In 1983, an Air Canada Boeing 767 ran out of fuel at 41,000 feet because fuel was calculated in pounds instead of kilograms; the pilots glided it onto a disused air base runway in Gimli, and all 69 on board survived

An Air Canada Boeing 767 carrying 61 passengers and eight crew members ran completely out of fuel at 41,000 feet over Manitoba after a mistake in converting metric measurements caused ground staff to put less than half the required fuel into the aircraft. The pilots managed to glide the 132-tonne plane for 17 minutes without engine power. They made an emergency landing on a former military runway that had been turned into a sports car race track. According to the official inquiry by the Aviation Safety Board of Canada, all 69 people on board survived the incident on 23 July 1983. Only minor injuries were reported during the evacuation.

Confusion over kilograms and pounds

The fueling mistake happened on the ground in Montreal before the flight departed for Edmonton via Ottawa. The aircraft’s digital Fuel Quantity Indicator System (FQIS) was not working because of a faulty channel. Maintenance workers had already recorded the problem. Since the automatic fuel gauge showed no readings, the ground crew and pilots had to work out the fuel amount manually. They used a dripstick, a tool that measured the volume of fuel in litres. At the time, Air Canada was changing its fleet over to the metric system. The newly purchased Boeing 767 was the airline’s first aircraft that used metric measurements throughout. The standard flight management computers required fuel amounts to be entered in kilograms. However, while doing the manual calculations, the crew used the conversion figure for pounds instead of kilograms. Instead of multiplying the fuel volume in litres by 0.8 to calculate its weight in kilograms, they multiplied it by 1.77. This was the conversion figure used for imperial measurements. Because of this mistake, the aircraft took off with just 22,300 pounds (10,100 kg) of fuel. This was only about 45 percent of the 49,200 pounds (22,300 kg) needed to complete the journey to Edmonton.

Total power loss in mid-air

While flying over Red Lake, Ontario, at 41,000 feet, the pilots received warnings about low fuel pressure in the cockpit. Captain Robert Pearson and First Officer Maurice Quintal first thought there was a problem with a fuel pump. They planned to divert the aircraft to Winnipeg. Within minutes, both Pratt & Whitney JT9D engines stopped working, cutting off power to all the main electrical generators. With both engines out, the cockpit displays went blank. The pilots were left with only a few emergency instruments powered by batteries. These backup instruments did not include a vertical speed indicator, which made it difficult for the crew to work out how quickly the aircraft was losing height. There was another serious problem. Without engine power to run the hydraulic pumps, the aircraft’s control surfaces could no longer be moved using the normal controls. The aircraft’s automatic emergency system released a ram air turbine. This was a small propeller powered by the airflow outside the aircraft. It produced just enough hydraulic pressure to let the pilots steer the plane and control its nose position manually.

Race track diversion at Gimli

After realising they could not reach Winnipeg, First Officer Quintal suggested landing at the former Royal Canadian Air Force Station Gimli. This was a military airfield where he had trained in the past. The crew did not know that the closed military base had been turned into the Gimli Motorsports Park. On the day of the incident, part of the main runway was being used for a sports car event organised by the Winnipeg Sports Car Club. Spectators, campers, and racing cars were parked along the runway. As Captain Pearson, who had years of experience as a glider pilot, brought the aircraft toward Gimli, he realised it was moving too fast and was too high to stop safely on the remaining paved runway. Since both engines had stopped, the crew could not use the wing flaps or slats to slow the aircraft down. Pearson used a forward slip, a rare move for commercial aircraft. It involves using the rudder and aileron controls in opposite directions to turn the aircraft sideways. This increases air resistance and helps the plane lose height quickly without increasing its forward speed. The sideways movement briefly reduced the airflow to the ram air turbine. This made the flight controls harder to operate just before landing. However, Pearson managed to straighten the aircraft in time.

Landing on the dragstrip

The crew lowered the landing gear using a manual gravity release system. The main landing gear locked into position, but the nose gear did not lock properly. The Boeing 767 touched down on the dragstrip section of the airfield. Pearson applied the main wheel brakes, causing two tyres to burst. Two boys riding bicycles on the runway managed to get out of the way as the silent aircraft approached them. Because the nose gear had not locked into place, the front of the aircraft dropped onto the runway. The nose scraped along the concrete, creating a great deal of friction that helped slow down the heavy plane. The front section then hit a steel guardrail installed along the middle of the converted dragstrip. The barrier helped keep the aircraft moving straight along the runway instead of turning toward the spectators. The aircraft came to a complete stop within 3,000 feet of touching down. A small fire near the nose was put out by race track staff using portable fire extinguishers. Passengers left the aircraft using emergency slides. Because the nose had collapsed, the slides hung at steep angles. Some passengers suffered minor cuts, scrapes, and sprains during the evacuation. The Canadian Aviation Safety Board report identified failures in procedures, gaps in staff training, and Air Canada’s use of both metric and imperial measurements across its aircraft fleet as the main factors behind the incident. The damaged Boeing 767, registered as C-GAUN, was repaired at the Gimli site and returned to commercial service with Air Canada. It continued flying for another 25 years before being retired in 2008.