AN ACR B727 DSNDED AND TURNED TO AVOID A GOV B737. THE B737 WAS FLYING VFR IN A DATA COLLECTION PATTERN KNOWN TO BWI TRACON APCH CTL. SEE AND AVOID.

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WHILE CLBING THROUGH 13000 FT TCASII ALERT WITH RA ACTIVATED. RA CALLED FOR CLB. I SPOTTED A B737 AT 11 O'CLOCK POS; HIGHER; SBOUND. I CALLED FOR DSND (RA CALLED FOR CLB); THE CAPT PUSHED THE NOSE OVER WITH 40 DEGS R TURN. RA CHANGED TO DSND ADVISORY. THE B737 PASSED ABOVE AND BEHIND US AT 14500 FT. WE LEVELED OFF AT 14000 FT. I BELIEVE THAT IF WE WERE TO FOLLOW RA INSTRUCTION (CLB); A CLOSER SIT WOULD HAVE OCCURRED. SUPPLEMENTAL INFO FROM ACN 364135: COPLT FOR A DATA COLLECTION FLT. THE ACFT IS A NON TCASII B737-200. THE DATA COLLECTION WAS PLANNED FOR 2 RUNS AT 14500 FT. THE PIC PRECOORDINATED THE DATA COLLECTION PATTERN WITH BALTIMORE TRACON; AN OVAL PATTERN; 12 MI LONG AND 6 MI WIDE. THE ACFT WAS OPERATED ON A VFR CLRNC WITH RADAR TA'S FROM BALTIMORE APCH WITH A MODE 3 XPONDER CODE. ALTHOUGH THERE APPEARED TO BE NO REAL COLLISION THREAT; THE ACR AIRPLANE WAS MANEUVERING AGGRESSIVELY IN A POORLY PLANNED COLLISION AVOIDANCE TURN AND DSCNT. I WAS SURPRISED BY THE ACR AIRPLANE'S INEFFECTIVE PITCH AND ROLL DIRECTIONS; AS WELL AS THE AGGRESSIVE PITCH AND ROLL RATES. THE ACR AIRPLANE SHOULD HAVE REMAINED ABOVE OUR ALT AND INITIALLY TURNED L; TO PASS BEHIND OUR AIRPLANE. THE R TURN PROLONGED THE XING SIT. THE ACR AIRCREW COULD USE SOME TRAINING IN VISUAL MANEUVERING TO CTL ACFT SEPARATION IN ACFT XING SITS; OR TCASII ALT AND TURN DIRECTION ALGORITHMS FAILED TO RECOGNIZE A TURNING ACFT XING SIT. NO TA CALL WAS RECEIVED BY OUR AIRPLANE FROM BALTIMORE APCH. OUR ACFT WAS CLOSE TO THE BOUNDARIES OF 4 TFC CTL SECTORS AND THE ACR AIRPLANE WAS TALKING TO WASHINGTON.