A C340 elevator trim ran away nose down during an ILS in low visibility with gusty winds. Due to control difficulties the ILS could not be maintained requiring two missed approaches before a successful approach was completed.

Narrative

Inbound IMC on Angel Flight positioning flight. I had been very slow going due to a 60 KT headwind throughout trip. At beginning of approach sequence; autopilot suddenly failed and caused runaway trim; nose down; weather was low ceiling; mist; gusting wind. Flew below glideslope and off localizer. Executed missed approach. Vectored for second approach; during which aircraft was determined to still be substantially out of trim; and quite difficult to control as a consequence; because of previous autopilot failure. Because aircraft still out of trim during second approach deviated below glideslope and off localizer. Executed a second missed approach. Retrimmed aircraft; entered third approach; completed third approach; not very artfully but landed without further incident. This event occurred primarily because of a problem attributable to an equipment failure. Autopilot was serviced in March 2009; and had been working perfectly until its sudden complete failure. Aircraft is currently in avionics shop for repairs to autopilot. I am going for annual simulator twin-aircraft IFR training within the next two weeks and I will ask instructions to emphasize autopilot failure.