NMAC; OPPOSITE DIRECTION CLBING TFC.

Narrative

OUR ACFT; AN SMA; WAS ON A BIENNIAL FLT REVIEW AND INST COMPETENCY CHK FLT FROM SHD. A CFII WAS BEING CHKED BY A SECOND CFII IN THE R SEAT. BOTH CFII'S HAVE ABOUT 1400 HRS EACH. WX VMC; NO CLOUDS; VISIBILITY EXCELLENT; GREATER THAN 10 MI. SUN ANGLE WAS LOW AND BRIGHT; BUT NOT A FACTOR TO EITHER PLT. THE AIR WORK HAD JUST BEEN COMPLETED AND THE ICC HAD JUST BEEN STARTED. A CLB TO 4500 FT MSL HAD JUST BEEN COMPLETED. SHD UNICOM WAS BEING MONITORED; WITH 1 OR 2 ACFT IN THE TOUCH-AND-GO PATTERN. AS WE WERE MANEUVERING AT 7-10 MI TO THE E AND NE WE WERE NOT PAYING STRICT ATTN TO THE RADIO XMISSIONS. THE L SEAT PLT WAS UNDER FOGGLES. WHILE TUNING THE ADF ALT HAD DRIFTED UP TO 4700. OUR PATH WOULD TAKE US FROM ABOUT 10 MI NNE OF SHD DOWN THE E SIDE OF THE ARPT TO THE NDB FOR A PRACTICE ILS APCH. WITHOUT PRIOR WARNING THE L SEAT PLT SAW AN ACFT PASS UNDER THE L WHEEL OUT OF HIS PERIPHERAL VISION BELOW THE FOGGLES OUT OF THE BOTTOM OF THE L SIDE WINDOW. AFTER A SURPRISED EXPRESSION A VERY STEEP L 180 DEG TURN REVEALED THE DEPARTING TWIN OUR ALT. OUR AIRSPD WAS 120 KTS; AND THEIRS IS ESTIMATED AT 200-250 KTS. AFTER THE TURN; THE DEPARTING TWIN WAS STILL WITHIN 1/4 MI. THE OTHER ACFT; A TWIN TURBO PROP COMMUTER ACFT; CALLED A THIRD ACFT IN THE TOUCH-AND-GO PATTERN AT SHD TO ASCERTAIN IF THEY HAD JUST PASSED UNDER THEM. THE THIRD ACFT REPLIED NO; THEY WERE STILL IN THE PATTERN. WE REPLIED THEY HAD JUST PASSED UNDER US AND WE HAD NOT SEEN THEM PRIOR TO THE PASS. THEY REPLIED THEY HAD SEEN US JUST PRIOR TO PASSAGE AND DSNDED UNDER OUR POS. MY ESTIMATE OF SEPARATION IS LESS THAN 50 FT VERT; 0 HORIZ. EVEN THOUGH WE WERE AT CRUISE PWR (180 HP CONVERSION) AND WEARING HEADPHONES; THE PASSAGE WAS SO CLOSE I HEARD THE ENGS AND FELT (IN A HEARING SENSE; NOT PROP WASH IN THE CTLS) THE PROP PULSE AS THE ACFT PASSED EACH OTHER. REFLECTION YIELDS THESE FACTORS. WE HAD JUST COMPLETED A CLB AND BEEN LEVEL AT 4500 FT FOR JUST A FEW MINS. LONG ENOUGH TO GET OUT AN APCH PLATE; LOOK UP SHD AND TUNE THE ADF AND DRIFT UP TO 4700 FT. THE BEST GUESS AT THE INSTANT VIEW OF THE TWIN WAS THAT THE FUSELAGE AND L ENG PASSED UNDER OUR L WHEEL. HDGS WERE VERY CLOSE TO RECIPROCAL. WE KNOW IT TO BE A COMMUTER BECAUSE THEY LANDED JUST PRIOR TO OUR DEP ABOUT 45 MINS PRIOR TO THE EVENT. WE RECORDED THEIR CALL SIGN AND VERIFIED THEIR IDENTITY WITH THE FBO LATER. FROM THE L SEAT UNDER FOGGLES I; OF COURSE; COULD NOT HAVE SEEN THEM. THEY WERE PROBABLY STILL CLBING OUT AND POSSIBLY WERE IN THE BLIND SPOT CAUSED BY THE NOSE OF OUR ACFT RELATIVE TO THE L SEAT POS. IT IS ALSO POSSIBLE THE L SEAT CFII WAS OBSERVING THE R SEAT PLT TUNE THE ADF. THIS IS UNKNOWN. BASED UPON SUSPECTED ACFT POS ONE WOULD EXPECT WE WOULD HAVE BEEN IN FULL VIEW FROM EITHER PLT POS FROM THE OTHER ACFT. WE WERE ONLY MONITORING SHD UNICOM AND HAVE NO KNOWLEDGE IF THE OTHER ACFT RECEIVED A WARNING FROM ZDC. THEY SHOULD HAVE BEEN IN COM AND ON RADAR CONTACT AS YOU CAN TALK TO WASHINGTON FROM THE GND AT SHD AND RADAR COVERAGE STARTS AT ABOUT 2000 FT. OUR ACFT IS EQUIPPED WITH DUAL NAV/COMS; ADF; DME; LORAN AND ENCODING XPONDER. CONTRIBUTING FACTORS MAY HAVE BEEN THE FOLLOWING: THE COOLING FAN ON OUR ACFT FAILED OVER 5 DAYS PRIOR. IT WAS FOUND IF YOU ONLY USED THE XPONDER AND 1 RADIO; AND MAYBE THE ADF THE RADIO STACK DIDN'T GET VERY HOT; THOUGH THE ACFT WAS FLOWN FOR 7 HRS ON THE PREVIOUS SATURDAY WITH ALL RADIOS ON (WHICH WAS A HOTTER DAY) WITH NO ILL EFFECTS. THE PREVIOUS PLT HAD TURNED OFF THE XPONDER; WHICH WAS USUALLY LEFT IN THE ON POS. I USUALLY AM CAREFUL TO FLY WITH STROBE; BEACON AND TAXI LIGHTS ON AND OF COURSE THE XPONDER IN ALT ENCODE MODE. I DID NOT VERIFY THAT WAS THE POS OF THE SWITCHES SUBSEQUENT TO THIS EVENT. HAD THE LIGHTS OR XPONDER BEEN LEFT OFF; THIS WOULD OF COURSE AFFECT OUR VISIBILITY TO THE OTHER ACFT AND ATC. HAVING EQUIP TURNED OFF BECAUSE OF THE FAILED FAN MAY HAVE CONTRIBUTED TO LEAVING THEM OFF AS IT SETS UP A DIFFERENT ROUTINE THAN TURNING ON THE RADIO MASTER. OTHER INSTRUCTOR INATTN TO OUTSIDE REFS IS UNKNOWN; BUT I WILL BE MUCH MORE OBSERVANT TO LIGHTS; XPONDER AND OUTSIDE OBSERVATION WHEN ACTING AS A CFII OR PLT IN THE FUTURE.