Air Canada Flight 143

Air Canada Flight 143
Air Canada Boeing 767-233
Accident summary
Accident type	Lack of fuel
place	Gimli, Manitoba, Canada
date	July 23, 1983
Fatalities	0
Survivors	69 (all)
Injured	0
Aircraft
Aircraft type	Boeing 767-233
operator	Air Canada
Mark	C-GAUN
Departure airport	Dorval International Airport
Destination airport	Edmonton International Airport
Passengers	61
crew	8th
Lists of aviation accidents

Air Canada Flight 143 was the flight number of a scheduled flight of Air Canada between Montreal ( Canada ) and Edmonton (Canada). On this flight on July 23, 1983, a Boeing 767-200, manned by 61 passengers and 8 crew members, ran out of fuel due to the mix-up of units of measurement when refueling. The crew made an emergency landing at the airport in Gimli , Canada. In the press, this aircraft, which was decommissioned on January 24, 2008 at Mojave Airport in California after a last flight with those involved, received the nickname “Gimli Glider” (translated “Gimli glider”).

Course of events

Malfunction of the Fuel Quantity Information System (FQIS)

During the pre-flight inspection by a technician, it was recognized that the system for displaying the fuel quantity was dark, i.e. not providing any display, and that it was not providing any corresponding values ​​to the front, central, electronic cockpit instruments for the pilots. Based on the technician's experience with a previous error of this type, the function in the other channel could be temporarily restored by switching off one of the two existing channels via the fuse box. The fuse was accordingly provided with a marking or cover, which indicated its deliberate deactivation. A corresponding entry was made in the log. Ideally, the unit could have been exchanged immediately, but on the one hand this part was no longer in stock at Air Canada, and on the other hand the technician was called from the cockpit to help determine the fuel quantity with the dipstick and to support further refueling outside .

Later another technician came into the cockpit, who checked the condition again, reactivated the fuse and then recognized the dark state. However, he did not pull the fuse out again, so that he made the unit, which had previously functioned on one side only, completely inoperable again.

During the subsequent examination of the protocol by the master, on the one hand it was not immediately apparent from the entry for the FQIS that a reduced function had been restored when it was drawn up, so that the problem was noted as less critical, and on the other hand the master accepted that the error already existed on the previous flight and therefore had no serious effects on the flight task. The general instructions on the ability to fly said that, as given, a flight without the FQIS is not permitted, but the entry in the protocol was understood as a revocation of this manual requirement - however, this referred to a functional state that had previously been achieved but had since been lost again unnoticed . It was still not possible for the pilot to understand the status of the covered fuse without further action, although it is not certain whether an active, but covered fuse should have appeared unusual to him.

The present modern aircraft type was still only intended for regular use with two pilots in the cockpit. The flight engineer who previously belonged to the crew and was also seated in the cockpit was no longer present. In this way, certain exceptional activities, such as the manual determination and calculation of the refueling amount, were transferred from this person to the pilots as well as to external persons.

Incorrect calculation of the required amount of kerosene

FQIS is usually used to refuel a Boeing 767 with kerosene . This monitors all pumps in the aircraft and gives a status of the amount of fuel in the tanks. However, the FQIS on this machine had a malfunction, which was known to both the technicians and the pilots. The fault was later attributed to a defective solder joint. As an alternative, a dipstick was used several times to determine the amount of kerosene in the tanks.

Note: The following information is based on different sources and analyzes. The associated figures for fuel are therefore not completely consistent with one another or alternative views are given in brackets.

As quasi-facts of the refueling process were reconstructed:

• Before the refueling process there was a total of 7,682 liters in the tanks.
• The pilots determined a required amount of fuel for the planned flights of 22,300 (20,400) kg. Here it is common to specify the amount in kilograms, since the calorific value and thus the drive power of the engines depends on this quantity. (The conversion between kilograms and liters requires the temperature of the fuel as an auxiliary variable in both directions for more precise calculations. In practice, such a conversion factor is therefore often read from a corresponding table. Whether and how the pilots proceeded is currently in the following text not incorporated.)
• The pilots calculated the amount of fuel that needed to be refueled from the two figures above.
• The aircraft was refueled by the ground crew as instructed by the pilots.
• According to the dipstick, there were a total of 12,589 (11,525) liters in the tanks after refueling.

