Narrative:

Destination was thv for practice NDB approachs. The engine suddenly lost power and began to vibrate excessively. I immediately reduced power to a point where vibration was tolerable (approximately 1700 RPM), however this was not enough power to sustain level flight. The aircraft began a slow descent of approximately 300-400 FPM. I instructed my student to look for a field while I attempted to 'correct' the problem. It quickly became obvious that there was no way to fix the problem. Up to this point, I had been on a direct course to hanover (6w6). Considering our altitude, descent rate, distance from 6w6 and the fact the engine was still producing some power, I decided to continue to 6w6. I arrived at 6w6 a few hundred ft below pattern altitude and, with a few s-turns on final, landed the aircraft west/O incident. I later found out that the #2 cylinder had choked on the exhaust valve. It is very interesting to note that day in and day out I teach students the recommended forced landing procedure (spiral down to field), and that in this situation, I elected not to spiral to a field. In fact, if I had spiraled to a field, I never would have made it to 6w6 and the outcome could have been much different. Another lesson which proves that judgement is very difficult, if not impossible to teach.

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Original NASA ASRS Text

Title: FLT TRAINING SMA EXPERIENCES PARTIAL POWER LOSS AND STRUGGLES TO AN EMERGENCY LNDG AT 6W6.

Narrative: DEST WAS THV FOR PRACTICE NDB APCHS. THE ENG SUDDENLY LOST PWR AND BEGAN TO VIBRATE EXCESSIVELY. I IMMEDIATELY REDUCED PWR TO A POINT WHERE VIBRATION WAS TOLERABLE (APPROX 1700 RPM), HOWEVER THIS WAS NOT ENOUGH PWR TO SUSTAIN LEVEL FLT. THE ACFT BEGAN A SLOW DSNT OF APPROX 300-400 FPM. I INSTRUCTED MY STUDENT TO LOOK FOR A FIELD WHILE I ATTEMPTED TO 'CORRECT' THE PROB. IT QUICKLY BECAME OBVIOUS THAT THERE WAS NO WAY TO FIX THE PROB. UP TO THIS POINT, I HAD BEEN ON A DIRECT COURSE TO HANOVER (6W6). CONSIDERING OUR ALT, DSNT RATE, DISTANCE FROM 6W6 AND THE FACT THE ENG WAS STILL PRODUCING SOME PWR, I DECIDED TO CONTINUE TO 6W6. I ARRIVED AT 6W6 A FEW HUNDRED FT BELOW PATTERN ALT AND, WITH A FEW S-TURNS ON FINAL, LANDED THE ACFT W/O INCIDENT. I LATER FOUND OUT THAT THE #2 CYLINDER HAD CHOKED ON THE EXHAUST VALVE. IT IS VERY INTERESTING TO NOTE THAT DAY IN AND DAY OUT I TEACH STUDENTS THE RECOMMENDED FORCED LNDG PROC (SPIRAL DOWN TO FIELD), AND THAT IN THIS SITUATION, I ELECTED NOT TO SPIRAL TO A FIELD. IN FACT, IF I HAD SPIRALED TO A FIELD, I NEVER WOULD HAVE MADE IT TO 6W6 AND THE OUTCOME COULD HAVE BEEN MUCH DIFFERENT. ANOTHER LESSON WHICH PROVES THAT JUDGEMENT IS VERY DIFFICULT, IF NOT IMPOSSIBLE TO TEACH.

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.