As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE N2 RPM NEEDLE FOR THE #2 ENGINE ON THE TRIPLE TACH MOVED TO ZERO INTERMITTENTLY. AT AIRSPEEDS SLOWER THAN 40 KNOTS THE N2 RPM NEEDLE SYNCHRONIZED WITH THE ROTOR RPM NEEDLE AGAIN. REMOVED AND REPLACED NUMBER TWO ENGINE N2 SENSOR IAW ENGINE MANUAL 77-12-00-900-801-B01. MOC SUCCESSFULLY COMPLETED.