The error finally occurred several times when converting volume to weight or vice versa. The aircraft type was the first in Air Canada's fleet to display the amount of fuel in kilograms, while all other aircraft and manuals used the Anglo-American weight unit pound (lbs) for calculations. Out of habit, however, those involved incorrectly used the conversion factor of 1.77 lb / l (British or imperial pounds, as opposed to US pounds), although 0.803 kg / l (0.8 kg / l) should have been used as the correct conversion factor . So one repeatedly came to a result that roughly equaled the desired amount of fuel, but did not correspond to the real amount without noticing it.

The number of (12,589 l * 1.77 lb / l = 22,283 kg) 20,400 kg, incorrectly calculated from the tank content, was  entered into the on-board computer as specified without any unit specification. This calculated that the tank content would be sufficient to reach the destination airport. In fact, however, there were only (12,589 l * 0.803 kg / l = 10,109 kg) 9,144 kg of fuel in the tanks, slightly less than half the amount required.

The captain and copilot had concerns about the calculations and recalculated them several times. However, they didn't notice the wrong conversion factor, so they kept coming back to the same result. Finally, with the words That's it, we're going , the captain decided to take off.

The flight plan initially provided for a stopover in not far away Ottawa . There the on-board computer was de-energized so that it lost its value for fuel. Therefore, the amount of fuel was measured again and then entered into the device, just before taking off again in the direction of Edmonton.

Flight without fuel

At an altitude of 41,000  feet (about 12,500 m) above Red Lake , Ontario , the cockpit warning system indicated a problem with the fuel pressure in the tank on the left wing by means of four warning tones. The master and copilot assumed that a fuel pump was malfunctioning and switched it off. Since the tanks are located above the engines, the fuel flows into the engine under its own weight, so that a pump failure is not serious.

At this point in time, the on-board computer still showed a sufficient amount of kerosene. However, this information was still based on the incorrect entry mentioned.

A few moments later, a second alarm came due to pressure problems in the fuel system. The pilots then decided to abort the flight and land in Winnipeg . Shortly afterwards, the left engine stood still due to the lack of fuel, so that the pilots prepared for a landing with only one engine.

While one was still trying to pump fuel from the right into the left tank in order to be able to start the left engine again and informing the air traffic controllers in the tower in Winnipeg about the imminent emergency landing, the right engine also suddenly came to a standstill, which caused the entire power supply collapsed. In the sudden silence of the cockpit, the (battery-powered) cockpit voice recorder recorded the expletive phrase “Oh fuck” very clearly.

In the event of a complete power failure, the indispensable hydraulic systems, without which an aircraft of this size would no longer be controllable, are supplied with hydraulic pressure by an automatically unfolding ram-air turbine . This also includes an emergency generator, which, however, is not sufficient for the entire electrical system. Since the 767 is equipped with an Electronic Flight Instrument System (EFIS) and therefore relies on electricity for complete control, the crew only had a small part of mechanical or battery-operated instruments after the power failure. One of the unusual instruments was the variometer , which shows the rate of descent, so that the crew was initially not clear how far they would get on gliding . The actual landing is still possible with the basic mechanical instruments alone.

According to the new flight schedule to Winnipeg, the Boeing had already left cruising altitude and dropped to 28,000 feet by the time it ran out of fuel.

Since there was no information in the manual on how to fly the aircraft without any engines, and this condition was not dealt with during training in the flight simulator , the captain controlled the glide angle so that a speed of 220 knots (approx. 407 km / h). He estimated that at this speed he had the flattest glide angle and thus the greatest range.

The copilot meanwhile tried to calculate whether the altitude would still be sufficient for a glide flight to Winnipeg. To do this, he used the information on the mechanical altimeter , while at the same time the distance covered was determined by radar and transmitted by the air traffic controller via radio . As it turned out, the Boeing lost 5,000 feet (1,524 m) altitude in about 10 nautical miles (18,520 m), which is a glide ratio of about 1:12. So it was clear that they wouldn't make it to Winnipeg.

Landing in Gimli

The copilot, a former military pilot with the Royal Canadian Air Force , then recommended his former base in Gimli , 12 miles away, as an emergency landing site, which, to the best of his knowledge, had two parallel runways, of which the southwest (32L) was the wider and primarily used. Neither he nor the air traffic controller in Winnipeg knew that the Gimli airport had now been converted into a public airfield. The 32L runway in particular was decommissioned and partially split up into several individual lanes for dragster and other car races with guard rails . On that day there was a big family celebration of a motorsport club with go-kart races, so that this part of the former runway was densely populated by the public, go-karts, vehicles and caravans.

