Gimli Glider
Air Canada Flight 143, commonly known as the Gimli Glider, was a Canadian scheduled domestic passenger flight between Montreal and Edmonton that ran out of fuel on Saturday, July 23, 1983,[1] at an altitude of 41,000 feet (12,500 m), midway through the flight. The flight crew successfully glided the Boeing 767 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.[2][3][4][5][6] It resulted in 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 incident earned the aircraft the nickname "Gimli Glider."[7]
Accident
July 23, 1983
Fuel exhaustion due to refuelling error
Emergency landing at
Gimli Industrial Park Airport, Gimli, Manitoba
50°37′44″N 97°02′38″W / 50.62889°N 97.04389°W
AC143
ACA143
AIR CANADA 143
C-GAUN
69
61
8
0
10
69
The incident was caused by a series of issues, starting with a failed fuel-quantity indicator sensor (FQIS). These had high failure rates in the 767, and the only available replacement was also nonfunctional. The problem was logged, but later, the maintenance crew misunderstood the problem and turned off the backup FQIS. This required the fuel to be manually measured using a dripstick. The navigational computer required the fuel to be entered in kilograms; however, an incorrect conversion from volume to mass was applied, which led the pilots and ground crew to agree that it was carrying enough fuel for the remaining trip. The aircraft was carrying only 45% of its required fuel load.[7][8] 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.[9]
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 metric units, since a mixed fleet was more dangerous than an all-Imperial or an all-metric fleet.[9]
History
Background
On July 22, 1983, Air Canada Boeing 767 C-GAUN[10] 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.[9]
At Montreal, Captain Robert "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.[9]
After taking a dripstick measurement, Pearson converted the reading from centimetres to litres to kilograms. However, he did his calculation with the density figure for jet fuel in pounds/litre from the Air Canada refueler's slip, used for all other aircraft in the fleet, instead of kilograms/litre for the all-metric 767 aircraft, which was new to the fleet.[11] Since the FQIS was not operational, he entered the reading into the flight management computer, which tracked the amount of fuel remaining in kilograms. The airplane flew to Ottawa without incident, where another dripstick measurement was taken and converted using the density in pounds/litre. Since the aircraft appeared to have enough fuel to reach Edmonton, no fuel was loaded at Ottawa.[9][12]
Running out of fuel
While Flight 143 was cruising over Red Lake, Ontario at 41,000 feet (12,500 m) shortly after 8 pm CDT,[2] the aircraft's cockpit warning system sounded, indicating a fuel-pressure problem on the aircraft's left side. Assuming that a fuel pump had failed, the pilots turned off the alarm,[13] knowing that the engine could be gravity-fed in level flight. A few seconds later, the fuel pressure alarm also sounded for the right engine. This prompted the pilots to divert to Winnipeg.
The left engine failed within seconds, 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 sharp "bong" that no one in the cockpit could recall having heard before.[13] The right-side engine stopped seconds later, and the 767 lost all power. Flying with all engines out was never expected to occur, so it had never been covered in training.[14] Adding to both the crew's and the controllers' problems, the plane's transponder failed, stopping the altitude reporting function, and forcing the controllers to revert to primary radar to track the plane.
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, and most screens went blank, leaving only a few basic battery-powered emergency flight instruments. While these provided sufficient information to land the aircraft, the backup instruments did not include a vertical speed indicator that could be used to determine how far the aircraft could glide.
On the Boeing 767, the control surfaces are so large that the pilots cannot move them with muscle power alone. Instead, hydraulic systems are used to multiply the forces applied by the pilots. Since the engines supply power for the hydraulic systems, in the case of a complete power outage, the aircraft was designed with a ram air turbine that swings out from a compartment located beneath the bottom of the 767,[13] and drives a hydraulic pump to supply power to hydraulic systems.
