Incident at near Sudbury Municipal Airport

1998-02-18: The aircraft (C-GMON, operating as ONT306) was on an IFR flight from Sudbury Municipal Airport (CYSB) to Toronto (LBPIA) (CYYZ). The Toronto ACC Controller was advised at 1606Z that the aircraft had engine problems when the flight was approximately 15 miles south of Sudbury. The flight crew requested a return to Sudbury and landed without further incident at 1613Z with ERS standing by. ERS were released at 1614Z. Ops. impact -- none. 33 S.O.B. -- three (3) crew; 30 passengers. Supplemental information from T.S.B. Initial Notification (#A96O0005): Shortly after take-off, the flight crew noted fluctuations in the torque of the left engine. The flight crew attempted, unsuccessfully, to control the fluctuations and returned to Sudbury for an uneventful landing with ERS on standby. The flow control valve and step-down limiters were replaced and the aircraft returned to service. The step-down limited has a history of freezing in cold weather causing fluctuations in the torque until the device thaws. 43 S.O.B. -- three (3) crew; 40 passengers.