C-GONJ, a Bombardier DHC-8-102 aircraft operated by Jazz Aviation LP, was conducting flight JZA8327 from Toronto/Lester B. Pearson Intl, ON (CYYZ) to Sault Ste. Marie, ON (CYAM) with 3 crew members and 33 passengers on board. Shortly after the departure from CYYZ, the flight crew felt a bump which was followed by a nose landing gear unsafe indication. After contacting the operator’s maintenance, the flight crew elected to return to CYYZ and declared an emergency. During the approach, the alternate landing gear extension was executed and the aircraft landed uneventfully with ARFF standing by.
The operator’s maintenance performed several landing gear operations without being able to duplicate the fault. As a precaution, the Proximity Switch Electronics Unit (PSEU) and nose landing gear down lock sensor were replaced and the aircraft was returned to service. No further nose landing gear faults were reported on subsequent flights.