- NEWSDAY.CO.TT - A la Une - 14/Aug 02:38

The ‘Gimli Glider’ accident

On July 23, 1983, a Boeing 767 aircraft operating Air Canada's scheduled domestic flight 143, between Montreal, Quebec and Edmonton, Alberta, ran out of fuel midway through the flight. The flight crew successfully glided the Boeing 767 from an altitude of 41,000 feet to an emergency landing at a former Royal Canadian Air Force base in Gimli, Manitoba, which had been converted to a racetrack called the Gimli Motorsports Park. There were no serious injuries to passengers or people on the ground, and the aircraft sustained only minor damage. The aircraft was repaired and remained in service until its retirement in 2008. This unusual aviation accident earned the aircraft the nickname "Gimli Glider." On July 22, 1983, the Boeing 767 in question underwent routine maintenance checks in Edmonton, Alberta. The technician found a defective fuel-quantity indicator sensor (FQIS) and disabled the defective channel, and made an entry in the aircraft technical logbook. The next morning, the captain and first officer were briefed 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. The captain converted the dripstick reading from centimetres to litres to kilogrammes, finding that it agreed with the FQIS. The plane flew to Toronto and then Montreal without incident. A dripstick is a thin hollow tube installed vertically in the bottoms of fuel tanks of many large aircraft and is used to check fuel levels. To read a dripstick, it is withdrawn from the lower surface of the wing. When the top of the dripstick is withdrawn below the level of the fuel, fuel enters it and drips through a hole in the cap. Graduations on it in either inches or centimetres are converted to pounds or kilogrammes to indicate the amount of fuel in the tank. At Montreal, another captain and first officer took over the airplane for Flight 143 to Edmonton with an intermediate stop at Ottawa, Ontario. During the handover briefing, the inbound captain informed the outbound captain that a problem existed with the FQIS, and the outbound captain decided to take on enough fuel to fly to Edmonton without refuelling in Ottawa. The all-metric 767 aircraft was new to Air Canada’s fleet and tracked fuel quantities in kilogrammes. After taking a dripstick measurement, the outbound captain converted the reading to kilogrammes. He used the density figure for jet fuel from the Air Canada refueller'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 fuel quantity calculated was incorrect. Since the FQIS was not operational, the captain 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. At the time of the accident, Canada's aviation sector was converting from imperial to metric units. As part of this process, the new Boeing 767s acquired by Air Canada were the first to be calibrated for metric units. While flying over Red Lake, Ontario, at 41,000 feet shortly after 8 pm Central Time, the aircraft's cockpit warning system sounded, indicating a fuel-pressure problem on the aircraft's left engine. Assuming that a fuel pump had failed, the pilots turned off the alarm, 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. 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. The engines provide both electric and hydraulic power to the aircraft. With loss of engine power, the ram air turbine (RAT) was deployed to provide hydraulic power for operating the flight controls. The aircraft cockpit electronic flight instrument system went dead, leaving only a few basic battery-powered emergency flight instruments operational. The pilots searched their emergency checklist for the section on flying the aircraft with both engines out, only to find that no such section existed. The captain was an experienced glider pilot, so he was familiar with flying techniques rarely used in commercial flight. He needed to fly the 767 at the optimum glide speed to have the maximum range and, therefore, the largest choice of possible landing sites. At this point, the first officer proposed landing at the former RCAF Station Gimli, a closed air force base. Without the main hydraulic 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. As the aircraft wheels touched down on the runway, two of the aircraft's tires blew out. 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. Air Canada Flight 143 came to a final stop on the ground 17 minutes after running out of fuel. The Canadian Aviation 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 older aircraft flown with a three-man crew. 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, and provide better, more thorough training on the metric system to its pilots and fuelling personnel. The final report of the investigation was published in April 1985.   The post The ‘Gimli Glider’ accident appeared first on Trinidad and Tobago Newsday.