What was found
PILOT REPORTED THAT ON RETURN FLIGHT AT NORMAL CRUISE POWER WITH NO CONTROL INPUT NG AND NR SPEEDS SUDDENLY DROPPED APPROXIMATELY 3 PERCENT AND RAPIDLY RECOVERED WITH A SLIGHT OVERSHOOT BEFORE RETURNING TO STEADY STATE. THIS OCCURRED SEVERAL TIMES OVER A .7 HOUR FLIGHT. REPLACEMENT OF THE OVERSPEED LIMITER CORRECTED THIS DEFECT AS CONFIRMED BY OPERATIONAL CHECK FLIGHTS TO CONFIRM A REPEATABLE DEFECT AND THAT AFTER LIMITER REPLACEMENT DEFECT WAS CORRECTED.