A320
Flight Crew Air Transport Pilot (ATP)
Conflict NMAC; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Human Factors; Procedure; Airspace Structure
We were approximately 25 NM from BAM VOR at 33;000 FT. The ATC Controller told us of traffic ahead; 12 o'clock descending to 34;000 FT and after passing you he will continue to descend. At about 7-8 NM (approximately 20 seconds from the event) we noticed on our TCAS that the aircraft directly ahead of us was at 33;800 and still descending; arrow still next to it indicating more than 500 FPM; I inquired to the ATC Controller; is he going to level off; to which I'm not sure what he responded since things happened very quickly at this moment due to our closure rate. Next thing we see is 500 FT on the TCAS; at that moment the other aircraft breaks out of the clouds the TCAS goes to TA for a fraction of a second; then immediately to RA; descend; and the Controller is saying turn left now. The First Officer disconnected the autopilot; started turning and descending at that moment the traffic was over and behind us at approximately 300 FT according to the TCAS. From the time the TCAS sounded to the event being over a maximum time of 6-8 seconds elapsed! The other aircraft was a B-737 (military) according to ATC and we never heard any communication between the ATC controller and the aircraft in question.Having military aircraft transmit on MHZ frequencies when operating in commercial RVSM airspace could have provided us with some situational awareness since we would have heard what was being said between them and ATC. Also; checking into why the TCAS didn't provide the normal sequence from TA to RA at the proper time would be worth investigating!
I disconnected the autopilot; turned left; and began a descent. I noted the target symbol showed +300 FT and still descending as it passed over us. The other aircraft was a military 737.A contributing factor was the cloud layer that prevented us from seeing the 737 until they were directly in front of us. We also never heard any communication between ATC and the 737.
TCAS TA and RA warnings were instrumental in separating the reporter's A320 and a military B737 which descended below its cleared altitude. Situational awareness was cited as a result of ATC and the B737 not communicating on the same frequency as civil operators.