Narrative:

[We] departed on an IFR flight plan to destination. I was pilot in command and letting rated pilot fly from left seat. When I received clearance; I requested they let departure know we will need a climb westbound; a delay vector; or a shuttle climb to higher altitude prior to proceeding on eastbound victor airway due to icing conditions we experienced during the flight inbound less than 45 minutes prior. On climb and after contacting departure; requested turn west or delay vector to avoid climbing in icing conditions into up-slope of surrounding mountains. [We were] denied due to traffic. [We] requested delay turning eastbound on present southeast heading to continue climb hoping to stay VMC and on-top conditions and denied again due to traffic. Turned eastbound as directed and entered IMC at 6;000 ft MSL. [We] picked up light mixed icing in the climb to 9;000 ft MSL. Requested FL110 and eventually climbed to FL130 cruising altitude. Icing continued and I used boots and little to no ice was cleared off wings. Autopilot was engaged during cruise; and while still IMC started to encounter turbulence. I began looking at approach plates and tuned in nearby ASOS. Weather was reported as good visibility and overcast around FL100. [I] started to tune in destination ASOS and review approach for destination. While looking for approach in chart book; discovered it was not filed correctly and on searching further; finally noticed it was incorrectly filed under another airport. While moving chart to correct place in the chart book; looked up and noticed we had deviated off heading and altitude. The turbulence had increased slightly and with the icing can only assume the autopilot disengaged or the trim button on yoke was accidentally bumped turning off autopilot. No aural warning was observed when autopilot disconnected. During this period; the aircraft had deviated from course and altitude. Center called and pointed out error at same time I was correcting deviations; and I advised we were correcting. At the same time; we encountered some updrafts and downdrafts and I asked for a block altitude to avoid having to correct deviations too quickly with the ice we were still unable to shed at that time. Center gave us a heading and block from FL120-FL130 and we leveled back at FL130 and eventually proceeded back direct to our fix. Approximately 25 miles from IAF; we were in VMC conditions and started a descent and ice started to sublimate off windshield and part of aircraft. Upon reaching 15 out from FAF airport was in site. Canceled IFR and squawked 1200 and landed with no other issues. Better familiarity with autopilot disconnect aural warnings would have helped and I would not have relied on this so much during times instruments were not monitored on a more regular basis; recognition of potential task saturation and tunnel vision syndrome while monitoring autopilot. As for ice and turbulence; pilot should not have accepted ATC clearance to proceed on course knowing that would put the aircraft in unfavorable icing up-slope conditions when a delay vector; 360 turns etc. Would have prevented the type of accumulation that occurred causing fewer distractions during the remainder of the flight.

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Original NASA ASRS Text

Title: A PA34 pilot reported ATC was unable to accommodate requests for ice free flight altitudes in mountainous terrain. He accumulated ice which caused an altitude excursion and track deviation after the autopilot disengaged.

Narrative: [We] departed on an IFR flight plan to destination. I was pilot in command and letting rated pilot fly from left seat. When I received clearance; I requested they let Departure know we will need a climb westbound; a delay vector; or a shuttle climb to higher altitude prior to proceeding on eastbound victor airway due to icing conditions we experienced during the flight inbound less than 45 minutes prior. On climb and after contacting Departure; requested turn west or delay vector to avoid climbing in icing conditions into up-slope of surrounding mountains. [We were] denied due to traffic. [We] requested delay turning eastbound on present southeast heading to continue climb hoping to stay VMC and on-top conditions and denied again due to traffic. Turned eastbound as directed and entered IMC at 6;000 FT MSL. [We] picked up light mixed icing in the climb to 9;000 FT MSL. Requested FL110 and eventually climbed to FL130 cruising altitude. Icing continued and I used boots and little to no ice was cleared off wings. Autopilot was engaged during cruise; and while still IMC started to encounter turbulence. I began looking at approach plates and tuned in nearby ASOS. Weather was reported as good visibility and overcast around FL100. [I] started to tune in destination ASOS and review approach for destination. While looking for approach in chart book; discovered it was not filed correctly and on searching further; finally noticed it was incorrectly filed under another airport. While moving chart to correct place in the chart book; looked up and noticed we had deviated off heading and altitude. The turbulence had increased slightly and with the icing can only assume the autopilot disengaged or the trim button on yoke was accidentally bumped turning off autopilot. No aural warning was observed when autopilot disconnected. During this period; the aircraft had deviated from course and altitude. Center called and pointed out error at same time I was correcting deviations; and I advised we were correcting. At the same time; we encountered some updrafts and downdrafts and I asked for a block altitude to avoid having to correct deviations too quickly with the ice we were still unable to shed at that time. Center gave us a heading and block from FL120-FL130 and we leveled back at FL130 and eventually proceeded back direct to our fix. Approximately 25 miles from IAF; we were in VMC conditions and started a descent and ice started to sublimate off windshield and part of aircraft. Upon reaching 15 out from FAF airport was in site. Canceled IFR and squawked 1200 and landed with no other issues. Better familiarity with autopilot disconnect aural warnings would have helped and I would not have relied on this so much during times instruments were not monitored on a more regular basis; recognition of potential task saturation and tunnel vision syndrome while monitoring autopilot. As for ice and turbulence; pilot should not have accepted ATC clearance to proceed on course knowing that would put the aircraft in unfavorable icing up-slope conditions when a delay vector; 360 turns etc. would have prevented the type of accumulation that occurred causing fewer distractions during the remainder of the flight.

Data retrieved from NASA's ASRS site as of April 2012 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.