Gimli Glider

Air Canada Flight 143 was a scheduled domestic passenger flight between Montreal and Edmonton. On July 23, 1983, the Boeing 767 servicing the route ran out of fuel midway through the flight.

The fuel gauge was not operating, and the plane's tanks had been underfilled because of an incorrect calculation.

The flight crew successfully glided the aircraft from an altitude of 41000 ft to an emergency landing at a former Royal Canadian Air Force base in Gimli, Manitoba, which had been converted to a racetrack, Gimli Motorsports Park. The landing caused no serious injuries to passengers or persons on the ground, and only minor damage to the aircraft. The aircraft was repaired, and remained in service until its retirement in 2008. This unusual aviation accident earned the aircraft the nickname "Gimli Glider".

The accident was caused by a series of issues, including a failed fuel-quantity indicator sensor (FQIS) and confusion between pounds and kilograms. The fuel sensors in 767s had high failure rates, and the only replacement sensor available when the failure was detected was also nonfunctional. This problem was logged when it was discovered, but later, the maintenance crew misunderstood the problem and turned off the backup FQIS. This required the volume of fuel to be manually measured using a dripstick.

The navigational computer required a number to be entered specifying the amount of fuel on board, in kilograms; however, an incorrect conversion from volume to mass was applied, which led the pilots and ground crew to agree that there was enough fuel for the remaining trip when it was actually 45% of the required amount. The aircraft ran out of fuel halfway to Edmonton, where maintenance staff were waiting to install a working FQIS that they had borrowed from another airline.

The Board of Inquiry found fault with Air Canada procedures, training, and manuals. It recommended the adoption of fuelling procedures and other safety measures that U.S. and European airlines were already using. The board also recommended the immediate conversion of all Air Canada aircraft from imperial units to SI units, since a fleet using a mix of units was more dangerous than an all-imperial or an all-metric fleet.

Background

On July 22, 1983, Air Canada Boeing 767 C-GAUN underwent routine checks in Edmonton. The technician found a defective FQIS, so he disabled the defective channel and made an entry in the logbook. The next morning, Captain John Weir and co-pilot Captain Donald Johnson were told about the problem. Since the FQIS was now operating on a single channel, a dripstick reading was taken to obtain a second fuel quantity measurement. Weir converted the dripstick reading from centimetres to litres to kilograms, finding that it agreed with the FQIS. The plane flew to Toronto and then Montreal without incident.

At Montreal, Captain Bob Pearson and First Officer Maurice Quintal took over the airplane for Flight 143 to Ottawa and Edmonton. During the handover, Weir told Pearson that a problem existed with the FQIS, and Pearson decided to take on enough fuel to fly to Edmonton without refuelling in Ottawa. Meanwhile, an avionics technician had entered the cockpit and read the logbook. While waiting for the fuel truck, he enabled the defective channel and performed an FQIS self-test. Distracted by the arrival of the fuel truck, he left the channel enabled after the FQIS failed the test. Pearson entered the cockpit to find the FQIS blank, as he expected.

The all-metric 767 aircraft, new to the fleet, tracked fuel quantities in kilograms. After taking a dripstick measurement, Pearson converted the reading from centimetres to litres to kilograms. But he used the density figure for jet fuel from the Air Canada refueler's slip. This figure, used for all other aircraft in the fleet, stated the density in pounds/litre. The correct figure to use was for kilograms/litre, and the result actually calculated was incorrect. Since the FQIS was not operational, he entered the miscalculated result into the flight management computer. The airplane flew to Ottawa without accident, where another dripstick measurement was taken, and again, in the same way, converted incorrectly. Since the aircraft appeared to have enough fuel to reach Edmonton, no fuel was loaded at Ottawa.