In an era of razor thin airline profit margins and bloated fuel prices, a data-driven, safety-sensitive fuel management program is increasingly essential to efficient operations. Fuel now accounts for 33 percent of airline operating costs, up from 14 percent in 2003, according to the International Air Transport Association (IATA). At most airlines, fuel is more expensive than labor, which traditionally had been the largest single operating cost item.
The fuel-induced pressure on profitability has some in the industry concerned that carriers could opt to carry less fuel on some flights to reduce aircraft weight and decrease fuel burn, but a properly run fuel management program can positively impact safety performance. IATA, in its Guidance Material and Best Practices for Fuel and Environmental Management (the 5th edition of which was released in 2011), said that “managing fuel accurately and efficiently improves safety through additional attention to planning, high accuracy of the flight planning system and precise execution of the flights, increased situational awareness, operational discipline to follow the flight plan, availability of appropriate analytical tools and statistics, adequate training for pilots and other operational personnel, a feedback mechanism to inform employees of airline policy, efficiency targets, and performance data within specified timelines.”
According to IATA, additional safety benefits include the opportunity to “exercise proper risk management by ensuring that sufficient fuel is carried to high-risk airports and less fuel to airports where it is not necessary; minimize the risk of unplanned diversions; ensure that flight crews and dispatchers maintain a safe and efficient approach to fuel management; monitor the use of fuel reserves for purposes other than intended, such as the improper use of alternate fuel while an alternate airport is still required; [and] develop a fuel management information system, which permits the tracking of fuel usage and the monitoring of deviations of flight plan fuel.”
To derive safety benefits from a fuel management program, it is important that the program be based on safety principles and be data driven. Accurate and reliable data have to be available to understand the status quo, to establish the saving targets and to continuously assess the safety implications. “You simply need to have accurate data to monitor [whether] your flights are really happening as you think they are happening,” said Rudolf Christen, CEO of Aviaso, a fuel management software provider. “Three examples illustrate what type of information can be relevant: compare the planned versus actual trip times, compare the planned versus actual lateral and vertical departure/arrival tracks, and compare the planned versus actual weights. Ideally, you have this information in correlation to the time of the day, weekday and further criteria such as weather, since, obviously, an arrival into a busy commercial airport looks different on a foggy early Monday morning compared to a sunny Sunday afternoon,” he said.
The availability of data means an opportunity for better decisions, said Christen, who advocates providing fuel efficiency information to flight crews as part of their briefing process. He said that during the preflight briefing, pilots should get fuel efficiency information on the upcoming sector to be flown. “Such information is coming from the fuel efficiency data warehouse and is based on information collected in [for example] the previous 12 months on the respective sector. This approach improves the pilots’ knowledge of the upcoming flight and allows for better decisions. Obviously it is important to not only present average figures but also highlight the deviations from the average figures.”
In addition, it is important that the data coming from a variety of sources be properly integrated, and that pilots and other operational personnel be familiar with the principles of statistical analysis, according to Christen. Collected data parameters can relate not only to actual fuel consumption, but also to parameters that affect consumption, such as weight, distance, time, engine, flight planning and weather information, he said.
Important fuel consumption data can be derived from flight data monitoring (FDM) systems and aircraft performance monitoring (APM). APM is important because “while FDM records data at certain preselected time intervals, like once per second or every two seconds, and then feeds the flight data recorder, APM allows the calculation of the deterioration of aircraft performance over time,” said Philipp Reichen, an aviation and aerospace consultant and contractor. “APM records very specific data to calculate aircraft performance, whereas FDM records a vast quantity of data, including flight control positions, which are intended to show excursion of values compared to limits. The APM and FDM systems share some of the same sensors; therefore, the accuracy of the acquired data should be the same,” Reichen said.
Neither system, however, will provide a complete understanding of how fuel consumption is affected on its own, said Reichen. “The risks of just using one or the other system are that decisions and results will be based on incomplete data and might, therefore, be inaccurate or even faulty. This, in turn, might lead to not being able to meet ROI [return on investment] goals in fuel savings and to introducing procedures that do not address the potential savings correctly. In order to have the best understanding of fuel consumption and reasons for maybe excessive use of it as well as potential savings, APM systems should be used together with FDM and even engine condition trend monitoring. Best practices would include a long-term data and trend view, as well as the short-term view for the more immediate decisions,” said Reichen.
Fuel Management on the Flight Deck
Even if other functions also have an important role to play in fuel management — for example the engineering function can prescribe aircraft drag and weight reduction efforts and support the collection of APM data — because the operational domain is the main target for fuel efficiency improvements, pilots and dispatchers tend to be the main recipients of safety recommendations. “Lately, there has been more and more emphasis on carrying the correct amount of fuel, no more, no less. It is critical that pilots do a very thorough analysis of the fuel requirements, perform risk management (using appropriate tools such as analyzed contingency fuel), learn how to check their fuel using advanced flight management systems [FMS] and properly manage their fuel during flight,” said Marcel Martineau, a former Airbus A330/A340 captain, manager of Air Canada’s fuel program and currently the owner of Total Fuel Management, a consulting firm.
