The 'Gimli Glider'

Image capture: Wayne Glowacki / Winnipeg Free Press

On 23 July 1983, flight 143 was cruising at 41000 ft., over Red Lake, Ontario. The aircraft's cockpit warning system sounded, indicating a fuel pressure problem on the aircraft's left side. Assuming a fuel pump had failed, the pilots turned it off, since gravity should feed fuel to the aircraft's two engines. The aircraft's fuel gauges were inoperative because of an electronic fault which was indicated on the instrument panel and airplane logs (the pilots believed flight to be legal with this malfunction).

The flight management computer indicated that there was still sufficient fuel for the flight; but the initial fuel load had been entered as pounds instead of kilograms. A few moments later, a second fuel pressure alarm sounded for the right engine, prompting the pilots to divert to Winnipeg. Within seconds, the left engine failed and they began preparing for a single-engine landing.

As they communicated their intentions to controllers in Winnipeg and tried to restart the left engine, the cockpit warning system sounded again with the "all engines out" sound, a long "bong" that no one in the cockpit could recall having heard before and that was not covered in flight simulator training. Flying with all engines out was something that was never expected to occur and had therefore never been covered in training.

Seconds later, the right-side engine also stopped, the 767 lost all power, and most of the instrument panels in the cockpit went blank.

In line with their planned diversion to Winnipeg, the pilots were already descending through 35,000 feet when the second engine shut down. They immediately searched their emergency checklist for the section on flying the aircraft with both engines out, only to find that no such section existed.

Captain Pearson made his best guess as to this speed for the 767, he flew the aircraft at 220 knots (410 km/h; 250 mph).

First Officer Maurice Quintal began to calculate whether they could reach Winnipeg. He used the altitude from one of the mechanical backup instruments, while the distance traveled was supplied by the air traffic controllers in Winnipeg, measuring the distance the aircraft's echo moved on their radar screens.

The aircraft lost 5,000 feet (1,500 m) in 10 nautical miles (19 km; 12 mi), giving a glide ratio of approximately 12:1.

At this point, Quintal proposed landing at the former RCAF Station Gimli, a closed air force base where he had once served as a Royal Canadian Air Force pilot.

Unknown to him, part of the facility had been converted to a race track complex, now known as Gimli Motorsports Park. It includes a road race course, a go-kart track, and a dragstrip.

A Canadian Automobile Sport Clubs-sanctioned sports car race hosted by the Winnipeg Sports Car Club was under way the Saturday of the accident and the area around the decommissioned runway was full of cars and campers. Part of the decommissioned runway was being used to stage the race.

Without power, the pilots had to try lowering the aircraft's main landing gear via a gravity drop. The main gear locked into position. But the nose wheel failed to lock into position, which later turned out to be a blessing in disguise. As the aircraft slowed on approach to landing, the ram air turbine generated less power, rendering the aircraft increasingly difficult to control.

As the runway drew near, it became apparent that the aircraft was too high and fast, raising the danger of running off the runway before the aircraft could be stopped. The lack of hydraulic pressure prevented flap/slat extension which would have, under normal landing conditions, reduced the stall speed of the aircraft and increased the lift coefficient of the wings allowing the aircraft to be slowed for a safe landing. The pilots briefly considered executing a 360-degree turn to reduce speed and altitude, but decided that they did not have enough altitude for the maneuver. Pearson decided to execute a forward slip to increase drag and lose altitude. This maneuver is commonly used with gliders and light aircraft to descend more quickly without increasing the already-too-fast forward speed.

As soon as the wheels touched the runway, Pearson "stood on the brakes", blowing out two of the aircraft's tires. The unlocked nose wheel collapsed and was forced back into its well, causing the aircraft's nose to slam into, bounce, and then scrape along the ground. The collapsed nose wheel helped to slow the airplane and prevent collateral damage to the people on the ground. The nose also grazed into the guardrail now dividing the strip, which further slowed it down.

None of the 61 passengers were seriously hurt. A minor fire in the nose area was extinguished by racers and course workers armed with fire extinguishers. As the aircraft's nose had collapsed onto the ground, its tail was elevated and there were some minor injuries when passengers exited the aircraft via the rear slides which were not long enough to accommodate the increased height.

Following Air Canada's internal investigation, Captain Pearson was demoted for six months, and First Officer Quintal was suspended for two weeks. Three maintenance workers were also suspended. In 1985 the pilots were awarded the first ever Fédération Aéronautique Internationale Diploma for Outstanding Airmanship. Several attempts by other crews who were given the same circumstances in a simulator at Vancouver resulted in crashes.

The cause of the accident was a simple mathematical error between the ground crew and pilots, they arrived at an incorrect conversion factor of 1.77, the weight of a litre of fuel in pounds. This was the conversion factor provided on the refueller's paperwork and which had always been used for the airline's imperial-calibrated fleet. Their calculation produced:

7682 L × 1.77 kg/L = 13597 kg
22300 kg − 13597 kg = 8703 kg
8703 kg ÷ (1.77 kg/L) = 4916 L

of fuel to be transferred Instead of 22,300 kg of fuel, they had 22,300 pounds on board — 10,100 kg, about half the amount required to reach their destination. Knowing the problems with the FQIS, Captain Pearson double-checked their calculations but was given the same incorrect conversion factor and inevitably came up with the same erroneous figures.

On 24 January 2008, the Gimli Glider took its final voyage, AC7067, from Montreal Trudeau to Tucson International Airport before its retirement in the Mojave Desert.

 


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