"AIR CRASHES AND MIRACLE LANDINGS: 85 CASES – HOW AND WHY"
Miscalculation Meant Only Half the Fuel Loaded (Gimli, 1983)
Considering there are relatively few instances of aircraft, such as Piché’s, gliding long distances to a safe landing, it is surprising that another Canada-registered aircraft had eighteen years before featured in a similar feat, but over land.
Air Canada Flight 143, July 23, 1983
Captain Bob Pearson and First Officer Quintal were flying their sophisticated Air Canada Boeing 767 between Ottawa and Edmonton when it ran out of fuel out of gliding range to an airport. They had set off with their fuel gauges not working, and the flight management computer (FMC) was calculating the amount of fuel in the tanks by deducting the amount consumed by the engines from the amount measured by dipsticks on departure. Thus, the amount shown depended on correctly knowing the amount of fuel initially in the tanks. Regardless of whatever the FMC said, they should have had no need to worry, as the dipstick checks at Montreal and then Ottawa had shown they had ample fuel for the 3,574-kilometer leg to Edmonton and would still have the required reserves. Just over halfway, with the readout from the FMC indicating several tons of fuel left, a beeping sound drew the relaxing pilots’ attention to low pressure in one of the two fuel pumps feeding the left engine. Soon afterward the instruments indicated low pressure in the other pump. Was it a computer glitch or faulty sensors? However, the aircraft was virtually new, and to have two pumps, or their pressure sensors, fail was troubling enough for Pearson to decide to divert to the nearest appropriate airport, which was Winnipeg. Still at forty-one thousand feet, they throttled back the engines to begin descent into Winnipeg, some 120 nautical miles away. Shortly afterward the displays warned of a similar low fuel-pump pressure situation for both pumps feeding the engine on the opposite side. For so many pumps to be affected simultaneously was a sure sign of a fuel problem, and their fears were confirmed when a few minutes later the number one engine flamed out, followed three minutes later by the number two engine. Normally, the fuel measurement system would have given a warning once the fuel level fell to two tons, giving them more than adequate time (over land) to make an emergency landing under power. But of course, that was not working. They were by then down to twenty-five thousand feet, with still sixty-five nautical miles to go to Winnipeg. As in the case of Piché’s aircraft, a small RAT (ram air turbine) had dropped down from the underside of the aircraft to provide just enough power for essential flying controls. The once-sophisticated screens were blank, and all they had was the artificial horizon, airspeed indicator, altimeter, and a magnetic compass, which was difficult to read because, unlike the usual gyrocompass, it was not stable. With no vertical speed indicator, judging the optimum glide path was exceedingly difficult, and amid his other tasks, the first officer had to get the Winnipeg controller to constantly give the distance remaining to Winnipeg and try to work it out from tables. With them down to 10,000 feet and descending to 9,500 feet, the distance remaining was forty-five nautical miles. They were losing height faster than expected, and at that rate all hope of making Winnipeg had gone. The situation was desperate. Just as the captain was about to ask Winnipeg for anything nearer, the first officer suggested they try Gimli Air Force Base, where he had been temporarily stationed during his military service. He knew it had two runways of sufficient length. Reassuringly, air traffic control informed them Gimli was only twelve nautical miles from their location. The air traffic controller guided them toward Gimli but with some difficulty, as not being operational, the field itself was not shown on the charts. The captain was informed of this but told light aircraft were using the right-hand runway. The controller could not guarantee the runway would be clear. They did not want to lose too much height before being sure they could identify the Gimli base, and the trouble was that although the first officer knew the general area he could not be sure exactly where it would be. When he finally did sight it, they were much too high, posing the problem of how to lose both height and speed in the distance that remained without the help of flaps or air brakes. By a lucky coincidence, Captain Pearson happened to be an experienced glider pilot. With no air brakes, he had to resort to a series of difficult sideslips and yaws, with the ailerons sending the aircraft one way and the rudder the opposite way to provide a braking effect that only a glider pilot could execute, he brought the speed and height down to a reasonable degree; and with the runway ahead, told the first officer to lower the landing gear. In the dusk, they could only see one clearly defined, whitish runway ahead and assumed incorrectly it must be the (actually darker) right-hand one on which they planned to land. Thus, they were unknowingly lining up with the disused left-hand runway, which that weekend was being used as a racing car circuit, with a strip down the middle and the cars going down one side and up the other.