Small Transport; Low Wing; 2 Recip Eng
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Private
Flight Crew Last 90 Days 10; Flight Crew Total 1530; Flight Crew Type 453
Workload; Situational Awareness; Distraction
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Unstabilized Approach
Flight Crew Executed Go Around / Missed Approach
Weather; Human Factors
Below recounts my possible deviation from an altitude clearance on a missed approach. I tried to verify with Flight Aware data but was not able to correlate precise time of receiving clearance with actual altitude. I became somewhat preoccupied with the Propeller Heat being inoperative in icing conditions. Climbing out of DLH; the propeller heat breaker/switch popped and would not reengage. The system had functioned normally during an IMC descent into DLH 3 hours earlier. Our enroute altitude of 6;000 ft kept us well above cloud tops. Cloud tops were reported to be 3;500 in the area of our destination; ANE. I mentioned our prop heat circuit anomaly and requested and received a clearance to remain above the clouds as long as possible. During descent we observed tops at 3;300 - 3;500 ft and had moderate rime accumulation. ANE was OVC 1;100 ft using ILS-27. MSP Approach cleared us for the approach while at 4;000 ft only 5 - 6 miles from BOKYA; the final approach fix. I put in an aggressive descent ~900 fpm. Approach handed us to Tower approximately at BOKYA and probably 3;000 ft; still about 400 ft high.Tower issued a low altitude alert twice. With the second alert; I confirmed that our altimeter agreed with Tower's indication of 2;200 ft. The controller said with rapid descents; sometimes the low altitude alert is the result of a rapid descent profile rather than the aircraft actually being low. In hindsight the rapid descent would have worked out but I was chasing the glide slope. I was uncomfortable with the repeated low altitude alert which concerned my passenger so I declared a missed and requested vectors to repeat the approach. I also requested a climb to 3;500 ft to reduce the time in the clouds and exposure to icing conditions. Tower cleared me 3;000 ft and I requested 3;500 ft again. Tower in his hand off to Approach obtained the clearance to 3;500 ft.Although neither Tower nor Approach questioned my altitude; I may have been above 3;000 ft by the time I confirmed the clearance to 3;500 ft. However; I am disappointed that my preoccupation with the prop heat anomaly caused me to lead the clearance to 3;500 ft. Other components of the deicing system were operating normally and accumulation was light. When I requested the higher than normal altitude into the approach phase of the flight; I also should have negotiated an appropriate descent plan with ATC. I was aware controllers were busy given frequency congestion; time of day and issuance of holds. An alternative to requesting an ad hoc plan would have been to request the DME Arc portion of the ILS approach which would have minimized the amount of attention from ATC and allowed more time for an orderly descent.
Concerned about icing; the pilot may have deviated from his assigned altitude after a missed approach at ANE.