NON-INSTRUMENT RATED PLT WAS ON VFR FLT AT NGT FM MANTEO, NC TO WINCHESTER, VA. HE STARTED THE FLT EARLIER THAN ORIGIN- ALLY PLANNED AFTER LEARNING WX WAS FORECAST TO DETERIORATE. WHEN ACFT DID NOT ARR, SEARCH WAS INITIATED. IT WAS FND ON 5/17/91 IN REMOTE AREA NR SHADY GROVE CORNER, VA. INV REVEALED RGT WING SEPD IN FLT; WING WAS FND ABT 700' EAST OF WHEREACFT IMPACTED GND. MAIN WRECKAGE WAS FND WEST OF IMPACT POINT. METALLURGICAL EXAM SHOWED WING SEPD FM OVERLOAD. RCRDD RADIO INFO REVEALED PLT HAD ENCTRD RAIN. RADAR DATA REVEALED THAT BFR ACDNT, ACFT WAS HDG NE AT 2100' MSL. IT CLIMBED TO2400', TURNED NORTH, DSCNDD TO 2000' & TURNED WEST, THEN DSCNDD TO 1500' BFR RADAR CTC WAS LOST. RADAR CTC ENDED LESS THAN 1 MI FM CRASH SITE. ABT 29 MI ENE AT QUANTICO, 0255 EDT WX WAS IN PART: 1300' BKN, VIS 3 MI IN RAIN & FOG, WND FM 230 DEG AT 12 KTS. EXAM INDCD NO ROTATIONAL DMG OF DRCTNL GYRO OR TURN COORDINATOR GYRO, ONLY SLGT RUBBING OF ATTITUDE GYRO & NO SCORING OF VACUUM PUMP VANES, THOUGH ALL RCVD HVY IMPACT DMG & DIRT WAS PACKED IN VACUUM PUMP PORTS/CAVITY.