Narrative:

Chain of events: I was flying south on V115 at 6000 ft. I was below the tops of numerous building cumulus clouds, going rapidly in and out. Each time I entered a cloud, I got vertigo, feeling as if I was in a steep dive. Upward thermals were causing me to slowly gain altitude, but because of the vertigo, my natural inclination was to concentrate on the attitude indicator, keeping the nose level. I was aware that I gained approximately 500 ft and was trying, but not adequately, to correct for it. At about this time, ZTL requested I check my altitude. I responded and forced myself to ignore the vertigo and descended back to my proper altitude. I was not using the autoplt, which does not have pitch control. Human performance considerations: most of my flying time is from helicopters while in the army (now retired). I have roughly 300 hours fixed wing time and only 30 hours actual instruments, mostly helicopters. This was an IFR training flight, and my first ever IFR flight without a copilot. I was apprehensive about the flight because a convective SIGMET had been earlier issued for the vicinity of my destination. At the time of the incident, it appeared that embedded thunderstorms were possible. I had flown practice IFR (hood) on 2 flight within the week preceding this flight and had extensively planned the flight. However, my overall recent experience was relatively low and I believe that this plus my worry about the WX made me more susceptible to the effects of vertigo. Obviously, there is no substitute for actual IMC experience. I now know I need to direct my training towards increased IMC time.

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Original NASA ASRS Text

Title: SINGLE PLT IFR HAS SPATIAL DISORIENTATION.

Narrative: CHAIN OF EVENTS: I WAS FLYING S ON V115 AT 6000 FT. I WAS BELOW THE TOPS OF NUMEROUS BUILDING CUMULUS CLOUDS, GOING RAPIDLY IN AND OUT. EACH TIME I ENTERED A CLOUD, I GOT VERTIGO, FEELING AS IF I WAS IN A STEEP DIVE. UPWARD THERMALS WERE CAUSING ME TO SLOWLY GAIN ALT, BUT BECAUSE OF THE VERTIGO, MY NATURAL INCLINATION WAS TO CONCENTRATE ON THE ATTITUDE INDICATOR, KEEPING THE NOSE LEVEL. I WAS AWARE THAT I GAINED APPROX 500 FT AND WAS TRYING, BUT NOT ADEQUATELY, TO CORRECT FOR IT. AT ABOUT THIS TIME, ZTL REQUESTED I CHK MY ALT. I RESPONDED AND FORCED MYSELF TO IGNORE THE VERTIGO AND DSNDED BACK TO MY PROPER ALT. I WAS NOT USING THE AUTOPLT, WHICH DOES NOT HAVE PITCH CTL. HUMAN PERFORMANCE CONSIDERATIONS: MOST OF MY FLYING TIME IS FROM HELIS WHILE IN THE ARMY (NOW RETIRED). I HAVE ROUGHLY 300 HRS FIXED WING TIME AND ONLY 30 HRS ACTUAL INSTS, MOSTLY HELIS. THIS WAS AN IFR TRAINING FLT, AND MY FIRST EVER IFR FLT WITHOUT A COPLT. I WAS APPREHENSIVE ABOUT THE FLT BECAUSE A CONVECTIVE SIGMET HAD BEEN EARLIER ISSUED FOR THE VICINITY OF MY DEST. AT THE TIME OF THE INCIDENT, IT APPEARED THAT EMBEDDED TSTMS WERE POSSIBLE. I HAD FLOWN PRACTICE IFR (HOOD) ON 2 FLT WITHIN THE WK PRECEDING THIS FLT AND HAD EXTENSIVELY PLANNED THE FLT. HOWEVER, MY OVERALL RECENT EXPERIENCE WAS RELATIVELY LOW AND I BELIEVE THAT THIS PLUS MY WORRY ABOUT THE WX MADE ME MORE SUSCEPTIBLE TO THE EFFECTS OF VERTIGO. OBVIOUSLY, THERE IS NO SUBSTITUTE FOR ACTUAL IMC EXPERIENCE. I NOW KNOW I NEED TO DIRECT MY TRAINING TOWARDS INCREASED IMC TIME.

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.