NMAC IN TCA.

Narrative

I WAS IN AN MLG AND JUST DEPARTED DCA N UP RIVER. AT ABOUT 800 FT AGL; WHEN TCASII BECAME UNINHIBITED; GOT A TA ON TFC APCHING US AT 2400 FT AGL. I WAS 20 DEGS OF PITCH (NORMAL BODY ANGLE FOR AN MLG) AND HAD A VSI OF ABOUT 3500-4500 FPM. ABOUT 2 SECONDS LATER; GOT A 'DSND' RA AND I STOPPED CLB ASAP AT ABOUT 2000 FT WHEN A SINGLE ENG SMA WENT OVERHEAD ABOUT 400 FT ABOVE US. WE WERE BOTH IN TCA. I WAS IN VFR CONDITIONS BUT IFR FLT PLAN. THE SMA HAD EITHER BRUSHED; OR BARELY BRUSHED P56 AND WAS SWBOUND TOWARD DCA (OR A POINT ABOUT 1 MI N OF ARPT CTR; THE CTLRS SAID THEY WERE UNAWARE OF ACFT TILL WE TOLD THEM; HOWEVER; THE SMA DID; IN FACT; HAVE A MODE C OPERATING OR WE WOULD NOT HAVE PICKED HIM UP AS AN INTRUDER. THE CTLRS SHOULD HAVE SEEN HIM; SHOULD HAVE TOLD US AND MAYBE THIS WOULD NOT HAVE HAPPENED. LATER ON DEP; CTLR TOLD US 'SORRY ABOUT THAT;' GAVE US A PHONE NUMBER AND; WHEN CALLED 2 HRS LATER; SAID TARGET SMA WAS STILL SWBOUND OVER RICHMOND; VA. JUST GOES TO SHOW YOU: EVEN VFR CONDITIONS IN A TCA (WITHIN 1 DME OF DCA AND 1 DME FROM P-56) SEE AND BE SEEN STILL APPLIES. ALSO NOTED; TCASII WORKS.