Landing at Gimli
In line with their planned diversion to Winnipeg, the pilots had been descending through 35,000 feet (10,700 m)[11] when the second engine shut down. They had searched their emergency checklist for the section on flying the aircraft with both engines out, only to find that no such section existed.[13] Captain Pearson was an experienced glider pilot, so he was familiar with flying techniques rarely used in commercial flight. Pearson needed to fly the 767 at the optimum glide speed to have the maximum range and, therefore, the largest choice of possible landing sites. 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 Quintal began to calculate whether they could reach Winnipeg. Quintal 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 roughly 12:1 (dedicated glider planes reach ratios of 50:1 to 70:1).[15]
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 the air traffic controller, a part of the facility had been converted to a race track complex, now known as Gimli Motorsports Park.[16] 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. The area around the decommissioned runway was full of cars and campers. Part of the decommissioned runway was being used to stage the race.[17]
As the aircraft slowed on approach to landing, the reduced power generated by the ram air turbine rendered the aircraft increasingly difficult to control.[18] Without main power, the pilots used a gravity drop to lower the landing gear and lock it into place. The main gear locked into position, but the nose wheel did not. The failure of the nose wheel to lock would later prove to be a serendipitous advantage after touchdown for the safety of those on the converted runway.
As the plane approached the runway, the pilots realized it was coming in too high and fast, increasing the likelihood that the 767 would run off the runway. The lack of hydraulic pressure prevented flap/slat extension that would have, under normal conditions, reduced the aircraft's stall speed and increased the lift coefficient of the wings, to slow the airliner for a safe landing. The pilots briefly considered a 360° turn to reduce speed and altitude, but they decided they did not have enough altitude for the manoeuvre. Pearson decided to execute a forward slip to increase drag and reduce altitude. This manoeuvre, performed by "crossing the controls" (applying the rudder in one direction and ailerons in the other direction), is commonly used in gliders and light aircraft to descend more quickly without increasing forward speed; it is rarely used in large jet airliners outside of rare circumstances like those of this flight.[18] The forward slip disrupted airflow past the ram air turbine, which decreased the hydraulic power available; the pilots were surprised to find the aircraft slow to respond when straightening after the forward slip.
With both engines completely starved of fuel, the plane made hardly any noise during its approach. This gave people on the ground no warning of the impromptu landing and little time to flee. As the gliding plane closed in on the decommissioned runway, the pilots noticed boys were riding bicycles within 1,000 feet (300 m) of the projected point of impact.[18]
Two factors helped avert disaster: the failure of the front landing gear to lock into position during the gravity drop, and a guardrail installed along the centre of the repurposed runway to facilitate its use as a drag race track. Pearson braked hard as soon as the wheels touched down on the runway, 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. 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.[18]
No serious injuries occurred among the 61 passengers or the people on the ground. As the aircraft's nose had collapsed onto the ground, its tail was elevated, so some minor injuries occurred when passengers exited the aircraft via the rear slides, which were not sufficiently long to accommodate the increased height. Racers and course workers with portable fire extinguishers extinguished a minor fire in the nose area.[19]
Aftermath
Following Air Canada's internal investigation, Captain Pearson was demoted for six months, and First Officer Quintal was suspended for two weeks for allowing the incident to happen. Three maintenance workers were also suspended.[24] In 1985, Pearson and Quintal were awarded the first ever Fédération Aéronautique Internationale Diploma for Outstanding Airmanship.[25] Several attempts by other crews who were given the same circumstances in a simulator at Vancouver resulted in crashes.[26] Quintal was promoted to captain in 1989.[27] Pearson remained with Air Canada for ten years and then moved to flying for Asiana Airlines; he retired in 1995.[12] Maurice Quintal died at the age of 68 on September 24, 2015, in Saint-Donat, Quebec.[28]
The aircraft was temporarily repaired at Gimli and flew out two days later to be fully repaired at a maintenance base in Winnipeg. The aircraft was returned to service with Air Canada after the full repair. Following a successful appeal against their suspensions, Pearson and Quintal were assigned as crew members aboard another Air Canada flight.
The 1995 television movie Falling from the Sky: Flight 174 is loosely based on this event.
The Discovery Channel Canada / National Geographic TV series Mayday covered the incident in a 2008 episode titled "Gimli Glider". The episode featured interviews with survivors, including Pearson and Quintal, and a dramatic flight recreation.[29]