SMA ENTERS TCA WITH XPONDER ON STANDBY.

Narrative

PROB: XPONDER NOT ACTIVE WHILE IN TCA BOUNDARY. ALT VIOLATION WHEN NOT IN CONTACT WITH ATC. HOW PROB AROSE: XPONDER SWITCH ROTATED TO ACTIVATE PRIOR TO TKOF BUT INADVERTENTLY IN STANDBY POS. FROM ARR; ORIGINAL FLT PLAN TO GO DUE N AT 3000 FT. TURB AT PLANNED ALT RESULTED IN ASCENDING TO SMOOTHER ALT; WHICH WOULD NOT HAVE BEEN A FACTOR ON ORIGINAL RTE. CHANGED RTE OF FLT; WHICH RESULTED IN PASSING OVER E BOUNDARY OF CRYSTAL LAKE (WATER); THAT WAS 1 STATUTE MI INSIDE 4000 FT TCA ALT BOUNDARY. PROB DISCOVERED: RECOGNIZED POS OVER E SIDE OF CRYSTAL LAKE IN ALT RESTR AREA WHILE AT 5000 FT. CHKED XPONDER TO BE SURE I WAS VISIBLE AND WAS ALARMED TO SEE XPONDER IN 'STANDBY' POS. CORRECTIVE ACTION: IMMEDIATELY TURNED XPONDER TO 'ON' POS TO BE SURE I WAS 'VISIBLE' AND DSNDED AS QUICKLY AND SAFELY AS POSSIBLE. FACTORS AFFECTING QUALITY OF DECISION: DEV OF RTE FROM ORIGINAL FLT PLAN. CHANGE IN ALT DUE TO MILD TURB CAUSING PAX DISCOMFORT. PREVENTIVE ACTIONS: NEED TO DOUBLE-CHK XPONDER TO VERIFY IN 'ON' VERSUS 'STANDBY' POS AFTER TKOF. AVOID RTE DEV IF ALT CHANGE. ENSURE GREATER POS OR ALT MARGIN FROM TCA ALT CEILINGS.