Narrative:

While cruising at a VFR altitude of 4;500 feet the engine experienced a sudden; rapid and unusual 500 RPM drop in power without input. The nearest airport was ZZZ and I made decision to land there. Center was providing VFR flight following and was notified of my situation. The procedure of verifying the correct engine control positions failed to increase RPM. The remaining engine output was sufficient to maintain altitude; but I judged it to be unreliable and opted to not reduce power for fear it would cause further undesirable operation. I was cleared to switch to CTAF and announced my intentions to land on the active runway. After slipping to lose excess altitude it became apparent a helicopter was on the end of the runway. I requested that he please move with no response.unsure of the planes ability to climb on a go around I decided to land on the parallel taxiway that was clear of traffic and obstruction. I made an announcement on CTAF that we would land on the taxiway. Unsure of the helicopter on the runways intentions; I asked he depart to the right and away from the taxiway. A slightly faster than normal landing was made without aircraft damage. Contacting CTAF was delayed by a few seconds because we did not have the CTAF frequency being unfamiliar with the airport. My passenger another pilot was trying to tune it while I controlled and looked for the airport and possible alternative landing sites. This delay might have caused the near conflict on the runway. The solution of landing at the nearest airport was complicated by lack of time to communicate with traffic in the area and the only clear landing spot was the taxiway.

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Original NASA ASRS Text

Title: A general aviation pilot reported having an issue with his aircraft's engine; which prompted the pilot to divert to an enroute field. The field was uncontrolled and conflicting traffic existed on the single runway and would not respond to transmissions from the engine issue aircraft. Pilot elected to do an emergency landing on the taxiway.

Narrative: While cruising at a VFR altitude of 4;500 feet the engine experienced a sudden; rapid and unusual 500 RPM drop in power without input. The nearest airport was ZZZ and I made decision to land there. Center was providing VFR flight following and was notified of my situation. The procedure of verifying the correct engine control positions failed to increase RPM. The remaining engine output was sufficient to maintain altitude; but I judged it to be unreliable and opted to not reduce power for fear it would cause further undesirable operation. I was cleared to switch to CTAF and announced my intentions to land on the active runway. After slipping to lose excess altitude it became apparent a helicopter was on the end of the runway. I requested that he please move with no response.Unsure of the planes ability to climb on a go around I decided to land on the parallel taxiway that was clear of traffic and obstruction. I made an announcement on CTAF that we would land on the taxiway. Unsure of the helicopter on the runways intentions; I asked he depart to the right and away from the taxiway. A slightly faster than normal landing was made without aircraft damage. Contacting CTAF was delayed by a few seconds because we did not have the CTAF frequency being unfamiliar with the airport. My passenger another pilot was trying to tune it while I controlled and looked for the airport and possible alternative landing sites. This delay might have caused the near conflict on the runway. The solution of landing at the nearest airport was complicated by lack of time to communicate with traffic in the area and the only clear landing spot was the taxiway.

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.