Flight Planning Systems
Some airlines still use legacy flight planning systems despite having invested heavily in modern aircraft. Upgrading the flight planning to support to more efficient fuel management offers several safety benefits. “There is a large variation regarding the optimization of various flight planning systems,” said Martineau. “Most flight planning systems on the market are reasonably accurate calculators, but often not great optimizers. In addition, many dispatchers are not well trained on their flight planning systems. The best systems will calculate fuel more accurately as they will consider the planned departure runway with appropriate SID [standard instrument departure route] and the planned landing runway with the correct STAR [standard terminal arrival route]. This eliminates a lot of guessing work as to how much fuel is required to compensate for inaccuracies. In addition, having runway-specific flight planning system capabilities is excellent to assist the pilots in programming the FMS so as to check the accuracy of the fuel requirements before departure. This will improve safety due to the fact that pilots will have a clear idea of their fuel and what it is used for,” he said.
Another driver of a good fuel management program is the cost index, which “provides a flexible tool to control fuel burn and trip time to get the best overall economics.”1 Some techniques for reducing fuel burn, such as cruising at a lower speed, often result in more trip time. In such a situation, fuel savings could be offset by increased time-related costs, such as crew-related costs or the expenses associated with passengers missing connections. The cost index is the cost of time compared with the cost of fuel and is used to obtain the best economics. If fuel costs are the main priority, then the cost index is low. With zero cost of time, the cost index would be zero and the FMS would fly the aircraft at maximum range cruise (MRC) speed. If the cost of fuel instead is cheap compared to the cost of time, then speed is important and the cost index is high. For zero cost of fuel, the cost index would be 999, and the flight management system would fly the aircraft just below Mach maximum operating (MMO). The best economics are between these two speeds and depend on the operator’s cost structure and operating priorities.2
Put another way, suppose crew costs work out to $10 per minute, maintenance is $10 per minute, the delay cost is $50 per minute and fuel is $1 per kg (or about $3.25 per gal). As long as an aircraft is burning less than 70 kg of fuel to save a minute of time, the airline comes out ahead, according to Martineau.
Flight Planning and Operations Control
“As the flight dispatch or flight planning function is integrated into the operations control process, one major aspect of improving the business decisions within operations control has been the provision of improved situational awareness tools that provide a variety of functions including flight watch,” reported IATA.3 According to Martineau, “This process can greatly enhance flight safety, and will ultimately produce the safest and most cost-effective operation, as the flight crew cannot adequately analyze the significant amount of data and factors involved in planning a flight without experienced, knowledgeable assistance from the ground.”
Flight dispatchers typically play a larger operational role in regulatory regimes like those of the United States and Canada than elsewhere in the world. “It is unfortunate that most dispatchers outside North America are relegated to a clerical function, leaving the [airplane] commander alone to determine fuel requirements often based on a seat-of-the-pants process,” said Martineau. “In an increasingly complex environment, dispatchers must be better trained and must not only participate in the fuel requirement risk analysis, but must provide proper flight following after the flight gets airborne. Many conditions can change during the flight, and dispatchers are in a better position to monitor and assess changes that can affect the safety of flight. Things such as volcanic ash, NOTAMs [notices to airmen], wind updates, turbulence reports, ETOPS [extended twin-engine operations] support, etc., can be better done from the ground with proper systems.”
Alternate Airport Selection
Selection of an alternate airport also is an important element of a safe and effective fuel management program. “All alternates shown on the operational flight plan must be in compliance with applicable regulatory and company policies. The following guidelines should be considered during the alternate selection process: Diversions very rarely occur, and when they do, the aircraft often does not proceed to the flight planned alternate. The cost of carrying the fuel for an alternate is high, [and] in business case terms, an occasional diversion is much cheaper than always carrying extra fuel as part of a ‘prevent a diversion’ strategy,” reported IATA. In explaining the “prevent a diversion” strategy, Martineau said that some airports present particular operational risks, such as unpredictable weather, heavy traffic or limited approach facilities that might prevent a flight from landing. To minimize the chances of having to divert, it is sometimes necessary to carry extra fuel to enable additional holding time or the ability for the flight to attempt more than one approach in cases when the weather is variable. If the flight carries the minimum amount of fuel, it might have to divert to the alternate airport as a result once its holding time is over.
