Narrative:

After climb to final altitude of FL210 I was leaning the engine using the engine analyzer 'lean find' mode. I saw the turbo inlet temperature (tit) exceed critical value and enriched the mixture quickly. The engine either stopped or was producing minimal power. I lost some altitude while reengaging engine to proper operation. Engine returned but with less than full power. ATC asked about deviation and I informed them I was working through engine issues and I asked for block from FL190 to FL210 and ATC authorized and asked if I needed assistance which; at that time; I declined. Reaching 19;300 MSL I was able to maintain altitude but only at eighty knots indicated. I asked for descent to 13;000 MSL and was authorized. When reaching 15;500 MSL I was in a slow descent but had twenty two inches manifold pressure and leveled. I was able to maintain a good forward speed about 125 knots indicated; 160 knots true airspeed. I asked for an amendment to make 15;000 my final and was authorized. While I continued to assess problem and determine whether to continue; land or return to home base; I deviated again by about 400-500 feet while adjusting for different engine settings but corrected as quickly as possible when I realized I was losing altitude. I flew the rest of the flight to destination without incident. All engine measurements were perfectly in expected ranges with the exception of manifold pressure which was six to eight inches low but steady. At around 5;000' in vicinity of airport full manifold pressure returned. I was throttling back for the final descent into the traffic pattern and when reaching and passing through twenty inches manifold pressure and below the engine began to run very badly; missing and backfiring. I increased the manifold pressure; remained high and flew the pattern close in and with additional altitude as a safety margin in case the engine quit. I landed and the engine continued to run badly at low RPM but adding power smoothed it out. I was able to find an a&P who provided service. A visual inspection quickly revealed the worm clamp on the air duct into the intake manifold had come loose and boosted air was leaking out before entering the manifold. Since the turbocharger system has an altitude compensating pressure controller the whole system was out of balance and providing erratic behavior. Repositioning the duct and tightening the worm clamp in place immediately corrected the problem; confirmed by a ground check. Return flight was uneventful.

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Original NASA ASRS Text

Title: An M20T Pilot suffered significant loss of power at FL210 when the hose clamp from the turbocharger to the intake came loose causing the manifold pressure to decrease to unacceptable levels.

Narrative: After climb to final altitude of FL210 I was leaning the engine using the engine analyzer 'lean find' mode. I saw the turbo inlet temperature (TIT) exceed critical value and enriched the mixture quickly. The engine either stopped or was producing minimal power. I lost some altitude while reengaging engine to proper operation. Engine returned but with less than full power. ATC asked about deviation and I informed them I was working through engine issues and I asked for block from FL190 to FL210 and ATC authorized and asked if I needed assistance which; at that time; I declined. Reaching 19;300 MSL I was able to maintain altitude but only at eighty knots indicated. I asked for descent to 13;000 MSL and was authorized. When reaching 15;500 MSL I was in a slow descent but had twenty two inches manifold pressure and leveled. I was able to maintain a good forward speed about 125 knots indicated; 160 knots true airspeed. I asked for an amendment to make 15;000 my final and was authorized. While I continued to assess problem and determine whether to continue; land or return to home base; I deviated again by about 400-500 feet while adjusting for different engine settings but corrected as quickly as possible when I realized I was losing altitude. I flew the rest of the flight to destination without incident. All engine measurements were perfectly in expected ranges with the exception of manifold pressure which was six to eight inches low but steady. At around 5;000' in vicinity of airport full manifold pressure returned. I was throttling back for the final descent into the traffic pattern and when reaching and passing through twenty inches manifold pressure and below the engine began to run very badly; missing and backfiring. I increased the manifold pressure; remained high and flew the pattern close in and with additional altitude as a safety margin in case the engine quit. I landed and the engine continued to run badly at low RPM but adding power smoothed it out. I was able to find an A&P who provided service. A visual inspection quickly revealed the worm clamp on the air duct into the intake manifold had come loose and boosted air was leaking out before entering the manifold. Since the turbocharger system has an altitude compensating pressure controller the whole system was out of balance and providing erratic behavior. Repositioning the duct and tightening the worm clamp in place immediately corrected the problem; confirmed by a ground check. Return flight was uneventful.

Data retrieved from NASA's ASRS site as of April 2012 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.