Out of Fuel!

Fuel calculations are part of the daily routine of hundreds of pilots, dispatchers and flight engineers across Canada. Once in a very long while, these numbers get mysteriously inaccurate to the point that they lead to a serious occurrence. Who does not remember the "Gimli Glider," a new Boeing 767 that was flying across the country when it ran out of fuel midway through the flight and glided safely to the Gimli airfield in Manitoba, then being used as a drag strip? Or the Boeing 707 that flamed-out and crashed on Long Island, New York, after being placed in a holding pattern by air traffic control (ATC) three times, for a total of about 1 hr 17 min? In that case, the investigation determined that the captain had failed to communicate an emergency fuel situation to ATC before fuel exhaustion occurred. Circumstances differ among fuel-starvation cases, but the common denominator for almost all occurrences is errors or omissions by the pilot-in-command, the captain, the commander, or the person known by whatever other title is assigned to the numero uno driver, the pilot.

Fuel quantity is usually measured by weight or litres added, looking at cockpit gauges, using calibrated dipsticks, conducting visual inspections, monitoring in-flight fuel consumption (in time), or taking the word of a "reliable" third party who oversaw the fuelling operation. Computer programs and fuel tables are also widely used to calculate fuel requirements. Using only one of the above methods may give some confidence in the fuel quantity, but combining two or more would considerably increase the accuracy. During flight planning, crews must balance fuel requirements with passengers and cargo weight, which means that the aircraft is rarely filled to capacity. All airlines — or at least all respectable ones — have a fuel policy that meets or exceeds the regulations but that will usually ensure that the aircraft has just enough fuel to meet the minimum fuel requirements. Air carriers are conscious of their bottom line and always make sure that they do not carry around extra fuel that is not needed.

The following two serious fuel occurrences have been selected to illustrate the hazards and risks associated with precarious fuel situations. Both events ended without any injuries — to our surprise, the Transportation Safety Board of Canada (TSB) reports relatively few fatalities directly attributed to fuel-exhaustion accidents — but both were very close calls.

The first occurrence is the subject of the recently released TSB Final Report A97P0169. A float-equipped de Havilland DHC-6 Twin Otter was 20 min into the fourth leg of two return flights between Alliford Bay and Langara, British Columbia, when the forward fuel tank low-level caution light illuminated. In level flight, this light should activate when 75 lb. of usable fuel remain, but the gauge indicated that 310 lb. of fuel remained. The emergency checklist was consulted and it indicated that this situation could be caused by a blocked ejector pump slowing the transfer of fuel to the collector cell. The captain continued the flight, taking no further action, since he judged that gravity feed would be sufficient to ensure proper fuel supply to the engine. About 5 min later, the low-fuel-pressure caution lights came on and the No. 2 engine stopped. The forward fuel gauge indicated about 200 lb. At that time, the aircraft was near Yakoun Lake, and the captain decided to land there to assess the problem. It was a very good decision indeed, as the No. 1 engine also stopped shortly after the landing as the captain attempted to taxi to the beach area. The fuel tanks were found to be empty. Another Twin Otter was dispatched to Yakoun Lake to deliver an aircraft maintenance engineer (AME) and two drums of fuel to the downed aircraft. The aircraft was refuelled from the drums and the engines were restarted. It was later ferried back to Alliford Bay without further incident.

The report indicates that pre-flight fuel calculations were underestimated and consumption was not properly monitored during the four legs of the day. Also, the fact that legs were longer than expected owing to weather was not taken into account in the calculation of fuel consumption as the day progressed. Fuel weights in the journey log-book were wrong all day as well, as the log-book indicated 850 lb. at departure and the pilot acknowledged that, prior to the first flight, he had measured 550 lb. with a dipstick before adding an extra 600 lb., giving an actual fuel weight of 1150 lb. Therefore, the quantities listed were not consistent with known and measured quantities or with the fuel calculations that should have been made as the flights progressed.

An inaccurate forward fuel gauge and an unserviceable aft fuel tank gauge did nothing to help the situation. The company had minimum equipment list (MEL) procedures in place for continuing operations with an unserviceable fuel gauge, but these were not followed. Had the procedures been followed, the tank would have been filled or additional fuel dipstick checks would have been carried out and the low fuel situation likely would have been prevented. In the end, the captain broke the accident chain by landing the aircraft on a lake immediately after the No. 2 engine stopped because of conflicting information about the fuel quantity. Had he attempted to push for the extra 10 min left to destination, a serious accident might well have been the outcome.

The TSB concluded that the aircraft ran out of fuel because the pilots did not establish the fuel quantity on board before or during the flight. Contributing to the incident were the fact that the fuel gauges were unserviceable and inaccurate, and the fact that the pilots did not accurately monitor fuel burn in flight or follow applicable MEL procedures. Since the incident, the company involved has instituted a procedure whereby the pilots must log the amount of fuel loaded into the aircraft and this entry must be witnessed by another person.

The second occurrence involved a jumbo jet with 16 crew members and 128 passengers on board, as reported in TSB Final Report A90P0389. A foreign-registered DC-10 on a planned flight from Calgary, Alberta, to Vancouver, British Columbia, almost ran out of fuel on December 18, 1990, and landed at the Victoria International Airport with a computed fuel weight remaining for 12 min of flight. The weather and runway conditions were unsuitable for a landing at Vancouver, and so, at 4 DME on the instrument landing system (ILS) final approach to Runway 08, the captain decided to discontinue the approach and divert to Victoria, the planned alternate airport. When the flight arrived at Victoria, the weather rapidly deteriorated and was eventually below landing minima. The crew did not know that the ILS was not available in Victoria, as the NOTAM information provided to them by a service company based in the United States was incomplete. The crew was unable to land on the first approach, an NDB/DME to Runway 27. On the missed approach, the captain declared a low-fuel emergency. The air traffic controller activated the ILS to Runway 09 and provided radar guidance to the final approach course. During the approach, the weather continued to deteriorate below instrument flight rules minima, with a reported runway visual range of 800 ft., a snow squall over the airport and a strong crosswind. However, owing to the extremely low amount of fuel, the captain was committed to land, and he was able to make a successful approach and landing.

The carrier’s fuel policy complied with Canadian regulations. However, this particular aircraft departed on a flight with a filed alternate (Victoria) that had weather forecast to be below alternate weather limits, and the crew neither obtained this forecast prior to departure from Calgary nor requested weather updates while en route to Vancouver. Factors that contributed to the incident included the incomplete NOTAM summary provided to the crew. The service company had requested NOTAM information for Victoria via the international distribution service, but Victoria was not designated for international use at the time; therefore, the company received a "No Current NOTAM" message, while the ILS outage at Victoria was included in the domestic NOTAM summary.

The TSB determined that the flight had departed for Vancouver without a suitable alternate airport because the crew had not received the amended weather forecast for the alternate airports, requested any updated weather information in Calgary or while en route, or received the complete NOTAM summary.

The lessons drawn from these and similar occurrences indicate clearly the importance of proper fuel management. The following A.I.P. references provide a quick review of fuel issues: for fuel and oil weights, see RAC 3.5.2; for fuel requirements, see RAC 3.13; and for fuel handling, see AIR 1.3.2.