This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
This event occurred in a Cessna 172 during a lesson with a student.
After rolling wings level from a clearing turn, engine RPM dropped to 1,000. After five seconds the RPM increased to 2,000. The RPM kept cycling in this manner with no change from throttle, mixture or pitch.
I believed a complete engine failure was possible, so I took command of the aircraft from the student, and started flying back to ZZZ since it was the closest airfield.
I pulled the carb heat on, verified the RPM was full and mixture rich, primer locked, master on, fuel on both.
I contacted Approach and requested priority handling to ensure I would receive priority handling and services if an off-field landing would be required. I was able to make it back to the field and performed a straight-in landing for Runway XX.
I contacted ZZZ after safely landing and ensured I no longer required assistance.
The cause of the partial engine failure was a bent push rod.
No pre-flight action nor run up would have caught this condition. It was a good reaction to make an immediate return to the field.
Primary Problem: Ambiguous
ACN: 2011294
