Narrative:

On approach at night to btm, cleared VOR DME-a approach. WX reported 5000' scattered, 10000' broken, wind calm. During the approach we overflew the airfield (hia 272 degree right/14.4 DME). Made right turn and descended to 7200' for modified downwind/circle to runway 15. Runway in sight. Radio contact with butte radio and had been cleared off of ZLC frequency. After starting turn to final, we lost sight of the field. Executed missed approach procedures direct to coppertown VOR and climbed to 9000'. We encountered significant turbulence and heavy icing approaching 9000', so we requested 14000' from ZLC. We were also in contact with butte radio and we relayed all information to them (missed approach/climb, etc). We got no answer from ZLC, but through butte radio we requested 14000'. This altitude would put us on top of WX. Butte radio acknowledged our request for 14000', and confirmed climb to 14000' and coordination with ZLC. While completing missed approach and in mtn terrain, we were unable to contact ZLC directly. When we were asked for reason for climb to 14000', we stated that significant turbulence plus heavy icing. We explained this flight condition to ZLC and no more questions were asked. We were then cleared for ILS runway 15 at butte. Approach and landing completed west/O incident. The controller at butte radio confirmed all our requests after we landed. He confirmed that he understood all the clrncs the same way we did. Supplemental information from acn 167664: initiated missed approach as published to 9000'. Encountered medium icing and turbulence and told butte CTAF to tell ZLC we were climbing to 14000' where we last had known we would be in the clear. Asked butte to do this because we couldn't reach ZLC. We were finally able to reach ZLC and they asked why we were at 14000 and not 9000'. Told him we had asked butte to relay our intentions to climb to 14000'. ZLC said they understood. Butte had told us prior to our talking to ZLC that ZLC had been informed and it was ok to climb to 14000'.

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Original NASA ASRS Text

Title: ALT EXCURSION DURING MISSED APCH PROC AFTER ACR LGT HAS INFLT ENCOUNTER WITH ICING SUBSEQUENT TO IAP VOR DME APCH TO VISUAL CONDITIONS.

Narrative: ON APCH AT NIGHT TO BTM, CLRED VOR DME-A APCH. WX RPTED 5000' SCATTERED, 10000' BROKEN, WIND CALM. DURING THE APCH WE OVERFLEW THE AIRFIELD (HIA 272 DEG R/14.4 DME). MADE RIGHT TURN AND DSNDED TO 7200' FOR MODIFIED DOWNWIND/CIRCLE TO RWY 15. RWY IN SIGHT. RADIO CONTACT WITH BUTTE RADIO AND HAD BEEN CLRED OFF OF ZLC FREQ. AFTER STARTING TURN TO FINAL, WE LOST SIGHT OF THE FIELD. EXECUTED MISSED APCH PROCS DIRECT TO COPPERTOWN VOR AND CLBED TO 9000'. WE ENCOUNTERED SIGNIFICANT TURB AND HEAVY ICING APCHING 9000', SO WE REQUESTED 14000' FROM ZLC. WE WERE ALSO IN CONTACT WITH BUTTE RADIO AND WE RELAYED ALL INFO TO THEM (MISSED APCH/CLB, ETC). WE GOT NO ANSWER FROM ZLC, BUT THROUGH BUTTE RADIO WE REQUESTED 14000'. THIS ALT WOULD PUT US ON TOP OF WX. BUTTE RADIO ACKNOWLEDGED OUR REQUEST FOR 14000', AND CONFIRMED CLB TO 14000' AND COORD WITH ZLC. WHILE COMPLETING MISSED APCH AND IN MTN TERRAIN, WE WERE UNABLE TO CONTACT ZLC DIRECTLY. WHEN WE WERE ASKED FOR REASON FOR CLB TO 14000', WE STATED THAT SIGNIFICANT TURB PLUS HEAVY ICING. WE EXPLAINED THIS FLT CONDITION TO ZLC AND NO MORE QUESTIONS WERE ASKED. WE WERE THEN CLRED FOR ILS RWY 15 AT BUTTE. APCH AND LNDG COMPLETED W/O INCIDENT. THE CTLR AT BUTTE RADIO CONFIRMED ALL OUR REQUESTS AFTER WE LANDED. HE CONFIRMED THAT HE UNDERSTOOD ALL THE CLRNCS THE SAME WAY WE DID. SUPPLEMENTAL INFO FROM ACN 167664: INITIATED MISSED APCH AS PUBLISHED TO 9000'. ENCOUNTERED MEDIUM ICING AND TURB AND TOLD BUTTE CTAF TO TELL ZLC WE WERE CLBING TO 14000' WHERE WE LAST HAD KNOWN WE WOULD BE IN THE CLR. ASKED BUTTE TO DO THIS BECAUSE WE COULDN'T REACH ZLC. WE WERE FINALLY ABLE TO REACH ZLC AND THEY ASKED WHY WE WERE AT 14000 AND NOT 9000'. TOLD HIM WE HAD ASKED BUTTE TO RELAY OUR INTENTIONS TO CLB TO 14000'. ZLC SAID THEY UNDERSTOOD. BUTTE HAD TOLD US PRIOR TO OUR TALKING TO ZLC THAT ZLC HAD BEEN INFORMED AND IT WAS OK TO CLB TO 14000'.

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.