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Small aircraft flown purposely in icing conditions ices up static system and indicated an altitude deviation.
| Attributes | |
| ACN | 225479 |
| Time | |
| Date | 199211 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : igu |
| State Reference | NY |
| Altitude | msl bound lower : 5700 msl bound upper : 6000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | general aviation : instructional |
| Make Model Name | Small Aircraft |
| Flight Phase | cruise other |
| Route In Use | enroute airway : zbw |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | instruction : instructor oversight : pic |
| Qualification | pilot : atp pilot : cfi pilot : flight engineer |
| Experience | flight time last 90 days : 200 flight time total : 2900 flight time type : 5 |
| ASRS Report | 225479 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : single pilot instruction : trainee |
| Qualification | pilot : instrument |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter : weather |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | controller : issued new clearance flight crew : exited adverse environment other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Weather |
| Air Traffic Incident | Pilot Deviation |
Narrative:
IFR on instrument competency check in thin cloud layer at 6000 ft. Good VFR above and below. In light single engine aircraft with no anti-ice/de-ice except pitot heat. Wanted to show pilot some light icing. After 10 mins, picked up trace of light rime ice. Pitot heat was on. Suddenly, vsi and altimeter went plus/minus 400 ft as water was ingested in static line froze in the line. Requested descent to 4000 ft to get out of thin cloud layer and ice. ATC advised to standby. I inquired as to our mode C altitude as altimeter and vsi were plus/minus 300 ft before we immediately selected alternate static air. ATC reported 5700 ft, and were we descending prior to his clearance? Replied no, climbed up and confirmed level 6000 ft. ATC then issued our descent to 4000 ft and frequency change. In hindsight, planning was definitely safe, good VFR above and below cloud layer was only 800 ft thick. There were other reports of trace of rime at 6000 ft, so I should not have been in the ice. However, in trying to give pilot realistic training experiences, I felt the proposed operation was safe. Also in hindsight, I should have selected alternate air once in clouds, not expecting pitot/static problems due to working pitot heat (checked on ground). Lesson: no matter how safe the planning is, extra vigilance is required if in conditions the airplane is not designed for.
Original NASA ASRS Text
Title: SMA FLOWN PURPOSELY IN ICING CONDITIONS ICES UP STATIC SYS AND INDICATED AN ALTDEV.
Narrative: IFR ON INST COMPETENCY CHK IN THIN CLOUD LAYER AT 6000 FT. GOOD VFR ABOVE AND BELOW. IN LIGHT SINGLE ENG ACFT WITH NO ANTI-ICE/DE-ICE EXCEPT PITOT HEAT. WANTED TO SHOW PLT SOME LIGHT ICING. AFTER 10 MINS, PICKED UP TRACE OF LIGHT RIME ICE. PITOT HEAT WAS ON. SUDDENLY, VSI AND ALTIMETER WENT PLUS/MINUS 400 FT AS WATER WAS INGESTED IN STATIC LINE FROZE IN THE LINE. REQUESTED DSCNT TO 4000 FT TO GET OUT OF THIN CLOUD LAYER AND ICE. ATC ADVISED TO STANDBY. I INQUIRED AS TO OUR MODE C ALT AS ALTIMETER AND VSI WERE PLUS/MINUS 300 FT BEFORE WE IMMEDIATELY SELECTED ALTERNATE STATIC AIR. ATC RPTED 5700 FT, AND WERE WE DSNDING PRIOR TO HIS CLRNC? REPLIED NO, CLBED UP AND CONFIRMED LEVEL 6000 FT. ATC THEN ISSUED OUR DSCNT TO 4000 FT AND FREQ CHANGE. IN HINDSIGHT, PLANNING WAS DEFINITELY SAFE, GOOD VFR ABOVE AND BELOW CLOUD LAYER WAS ONLY 800 FT THICK. THERE WERE OTHER RPTS OF TRACE OF RIME AT 6000 FT, SO I SHOULD NOT HAVE BEEN IN THE ICE. HOWEVER, IN TRYING TO GIVE PLT REALISTIC TRAINING EXPERIENCES, I FELT THE PROPOSED OP WAS SAFE. ALSO IN HINDSIGHT, I SHOULD HAVE SELECTED ALTERNATE AIR ONCE IN CLOUDS, NOT EXPECTING PITOT/STATIC PROBLEMS DUE TO WORKING PITOT HEAT (CHKED ON GND). LESSON: NO MATTER HOW SAFE THE PLANNING IS, EXTRA VIGILANCE IS REQUIRED IF IN CONDITIONS THE AIRPLANE IS NOT DESIGNED FOR.
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.