Air Canada Flight 143

Information
Air Canada Flight 143 (also known as the Gimli Glider) is an incident on July 23, 1983, in which the plane ran out of fuel at 41,000 feet and glided to the nearest runway.

Pilots
The pilots consisted of Captain Robert (Bob) Pearson, 48, and First Officer Maurice Quintal, 36. Captain Pearson was a highly experienced pilot, having accumulated more than 15,000 flight hours. First Officer Quintal was also experienced, having logged over 7,000 hours of total flight time.

Background
On July 23, 1983, Flight 143 was cruising at 41,000 feet (12,000 m) over Red Lake, Ontario. The aircraft's cockpit warning system sounded, indicating a fuel pressure problem on the aircraft's left side. The pilots turned it off, assuming a fuel pump had failed; gravity should feed fuel to the aircraft's two engines (at least in near-level flight) even without the fuel pumps operating.

The aircraft's fuel gauges were inoperative because of an electronic fault indicated on the instrument panel and airplane logs; this fault was known before takeoff to the pilots, who took steps to work around it. During the flight, the management computer indicated that there was still sufficient fuel for the flight, but only because the initial fuel load had been incorrectly entered: the fuel had been calculated in pounds instead of kilograms by the ground crew, and the erroneous calculation had been approved by the flight crew. This error meant that less than half the amount of intended fuel had been loaded. Because the incorrect fuel weight data had been entered into the system, it was providing incorrect readings.

A few moments after the crew silenced the left-side fuel pressure alarm, a second fuel pressure alarm sounded for the right engine. This prompted the pilots to divert to Winnipeg. Then, within seconds, the left engine failed and the pilots 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. Flying with all engines out was something that was never expected to occur and that therefore had not been covered in training, either on a flight simulator or otherwise. Seconds later, with the right-side engine also stopped, the 767 lost all power, and most of the instrument displays in the cockpit went blank.

The 767 was one of the first airliners to include an electronic flight instrument system, which operated on the electricity generated by the aircraft's jet engines. With both engines stopped, the system went dead, leaving only a few basic battery-powered emergency flight instruments. While these provided sufficient information with which to land the aircraft, a vertical speed indicator—that would indicate the rate at which the aircraft was descending, information which could be used to predict how long it could glide unpowered—was not among them.

On airliners the size of the 767, the engines also supply power for the hydraulic systems, without which the aircraft cannot be controlled. Such aircraft are therefore required to be equipped with a means to compensate for this kind of power failure. With the 767, that compensation is usually achieved through the automated deployment of a ram air turbine, a backup generator that generates power from air movement, like a wind turbine. As the Gimli pilots reduced speed for landing, the resultant reduced airflow meant a decrease in the hydraulic power, power that was critically needed for control during landing.

In line with their planned diversion to Winnipeg, the pilots were already descending through 35,000 feet (11,000 m) 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 was an experienced glider pilot, so he was familiar with flying techniques almost never used in commercial flight. To have the maximum range and therefore the largest choice of possible landing sites, he needed to fly the 767 at the optimum glide speed. Making 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 travelled was supplied by the air traffic controllers in Winnipeg, measured by the aircraft's radar echo observed at Winnipeg. In 10 nautical miles (19 km; 12 mi) the aircraft lost 5,000 feet (1,500 m), giving a glide ratio of approximately 12:1 (dedicated glider planes reach ratios of 50:1 to 70:1).

At this point, Quintal proposed landing at the former RCAF Station Gimli, a closed air force base where he had once served as a pilot for the Royal Canadian Air Force. Unbeknownst to Quintal or to the air traffic controller, a part of the facility had been converted to a race track complex, now known as Gimli Motorsports Park. It included 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 underway at the time of the incident 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 main power, the pilots used a gravity drop, which allows gravity to lower the landing gear and lock it into place. The main gear locked into position, but the nose wheel did not; this later turned out to be advantageous. As the aircraft slowed on approach to landing, the reduced power generated by the ram air turbine rendered the aircraft increasingly difficult to control.

As the plane drew near the runway, it became apparent that the aircraft was coming in too high and fast, raising the danger of the 767 running off the runway before it could be stopped. The lack of hydraulic pressure prevented flap/slat extension that would have, under normal landing conditions, reduced the stall speed of the aircraft and increased the lift coefficient of the wings to allow the airliner to be slowed for a safe landing. The pilots briefly considered a 360-degree turn to reduce speed and altitude, but they decided that they did not have enough altitude for the manoeuvre. Pearson decided to execute a forward slip to increase drag and lose altitude. This manoeuvre is commonly used in gliders and light aircraft to descend more quickly without increasing forward speed, but it is practically never executed in large jet airliners outside of rare circumstances like those of this flight.

Complicating matters yet further was the fact that with both of its engines out, the plane made virtually no noise during its approach. People on the ground thus had no advance warning of the impromptu landing and little time to flee. As the gliding plane closed in on the decommissioned runway, the pilots noticed that there were two boys riding bicycles within 1,000 feet (300 m) of the projected point of impact. Captain Pearson would later remark that the boys were so close that he could see the looks of sheer terror on their faces as they realized that a commercial airliner was bearing down on them.

Two factors helped avert disaster: the failure of the front landing gear to lock into position during the gravity drop, and the presence of a guardrail that had been installed along the centre of the repurposed runway to facilitate its use as a drag race track. As soon as the wheels touched down on the runway, Pearson braked hard, skidding and promptly 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 off, and then scrape along the ground. This additional friction helped to slow the airplane and kept it from crashing into the crowds surrounding the runway. After the airliner had touched down, the nose began to scrape along the guardrail in the centre of the race track, creating additional frictional drag that helped to decelerate the plane; Pearson applied extra right brake, which caused the main landing gear to straddle the guardrail. Air Canada Flight 143 came to a final stop on the ground 17 minutes after running out of fuel.

There were no serious injuries among the 61 passengers or the people on the ground. 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 sufficiently accommodate the increased height. A minor fire in the nose area was extinguished by racers and course workers equipped with portable fire extinguishers.