SMA MAKES WRONG RWY APCH LNDG UNAUTH LNDG. ROTARY WINGED TFC COMPLAINS OF RPTR'S ACFT ON HIS RWY.

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AT APPROX PM45 HRS AND APPROX 95 NM SW MANASSAS ARPT; THE ACFT ALTERNATOR LIGHT ILLUMINATED. I ADVISED ZDC OF THE PROB. THEY ASKED IF I WANTED TO BE VECTORED FOR AN IMMEDIATE LNDG. I ADVISED I WOULD CONTINUE TO MANASSAS AND ASKED FOR A DIRECT HDG. MY DECISION WAS BASED ON THE FOLLOWING FACTORS: WX WAS VFR AT DEST; HAD POSITIVE RADAR CONTACT WITH HDOF CAPABILITY TO DULLES APCH AND MANASSAS TWR. OTHER SMALL ARPTS IN MY VICINITY DIDN'T OFFER THIS CAPABILITY OR SECURITY. I ADVISED CTR I WAS CLOSING DOWN ALL MY NAV AND COM EQUIP EXCEPT FOR 1 VHF COM AND XPONDER TO CONSERVE THE BATTERY. ADVISED CTR MY XMISSIONS WOULD BE SHORT AND LIMITED TO ESSENTIAL COM. HDGS AND PERIODIC POS WERE FURNISHED BY CTR. A HDOF AND FREQ CHANGE TO DULLES APCH TOOK PLACE APPROX 36 MI FROM MANASSAS. DULLES HAD BEEN ADVISED OF MY PROB. DSCNT WAS GIVEN AND A VISUAL CONTACT WITH THE ARPT WAS MADE AT APPROX 5 NM. CONTACT WAS MADE WITH TWR; WHICH SAID THEY WERE ADVISED OF MY PROB. I WAS CLRED TO LAND 16L; HOWEVER; I ONLY HAD 1 SET OF RWY LIGHTS IN SIGHT AT APPROX 800 FT ALT. THROUGHOUT MY MANEUVERING I WAS USING A FLASHLIGHT TO SEE THE INST LIGHTS WHILE FLYING THE ACFT AND KEEPING SIGHT OF THE RWY. ALL LIGHTS WERE DIM AND NO INDICATION THAT EXTERIOR ROTATING BEACON WAS OPERATING. AMMETER READ NEAR ZERO. AFTER LNDG; TWR ADVISED ME I LANDED 16R RATHER THAN 16L. WHILE ROLLING OUT AFTER LNDG; I SAW A HELI PASS APPROX 300 FT AND 100 FT ALT TO MY R. I RECALL TWR HAD CLRED HIM FOR THE 'OPTION.' APPARENTLY; HE WAS CLRED FOR THE 'OPTION' ON 16R; WHICH I MISTAKENLY TOOK FOR 16L. THE 'CHOPPER' PLT WAS UPSET BECAUSE HE DIDN'T SEE ME UNTIL MY ROLLOUT ON THE RWY. TO CONSERVE BATTERY PWR; I DID NOT RPT MY PROGRESS THROUGHOUT THE TFC PATTERN. THERE WAS NO NEED FOR EVASIVE ACTION ON HIS PART NOR WAS THERE A NEAR MISS. I HAD NO VISUAL CONTACT WITH THE HELI DURING MY APCH SINCE HE WAS APPARENTLY FLYING HIS PATTERN INSIDE; BELOW; AND BEHIND ME. TO AVERT A SIMILAR SIT AND POSSIBLE ACCIDENT; I WOULD RECOMMEND THE TWR NOT HAVE CLRED THE HELI FOR THE OPTION UNTIL I HAD COMPLETED MY LNDG.