR DSCNT RATE. AT APPROX FL290, I SPOTTED AN ACFT Y, DC9, IN OUR 10 O'CLOCK POS MOVING TO 12 O'CLOCK POS. AS WE WERE NEVER INSTRUCTED TO LOOK FOR TFC, MY COPLT AND I WERE SHOCKED. ASSUMING OUR PREVIOUS INSTRUCTIONS TO INCREASE RATE OF DSCNT WERE NEEDED TO RESOLVE A CONFLICT WITH THE DC9, I TOOK EVASIVE MEASURES AND DSNDED BELOW THE TFC. ONCE CLR OF THE TFC, I QUERIED MY COPLT ABOUT OUR ASSIGNED ALT, WHICH HE THOUGHT WAS FL290. WE WERE BTWN FL260 AND FL270 SO I CLBED WITHOUT DELAY TO FL290. SUPPLEMENTAL INFO FROM ACN 477180: IT IS MY OPINION THAT HAD WE SEEN THE DC9 EARLIER, WE MIGHT NOT HAVE HAD TO RESORT TO SUCH EXTREME MANEUVERS TO AVOID THE ACFT. (WE POSSIBLY COULD HAVE REDUCED OUR RATE OF DSCNT OR CHANGED HDG.) WE DID NOT SEE THE DC9 UNTIL IT EMERGED FROM BEHIND CLOUDS THAT WERE BTWN US THE DC9. IF WE WERE ADVISED ABOUT POSSIBLE TFC BY ATC, THIS COULD HAVE ALSO HELPED THE SIT. SUPPLEMENTAL INFO FROM ACN 478316: I WAS WORKING A HIGH ALT ENRTE SECTOR WITH WX AFFECTING ABOUT 20% OF THE SECTOR AND ACFT DEVIATING OFF THEIR ASSIGNED RTES. A LEAR 23 (ACFT X) WAS ABOVE OTHER TFC AND NEEDED TO BE DSNDED SINCE HIS DEST WAS NEARBY. I PLACED THE LEAR ON A HDG AND ASSIGNED HIM AN ALT OF FL290 AND ASKED HIM FOR HIS BEST RATE OF DSCNT. HE ACKNOWLEDGED FOR THE HDG AND THE CORRECT ALT. HE WAS DSNDING IN THE VICINITY OF A DC9 AT FL280. THE DC9 RPTED A LEARJET DSNDING THROUGH HIS ALT AND ASKED IF WE WERE WORKING THAT ACFT. I REPLIED THAT HE SHOULD BE AT FL290 AND ASKED THE LEAR TO SAY HIS ALT. THE LEAR SAID HE WAS AT FL290. THE LEAR ALSO SAID THE PROX OF THE ACFT SEEMED CLOSE. THE DC9 LATER REITERATED THAT THE LEARJET WAS BELOW HIS ALT.

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.