According to Martineau, “The likelihood of going to an alternate when the weather is bad will contribute to the choice of the alternate. The flight planning system must calculate realistic fuel requirements to the alternate. For instance, if Newark [Liberty International] Airport is used as an alternate while going to [John F. Kennedy International Airport] (which is about 12 nm [22 km] away), there will be a requirement for about 80 nm [148 km] of travel to fly to the alternate airport. Pilots must be careful to plan the proper routing to the alternate in the FMS to ensure accurate alternate fuel prediction. In addition, in the likelihood of a diversion, pilots must ensure they have some fuel reserve available above the final 30 minutes fuel, as many other flights might be diverting at the same time and there might be a need for some holding capability. Also, one must know how this 30 minutes holding is calculated by the flight planning system and how much of it is usable, along with the flight maneuvering restrictions if using fuel from the final holding fuel.”
Center of Gravity
“Depending on the aircraft type, drag created by loading an aircraft to the forward limit of its forward center of gravity can increase drag by as much as 3 percent compared to loading the aircraft at its most rearward center of gravity limit. Mismanaging an aircraft’s center of gravity can have a significant impact on fuel efficiency. The actual center of gravity plays a significant role in aircraft en route performance; the more aft the center of gravity can be placed, the less induced drag will be produced, which, in turn, improves the specific range of the aircraft. This reduction in induced drag results in reduced fuel consumption,” reported IATA.
Accuracy in managing aircraft center of gravity is thus very important. Unfortunately, most flight planning systems do not consider the variation of fuel burn caused by the variation of the center of gravity, Martineau said, “The variation can go from plus or minus 2 percent, depending on the aircraft type. Consequently, on long flights, a 2 percent error can eat up the contingency fuel. If the flight plan fuel biases are not accurate, pilots can end up arriving at the destination with less of the required fuel.”
Reduced Fuel Consumption Procedures
An approach based on risk analysis should also lead to the adoption of reduced fuel consumption procedures. A wide range of flight operations procedures reduce fuel consumption, are safety sensitive and need appropriate control actions: engine-out taxi-out, reduced takeoff flaps, reduced acceleration altitudes on takeoff, continuous climb operation, constant descent operation, low noise–low drag approach, reduced flaps landing, idle reverse on landing, and engine out–taxi in.
“Many of these procedures are used safely by many airlines,” said Martineau. ”The idea is having good guidelines, training and awareness for each initiative. Landing on a 10,000-ft (3,048-m) runway where the airplane must exit at the end of the runway certainly does not require the use of full reversers and maximum brake on landing. All of these procedures are a question of airmanship and common sense. Regular line pilots who are well trained with proper guidelines are quite capable of judging when such procedures should be applied. All of these initiatives should be recommended procedures and not standard procedures, as they should only be applied when the conditions are appropriate.”
Risk-Based Approach and Regulatory Compliance
The key to a data-driven fuel program is to follow a risk-based approach. The question may arise of how it is possible to manage fuel performance in a risk-based mode, that is, based on the particular operational history of the airline, while remaining compliant with applicable regulations, which are, of course, prescriptive, regardless of the peculiarities of a specific operator.
Risk-based fuel management does not imply going against regulatory requirements or manufacturer’s recommendations. A risk-based approach allows for pushing the envelope wherever there is a margin of safety and for making more conservative decisions where the risks are known to be higher. “The several actions implemented by a fuel management system in flight certainly have a financial motivation,” said Luigi Bellini, an airline training captain. “The need is for a functional safety risk management effort which counterbalances the strictly financial motivation.”
A risk-based approach can also be applied in updating relevant regulations on fuel reserves. “In the European regulatory environment, there has been a lot of work in clarifying the process of fuel planning and how fuel should be managed during flight,” said Martineau. ICAO [the International Civil Aviation Organization] has been doing a lot of work trying to catch up with Europe, and its Flight Planning and Fuel Management Manual is expected to become an ICAO Annex shortly, Martineau said. In the United States, if an operator wants to use a risk-based approach to managing contingency fuel, it needs to request a special exemption to the FARs from FAA, he said. “Needless to say, all of the changes are causing some problems of interpretation of the rules,” he noted. “Often, the government agencies from many countries introduce various regulations without proper consideration of the effect of such rules. So you end up with flights landing at the same airport at the same time with completely disparate fuel requirements. This shows that there is a lot of room for improvement in the area of training and achieving commonality in regulations on fuel reserves. The adoption of a risk-based approach in the rulemaking process is certainly a priority.”
To summarize, fuel management serves to increase operating efficiencies, resulting in reduced fuel bills, and at the same time, it improves flight safety by enabling better front-line decision making. A data-driven and risk-based fuel management program based on a combination, as applicable, of the above best industry practices for optimized fuel consumption will also reduce the risk of systemic errors.
Mario Pierobon works in business development and project support at Great Circle Services in Lucerne, Switzerland, and was formerly with the International Air Transport Association in Montreal.
- Airbus. “Getting to grips with fuel economy.” Airbus, Issue 3, July 2004.
- IATA. Guidance Material and Best Practices for Fuel and Environmental Management. 5th edition, 2011.