Flight 143 after landing at Gimli, Manitoba.
|Date||July 23, 1983|
|Summary||Fuel exhaustion due to maintenance error and loading insufficient fuel|
|Site||Emergency landing at Gimli Industrial Park Airport, Gimli, Manitoba
|Aircraft type||Boeing 767–233|
|Flight origin||Montreal-Dorval International Airport|
|Destination||Edmonton International Airport|
The Gimli Glider is the nickname of an Air Canada aircraft that was involved in an unusual aviation incident. On July 23, 1983, Air Canada Flight 143, a Boeing 767–233 jet, ran out of fuel at an altitude of 12,500 metres (41,000 ft) MSL, about halfway through its flight originating in Montreal to Edmonton. The crew were able to glide the aircraft safely to an emergency landing at Gimli Industrial Park Airport, a former Royal Canadian Air Force base in Gimli, Manitoba.
The subsequent investigation revealed a combination of company failures and a chain of human errors that defeated built-in safeguards. Fuel loading was miscalculated because of a misunderstanding of the recently adopted metric system which replaced the imperial system.
On July 22, 1983, Air Canada's Boeing 767 (registration C-GAUN, c/n 22520/47) flew from Toronto to Edmonton where it underwent routine checks. The next day, it was flown to Montreal. Following a crew change, it departed Montreal as Flight 143 for the return trip to Edmonton (with a stopover in Ottawa), with Captain Robert (Bob) Pearson, 48, and First Officer Maurice Quintal at the controls. Captain Pearson was a highly experienced pilot, having accumulated more than 15,000 flight hours. First Officer Quintal was also very experienced, having logged over 7,000 hours of total flight time.
Running out of fuel
On July 23, 1983, flight 143 was cruising at 12,500 metres (41,000 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 the flight was 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 measured in 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, with the right-side engine also stopped, the 767 lost all power, and most of the instrument panels in the cockpit went blank.
The 767 was one of the first airliners to include an Electronic Flight Instrument System (EFIS), 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 and therefore 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 accommodate this kind of power failure. With the 767, this is usually achieved through the automated deployment of a ram air turbine, a hydraulic pump (and on some airplanes a generator) driven by a small turbine, which in turn is driven by the forward motion of the aircraft through the air in the manner of a windmill. As the Gimli pilots were to experience on their landing approach, a decrease in this forward speed means a decrease in the power available to control the aircraft.
Landing at Gimli
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 optimal 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 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 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 power, the pilots attempted lowering the aircraft's main landing gear via a gravity drop. The main gear locked into position, but the nose wheel did not, which later turned out to be advantageous. 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 coming in too high and fast, raising the danger of running off the runway before it 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 to allow the aircraft to be slowed for a safe landing. The pilots briefly considered 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 forward speed.
As soon as the wheels touched down on the runway, Pearson braked hard, 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 helped to slow the airplane and avoid injuring the people on the ground. The nose also grazed the guardrail now dividing the strip, which further slowed it down. Seventeen minutes after running out of fuel, Air Canada flight 143 came to a final stop on the ground.
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.
The Aviation Safety Board of Canada (predecessor of the modern Transportation Safety Board of Canada) found the airline at fault, while[clarification needed] an Air Canada investigation concluded that the pilots and mechanics were at fault.
The safety board reported that Air Canada management was responsible for "corporate and equipment deficiencies". The report praised the flight and cabin crews for their "professionalism and skill". It noted that Air Canada "neglected to assign —clearly and specifically— the responsibility for calculating the fuel load in an abnormal situation". It further found that the airline had failed to reallocate the task of checking fuel load (which had been the responsibility of the flight engineer on the older, three-crew, aircraft). The safety board also said that Air Canada needed to keep more spare parts, including replacements for the defective fuel quantity indicator, in its maintenance inventory, as well as provide better, adequate training on the metric system to its pilots and fuelling personnel. The final report of the investigation was published in 1985.
Fuel quantity indicator system
The amount of fuel in the tanks of a Boeing 767 is computed by the Fuel Quantity Indicator System (FQIS) and displayed in the cockpit. The FQIS on the aircraft was a dual-processor channel, each independently calculating the fuel load and cross-checking with the other. In the event of one failing the other could still operate alone, but under these unusual circumstances the indicated quantity was required to be cross-checked against a floatstick measurement before departure. In the event of both channels failing, there would be no fuel display in the cockpit, and the aircraft would be considered non-serviceable and not authorized to fly.
Because inconsistencies had been found with the FQIS in other 767s, Boeing had issued a service bulletin for the routine checking of this system. An engineer in Edmonton duly did so when the aircraft arrived from Toronto following a trouble-free flight the day before the incident. While conducting this check, the FQIS failed and the cockpit fuel gauges went blank. The engineer had encountered the same problem earlier in the month when this same aircraft had arrived from Toronto with an FQIS fault. He found then that disabling the second channel by pulling the circuit breaker in the cockpit restored the fuel gauges to working order albeit with only the single FQIS channel operative. In the absence of any spares he simply repeated this temporary fix by pulling and tagging the circuit breaker.
