Narrative:

We were departing dca and climbing to an assigned altitude of 17000 ft. Passing approximately 13000 ft the controller instructed us to maintain 14000 ft. As I was setting the altitude alert, I noticed an aircraft on the TCASII approximately 1000 ft above our current altitude. I brought this to the attention of the copilot but was unable to question the controller due to congestion on the frequency. I then suggested to the copilot that we level off at which time we received a traffic alert on the TCASII. Shortly thereafter, we received a RA on the TCASII to descend, which we followed. After a shallow descent, we received a 'clear of conflict' from the TCASII. We then resumed our climb to 14000 ft. During all of this we were unable to contact ATC due to congestion on the frequency. After we were clear, the other aircraft involved, air carrier Y, a B737, advised the controller of his need to follow a RA on his TCASII. I did not report our RA response on the frequency because: 1) air carrier Y had reported it, 2) the congestion on the frequency, 3) our deviation was minor and momentary and, 4) I perceived that the controller was aware of his mistake. In retrospect, I feel I should have reported it on frequency as my copilot had suggested. A contributing factor to this incident was the fact that the controller was apparently transmitting to aircraft on 2 different frequencys. Supplemental information from acn 346400: we would have most likely run into traffic had it not been for the TCASII. Traffic separation was reduced to about 500 ft.

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Original NASA ASRS Text

Title: NMAC AVERTED BY TCASII RA. OPPOSITE DIRECTION TFC AT CLRED TO ALT. EVASIVE ACTION DSCNT. SAME ASSIGNED ALT.

Narrative: WE WERE DEPARTING DCA AND CLBING TO AN ASSIGNED ALT OF 17000 FT. PASSING APPROX 13000 FT THE CTLR INSTRUCTED US TO MAINTAIN 14000 FT. AS I WAS SETTING THE ALT ALERT, I NOTICED AN ACFT ON THE TCASII APPROX 1000 FT ABOVE OUR CURRENT ALT. I BROUGHT THIS TO THE ATTN OF THE COPLT BUT WAS UNABLE TO QUESTION THE CTLR DUE TO CONGESTION ON THE FREQ. I THEN SUGGESTED TO THE COPLT THAT WE LEVEL OFF AT WHICH TIME WE RECEIVED A TFC ALERT ON THE TCASII. SHORTLY THEREAFTER, WE RECEIVED A RA ON THE TCASII TO DSND, WHICH WE FOLLOWED. AFTER A SHALLOW DSCNT, WE RECEIVED A 'CLR OF CONFLICT' FROM THE TCASII. WE THEN RESUMED OUR CLB TO 14000 FT. DURING ALL OF THIS WE WERE UNABLE TO CONTACT ATC DUE TO CONGESTION ON THE FREQ. AFTER WE WERE CLR, THE OTHER ACFT INVOLVED, ACR Y, A B737, ADVISED THE CTLR OF HIS NEED TO FOLLOW A RA ON HIS TCASII. I DID NOT RPT OUR RA RESPONSE ON THE FREQ BECAUSE: 1) ACR Y HAD RPTED IT, 2) THE CONGESTION ON THE FREQ, 3) OUR DEV WAS MINOR AND MOMENTARY AND, 4) I PERCEIVED THAT THE CTLR WAS AWARE OF HIS MISTAKE. IN RETROSPECT, I FEEL I SHOULD HAVE RPTED IT ON FREQ AS MY COPLT HAD SUGGESTED. A CONTRIBUTING FACTOR TO THIS INCIDENT WAS THE FACT THAT THE CTLR WAS APPARENTLY XMITTING TO ACFT ON 2 DIFFERENT FREQS. SUPPLEMENTAL INFO FROM ACN 346400: WE WOULD HAVE MOST LIKELY RUN INTO TFC HAD IT NOT BEEN FOR THE TCASII. TFC SEPARATION WAS REDUCED TO ABOUT 500 FT.

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.