During the approach, the landing gear only had to be extended by its own weight without hydraulic support ( gravity drop ). The main landing gear engaged, the nose landing gear not. The air resistance of the extended landing gear reduced the performance of the ram air turbine and thus the pressure in the hydraulics, so that the control was increasingly difficult to operate.

When it turned out that the aircraft was still too high and would shoot out over the runway, the captain, an experienced glider pilot, initiated a side glide flight . This maneuver , which is common in gliding, enables a controlled, strong descent without increasing speed. In commercial aircraft , it is technically possible, but very unusual, because the aircraft assumes a strong bank angle when flying straight ahead and the passengers have the uncomfortable feeling of falling to the side, even though the flight condition is stable, safe and controllable.

The steep incline meant that the ram-air turbine now again delivered significantly less power, as it was no longer hit by the frontal flow. The control became very difficult at a critical point: a side glide must be normalized (diverted) in good time before touchdown so that the aircraft touches down in a straight direction. It was not certain whether rejection would even be possible with so little hydraulic support.

The recovery succeeded in the last moment before touching down. The usual approach aids (such as landing flaps) were not available as a result of the power failure, so that the approach speed was significantly higher than normal, which made landing even more difficult.

The crew could only see the situation on the unusable runway from a short distance, but by then it was too late to switch to the parallel runway. There was only one chance left to attempt a landing on the remaining runway, while the people on the ground, who noticed the low-noise aircraft approaching late, fled the runway.

Immediately after touchdown, as a reaction to the partially blocked lane, instead of normal braking, emergency braking was initiated, during which two tires burst. The nose wheel was buckled during landing due to the lack of locking, so that the nose dragged along the runway and thus also made a certain contribution to the braking. The thrust reverser as a braking aid was not available because of the engine failure - the aircraft came to a standstill less than 30 meters from the event zone.

None of the passengers were injured on landing. Only when evacuating the aircraft via the emergency slides did a few minor injuries occur, as the stern was higher than usual above the ground due to the folded nose landing gear and this slide was therefore steeper. A small fire on the nose landing gear could be brought under control immediately by approaching participants and marshals. The few injured received first aid on site.

Mechanics who were sent from Winnipeg Airport to Gimli, ironically, also got stuck due to lack of fuel when they arrived and had to be picked up by another company vehicle.

Consequences

The minor damage caused by the landing could be repaired quickly. Just two days later, the aircraft left Gimli airfield on its own and was in service with Air Canada until January 24, 2008.

After an investigation, the captain was demoted for a period of six months . The copilot and some mechanics have been temporarily suspended.

Similar incidents

• Air Transat Flight 236
• Avianca flight 052
• Hapag-Lloyd flight 3378
• LaMia flight 2933
• Tuninter Flight 1153

Others

C-GAUN out of service (August 2011)

• The events of the flight were filmed under the title Schreckensflug der Boeing 767 ( Falling from the Sky: Flight 174 ) with William Devane in the lead role. However, in some central points, such as the role of the pilot in refueling, the film is not based on the facts and is therefore more to be understood as a dramaturgical-fictional adaptation of the original story.
• In the series Mayday , the flight is dealt with in episode 2 of season 5 ("Jet gliding").
• C-GAUN was decommissioned in January 2008 and was scrapped at Mojave Airport in California in September 2017 .

literature

• Merran Williams: The 156-ton Gimli Glider (PDF; 949 kB). In: Flight Safety Australia , July / August 2003 edition, pp. 22-27.
• William Hoffer, Marilyn Hoffer: Freefall: altitude 12000 m and empty tanks. The story of Air Canada Flight 143 . Maven Press, Flensburg 2011, ISBN 978-3-941719-06-4 (English: Freefall: From 41,000 feet to zero - a true story . Translated by G & U Language & Publishing Services GmbH).

Web links

Commons : Images of the Gimli Glider  - Collection of images, videos and audio files

• C-GAUN operator history at Planespotters.net

• Aircraft accident data and report in the Aviation Safety Network (English)
• Report on the "Gimli Glider"
• Photo of the C-GAUN after landing

Individual evidence

1. ^ Report by the Canadian broadcaster CBC
2. ↑ Williams (2003) p. 25.
3. ↑ The Gimli Glider. Retrieved August 27, 2014 . 
4. ↑ 'Gimli glider' recalled at trial of pilot in crash . CBC. 2007. Retrieved on March 19, 2007.  ( Page no longer available , search in web archives )
5. ↑ C-GAUN Air Canada Boeing 767-233 Airframe Info . planespotters.net. Retrieved July 6, 2018.

Coordinates: 50 ° 37 '44 "  N , 97 ° 2' 38"  W.