A LIFEGUARD HELI PLT DEVIATES FROM HIS ASSIGNED ALT WHEN THE AUTOPLT DROPS OFF THE SYS NEAR ZZZ; US. PLT WAS EXPECTING APCH TO THE ATIS LISTED RWY WHICH HAD BEEN CHANGED.

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I WAS HANDED OFF FROM XYZ APCH TO ZZZ APCH 7 MINS N. I CALLED ZZZ APCH AND SAID 'LIFEGUARD FLT; 4000 FT WITH ATIS INFO.' ATIS WAS GIVING ILS RWY 6 AND GPS RWY 36 AS APCHS IN USE. I RECEIVED A CLRNC TO DSND TO 3000 FT AND JOIN THE LOC FOR RWY 6. I THOUGHT HE SAID RWY 6; HOWEVER; WHEN I TUNED THE LOC FOR RWY 6; THE INTERCEPT HDG COULD NOT HAVE BEEN CORRECT. APCH HAD TOLD ME TO TURN R 10 DEGS TO INTERCEPT THE LOC. WHICH MADE MY HDG ABOUT 210 DEGS. STILL DSNDING; I CALLED APCH BACK TO VERIFY RWY 6 LOC. HE THEN SAID; 'NO IT WAS FOR LOC RWY 18.' WHILE RETUNING THE RADIO; I MISSED THE #1 AUTOPLT KICK OFF AND IN DOING SO; DROPPED THE CAPTURE COMMAND FOR 3000 FT. STOPPING THE DSCNT TOOK ME TO 2800 FT. BY THEN I WAS VMC; AND ADVISED APCH I WAS VMC AND CANCELED IFR. HE CLRED ME DIRECT TO THE HOSPITAL AND ADVISED ME TO CONTACT TWR; WHICH I DID WITH NO FURTHER INCIDENT. SINGLE PLT IFR IS DEMANDING IN ITSELF. I WAS EXPECTING TO HEAR ILS OR LOC RWY 6 AND DIRECT TO THE HOSPITAL AFTER BREAKING OUT ON APCH. I WAS ALSO EXPECTING TO BE HANDED OFF EARLIER FROM APCH CTL; ALL OF WHICH HAS OCCURRED MANY TIMES IN THE PAST. I WASN'T EXPECTING THE AUTOPLT TO MALFUNCTION AT A RUSHED; CRITICAL TIME LIKE THAT. HAD I ASKED FOR AN EARLIER HDOF FROM APCH; I WOULD POSSIBLY ONLY HAVE HAD 1 ERROR AT A TIME INSTEAD OF ALL AT ONCE; AND LISTENING CLOSER TO WHAT IS SAID INSTEAD OF WHAT IS ANTICIPATED.