Now More Than Ever Fuel Efficiency Crucial to Ops

Now More Than Ever Fuel Efficiency Crucial to Ops

François Chazelle, head of sales support, flight efficiency – SITA FOR AIRCRAFT shares how innovative fuel optimization technology is helping the aviation industry to reduce their emissions today.

Sustainability is becoming more important to airlines, especially with IATA’s Fly Net Zero by 2050 commitment to consider. Reducing CO2 emissions is more front of mind when considering fuel optimization than seeing it as a way to save money. Even though newer generation aircraft with more efficient engines are a ‘quick win’, there is still a need to find ways of further reducing emissions.

When talking to an airline’s head of sustainability, Sustainable Aviation Fuel (SAF) is often mentioned. However, SAF is currently more expensive than conventional jet fuel, so the economic argument still carries weight. It can also be difficult to obtain, as availability is still limited. In addition, the green savings from SAF come from its manufacture especially as, having gone through an engine, the exhaust emissions from SAF are just the same as JET A-1 aviation fuel.

The Opportunities Today

There is a real opportunity for airlines to make fuel savings today to decrease emissions while maximizing the full performance potential for every aircraft they use, through fuel efficiency solutions. Today, SITA has a suite of fuel optimization solutions, SITA OptiFlight, comprising:

– SITA OptiClimb, which recommends customized climb speeds and acceleration levels for each flight using machine learning predictive performance models to save up to 5% of climb-out fuel.

– SITA OptiDirect, which recommends shortcuts that pilots can request from Air Traffic Control (ATC) based on historical tracks flown, with an indication of fuel and time savings taking into account the wind and temperature forecasts for the flight.

– SITA OptiLevel, which advises pilots on the best initial flight level and potential cruise level changes taking winds into account.

– SITA OptiDescent, which helps pilots better anticipate on Distance to Go and Top of Descent based on machine learning of historical approach patterns.

Despite COVID-19, the customer base for these solutions has grown, with 26 airlines operating more than 1,000 aircraft, including Singapore Airlines; a flag carrier and a large leisure operator in Europe; and a large freight operator in the U.S. Other customers that can be named include Aerologic, Air Austral, Air Asia, Sky Airline, Transavia and VivaAerobus.

The range of aircraft currently covered by SITA fuel optimization solutions includes Airbus A320 Family, A330 and A350; Boeing 737, 757, 767, 777 and 787; and Embraer E190, and SITA OptiClimb can be applied to any jet aircraft type.

SITA OptiDirect uses machine learning algorithms applied to historical flight data to recommend shortcuts with time and fuel savings information to pilots. SITA image.
SITA OptiDirect uses machine learning algorithms applied to historical flight data to recommend shortcuts with time and fuel savings information to pilots. SITA image.

The solutions do not need certification as all the recommended speeds are advisory and always within the flight envelope for each type. In addition, SITA supports its airline customers by carrying out a safety impact assessment. There is a highly experienced SITA team supporting customers including a former airline pilot and an air accident investigator, which is reassuring to potential customers.

Singapore Airlines selected SITA OptiClimb late last year following a successful test period and validation on the Airbus A350 fleet since August 2022. SITA has calculated that the solution will help the carrier cut aircraft carbon emissions by up to 15,000 tons annually. It estimates that airlines can derive fuel savings of up to 5% during climb-out on each flight using SITA OptiClimb, with around 5.6 million tons of CO2 emissions avoided annually if every airline worldwide used the system.

Innovating with Customers

Feedback from the customer is important in the development and evolution of solutions in SITA. Back in 2015 when launch customer Transavia France selected SITA OptiClimb, the original thinking was to have more than three speed settings for the product, as the more detailed the climb profile, the greater the potential savings. However, Transavia’s pilots said three speeds could be correlated to and entered into the flight management system during cockpit preparation, allowing the profile to be flown automatically.

