Narrative:

Crossing mountains from the east with significant winds and turbulence expected we traveled northward toward lower terrain while testing the turbulence and headwinds at various altitudes. Several scattered and broken cloud layers with sweeping openings allowed for higher operations and we found smoother air with lower tops and bright sunshine. Turning on course and beginning to cross the mountains we encountered rising billows at the cloud tops above 17k. We turned around and flew to the east to return to better weather; and continued our routing north where the terrain was lower and sunshine was more dominate.we continued north and east flying VFR over the top; planning to land ahead for fuel and to finalize our planning over the mountains. During the climb the pitot heat was switched on; and soon the indicated airspeed degraded and the primary flight display indicated 'GPS assist' mode. At this point I incorrectly began to reference altitude on GPS and not pressure data (the GPS reported elevation was significantly lower than pressure altitude).enroute over the mountains we encountered rising cloud tops and turbulence that pushed us up to non-standard altitudes heading west below 18;000 ft (incorrectly referenced to GPS elevation after the GPS assist mode encounter; which put our pressure altitude hundreds of feet higher). Our autopilot disengaged several times unexpectedly and we inadvertently penetrated class a.the pitot derived airspeed would not maintain a reliable indication and the autopilot was abandoned as the flight continued. Weather conditions continued to improve north and west as we continued. We encountered several dramatic updrafts and downdrafts throughout this area from mountain waves and turbulence that were amplified by hand flying with the autopilot disengaged; and we descended to 14.5 and later climbed back to 16.5 for better winds and smoother air. Further on we encountered a significant mountain wave; and shortly afterwards we descended to 6.5. A reliable airspeed was restored passing through 8;000 ft. Supplemental oxygen was in use but not readjusted after a higher climb at altitude. A long day of flight was being made longer from windy and turbulent conditions; and the loss of a reliable pitot indication and the autopilot added to pilot workload.center was being monitored but flight following had not been requested; and a cold cabin at altitude made the sunshine more attractive than descending to a lower layer. Pitot heat was insufficient to restore pitot function at these temperatures and may have actually contributed to the blockage and the resulting unreliable readings.

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Original NASA ASRS Text

Title: RV-7 pilot deviated into Class A airspace without clearance. Weather and a malfunctioning pitot system were contributing factors to the event.

Narrative: Crossing mountains from the east with significant winds and turbulence expected we traveled northward toward lower terrain while testing the turbulence and headwinds at various altitudes. Several scattered and broken cloud layers with sweeping openings allowed for higher operations and we found smoother air with lower tops and bright sunshine. Turning on course and beginning to cross the mountains we encountered rising billows at the cloud tops above 17k. We turned around and flew to the east to return to better weather; and continued our routing north where the terrain was lower and sunshine was more dominate.We continued north and east flying VFR over the top; planning to land ahead for fuel and to finalize our planning over the mountains. During the climb the pitot heat was switched on; and soon the indicated airspeed degraded and the primary flight display indicated 'GPS Assist' mode. At this point I incorrectly began to reference altitude on GPS and not pressure data (the GPS reported elevation was significantly lower than pressure altitude).Enroute over the mountains we encountered rising cloud tops and turbulence that pushed us up to non-standard altitudes heading west below 18;000 FT (incorrectly referenced to GPS elevation after the GPS Assist mode encounter; which put our pressure altitude hundreds of feet higher). Our autopilot disengaged several times unexpectedly and we inadvertently penetrated Class A.The pitot derived airspeed would not maintain a reliable indication and the autopilot was abandoned as the flight continued. Weather conditions continued to improve north and west as we continued. We encountered several dramatic updrafts and downdrafts throughout this area from mountain waves and turbulence that were amplified by hand flying with the autopilot disengaged; and we descended to 14.5 and later climbed back to 16.5 for better winds and smoother air. Further on we encountered a significant mountain wave; and shortly afterwards we descended to 6.5. A reliable airspeed was restored passing through 8;000 FT. Supplemental oxygen was in use but not readjusted after a higher climb at altitude. A long day of flight was being made longer from windy and turbulent conditions; and the loss of a reliable pitot indication and the autopilot added to pilot workload.Center was being monitored but flight following had not been requested; and a cold cabin at altitude made the sunshine more attractive than descending to a lower layer. Pitot heat was insufficient to restore pitot function at these temperatures and may have actually contributed to the blockage and the resulting unreliable readings.

Data retrieved from NASA's ASRS site as of July 2013 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.