AOPA Pilot magazine, July,
A True Story By: Bruce W. Frazer
Copyright © Bruce W. Frazer, 2002
When a giant Boeing 767 runs out of fuel at 41,000 feet, the old saying “silence is deafening” takes on new meaning. This happened to Air Canada flight 143 carrying 61 passengers and a crew of eight at 8:15 P.M., July 23, 1983. En route from Montreal to Edmonton with an intermediate stop in Ottawa, the flight was piloted by Captain Robert Pearson and First Officer Maurice Quintal.
Never in the history of commercial aviation have events involved with an accident gone so wrong in the beginning and so right in the end.
Bearing number 604, the aircraft designated as flight 143 was one of the first of 12 767s Air Canada purchased from Boeing. These were, and still are, among the largest and most sophisticated airliners in service. Two turbo fan engines provide 96,000 pounds of thrust, a cruising speed of 0.8 mach, or about 480 nautical miles per hour (knots), and a 5,000 mile range. Seating seven passengers abreast with two aisles; the fuselage is four-and-a-half feet wider than single aisle jetliners. But it’s the computerization that really sets it apart; virtually every instrument and function runs by computer, and all critical systems have back-ups.
Pilots are a bit double-minded about flying these behemoths: they marvel at the state-of-the-art, “gee whiz” computerization but, at least subconsciously, they resent relinquishing so much control to black boxes. Perhaps for this reason, many airline pilots who learned yesteryear’s “stick and rudder” flying skills maintain this kind of proficiency by flying gliders or aircraft dwarfed by jetliners they fly professionally. In a totally unpredictable, even unimaginable way, Captain Pearson’s extensive glider experience would force the world’s aviation community to reconsider the value of these “out of date” skills.
Most new aircraft have snags, usually minor, but they need attention. The 767 was no exception, and one of its most significant problems was the fuel processor. It had malfunctioned on several 767's newly delivered to various carriers, including Air Canada. The failure of this assembly, and its backup, were central to the problems of flight 143. As stated in the Final Report concerning the accident, “There would have been no accident on July 23, 1983 ... had the fuel processor on aircraft 604 not malfunctioned. The human errors would never have occurred had the fuel processor which operates the fuel gauges been functioning properly. Nor would the shortcomings of Air Canada, Transport Canada and the fueling companies have been exposed.”
There were human errors aplenty, but a major contributing factor was that Air Canada yielded to insistent government pressure for metrification, and, beginning with the new 767s, measurements, including fuel, were part metric and part Imperial (non-metric). These two factors led to a chain of circumstances, events and miscommunications that certainly would have resulted in a major tragedy but for the nearly unbelievable airmanship of the flight crew.
Captain Pearson had a chance meeting in a parking lot with Captain John Weir, who had just flown 604 back to Montreal from Edmonton, and they discussed briefly problems relating to the fuel system. There was one fuel gauge for the left tank, one for the right, and a third showed total fuel aboard. Pearson understood Weir to say he had flown the aircraft with all three gauges inoperative after he had the fuel level in both tanks checked manually. Thus it was no surprise to Captain Pearson that all three fuel gauges were blank when he entered the cockpit and, like Captain Weir, he ordered the fuel levels checked manually. He obtained verbal assurance this had been done when he pursued the matter with two mechanics.
The Minimum Equipment List (MEL), which had been developed cooperatively by the U.S. Federal Aviation Authority (FAA), Air Canada and Transport Canada, lists circumstances under which an aircraft can be dispatched even though some equipment is inoperable. It clearly states two of the three fuel gauges must be operable. However, Air Canada’s maintenance system had just been reorganized and Maintenance Control was given considerable say about the airworthiness of airplanes. For a multiplicity of reasons, Captain Pearson thought Maintenance Control approved the dispatch of 604 despite its inoperable fuel gauges. This assumption coupled with twice-repeated manual measurements of the fuel in each tank, and considerable extra attention given the matter by qualified mechanics and First Officer Quintal, convinced Captain Pearson to accept and fly the airplane.
The flight to Ottawa and en route weather on this mid-summer evening were near perfect. It was a welcome respite from the confusion involved with the refueling episode in Montreal.
Troubles started shortly after the aircraft departed Ottawa at a cruising altitude of 41,000 feet. Rapid beeps and near-simultaneous amber warning lights were followed in seconds by displays on computer-like screens in front of both pilots indicating one of two fuel pumps in the left wing tank was failing.
Captain Pearson decided to divert to Winnipeg, the closest major airport, 120 miles to the southwest. First Officer Quintal explained the emergency to Winnipeg Air Traffic Control (ATC) and was immediately cleared to Winnipeg Airport. When Captain Pearson began a gradual descending turn, more buzzers, lights and displays told the crew fuel pressure was failing in the right main tank. In scant minutes, the left engine failed followed by failure of the right engine. Then the lights went out! Engine driven generators stopped delivering power; every electrical and electronic device throughout the aircraft simply stopped working.
The Flight Management Computer (FMC) no longer provided vital information to the pilots and only four stand-by instruments remained: a magnetic compass, an artificial horizon, an airspeed indicator and an altimeter. Worse, the compass was virtually impossible to read because it was poorly located.
One of the largest and most sophisticated aircraft in the world was gliding at 35,000 feet with fewer instruments than Charles Lindbergh’s Spirit of St. Louis. It was at 35,000 feet, 65 miles from Winnipeg and 45 miles from a largely abandoned Royal Canadian Air Force training field at Gimli, Manitoba.
