C310 PLT UNABLE TO MAINTAIN ALT AND HDG DUE TO ICING AND DIVERTS TO PRC WITH CTLR ASSISTANCE.

Narrative

I WAS FLYING AT 16000 FT ON OXYGEN WHEN THE CLOUDS CAME UP TO MEET ME. COULDN'T CLB ANY HIGHER AND STARTED TO COLLECT RIME ICE. NOTIFIED ATC THAT I NEEDED TO COME DOWN TO GET OUT OF ICE; WAS CLRED TO 10000 FT AND STARTED TO DSND. ICE GOT WORSE AND NOTIFIED ATC. REQUESTED LNDG FLAGSTAFF (BELOW MINIMUMS). ATC TOLD ME I COULD DO THE ILS AT PRESCOTT; AZ; AND DID I HAVE THE APCH PLATES. I REPLIED; AFFIRMATIVE; I HAD THE PLATES. AS I LEVELED OFF; THE PLANE WAS HARD TO FLY (TURB; ICE) AND ATC VECTORED ME TO THE ILS AT PRESCOTT. ATC TOLD ME I WAS 1400 FT HIGH AND OFF MY HDG. I REPLIED THAT I HAD A STABILITY PROB AND ALSO THAT WHILE FLYING I COULDN'T GET MY APCH PLATE OUT. EVERY TIME I TRIED; THE ACFT WOULD GET AWAY FROM ME AND I REQUESTED HE GET ME THE FREQ AND HDG FOR THE ILS AT PRESCOTT. HE ASKED ME IF I COULD FLY THE APCH; AND I REPLIED AFFIRMATIVE. HE THEN GOT ME THE NUMBERS AND VECTORED ME TO THE APCH. WHEN I GOT TO 10000 FT; THE ICE CAME OFF; THE PLANE BECAME STABLE; AND I WAS ABLE TO GET OUT THE APCH PLATE. I INFORMED ATC OF THIS. THEN I FLEW THE ILS AND LANDED AT PRESCOTT. THE CTLR DID A GREAT JOB! THE OXYGEN MAY NOT HAVE BEEN TURNED HIGH ENOUGH AND SOME OF THE STABILITY PROB MAY HAVE BEEN HYPOXIA.