A record of all actions and findings was made in the maintenance log, including the entry; "SERVICE CHK – FOUND FUEL QTY IND BLANK – FUEL QTY #2 C/B PULLED & TAGGED...". This reports that the fuel gauges were blank and that the second FQIS channel was disabled, but does not make clear that the latter fixed the former.
On the day of the incident, the aircraft flew from Edmonton to Montreal. Before departure the engineer informed the pilot of the problem and confirmed that the tanks would have to be verified with a floatstick. In a misunderstanding, the pilot believed that the aircraft had been flown with the fault from Toronto the previous afternoon. That flight proceeded uneventfully with fuel gauges operating correctly on the single channel.
On arrival at Montreal, there was a crew change for the return flight back to Edmonton. The outgoing pilot informed Captain Pearson and First Officer Quintal of the problem with the FQIS and passed along his mistaken belief that the aircraft had flown the previous day with this problem. In a further misunderstanding, Captain Pearson believed that he was also being told that the FQIS had been completely unserviceable since then.
While the aircraft was being prepared for its return to Edmonton, a maintenance worker decided to investigate the problem with the faulty FQIS. To test the system he re-enabled the second channel, at which point the fuel gauges in the cockpit went blank. He was called away to perform a floatstick measurement of fuel remaining in the tanks. Distracted, he failed to disable the second channel, leaving the circuit breaker tagged (which masked the fact that it was no longer pulled). The FQIS was now completely unserviceable and the fuel gauges were blank.
On entering the cockpit, Captain Pearson saw what he was expecting to see: blank fuel gauges and a tagged circuit breaker. He consulted the aircraft's Minimum Equipment List (MEL), which told him that the aircraft could not be flown in this condition. The 767 was still a very new aircraft, having flown its maiden flight in September 1981. C-GAUN was the 47th Boeing 767 off the production line, and had been delivered to Air Canada less than four months previously. In that time period there had been 55 changes to the MEL, and some pages were blank pending development of procedures.
Because of this unreliability, it had become practice for flights to be authorized by maintenance personnel. To add to his own misconceptions about the condition the aircraft had been flying in since the previous day, reinforced by what he saw in the cockpit, Pearson now had a signed-off maintenance log that it had become custom to prefer over the MEL.
At the time of the incident, Canada was converting to the metric system. As part of this process, the new 767s being acquired by Air Canada were the first to be calibrated for metric units (litres and kilograms) instead of customary units (gallons and pounds). All other aircraft were still operating with Imperial units (gallons and pounds). For the trip to Edmonton, the pilot calculated a fuel requirement of 22,300 kilograms (49,200 lb). A dripstick check indicated that there were 7,682 litres (1,690 imp gal; 2,029 US gal) already in the tanks. To calculate how much more fuel had to be added, the crew needed to convert the quantity in the tanks to a mass, subtract that figure from 22,300 kg and convert the result back into a volume. In previous times, this task would have been completed by a flight engineer, but the 767 was the first of a new generation of airliners that flew only with a pilot and co-pilot, and without a flight engineer.
The volume of jet fuel varies with temperature. In this case, the mass of a litre of fuel was 0.803 kg, so the correct calculation was:
- 7,682 L × 0.803 kg/L = 6,169 kg : fuel already onboard
- 20,088 L × 0.803 kg/L = 16,131 kg : fuel to be transferred to plane
- 27,770 L × 0.803 kg/L = 22,300 kg : fuel for flight
Between the ground crew and pilots, they arrived at an incorrect conversion factor of 1.77, which was 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 incorrect calculation was:
- 7,682 L × 1.77 lb/L = 13,597 lb : fuel already onboard
- 4,916 L × 1.77 lb/L = 8,703 lb : fuel to be transferred to plane
- 12,598 L × 1.77 lb/L = 22,300 lb : fuel for flight
Instead of 22,300 kg (27,770 L ) of fuel, they had 22,300 pounds (12,598 L ) 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.
The Flight Management Computer (FMC) measures fuel consumption, allowing the crew to keep track of fuel burned as the flight progresses. It is normally updated automatically by the FQIS, but in the absence of this facility it can be updated manually. Believing he had 22,300 kg of fuel on board, this is the figure the captain entered.
Because the FMC would reset during the stopover in Ottawa, the captain had the fuel tanks measured again with the dipstick while there. In converting the quantity to kilograms, the same incorrect conversion factor was used, leading him to believe he now had 20,400 kg of fuel; in reality, he had less than half that amount.
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. Quintal was promoted to captain in 1989, and Pearson retired in 1993.
The aircraft was temporarily repaired at Gimli and flew out two days later to be fully repaired at a maintenance base in Winnipeg. Following the successful appeal against their suspensions, Pearson and Quintal were assigned as crew members aboard another Air Canada flight. As they boarded the aircraft, and realized that it was the same one that was involved in the Gimli incident. After almost 25 years of service, the aircraft flew its last revenue flight on January 1, 2008. Air Canada still uses the flight number 143, but the route is now Montreal–Ottawa–Edmonton, or St. John's–Halifax–Ottawa–Edmonton (depending on season) using an Embraer 190 aircraft. However this was not the only incident involving this flight number of Air Canada as of June 26, 2015, where an E-190 at St. John's with this same flight number was targeted in an alleged bomb threat.
