Narrative:

I was making a 500 NM x-country trip VFR, to build time for an INS rating. I rented a plane from the local flight school for the trip. The first leg was uneventful. A friend who was INS rated flew the right seat, helping with navigation. At the end of the first leg, the plane was refueled, another flight plan filed and the second leg went smoothly. Aircraft was again refueled for the last leg of 256 NM to the home airport. We cruised at 5500' MSL for the 3 hour return trip. Approximately 20 NM from the airport, I started a shallow, power-on descent from 5500'. Engine gauges all checked normal and aircraft was running smoothly. Vertical speed indicated 300-400 FPM. At approximately 4300' MSL. Engine immediately began running rough with no warning and severe vibration. I immediately followed the engine-out checklist with right seat pilot double-checking called unicom and advised of partial power. Engine was running at 1900 rmp with heavy vibration, but with enough power to just hold altitude, approached airfield at 4000' MSL and spiraled down to a landing. I found out the next day that the exhaust valve had broken, 1/2 of it was missing. Also the engine had low compression. FBO mechanics said they knew it was a 'weak' engine. They also said it was due for an oil change and should not have been rented out. In addition the tbo was over by 150 hours. I learned the FBO already had a new engine to replace it. Mechanics also said broken valves were not uncommon in this engine and that an ad needed to be issued. The dispatcher failed to relay any of this information to me. In the future, I plan to check engine log books for tbo's and squawks before rental.

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Original NASA ASRS Text

Title: SMA EXPERIENCES PARTIAL POWER LOSS.

Narrative: I WAS MAKING A 500 NM X-COUNTRY TRIP VFR, TO BUILD TIME FOR AN INS RATING. I RENTED A PLANE FROM THE LCL FLT SCHOOL FOR THE TRIP. THE FIRST LEG WAS UNEVENTFUL. A FRIEND WHO WAS INS RATED FLEW THE RIGHT SEAT, HELPING WITH NAV. AT THE END OF THE FIRST LEG, THE PLANE WAS REFUELED, ANOTHER FLT PLAN FILED AND THE SECOND LEG WENT SMOOTHLY. ACFT WAS AGAIN REFUELED FOR THE LAST LEG OF 256 NM TO THE HOME ARPT. WE CRUISED AT 5500' MSL FOR THE 3 HR RETURN TRIP. APPROX 20 NM FROM THE ARPT, I STARTED A SHALLOW, PWR-ON DSNT FROM 5500'. ENG GAUGES ALL CHKED NORMAL AND ACFT WAS RUNNING SMOOTHLY. VERT SPD INDICATED 300-400 FPM. AT APPROX 4300' MSL. ENG IMMEDIATELY BEGAN RUNNING ROUGH WITH NO WARNING AND SEVERE VIBRATION. I IMMEDIATELY FOLLOWED THE ENG-OUT CHKLIST WITH RIGHT SEAT PLT DOUBLE-CHKING CALLED UNICOM AND ADVISED OF PARTIAL PWR. ENG WAS RUNNING AT 1900 RMP WITH HVY VIBRATION, BUT WITH ENOUGH PWR TO JUST HOLD ALT, APCHED AIRFIELD AT 4000' MSL AND SPIRALED DOWN TO A LNDG. I FOUND OUT THE NEXT DAY THAT THE EXHAUST VALVE HAD BROKEN, 1/2 OF IT WAS MISSING. ALSO THE ENG HAD LOW COMPRESSION. FBO MECHS SAID THEY KNEW IT WAS A 'WEAK' ENG. THEY ALSO SAID IT WAS DUE FOR AN OIL CHANGE AND SHOULD NOT HAVE BEEN RENTED OUT. IN ADDITION THE TBO WAS OVER BY 150 HRS. I LEARNED THE FBO ALREADY HAD A NEW ENG TO REPLACE IT. MECHS ALSO SAID BROKEN VALVES WERE NOT UNCOMMON IN THIS ENG AND THAT AN AD NEEDED TO BE ISSUED. THE DISPATCHER FAILED TO RELAY ANY OF THIS INFO TO ME. IN THE FUTURE, I PLAN TO CHK ENG LOG BOOKS FOR TBO'S AND SQUAWKS BEFORE RENTAL.

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.