Narrative:

En route to rdu; we received a TCAS RA. We were originally assigned FL320 as a final. The frequency and controller appeared to be busy. It also was apparent that the controller was working 2 frequencys at the same time. While on vectors for traffic; we were given a descent to FL300. It should be noted that there was an air carrier abc on the other frequency. We know this because the controller was issuing instructions to them; but we could not hear their response. Shortly after the descent was given to us; we thought we were given an instruction to turn 10 degrees right for traffic. We were unsure if the instruction was for us. I asked the controller once; but received no response. I asked again; 'was that 10 degrees right for air carrier dec?' the controller responded with ; 'yes air carrier abc; 10 degrees right....' we; of course; could not hear air carrier abc's response. Shortly after this exchange; we saw an aircraft go over us (1000 ft above); then noticed a red diamond at about 10:30 - 11 O'clock position on the TCAS screen. The target was approximately 5 NM at 500 ft above and descending. This was immediately followed by a 'descend; descend' command. On the vsi; the descent commanded was greater than 2000 FPM. Seconds later; the controller told us to climb to FL330. I responded with 'air carrier dec TCAS descent' and we continued descending. Around FL260 we heard the 'clear of conflict' annunciation. We were then given direct to the last fix on the arrival and a descent to FL220. The landing was accomplished without incident. We did acquire a visual on our traffic; but we were well into our descent and the traffic appeared to be a B757 in a climbing left turn away from us. I cannot be sure of what caused this; but my opinion is that the controller was mixing up 'air carrier dec' and 'air carrier abc.' since we were on different frequencys; we found it difficult to help him out and could not really tell what was going on. High workload may have been an issue. After the RA; he told us to climb to FL330. This makes me wonder if he thought we were still at FL320. Perhaps he gave us an instruction to descend to FL330 and he meant air carrier abc. When given the descent; I read back 'FL330 air carrier dec' and was never corrected. Neither I; nor the PIC; believed we were in error. FL300 was selected in the altitude alerter; we both verified it; and then descended to FL300. As far as either of us can remember; the descent clearance was for air carrier dec. The RA occurred after we were level at FL300.

Related reports:

Google
 

Original NASA ASRS Text

Title: BE400 AT FL320 IS GIVEN DSCNT CLRNC TO FL300 AND A 10 DEG R TURN FOR TFC. THE BE400 THEN EXPERIENCED A TCAS RA AND MADE AN EVASIVE DSCNT TO MAINTAIN SEPARATION.

Narrative: ENRTE TO RDU; WE RECEIVED A TCAS RA. WE WERE ORIGINALLY ASSIGNED FL320 AS A FINAL. THE FREQ AND CTLR APPEARED TO BE BUSY. IT ALSO WAS APPARENT THAT THE CTLR WAS WORKING 2 FREQS AT THE SAME TIME. WHILE ON VECTORS FOR TFC; WE WERE GIVEN A DSCNT TO FL300. IT SHOULD BE NOTED THAT THERE WAS AN ACR ABC ON THE OTHER FREQ. WE KNOW THIS BECAUSE THE CTLR WAS ISSUING INSTRUCTIONS TO THEM; BUT WE COULD NOT HEAR THEIR RESPONSE. SHORTLY AFTER THE DSCNT WAS GIVEN TO US; WE THOUGHT WE WERE GIVEN AN INSTRUCTION TO TURN 10 DEGS R FOR TFC. WE WERE UNSURE IF THE INSTRUCTION WAS FOR US. I ASKED THE CTLR ONCE; BUT RECEIVED NO RESPONSE. I ASKED AGAIN; 'WAS THAT 10 DEGS R FOR ACR DEC?' THE CTLR RESPONDED WITH ; 'YES ACR ABC; 10 DEGS R....' WE; OF COURSE; COULD NOT HEAR ACR ABC'S RESPONSE. SHORTLY AFTER THIS EXCHANGE; WE SAW AN ACFT GO OVER US (1000 FT ABOVE); THEN NOTICED A RED DIAMOND AT ABOUT 10:30 - 11 O'CLOCK POS ON THE TCAS SCREEN. THE TARGET WAS APPROX 5 NM AT 500 FT ABOVE AND DSNDING. THIS WAS IMMEDIATELY FOLLOWED BY A 'DSND; DSND' COMMAND. ON THE VSI; THE DSCNT COMMANDED WAS GREATER THAN 2000 FPM. SECONDS LATER; THE CTLR TOLD US TO CLB TO FL330. I RESPONDED WITH 'ACR DEC TCAS DSCNT' AND WE CONTINUED DSNDING. AROUND FL260 WE HEARD THE 'CLR OF CONFLICT' ANNUNCIATION. WE WERE THEN GIVEN DIRECT TO THE LAST FIX ON THE ARR AND A DSCNT TO FL220. THE LNDG WAS ACCOMPLISHED WITHOUT INCIDENT. WE DID ACQUIRE A VISUAL ON OUR TFC; BUT WE WERE WELL INTO OUR DSCNT AND THE TFC APPEARED TO BE A B757 IN A CLBING L TURN AWAY FROM US. I CANNOT BE SURE OF WHAT CAUSED THIS; BUT MY OPINION IS THAT THE CTLR WAS MIXING UP 'ACR DEC' AND 'ACR ABC.' SINCE WE WERE ON DIFFERENT FREQS; WE FOUND IT DIFFICULT TO HELP HIM OUT AND COULD NOT REALLY TELL WHAT WAS GOING ON. HIGH WORKLOAD MAY HAVE BEEN AN ISSUE. AFTER THE RA; HE TOLD US TO CLB TO FL330. THIS MAKES ME WONDER IF HE THOUGHT WE WERE STILL AT FL320. PERHAPS HE GAVE US AN INSTRUCTION TO DSND TO FL330 AND HE MEANT ACR ABC. WHEN GIVEN THE DSCNT; I READ BACK 'FL330 ACR DEC' AND WAS NEVER CORRECTED. NEITHER I; NOR THE PIC; BELIEVED WE WERE IN ERROR. FL300 WAS SELECTED IN THE ALT ALERTER; WE BOTH VERIFIED IT; AND THEN DSNDED TO FL300. AS FAR AS EITHER OF US CAN REMEMBER; THE DSCNT CLRNC WAS FOR ACR DEC. THE RA OCCURRED AFTER WE WERE LEVEL AT FL300.

Data retrieved from NASA's ASRS site as of January 2009 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.