Narrative:

Cleared for visual approach and landing. In the descent; reduced power; props moved to 2500 RPM; and slowed to gear/flap speed approximately 2;500 ft MSL; 5 miles from the runway. Aircraft immediately yawed significantly to the right. Suspected possible right engine failure based on yaw and also in mind - in the past 2-3 weeks since engine overhaul; right oil pressure had been indicating bottom of green arc and right oil temperature was consistently 20 degrees higher than the left. Other pilots had noted these readings and I believe they had been addressed. I had been told to watch and monitor the right engine. Other pilots had also noted the presence of some oil on the right engine. My experience with these pressure and temperature readings in the last two flights was consistent with other pilot observations; but I had not seen any oil leaks in pre-flights. Since configuration of the aircraft and location to the runway was the final approach phase; I did not execute normal engine out procedure of full throttle and RPM on both engines. Altitude and airspeed were sufficient and runway was going to be easily made. I reduced right throttle to further identify the right engine as a possible problem. Aircraft continued to fly as if left engine generating power. [I] elected to shut down/feather right engine to gain better control on landing. Added full throttle to left engine and shut down and feathered right engine. Airspeed still above gear/flap speed and focus then went to reducing power on left engine. Pulled left throttle back and realized it had no effect - engine still produced full power. I realized at that point that the problem was not an inoperative right engine but an overspeed/full power problem with the left engine. Runway [was] getting closer and still easy to make under any condition including power off. [I] considered option of restarting right engine and shutting down left engine. Altitude at this point was approximately 1;500 MSL/1;300 AGL. With runway so close it seemed like too much work to shut down the left and restart the right. However; I knew I would have to secure the overpowered left engine in order to safely land. Since altitude and airspeed were sufficient I elected to also shut down/feather the left engine and glide power off to land. I declared an emergency and told the tower I had lost power in both engines and was gliding in for landing. Airspeed was within gear/flap limits; lowered the gear and applied approach flaps; flared and easily landed without further incident. While waiting for tow; started the left engine two times and both times it went to full throttle with no ability to control it. It was determined the next day that the spline inside a throttle control arm was worn/stripped smooth which caused a failure and resulted in the spring loaded throttle control to go to full power. Simulator training over the past 25 years has focused on engine failures. I only recall a couple of sessions where I was given a propeller governor failure in cruise flight. There is no procedure I could find in the flight manual for this situation. It would be helpful in future training to simulate and practice the proper procedure for identifying and managing this type of incident.

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Original NASA ASRS Text

Title: BE58 pilot misidentified left engine full power throttle control failure as a right engine loss of power; shut down right engine and; after identifying left engine problem; shut it down also and successfully landed power off.

Narrative: Cleared for visual approach and landing. In the descent; reduced power; props moved to 2500 RPM; and slowed to gear/flap speed approximately 2;500 FT MSL; 5 miles from the runway. Aircraft immediately yawed significantly to the right. Suspected possible right engine failure based on yaw and also in mind - in the past 2-3 weeks since engine overhaul; right oil pressure had been indicating bottom of green arc and right oil temperature was consistently 20 degrees higher than the left. Other pilots had noted these readings and I believe they had been addressed. I had been told to watch and monitor the right engine. Other pilots had also noted the presence of some oil on the right engine. My experience with these pressure and temperature readings in the last two flights was consistent with other pilot observations; but I had not seen any oil leaks in pre-flights. Since configuration of the aircraft and location to the runway was the final approach phase; I did not execute normal engine out procedure of full throttle and RPM on both engines. Altitude and airspeed were sufficient and runway was going to be easily made. I reduced right throttle to further identify the right engine as a possible problem. Aircraft continued to fly as if left engine generating power. [I] elected to shut down/feather right engine to gain better control on landing. Added full throttle to left engine and shut down and feathered right engine. Airspeed still above gear/flap speed and focus then went to reducing power on left engine. Pulled left throttle back and realized it had no effect - engine still produced full power. I realized at that point that the problem was not an inoperative right engine but an overspeed/full power problem with the left engine. Runway [was] getting closer and still easy to make under any condition including power off. [I] considered option of restarting right engine and shutting down left engine. Altitude at this point was approximately 1;500 MSL/1;300 AGL. With runway so close it seemed like too much work to shut down the left and restart the right. However; I knew I would have to secure the overpowered left engine in order to safely land. Since altitude and airspeed were sufficient I elected to also shut down/feather the left engine and glide power off to land. I declared an emergency and told the Tower I had lost power in both engines and was gliding in for landing. Airspeed was within gear/flap limits; lowered the gear and applied approach flaps; flared and easily landed without further incident. While waiting for tow; started the left engine two times and both times it went to full throttle with no ability to control it. It was determined the next day that the spline inside a throttle control arm was worn/stripped smooth which caused a failure and resulted in the spring loaded throttle control to go to full power. Simulator training over the past 25 years has focused on engine failures. I only recall a couple of sessions where I was given a propeller governor failure in cruise flight. There is no procedure I could find in the flight manual for this situation. It would be helpful in future training to simulate and practice the proper procedure for identifying and managing this type of incident.

Data retrieved from NASA's ASRS site 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.