SR22 PLT MAKES TWO GARS WHEN AUTOPLT FAILS TO COUPLE WITH GS. ALT DEV OCCURS ON SECOND GAR AS PLT ATTEMPTS TO RESOLVE ROLL TRIM ISSUE.

Narrative

CLRED FOR ILS RWY 33 APCH; ON AUTOPLT (STGC 55X) CAPABLE OF FLYING A GS. AUTOPLT DID NOT CAPTURE GS. OVERFLEW RWY IN IMC; DECLARED MISSED APCH. VECTORED BACK AROUND; SET UP SAME APCH. DOUBLE-VERIFIED GNS 430 AND AUTOPLT SETTINGS WERE CORRECT FOR COUPLED ILS APCH. FAILED TO CAPTURE GS. EXPECTED THIS; DISCONNECTED AUTOPLT TO FLY APCH MANUALLY. ACFT BANKED SHARPLY TO L WHEN AUTOPLT DISCONNECTED. TRIM SWITCH DID NOT APPEAR TO CORRECT THE BANK. FLEW LOC WITH CONSIDERABLE PRESSURE ON STICK TO MAINTAIN WINGS LEVEL. BROKE OUT OF OVCST OVER END OF RWY; BUT TOO HIGH/FAST TO SAFELY LAND. DECLARED SECOND MISSED APCH. ATTEMPTED TO DEAL WITH TRIM ISSUE; OVERFLEW ASSIGNED ALT. GOT ACFT TRIMMED WITH SEVERAL SECONDS ON THE TRIM SWITCH. UNKNOWN WHY ACFT WAS SO BADLY OUT OF TRIM WHEN AUTOPLT ENGAGED. FLEW THIRD APCH MANUALLY AND LANDED. ATC VECTORS TO FINAL WERE VERY CLOSE TO FAF. MY GUESS IS THAT AUTOPLT DID NOT HAVE ADEQUATE TIME TO STABILIZE BEFORE INTERCEPTING THE GS. I DID NOT ATTEMPT TO MANUALLY ENGAGE GS -- I WAS DISTR BY UNEXPECTED AUTOPLT OP AND TRIM ISSUE.