SMA BECOMES DISORIENTED AND ENTERS THEN EXITS TCA.

Narrative

THE ACFT TOOK OFF FROM ADDISON; TX; AT ABOUT PM00 HRS LCL TIME FEB/FRI/92. DURING THE CLB OUT THE PLANE EXPERIENCED A MODERATE LEVEL OF VIBRATION OF UNKNOWN ORIGIN. AS THE PLANE LEVELED OFF AND SETUP FOR CRUISE; THE VIBRATION CEASED. DUE TO THIS; I MAINTAINED A SCAN THAT INCLUDED THE ENG INSTS MORE OFTEN. THE REST OF THIS LEG OF THE FLT; TO DENTON TO PRACTICE SOME APCHS; WENT ON WITHOUT INCIDENT. AFTER 1 APCH; WE DECIDED TO LAND AND STRETCH OUT LEGS. 15 MINS AFTER SHUTDOWN THE PLANE WOULD NOT START; SO I PULLED THE PROP THROUGH MYSELF TO GET IT RUNNING. THAT WAS A FIRST FOR ME. AGAIN; ON TKOF WE FELT THAT SAME VIBRATION; AND ON A HDG OF ABOUT 170 DEG; RWY HDG; WE CLBED OUT TO 2300 FT MSL. WE THEN TURNED TO 120 DEG TO RETURN TO ADDISON. WE FLEW FOR ABOUT 5 MIN ON THIS HDG AND SIGHTED AHEAD WHAT WE THOUGHT WAS LAKE LEWISVILLE DAM. WE CALLED IN TO ADDISON OUR INTENTION TO LAND; AND WAS TOLD TO ENTER A L DOWNWIND CLOSE IN; TO AVOID THE DFW TCA. A FEW SECONDS AFTER MAKING THAT CALL; I REALIZED THAT WE WERE APCHING LAKE GRAPEVINE; N OF DFW. WE IMMEDIATELY TURNED NE AND DSNDED TO 1900 FT. WE PROCEED TO ADDISON WITHOUT FURTHER INCIDENT. WE HAD FLOWN TOO FAR S ON OUR TKOF FROM DENTON; BEFORE TURNING E; BECAUSE WE WERE TRYING TO DISCOVER THE ORIGIN OF THE VIBRATION; AND I WAS ALSO STILL THINKING ABOUT HAVING TO HAND-START THE PLANE. THESE 2 FACTORS AND SOME INATTN CAUSED US TO MIS- IDENT THE LAKE WE WERE APCHING. WE FELT THAT OUR POS AS WE APCHED THE LAKE WAS VERY CLOSE TO TCA BOUNDARY AND TOOK IMMEDIATE ACTION; WE TURNED AND DSNDED TO ARRIVE AT A LOCATION THAT WE WERE SURE WAS OUT OF THE TCA.