Events on July 23 in history

Gimli Glider: Air Canada Flight 143 runs out of fuel and makes a deadstick landing at Gimli, Manitoba.

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 July 23, 1983, 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 that resulted in no serious injuries to passengers or persons on the ground, at a former Royal Canadian Air Force base in Gimli, Manitoba, that had been converted to a motor racing track. This unusual aviation incident earned the aircraft the nickname "Gimli Glider". The accident is commonly blamed on mistaking pounds for kilograms, which resulted in the aircraft carrying only 45% of its required fuel load. However, the units error was the last in a series of failures that aligned in a Swiss cheese model to cause the accident.The Boeing 767 had a fuel-quantity indication system (FQIS) with two redundant channels, but a design flaw caused it to fail if only one channel failed. This caused a much higher failure rate than expected. The FQIS on the aircraft had failed, and Air Canada's only spare FQIS had also failed. A technician applied a temporary workaround to the aircraft's FQIS and logged the repair, but another technician misunderstood the logbook entry and undid the repair. The Boeing 767 was not flown with inoperative fuel gauges, but a miscommunication led the flight crew to fly using only a dripstick measurement of the fuel tanks. The crew needed to enter the fuel quantity into the flight computer in kilograms, but they mistakenly did the calculation with the density of jet fuel in pounds/litre. The aircraft ran out of fuel halfway to Edmonton, where Air Canada maintenance staff were waiting to install a working FQIS that they had borrowed from another airline.The Board of Inquiry found fault with Air Canada procedures, training, and manuals. It recommended the adoption of fueling procedures and other safety measures that were already being used by US and European airlines. 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.Today, Air Canada still uses flight number 143, currently for a service to Calgary from its primary hub Toronto.