On January 24, 2008, the Gimli Glider took its final voyage, AC7067, from Montreal Trudeau to Tucson International Airport before its retirement in the Mojave Desert. An Air Canada newsletter "The Daily" states:
The Gimli Glider retires to the desert. On Thursday, 24 January, fin 604, the Boeing 767–200 better known as the Gimli Glider, will undertake its final voyage from Montreal to Mojave Airport (MHV) before it is retired to the desert. Employees and retirees (bring valid employee ID) are invited to come and say goodbye to the aircraft, which has now become part of Canadian aviation history. Fin 604 is set to depart as flight AC7067, at 9:00 a.m. from the Montreal Line Maintenance hangar – Air Canada Base, 750 Côte Vertu West; Building 7, Bay 8/13 (West end), Gate entrance 5. Captain Robert Pearson and First Officer Maurice Quintal, the flight crew who landed the aircraft to safety in Gimli on 23 July 1983 are expected to be on hand for the aircraft's departure. The hangar will be open to well-wishers from 8:00 a.m.
Flight AC7067 was captained by Jean-Marc Bélanger, a former head of the Air Canada Pilots Association, while captains Robert Pearson and Maurice Quintal were on board to oversee the flight from Montreal to California's Mojave Airport. Also on board were three of the six flight attendants who were on Flight 143.
Flight tracking services FlightAware and FlightView indicated on January 24, 2008 that 604's initial flight was from Montreal (CYUL) to Tucson International Airport (KTUS), having a planned cruise altitude of FL400. According to FlightAware, 604 landed at 12:53 p.m. (MST) at Tucson International Airport (KTUS). The Gimli Glider was then scheduled to depart Tucson and make the final flight to the Mojave Airport (KMHV) for retirement, but was delayed.
On the 25th anniversary of the incident in 2008, pilots Pearson and Quintal were celebrated in a parade in Gimli, and a mural was dedicated to commemorate the landing.
According to the website dedicated to saving the aircraft, it was dismantled in early 2014, but not scrapped.
- Falling from the Sky: Flight 174, TV movie loosely based on this event
- Mayday (TV series) (AKA Air Emergency, Air Crash Investigation), incident covered in season 5 episode 2.
- Mars Climate Orbiter, which was lost because of a navigation error when a subcontractor used Imperial units (pound-seconds) instead of the metric units (newton-seconds) as specified by NASA.
- Air Transat Flight 236, an Airbus A330 that ran out of fuel over the Atlantic Ocean in August 2001, but was successfully glided to a safe landing in the Azores.
- List of airline flights that required gliding
- Witkin, Richard (July 30, 1983). "Jet's Fuel Ran Out After Metric Conversion Errors". The New York Times. Retrieved 2007-08-21.
Air Canada said yesterday that its Boeing 767 jet ran out of fuel in mid-flight last week because of two mistakes in figuring the fuel supply of the airline's first aircraft to use metric measurements. After both engines lost their power, the pilots made what is now thought to be the first successful emergency "dead stick" landing of a commercial jetliner.
- Accident description aviation-safety.net(Accessed 2008-07-24)
- Nelson, Wade H. (October 1997). "The Gimli Glider". WadeNelson.com (Originally published in Soaring Magazine). Retrieved 2013-11-09.
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- Gimli Motorsports Park website
- Red River PCA website
- "The Gimli Glider". www.damninteresting.com. Retrieved 2015-07-23.
- Final report of the Board of Inquiry investigating the circumstances of an accident involving the Air Canada Boeing 767 aircraft C-GAUN that effected an emergency landing at Gimli, Manitoba on the 23rd day of July, 1983; Commissioner, George H. Lockwood; Ottawa; Government of Canada; 1985; vi; 199 p. 28cm.; ISBN 066011884X
- Stewart, Stanley (1992). Emergency, Crisis on the Flightdeck. Airlife Publishing Ltd. p. 123. ISBN 1-85310-348-9.
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- Emergency, Crisis on the Flight Deck, Stanley Stewart, Airlife Publishing Ltd., 1992, ISBN 1-85310-348-9
- Freefall: From 41,000 feet to zero – a true story, William and Marilyn Hoffer, Simon & Schuster, 1989 ISBN 978-0-671-69689-4
- Engineering Disasters – Lessons to be Learned, Don Lawson, ASME Press, 2005, ISBN 0-7918-0230-2. Pages 221–9 deal specifically with Gimli Glider.
- Damn Interesting: The Gimli Glider
- CBC Digital Archives: 'Gimli Glider' lands without fuel
- Photo of C-GAUN after the landing
- Picture of C-GAUN in storage (airliners.net)
- Video of retirement fly-by