MULTIPLE RWY OP INTERSECTING RWYS ACR X HAD NMAC WITH ACR Y.

Narrative

DURING VISUAL MT VERNON TO RWY 36 AT DCA ACR X; WHICH I WAS THE CAPT OF WAS BEHIND A 727 APPROX 3 NM. WASHINGTON NATIONAL TWR ASKED IF WE WOULD ACCEPT RWY 33 FOR LNDG AND WE DID. DURING THE L BASE TO RWY 33 DCA TWR CLRED A 737- 300 FOR TKOF ON RWY 36. AT THAT TIME MY COPLT AND I AGREED THAT THIS WAS GOING TO BE CLOSE AT THE INTXN ON RWY 33 AND RWY 36. WE CONTINUED TO MONITOR THE SIT UNTIL SHORT FINAL. AT ABOUT 200 FT AGL; IT WAS APPARENT THAT IT WAS GOING TO BE TOO CLOSE AND WE INITIATED A GAR AND PASSED OVER AND SLIGHTLY BEHIND THE 737. THE TWR CTLR ALSO CALLED THE GAR ABOUT THE SAME TIME. AT NO TIME WAS THE SIT DANGEROUS BUT LESS THAN COMFORTABLE SEPARATION. SUPPLEMENTAL INFO FROM ACN 286556: TWR CLRED TO MAKE AN IMMEDIATE TKOF ON RWY 36 (DCA). THERE WAS COMPANY MD80 ON FINAL FOR RWY 33 WHOM WAS ORIGINALLY ON FINAL FOR RWY 36. ON OUR TKOF ROLL AT APPROX 80-90 KTS (RWY 36 LENGTH 6900 FT); I FELT THE TFC ON RWY 33 WAS GOING TO BE CLOSER THAN ANYBODY THOUGHT SO I TOLD THE CAPT; WHO WAS FLYING THAT IT WAS GOING TO BE VERY CLOSE. THE CAPT WAS UNABLE TO SEE THE OTHER ACFT. ABOUT THAT TIME THE TWR CTLR TOLD THE LNDG ARPT TO GAR AND MAINTAIN RWY HDG. THE CTLR THEN TOLD US TO MAKE AN IMMEDIATE TURN TO THE R OR SLOW OUR CLB RATE (NOTE: R TURNS OUT OF DCA ARE VERY UNUSUAL DUE TO PROHIBITED AREA AND TALL OBSTRUCTIONS).