Air traffic management is already highly efficient in Australia by global standards. However, fuel efficiency opportunities may still exist through reviewing and optimising fleet management, flight logistics and the utilisation of jet streams.
Gathering and analysing data stored on the automated flight log can open up new ways for airlines to better manage and operate their fleets to save fuel and costs.
Traditionally, jet airliners have approached a runway by ‘stepping down’ rather than making a smooth steady descent. This has meant that at each step, the pilots have needed to adjust the thrust of the engines. New technology means that airlines can work with air traffic control and airports to create a much smoother descent to the runway, thereby improving fuel efficiency.
Airlines can also work with air traffic service providers to reduce the burning of fuel while in holding patterns. Adjusting the timing of flights also enables aircraft to achieve better fuel efficiency through reducing the length of holding periods.
Fuel can also be saved by using just one engine to taxi the aircraft when landed at the airport. Studies suggest that one minute of single-engine taxiing per aircraft flight saves 430,000L of fuel annually. Electrical taxi systems can save even more fuel by using the aircraft’s auxiliary electrical power so that the main engines can remain off until immediately before take-off.
The location of jet streams is vital in aviation. In addition to cutting time off the flight, it also nets fuel savings. In Australia, flights from west to east can take advantage of tailwind jet streams, whilst flights east to west need to avoid the jet stream as much as possible.
Companies are finding it is possible to improve fuel efficiency for international flights by raising the quality of forecasting of jet streams, notably over oceanic and sparsely populated areas. New technology is also available to help pilots avoid clear air turbulence, helping to improve fuel efficiency and passenger safety.
Improvements in air transportation logistics, chiefly from information technology, are expected to save 5–10% of system fuel at negative cost.
State of the art aircraft now have the technology to enable flight paths to be optimised in real time in response to changing weather patterns. Re-routing in flight can save significant fuel on international long hauls, where upper-level winds, jet streams and other meteorological parameters can change quickly. Such real-time flight logistics technologies can be used when airspace restrictions are lifted.
Flying at higher altitudes can also reduce drag and increase fuel efficiency.
The way an aircraft is loaded can also significantly impact the fuel efficiency of a flight. If the aircraft’s load is not balanced, then the pilot will need to trim the aircraft continually throughout the flight to compensate. Operating an aircraft in trim mode uses more fuel.
Combining optimal flight logistics with optimal take-off and landing techniques can yield significant fuel efficiency savings.
Numerous opportunities exist to reduce weight and improve the fuel efficiency of aircraft. They include ensuring the fuel carried is not excessive for each flight, fitting carbon brakes as well as redesigning aircraft with lighter engines, fittings and composite-fibre components.
New data analytics techniques are enabling more accurate predictions of fuel requirements, helping to avoid the weight and waste of excess reserve fuel. Lightweight seats can save hundreds of kilograms of weight.
Combining many small weight reduction initiatives can add up to significant savings, and produce additional benefits.
For example, the use of tablet devices instead of bulky paper flight manuals saves around 16kg per aircraft leading to millions of dollars in fuel savings across the fleet. Tablets also have the advantage of being searchable and can be instantly updated, which also eliminates printing costs and paper.
The Civil Aviation Safety Authority has rules around the ‘paperless cockpit’ in Australia.
The two main sources of drag for aircraft are skin-friction drag and lift-induced drag. These constitute approximately one-half and one-third of the total drag, respectively, for a typical long-range flight at cruise conditions.
Significant levels of research and testing show that riblets, large eddy break-up devices, hybrid laminar flow technology, and innovative wing-tip devices offer the greatest potential for reducing drag.
Aircraft aerodynamic performance improvement can also be obtained through trailing-edge optimisation, control of the shock boundary layer interaction and control of boundary layer separation. For example, special aerodynamic coatings can be applied to the nose cone and other key regions of the craft.
Changes to reduce drag can offer significant fuel efficiency savings.
Although it may not show up as a major component of total costs, electrical efficiency in aircraft can add up to substantial savings when applied fleet wide. The electricity used on a plane is generated by an auxiliary power unit. These units tend to use a relatively inefficient gas turbine which is run on expensive jet fuel. More energy efficient types of auxiliary power units are available on the market, but they do have substantial up-front costs.
In-flight energy efficiency measures can be cost effectively applied in areas such as lighting and in-flight TV systems.
When aircraft are docked at airports, it may be preferable to source electricity from the airport itself than from the plane’s own power unit.
Investing in new, lighter more efficient engines is a wise strategy to improve fuel efficiency. There are aircraft engines on the market that are 10–15% more fuel efficient than best technologies available ten years ago. Similarly, upgrading airline fleets to more efficiently designed aircraft can yield significant fuel savings.
Combining these measures can generate significant energy efficiency gains in the short and longer terms.
Technologies required to achieve significant engine-weight reductions include:
- improved materials (composites and high-temperature materials in particular)
- improved aerodynamics (to reduce the number of turbine and compressor stages)
- increased turbine entry temperatures (to reduce airflow and core engine size required for a given power output).
Many years of lab and flight testing have demonstrated that bio-derived jet fuel blends can meet safety, technical and quality standards for the aviation industry.
Biofuels differ from fossil fuels in that they are renewable and don’t need to be drilled for or mined. Biofuels are derived from vegetation, municipal waste and recycled oils, and can have substantially lower life cycle greenhouse gas emissions than standard jet fuel. Jet biofuel has also been found to be slightly more fuel efficient.
In January 2018, Qantas operated the world's first dedicated biofuel flight between the US and Australia. The 15-hour Melbourne to Los Angeles flight used 24,000kg of blended biofuel (50%), abating 18,000kg in CO2 emissions.
Bio-derived jet fuels Bioenergy Australia