Making it easy to use meant the application rate increased rapidly and the more often SITA OptiClimb is used, the greater the savings, so it was a valuable trade-off. Across the worldwide fleet, application rate is around 75%. The remaining 25% is mostly ATC-imposed limitations such as a level off or a particular speed for separation reasons. Pilots may also need to adapt their speeds in case of turbulence.

SITA OptiClimb helps airline operators optimize fuel utilization during the aircraft’s climb-out phase. The solution combines aircraft tail-specific machine-learning models with 4D weather forecasts to recommend customized climb speeds at different altitudes. SITA image.
SITA OptiClimb helps airline operators optimize fuel utilization during the aircraft’s climb-out phase. The solution combines aircraft tail-specific machine-learning models with 4D weather forecasts to recommend customized climb speeds at different altitudes. SITA image.

In fact, Transavia France carried out a comparison of the respective contribution to overall operational fuel savings of SITA OptiClimb and four other legacy best practices that could be monitored via a fuel dashboard – using reverse thrust at idle accounted for 5.6% of total fuel savings; reducing reserve fuel represented 12.8%; continuous descent approaches (CDA) represented 15.2%; and reduced altitude acceleration represented 16.7%. SITA OptiClimb represented 48% of total savings which is basically equivalent to savings brought by the four legacy best practices. In a nutshell SITA OptiClimb enabled to double the savings achievable by the airline.

Adaptable Solutions

Of course, there are variations between aircraft that have to be accounted for. The A350 flies much higher than some other wide-body aircraft and there is a particular altitude at which airspeed automatically switches to Mach from knots. SITA OptiClimb takes account of this in its calculation.

There are also differences between airports. Regulations often that say climb-out should be at a maximum of 250 knots to a minimum of 10,000 feet, but this does not apply in Malaysia, so SITA OptiClimb can be optimized on an airport-by-airport basis. This is important as the first 30 minutes of the flight are where the greatest savings can be made, as the greatest thrust levels are in use. The system balances horizontal and vertical speeds to reach a certain point at a designated distance and altitude within the same time as the aircraft’s Econ climb rate, respecting the airline’s Cost Index for the flight.

This doesn’t deviate from the flight plan, so no ATC clearance is required (although ATC at one European airport does ask pilots to advise if they are using SITA OptiClimb). In cruise, any changes do have to be cleared with ATC, for example, if SITA OptiDirect recommends a shortcut or SITA OptiLevel suggests a level change. This has led to OptiATC, an exploratory collaboration with SkyGuide, the Swiss air navigation services provider.

Fuel Optimization for ATC

OptiATC is intended to assist both shortcut recommendations and in the descent phase, which is always determined by ATC. However, as SITA OptiDescent has a history of approaches into each airport, the pilots can select their preferred approach and send the new route to the ATC center, where it is displayed on the controller’s screen, saying this is the approach the airline normally uses. This enables the ideal Top of Descent to be calculated followed by a Continuous Descent Arrival (CDA).

jet wing

There is also a reporting tool for the ATC manager, enabling them to quantify the fuel and emissions savings that they have helped to achieve.

Work on OptiATC was carried out by a strong research team in SITA, with a history of involvement in several other industry research projects, including the European Commission’s Clean Sky 2 project. Looking into the future, collaboration between all the parties involved in commercial aviation is the way forward as it’s part of an ecosystem and greater savings can be made.

Some airlines are beginning to look at a connected cockpit, either by satcom or from a tablet via Wi-Fi to ACARS. SITA OptiClimb and SITA OptiDirect are fully integrated in the eWAS Pilot mobile weather application which provides accurate 4D weather forecasts and real-time updates from various sources to warn about weather hazards such as thunderstorms, lightning, clear air turbulence, strong winds, icing and even volcanic ash.

Updated weather is perhaps the most important part of cockpit connectivity, particularly for meteorological events that are short lived. SITA OptiFlight then benefits from that connectivity to provide updated fuel saving recommendations.


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