What was found
FLIGHT 8662, THE CONDITION LEVER WAS ADVANCED AND THE ENGINE ACCELERATED TO TAKEOFF POWER WITH NO POWER LEVER INPUT. WHEN THE PILOT WENT INTO BETA AND BRAKING WHICH RESULTED IN A CHANGE OF NOISE/PITCH WITH NO NOTICEABLE POWER REDUCTION. PILOT RETURNED CONDITION LEVER TO LOW IDLE BUT DID NOT NOTICE ENOUGH CHANGE TO SLOW DOWN. THE ENGINE WAS SECURED BY CONDITION LEVER CUTOFF. AIRCRAFT WAS BROUGHT TO A STOP BY USE OF AIRCRAFT BRAKES. AFTER COMING TO A STOP A FIRE IMMEDIATELY STARTED AT THE MAIN WHEELS OF AIRCRAFT. FIRE WAS EXTINGUISHED BY ONTARIO FIRE PERSONNEL.