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C-208 pilot reported deviating from assigned altitude when he experienced abnormal airspeed indications while in icing conditions; pitot/static heat switch problem was suspected to be a factor.
| Attributes | |
| ACN | 1224925 |
| Time | |
| Date | 201412 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZLA.ARTCC |
| State Reference | CA |
| Environment | |
| Flight Conditions | IMC |
| Aircraft 1 | |
| Make Model Name | Caravan 208B |
| Operating Under FAR Part | Part 135 |
| Flight Phase | Cruise |
| Route In Use | Airway V459 |
| Component | |
| Aircraft Component | Pitot/Static Ice System |
| Person 1 | |
| Function | Single Pilot Pilot Flying |
| Events | |
| Anomaly | Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence |
Narrative:
Altitude deviation; few miles south of lhs VOR on V459 at 10;000 feet. IMC with light icing condition. Airspeed indicator showed slow decrease from 135 KIAS. I checked that pitot heat switch was on position and wing boots clear the ice. I thought that ice was over and or under the wing. As the airspeed indicator approached 110; I requested 9;000 feet to ATC. ATC said 'stand by'. Airspeed indicator kept decreasing. Airspeed approached 100; I reported 'unable to maintain 10;000' and lowered the pitch [to] gain airspeed. But airspeed did not increase; then I tried to recycle pitot heat switch. Few second later airspeed showed normal; and I climbed back to 10;000. I deviated 800 feet.cause:1. Pitot/static heat switch did not work properly. 2. I did not check other side of instruments (lack of scan). 3. When I requested 9;000; I should say why (due to icing etc.) 4. When I started to descend; I should declare emergency.
Original NASA ASRS Text
Title: C-208 pilot reported deviating from assigned altitude when he experienced abnormal airspeed indications while in icing conditions; pitot/static heat switch problem was suspected to be a factor.
Narrative: Altitude deviation; few miles south of LHS VOR on V459 at 10;000 feet. IMC with light icing condition. Airspeed indicator showed slow decrease from 135 KIAS. I checked that pitot heat switch was on position and wing boots clear the ice. I thought that ice was over and or under the wing. As the airspeed indicator approached 110; I requested 9;000 feet to ATC. ATC said 'stand by'. Airspeed indicator kept decreasing. Airspeed approached 100; I reported 'unable to maintain 10;000' and lowered the pitch [to] gain airspeed. But airspeed did not increase; then I tried to recycle pitot heat switch. Few second later airspeed showed normal; and I climbed back to 10;000. I deviated 800 feet.Cause:1. Pitot/Static heat switch did not work properly. 2. I did not check other side of instruments (lack of scan). 3. When I requested 9;000; I should say why (due to icing etc.) 4. When I started to descend; I should declare emergency.
Data retrieved from NASA's ASRS site 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.