Narrative:

I was flying at 16000 ft on oxygen when the clouds came up to meet me. Couldn't climb any higher and started to collect rime ice. Notified ATC that I needed to come down to get out of ice, was cleared to 10000 ft and started to descend. Ice got worse and notified ATC. Requested landing flagstaff (below minimums). ATC told me I could do the ILS at prescott, az, and did I have the approach plates. I replied, affirmative, I had the plates. As I leveled off, the plane was hard to fly (turbulence, ice) and ATC vectored me to the ILS at prescott. ATC told me I was 1400 ft high and off my heading. I replied that I had a stability problem and also that while flying I couldn't get my approach plate out. Every time I tried, the aircraft would get away from me and I requested he get me the frequency and heading for the ILS at prescott. He asked me if I could fly the approach, and I replied affirmative. He then got me the numbers and vectored me to the approach. When I got to 10000 ft, the ice came off, the plane became stable, and I was able to get out the approach plate. I informed ATC of this. Then I flew the ILS and landed at prescott. The controller did a great job! The oxygen may not have been turned high enough and some of the stability problem may have been hypoxia.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.