AN SMA HAD AN NMAC WITH AN MTR.

Narrative

I WAS IN LEVEL VFR CRUISE AT 4450 MSL; HDG 300 DEGS. I WAS 10 MI SW OF THE ARSA AND I WAS MONITORING ATC. I HAVE MODE A ONLY AND I WAS INADVERTENTLY SQUAWKING A DISCRETE CODE INSTEAD OF 1200. AN MTR PASSED ABOUT 50 FT UNDER ME EBOUND. I LATER LEARNED THAT HE WAS DSNDING TO 4000 AT 300 KTS. THE FIRST VISUAL CONTACT I HAD OF THE MTR WAS A WHITE FLASH OUT OF THE CORNER OF MY EYE AS HE PASSED UNDER ME. HE WAS SO CLOSE THAT I ACTUALLY HEARD HIM OVER THE SOUND OF MY ENG. I HEARD NO ATC CALL GIVING MY POS TO THE MTR. SINCE THE ACFT WAS XMITTING ON A MIL FREQ I COULD NOT HEAR HIM. HOWEVER; HE APPARENTLY IMMEDIATELY ASKED ATC WHY HE HADN'T BEEN GIVEN THE TFC BECAUSE I HEARD ATC REPLY WITH SOMETHING LIKE '...I SAW IT BUT I DIDN'T KNOW THE ALT.' POSSIBLE CORRECTIVE/PREVENTIVE MEASURES: 1) MIL ACFT APPARENTLY HAVE NO SPD LIMITATIONS. HOWEVER; THEY USE THE SAME AIRSPACE AS GENERAL AND COMMERCIAL AVIATION ACFT; WHICH; FOR SAFETY REASONS; MUST OBEY CERTAIN SPD LIMITS IN CERTAIN AREAS AND ALT RANGES. IF MIL ACFT ARE TO BE EXEMPT FROM SAFETY ORIENTED SPD RESTRICTIONS; THEY SHOULD HAVE SOME FORM OF SELF- CONTAINED ANTICOLLISION DEVICE AND/OR DEDICATED CTLR SURVEILLANCE WHICH WOULD GIVEN THEM EVERY TARGET AND NOT JUST ON A 'WORKLOAD PERMITTING BASIS.' 2) CTLRS MUST MAKE EVERY EFFORT TO CALL AS MANY TARGETS AS POSSIBLE. A CTLR WHO WAS NOT INVOLVED IN THIS INCIDENT SUGGESTED THAT PERHAPS THE CTLR WHO WAS WORKING THIS INCIDENT MAY HAVE THOUGHT THAT I WAS IN CONTACT WITH CTR AND THAT I WAS ABOVE THE LCL CTLR'S JURISDICTION. THIS IS VERY UNLIKELY SINCE I WAS MODE A ONLY WITH A GNDSPD OF 75-80 KTS. BESIDES; IF HE DOESN'T KNOW MY ALT HE SHOULD MAKE THE TFC CALL TO THE MTR. 3) JUST IN CASE MY DISCRETE CODE CONFUSED THE CTLR; I HAVE ADDED A SEPARATE ITEM TO MY PRE-TKOF CHKLIST FOR SETTING THE TRANSPONDER. BEFORE; I HAD INCLUDED THE TRANSPONDER CHK/SET UNDER RADIO CHK. TO MY KNOWLEDGE THIS WAS THE FIRST TIME I HAD NOT HAD THE TRANSPONDER AT 1200 AT TKOF. 4) I PLAN TO HAVE AN ENCODER INSTALLED. STILL; THE CTLR MUST MAKE THE CALL. 5) EACH OF US NEEDS TO BE MORE VIGILANT. THIS METHOD STILL REMAINS THE ONLY METHOD WHERE WE DO NOT HAVE TO RELY ON SOMEONE ELSE FOR COLLISION AVOIDANCE.