ATC in the western hemisphere is able to track virtually all aircraft with radar provided they have “transponders”: transmitters that show the aircraft’s identification, location and altitude. But Flight 143's transponder was not operating because it lacked necessary power. Fortunately, Winnipeg ATC had an obsolescent radar that could track aircraft without transponders. Without a readable compass, however, Captain Pearson had to estimate heading changes from ATC by reference to the top of the clouds.
Most passenger aircraft manufactured between the mid-thirties and the late seventies had hydraulicly boosted controls, usually powered by electric motors; if the power went out and the hydraulic system failed, it was possible to fly them manually. But this wasn’t the case with the Lockheed 1011, another wide-bodied jetliner that went into service shortly before the 767. So Lockheed, Boeing and other wide-body airframe manufacturers designed ram air turbines (RATs) that, in case of major power failures, could be extended from the aircraft to provide supplementary power from the flow of the slip stream over its small impeller. First Officer Quintal wasted no time in extending 604's RAT from a compartment near the right wheel well.
Power from the RAT was just enough to operate the primary control surfaces – the ailerons, elevator and rudder -- but not enough to operate the systems that slow an aircraft’s descent or landing – flaps, speed brakes or reverse thrust. Nor, as time would tell, was there sufficient power to completely lower the landing gear.
To avoid under or overshooting the runway, it was essential for the crew to know their altitude, rate of descent and distance from the point of intended landing. The FMC would ordinarily provide this information as a descent profile, but it wasn’t functioning and, worse, the vertical speed indicator which displays the rate of descent was not working. By remembering the altitudes and constantly getting distances from ATC, First Officer Quintal managed to work out a descent profile in his head.
No one dreamed a modern airliner would run completely out of fuel, so gliding performance had not been computed. Captain Pearson knew the 767 rate of descent with both engines idling was 1,500 feet per minute, but how much should he allow for the “parasite drag” of two dead engines? What airspeed would give him the greatest range? He settled on just over 200 knots.
It was Quintal who voiced what both pilots knew deep down: they would never make Winnipeg. Gimli was the only alternative. ATC gave them radar vectors, cleared all traffic in the vicinity and called all available emergency equipment to the scene.
Gimli’s eastern runway was still used by small aircraft, but, unbeknownst to either pilot, the parallel western runway they selected had been taken over by a sports car racing club; the first two thousand feet from the approach end was the race course home stretch.
Lowering the landing gear prematurely would have slowed the aircraft and shortened its range even further, and Officer Quintal put off doing so until about 60 seconds before touchdown. His attempt to do so was in vain, because the minimal electrical power meant there was insufficient hydraulic power to extend and lock the gear into position. The Emergency and Abnormal Procedures section of the 767's Operating Manual on Quintal’s lap made no reference to landing gear free fall, so on his own initiative he pulled an alternate gear extension switch. The heavy main wheel assembly dropped into the down and locked position, but the lighter nose gear only partially deployed.
With flaps and speed brakes extended, the approach speed in a 767 ranges between 125 and 150 knots (depending on weight), and there is usually good braking and reverse thrust to slow the landing roll. But not one of these systems was available to flight 143. This presented Captain Pearson with a terrible alternative. To avoid a stall and disastrous undershoot as he approached the beginning of the runway, his airspeed had to be at least 180 knots, but, with this much speed and so few options for slowing the landing roll, it was distinctly possible he would overshoot the runway.
Then the final – and by far most challenging problem – occurred: With only about 35 seconds of gliding time left, two miles short of the “runway” threshold, Captain Pearson saw that he was too high – not high enough to circle and land, but still much too high. At this instant, he drew upon his sail plane experience and executed a maneuver that no other pilot in the world would have thought possible in one of the world’s largest jetliners. He simultaneously moved the ailerons full left and the rudder full right. This was a sideslip, a light airplane maneuver that pointed the left wing sharply downward toward the runway. This manuever compensated for the lack of flaps and speed brakes; the aircraft lost altitude without gaining unwanted airspeed.
Teenager Art Zuke, riding his bicycle down the drag strip, saw flight 143 silently bearing down on him. Along with two of his friends, he barely managed to get out of the way. His comment after the narrow escape was telling: “I saw this thing flying sort of sideways and cockeyed ....” Zuke’s observation was accurate; he saw the sideslip.
Pearson maintained this slip attitude to within a few feet of the ground, straightened out just before touchdown, and landed 800 feet from the threshold. Tires on the right main gear blew out, and the aircraft skidded 4,000 feet down the runway on its nose and the right engine nacelle, stopping just 500 feet from amazed sport car racers and their families.
There were no deaths or serious injuries, and within a few days the airplane was flown back to its base for repairs. Known as the “Gimli Glider,” it is still in service.
Air Canada at first laid the blame for the accident on Captain Pearson, First Officer Quintal and two mechanics, but public opinion caused the Canadian government to convene a Board of Inquiry to launch a year-long inquiry about all the circumstances.No punitive action resulted and blame for the accident was distributed among numerous individuals and organizations.
The Diploma for Outstanding Airmanship, first awarded in 1985 by the world acclaimed Fédération Aéronautique Internationale, is conferred on only two pilots in the world each year. Captain Robert O. Pearson and First Officer Maurice Quintal were the first recipients.