Editing Gimli Glider (section)

==Accident==
===Background===
On July 22, 1983, Air Canada Boeing 767 {{Airreg|C|GAUN|}} 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.<ref name="final_report">{{cite web|author=Lockwood|first=George H.|date=April 1985|title=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|url=http://data2.collectionscanada.gc.ca/e/e444/e011083519.pdf|access-date=January 9, 2016|website=Government of Canada}}</ref>

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.<ref name="final_report" />

The all-metric 767 aircraft, new to the fleet, tracked fuel quantities in kilograms.  After taking a dripstick measurement, Pearson converted the reading from centimetres to litres to kilograms. But he used the density figure for jet fuel from the Air Canada refueler's slip. This figure, used for all other aircraft in the fleet, stated the density in pounds/litre. The correct figure to use was for kilograms/litre, and the  result actually calculated was incorrect.<ref name="ASWEB" /> Since the FQIS was not operational, he entered the miscalculated result into the flight management computer. The airplane flew to Ottawa without accident, where another dripstick measurement was taken, and again, in the same way, converted incorrectly.  Since the aircraft appeared to have enough fuel to reach Edmonton, no fuel was loaded at Ottawa.<ref name="final_report" /><ref name="Deveau">{{cite news |last=Deveau |first=Scott |date=April 14, 2015 |title='Gimli Glider' pilot recalls heroic landing of Air Canada 767 as famed plane put up for sale |url=http://news.nationalpost.com/news/canada/gimli-glider-pilot-recalls-heroic-landing-of-air-canada-767-as-famed-plane-put-up-for-sale |newspaper=National Post |location=Toronto, Ontario, Canada |access-date=January 9, 2016}}</ref>

===Running out of fuel===
While Flight 143 was flying over [[Red Lake, Ontario]] at {{convert|41000|ft|-2}} shortly after 8 pm [[Central Time Zone|CDT]],<ref name=clojt /> 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, knowing that the engine could be gravity-fed in level flight.<ref name="WNelson">{{cite web |last=Nelson |first=Wade H. |date=October 1997 |title=The Gimli Glider |url=http://www.wadenelson.com/gimli.html |url-status=live |archive-url=https://archive.today/20121205003036/http://www.wadenelson.com/gimli.html |archive-date=2012-12-05 |access-date=November 9, 2013 |website=WadeNelson.com |publisher=Originally published in [[Soaring (magazine)]]}}</ref> A few seconds later, the fuel pressure alarm also sounded for the right engine. This prompted the pilots to divert to [[Winnipeg James Armstrong Richardson International Airport|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.<ref name="WNelson" /> 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.<ref name=Willams03>{{cite journal |last=Williams |first=Merran |date=July–August 2003 |title=The 156-tonne Gimli Glider |journal=Flight Safety Australia |pages=27 |url=http://www.casa.gov.au/wcmswr/_assets/main/fsa/2003/jul/22-27.pdf| access-date=February 20, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20120326042427/http://casa.gov.au/wcmswr/_assets/main/fsa/2003/jul/22-27.pdf |archive-date=March 26, 2012}}</ref> Adding to both the crew's and the controllers' problems, the plane's [[Transponder (aeronautics)|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 [[Flight control surfaces|control surfaces]] are so large that the pilots cannot move them with muscle power alone. Instead, [[Hydraulic drive system|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,<ref name="WNelson" /> 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 {{convert|35000|ft|-2}}<ref name="ASWEB">{{Cite web |last=Ranter |first=Harro |title=Accident description |url=http://aviation-safety.net/database/record.php?id=19830723-0 |url-status=live |archive-url=https://web.archive.org/web/20120128231906/http://aviation-safety.net/database/record.php?id=19830723-0 |archive-date=January 28, 2012 |access-date=July 24, 2008 |website=Aviation Safety Network}}</ref> 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.<ref name="WNelson" /> Captain Pearson was an experienced [[Glider aircraft|glider]] pilot, so he was familiar with flying techniques rarely used in commercial flight. Pearson needed to fly the 767 at the optimum [[glide ratio|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 {{convert|220|kn}}. First Officer Quintal started 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 {{convert|10|nmi}}, the aircraft lost {{convert|5000|ft|m}}, giving a [[glide ratio]] of roughly 12:1 (dedicated glider planes reach ratios of 50:1 to 70:1).<ref>{{cite web |date=June 20, 2002 |title=Flugerprobung – Leisting – Leistungsvermessung |trans-title=Flight testing – performance – performance measurement |url=http://www.leichtwerk.de/eta/de/flugerprobung/leistung.html |url-status=dead |archive-url=https://web.archive.org/web/20171113181040/http://www.leichtwerk.de/eta/de/flugerprobung/leistung.html |archive-date=November 13, 2017 |access-date=January 6, 2018 |language=de}}</ref>

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]].<ref>{{Cite web |url=http://www.gimlimotorsportspark.com/default.asp |title=Gimli Motorsports Park website |access-date=May 8, 2014 |archive-date=May 8, 2014 |archive-url=https://web.archive.org/web/20140508043049/http://www.gimlimotorsportspark.com/default.asp |url-status=dead}}</ref> 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 accident. The area around the decommissioned runway was full of cars and campers. Part of the decommissioned runway was being used to stage the race.<ref>{{Cite web|url=http://redriverpca.org/newsletters/2008/PCAprint%20July%20%202008.pdf|archive-url=https://web.archive.org/web/20110727205019/http://redriverpca.org/newsletters/2008/PCAprint%20July%20%202008.pdf|url-status=dead|title=Red River PCA website|archive-date=July 27, 2011}}</ref>

As the aircraft slowed on approach to landing, the reduced power generated by the [[ram air turbine]] rendered the aircraft increasingly difficult to control.<ref name="soaring" /> Without main power, the pilots used a [[Landing gear#Emergency extension systems|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 (aircraft)|flap]]/[[slat (aircraft)|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 [[Slip (aerodynamics)#Forward-slip|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.<ref name=soaring /> 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 [[Fuel starvation|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 {{convert|1,000|ft}} of the projected point of impact.<ref name=soaring />

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.<ref name="soaring">{{cite web |author=Nelson |first=Wade H. |date=1997 |title=The Gimli Glider Incident – From an article published in Soaring Magazine |url=http://hawaii.hawaii.edu/math/Courses/Math100/Chapter1/Extra/CanFlt143.htm |access-date=January 8, 2016 |website=hawaii.hawaii.edu/math/Courses/Math100 |publisher=University of Hawai'i |quote=(The dragstrip began in the middle of the runway with the guardrail extending towards 32L's threshold) Pearson applied extra right brake so the main gear would straddle the guardrail.}}</ref>

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 [[Evacuation slide|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.<ref>{{Cite web |title=The Gimli Glider |url=http://www.damninteresting.com/the-gimli-glider/ |website=www.damninteresting.com |access-date=July 23, 2015}}</ref>