June 10, 2025
Director General, Civil Aviation
Transport Canada
On 13 January 2025, the De Havilland DHC-8-314 aircraft (registration C-GXAI, serial number 481), operated by Air Inuit as flight AIE866, was conducting an instrument flight rules flight from La Grande Rivière Airport (CYGL), Quebec, to Montréal/Pierre Elliott Trudeau International Airport (CYUL), Quebec, with 6 passengers and 3 crew members on board. Approximately 1 hour and 13 minutes into the flight, while the aircraft was in cruise flight, the left engine ran out of fuel and shut down. The crew called the air traffic control unit to declare an emergency and diverted to Chibougamau/Chapais Airport (CYMT), Quebec, where the aircraft landed without incident. There were no injuries.
The Transportation Safety Board of Canada investigation into this occurrence (A25Q0007) is ongoing.
On De Havilland DHC-8-314 aircraft, the fuel is contained in 2 main tanks: the No. 1 tank in the left wing and the No. 2 tank in the right wing. The quantity of fuel detected by sensors in both tanks is displayed in mass units (pounds [lb] or kilograms [kg]) on 2 corresponding indicators in the cockpit. This fuel quantity is relayed by signal to 2 other external indicators on the refuelling panel located behind the right-engine nacelle. Each tank is also equipped with a device for manually measuring the quantity of fuel while the aircraft is on the ground; this device consists of magnetic floats and graduated rods (magnasticks).These rods, positioned at float level when deployed, indicate the volume contained in each tank; the volume is then converted to mass.
After the aircraft was refuelled before the occurrence flight, the left fuel quantity indicator in the cockpit showed a quantity that was lower than that requested by the flight crew. A technician cross-checked the quantities by comparing the values indicated in the cockpit with those displayed on the refuelling panel and noted a discrepancy between the values on the 2 left indicators. However, both refuelling panel indicators displayed the same quantity, which was consistent with the quantity previously requested by the crew.
Air Inuit’s minimum equipment list (MEL) maintenance procedure, which allows the aircraft to be used with certain inoperative equipment was followed. According to this procedure, the actual quantity can be confirmed in 2 ways: either by using the external indicator if it is in working condition or by physically checking the volume contained in the relevant tank using the graduated rods. Because the left external indicator displayed the requested quantity, it was concluded that the left indicator in the cockpit was defective, and the aircraft was returned to service. The aircraft then proceeded to take off with insufficient fuel for the planned flight, and the left engine ran out of fuel.
Given that refuelling panel indicators receive their signal from the cockpit indicators and are exposed to vibrations and contaminants due to their location, their indications are less reliable than those of the cockpit indicators and graduated rods. Some operators with the same type of aircraft recognized the increased risk of using external indicators alone to determine the quantity of fuel. Therefore, they removed this measurement method from their MEL procedure and had this change approved by Transport Canada.
Operators are advised that the use of the refuelling panel quantity indicator alone may not guarantee that the quantity of fuel on board is accurate. Therefore, an additional verification method, for example using the graduated rods, may be required if there is a discrepancy between the fuel quantity indicators.
The foregoing is provided for whatever follow-up action is deemed appropriate.
The TSB would appreciate being advised of any action that is taken or proposed in this regard within 90 days following receipt of this safety advisory letter. An investigator may follow up with you at a later date.
Upon completion of investigation A25Q0007, the Board will release its investigation report into the occurrence.
Original signed by:
Craig Johnston
Director of Investigations, Air
Cc. Director, Aviation Intelligence and Risk, Transport Canada