UNAUTH PENETRATION OF AIRSPACE RESTR AREA AND WRONG ARPT LNDG. DIVERSION TO ALTERNATE.

Narrative

I; A STUDENT AIRPLANE PLT; RECEIVED A WX BRIEFING AND FILED A VFR (ROUND ROBIN) XCOUNTRY FLT PLAN IN A PA28161 ON THE MORNING OF MAR/XX/94. I DEPARTED LONG BEACH ARPT AT XA22 AM. RTE OF FLT LGB-SLI-OCN-OCNR110-L39 AND RETURN. AFTER DEPARTING RAMONA; I TUNED IN PALOMAR ARPT (CRQ) ATIS; WHICH STATED 3600 OVCST; 1500 SCATTERED; VISIBILITY 5; FOG SINCE THE CONDITIONS SEEMED TO BE DETERIORATING. THE ACFT EXPERIENCED ENG ROUGHNESS A COUPLE OF MI NE OF OCEANSIDE ARPT. I BEGAN IMMEDIATELY DSNDING WHILE ADJUSTING THE MIXTURE. MONITORING OCEANSIDE UNICOM; I OBTAINED INFO THAT RWY 21 WAS FAVORED. FEARING THAT THE ENG WOULD QUIT; I DECIDED THAT IT WAS IN MY BEST INTEREST TO MAKE A PRECAUTIONARY LNDG. I DIDN'T; 'DECLARE AN EMER' SINCE OCEANSIDE ARPT (L32) HAS A UNICOM FREQ; NOT AN AIR TFC CTLING AGENCY. I CHOSE THE NEAREST ARPT BECAUSE I FELT THAT I WAS UNABLE TO COMPLY WITH FAR 91.155(A) VFR CLOUD CRITERIA. I BEGAN REVIEWING THE EMER CHKLIST FOR ENG ROUGHNESS INFLT. THE PROB DID NOT GO AWAY. I ANNOUNCED MY POS MIDFIELD ENTERING R DOWNWIND; COMPLETING THE LNDG CHKLIST FOR RWY 21. UPON LNDG I REALIZED I HAD MADE A MISTAKE. I ACTUALLY LANDED AT A MIL AIR BASE. CAMP PENDLETON (NFG) IN RESTR AREA; R2503. I DISCUSSED MY SIT WITH A CAPT AT CAMP PENDLETON. THE CAPT STATED THAT I HAD TAKEN THE CORRECT EVASIVE COURSE OF ACTION. HE ALSO STATED; THAT THE ARPTS ARE 4 1/2 MI APART AND EXPLAINED THAT MISTAKING ARPTS WAS A COMMON SIT WITH CAMP PENDLETON AND OCEANSIDE ARPT. BOTH ARPTS USE THE SAME RWY NUMBERS; 21; WHICH HAVE RESULTED IN CONFUSING OTHER PLTS IN THE PAST. THE CAPT WAS VERY UNDERSTANDING; HOWEVER; I DO NOT THINK THAT HE LOOKED FORWARD TO THE NECESSARY PAPERWORK INVOLVED. AS PIC; I HAD FELT IT WAS NECESSARY TO TAKE THE ACTIONS THAT I TOOK IN ORDER TO PREVENT POSSIBLE LOSS OF LIFE AND PROPERTY.