Narrative:

I had been flying in and out of the clouds for most of this trip and it had been fairly smooth. ATC gave me vectors to the ILS 13 approach and had notified me that they were not receiving my transponder. I cycled the power on my transponder and that seemed to fix the problem. Now inbound on the ILS 13 approach; I was cleared down to and requested by ATC to maintain 3;000 ft MSL. I was still in and out of the clouds at 3;000 ft and noticed a tall cloud in front of me which stood above everything around it. I didn't give it much thought as I had just disengaged the autopilot; reduced power; and was trimming the airplane to relieve the control pressures. I was also busy with the items on my pre-landing checklist; as well as watching that I kept the needle centered on my HSI. I reached up to tune the tower frequency into my standby so I could quickly switch when I got handed off just as I entered the clouds again. About 10 miles from the airport; I felt a jolt down that tried to lift me out of my seat and instinctively pulled back on the yoke. I looked at my attitude indicator and saw that I was nose high and immediately started pushing the yoke forward. I also saw my airspeed indicator dropping so I added power to keep from stalling. The added power caused the airplane to want to pitch up more because it was trimmed for low power level flight. I was continuously trimming nose down to counter the added power. I then felt the airplane seem to rise and looked at the altimeter. It was going up now even though when I looked back at the attitude indicator I was now in a nose down attitude. I pushed the yoke further forward as I pulled some power back out to arrest the rise and saw 3;300 ft on my altimeter. Approach advised me that there was someone above me in the holding pattern. I was able to get back to 3;000 ft and continued the approach. I broke out of the clouds just after beginning my descent on the glideslope and continued in visually.after landing; the full impact of how tragic this could have ended was very apparent to me. In thinking about the event and my actions; there are several things that stand out. I was unprepared mentally for the downdraft and subsequent updraft that occurred. The height of the cloud probably should have forewarned me that there were rising and possibly falling columns of air. My reflex probably compounded the problem. If I had ridden the downdraft without pulling back as far on the yoke; I may not have had to add power and maybe minimized the subsequent altitude excursion when I entered the updraft. I did not know how far I dropped initially but should have made a quick glance to the altimeter to find out. I will be getting an instrument proficiency check prior to flying in IMC again. I also plan to do more of my practice approaches with a focus on basic aircraft control while under the hood.

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Original NASA ASRS Text

Title: An M-20 pilot at 3;000 FT encountered an updraft on approach which caused a pitch up; a 300 FT altitude gain and airspeed loss from which he recovered to complete a successful approach.

Narrative: I had been flying in and out of the clouds for most of this trip and it had been fairly smooth. ATC gave me vectors to the ILS 13 approach and had notified me that they were not receiving my transponder. I cycled the power on my transponder and that seemed to fix the problem. Now inbound on the ILS 13 approach; I was cleared down to and requested by ATC to maintain 3;000 FT MSL. I was still in and out of the clouds at 3;000 FT and noticed a tall cloud in front of me which stood above everything around it. I didn't give it much thought as I had just disengaged the autopilot; reduced power; and was trimming the airplane to relieve the control pressures. I was also busy with the items on my Pre-Landing Checklist; as well as watching that I kept the needle centered on my HSI. I reached up to tune the Tower frequency into my standby so I could quickly switch when I got handed off just as I entered the clouds again. About 10 miles from the airport; I felt a jolt down that tried to lift me out of my seat and instinctively pulled back on the yoke. I looked at my attitude indicator and saw that I was nose high and immediately started pushing the yoke forward. I also saw my airspeed indicator dropping so I added power to keep from stalling. The added power caused the airplane to want to pitch up more because it was trimmed for low power level flight. I was continuously trimming nose down to counter the added power. I then felt the airplane seem to rise and looked at the altimeter. It was going up now even though when I looked back at the attitude indicator I was now in a nose down attitude. I pushed the yoke further forward as I pulled some power back out to arrest the rise and saw 3;300 FT on my altimeter. Approach advised me that there was someone above me in the holding pattern. I was able to get back to 3;000 FT and continued the approach. I broke out of the clouds just after beginning my descent on the glideslope and continued in visually.After landing; the full impact of how tragic this could have ended was very apparent to me. In thinking about the event and my actions; there are several things that stand out. I was unprepared mentally for the downdraft and subsequent updraft that occurred. The height of the cloud probably should have forewarned me that there were rising and possibly falling columns of air. My reflex probably compounded the problem. If I had ridden the downdraft without pulling back as far on the yoke; I may not have had to add power and maybe minimized the subsequent altitude excursion when I entered the updraft. I did not know how far I dropped initially but should have made a quick glance to the altimeter to find out. I will be getting an Instrument Proficiency Check prior to flying in IMC again. I also plan to do more of my practice approaches with a focus on basic aircraft control while under the hood.

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.