Narrative:

I was PIC and had a multi-engine rated student in the right seat. After departure and established direct to our destination while on top I turned the plane over to the student and was providing instrument instruction. We had a left alternator caution light come on; ran the check list and the light extinguished. In preparation for landing at the airport I picked up the ATIS and requested the ILS xx circle to land on yy. I was cleared to 5;000 ft and took controls since we were IMC. I selected the approach in the GPS and was cleared to intercept the localizer; report established.this is where it gets embarrassing; I couldn't intercept the localizer. According to the moving map I was right where I was supposed to be; but the HSI was showing the localizer and the glide slope were not coming in. Center asked if I was established to which I replied negative and he vectored me around to give it another shot. At this point I began having some spatial disorientation issues (vertigo) and it was taking almost all my attention to just fly the plane let alone troubleshoot the navigation/GPS issues. My student was unfamiliar with the aircraft and its instrumentation so I asked my backseater (a CFI with time in the aircraft) to talk her through setting up the approach. My altitudes got off by approximately 300 ft and my heading varied by 20-30 degrees. I was fighting the leans [vertigo].I [ultimately] appeared to be on course and established on the localizer and reported as such. I was cleared for the approach and told to contact tower. After making contact with tower I had a full scale deflection. I reported the situation to tower and requested vectors to the VOR for the VOR yy approach. Of course he had me contact center for that. At this point I knew that whether the GPS was not working; or I had it programmed incorrectly; I had no faith in it and thus used my NAV2 for navigation to the VOR.meanwhile with the leans messing with me I opted to use the autopilot in altitude and heading mode to reduce the workload and get stabilized. Center asked if I wanted to immediately start the approach or if I wanted vectored out so another aircraft could get in. I opted to be vectored out. I used this time to regroup and get set up. We then got cleared direct to the VOR and proceeded towards it; were handed off to tower and completed the approach and landed without incident.I believe the problem arose by being overconfident in my knowledge of the GPS unit; I would love to blame it on some solar flares; but even in hind sight; which is supposed to be 20/20; I do not know exactly why I was not able to get it to give me the information I needed. Secondly; I had never experienced the leans and that took me by surprise. I had a sinus infection and I wonder if that led to the leans. My training had taught about the leans and to trust my instruments. I did recognize I was being affected by the leans but I felt I could not trust my instruments. I am proud of my decisions to always plan for the missed approach; that decision is what had me set up to go to the VOR on NAV2 without having to mess the GPS unit. And pleased with the decision to utilize the auto pilot to help overcome the spatial disorientation. My decision to utilize the assistance of those in the cabin really taught me a lesson about the importance of CRM. I hate that this happened; but I did learn so much because of this flight and am a better pilot for having this experience. I will be receiving additional training in IMC to make sure I am proficient and capable of handling the instrumentation; and the aero medical factors; so that I never find myself in this situation again.

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Original NASA ASRS Text

Title: Vertigo combined with either a malfunctioning or improperly operated GPS in IMC had to be overcome by the instrument rated Instructor pilot in command of a BE58 to affect a safe landing. Assistance from ATC; her multiengine rated student and another CFII in the back seat contributed to a safe recovery from the event.

Narrative: I was PIC and had a multi-engine rated student in the right seat. After departure and established direct to our destination while on top I turned the plane over to the student and was providing instrument instruction. We had a left alternator caution light come on; ran the check list and the light extinguished. In preparation for landing at the airport I picked up the ATIS and requested the ILS XX circle to land on YY. I was cleared to 5;000 FT and took controls since we were IMC. I selected the approach in the GPS and was cleared to intercept the localizer; report established.This is where it gets embarrassing; I couldn't intercept the localizer. According to the moving map I was right where I was supposed to be; but the HSI was showing the localizer and the glide slope were not coming in. Center asked if I was established to which I replied negative and he vectored me around to give it another shot. At this point I began having some spatial disorientation issues (vertigo) and it was taking almost all my attention to just fly the plane let alone troubleshoot the NAV/GPS issues. My student was unfamiliar with the aircraft and its instrumentation so I asked my backseater (A CFI with time in the aircraft) to talk her through setting up the approach. My altitudes got off by approximately 300 FT and my heading varied by 20-30 degrees. I was fighting the leans [vertigo].I [ultimately] appeared to be on course and established on the localizer and reported as such. I was cleared for the approach and told to contact Tower. After making contact with Tower I had a full scale deflection. I reported the situation to Tower and requested vectors to the VOR for the VOR YY approach. Of course he had me contact Center for that. At this point I knew that whether the GPS was not working; or I had it programmed incorrectly; I had no faith in it and thus used my NAV2 for navigation to the VOR.Meanwhile with the leans messing with me I opted to use the autopilot in altitude and heading mode to reduce the workload and get stabilized. Center asked if I wanted to immediately start the approach or if I wanted vectored out so another aircraft could get in. I opted to be vectored out. I used this time to regroup and get set up. We then got cleared direct to the VOR and proceeded towards it; were handed off to Tower and completed the approach and landed without incident.I believe the problem arose by being overconfident in my knowledge of the GPS unit; I would love to blame it on some solar flares; but even in hind sight; which is supposed to be 20/20; I do not know exactly why I was not able to get it to give me the information I needed. Secondly; I had never experienced the leans and that took me by surprise. I had a sinus infection and I wonder if that led to the leans. My training had taught about the leans and to trust my instruments. I did recognize I was being affected by the leans but I felt I could not trust my instruments. I am proud of my decisions to always plan for the missed approach; that decision is what had me set up to go to the VOR on NAV2 without having to mess the GPS unit. And pleased with the decision to utilize the auto pilot to help overcome the spatial disorientation. My decision to utilize the assistance of those in the cabin really taught me a lesson about the importance of CRM. I hate that this happened; but I did learn so much because of this flight and am a better pilot for having this experience. I will be receiving additional training in IMC to make sure I am proficient and capable of handling the instrumentation; and the aero medical factors; so that I never find myself in this situation again.

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.