Flight Crew Private; Flight Crew Instrument
Flight Crew Last 90 Days 59; Flight Crew Total 1335
Distraction; Workload; Troubleshooting; Situational Awareness; Human-Machine Interface; Confusion
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Aircraft Equipment Problem Dissipated; Flight Crew Landed As Precaution; Flight Crew Took Evasive Action; General Flight Cancelled / Delayed
Human Factors; Aircraft; Weather
The conditions were a solid overcast layer with bases at 8100 MSL and tops at 9800 MSL with an aerodrome field elevation of 6200 MSL. I was conducting practice approaches under an IFR flight plan. My first approach was relatively normal with much of the flying above the overcast. However; during this approach; I was noticing that I was having difficulty maintaining altitude and heading. I was experiencing altitude differences of up to 500 feet and heading errors of 10-15 degrees. The heading errors were largely due to excessive time spent addressing altitude problems. While experiencing continued difficulty controlling altitude I eventually noticed air rushing sounds consistent with increasing airspeed while the altimeter was indicating a continuous climb. This significantly puzzled me for a while and I responded as if the aircraft was in a descent to stop the rushing air sound. I turned on the pitot heat and after about a minute the pitot static readings all jumped; probably due to unblocking the pitot tube. The approach proceeded normally thereafter once I re-aligned the track on the initial approach course; and terminated in a low approach. During a second approach I continued to experience erratic problems holding altitude; some of which was due to my continued concern about the erroneous pitot static readings; but also my ability to control the aircraft was not good and seemed to be getting worse. During this second approach the controller had me fly at 9000 MSL and then at 9500 MSL; putting the aircraft squarely in the layer during much of the time. Although the field was reporting +6C; the temperature at 9500 MSL was -4C. The controller initially vectored me for the approach; but then away from the approach path and outside of the airspace; for traffic de-confliction. After being in the layer for five minutes I noticed rime ice accumulating on the wings. I requested lower and tower responded that they could not give me lower than 9000 MSL. I then cancelled my IFR flight plan and simultaneously started a rapid descent from 9500 MSL to 8000 MSL; below the layer. I then concluded the flight under VFR with a straight in visual approach.
A PA32 pilot shooting practice instrument approaches into a high altitude airport in IMC suffered erratic altitude and heading readings which were likely the result of pitot static blockage.