Improve fleet management and flight logistics

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.

Optimise descent paths, scheduling and taxiing aircraft

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. Use of flight management systems to optimise descent paths can save between 121 and 246 litres of jet fuel per descent compared to a traditional approach.

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 430,000 litres of fuel annually.

Fly with or avoid jet streams

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.

There is potential to improve fuel efficiency for international flights by raising the quality of forecasting of jet streams, notably over oceanic and sparsely populated areas.

Logistics

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.

Retrofit aircraft to achieve weight reductions

Numerous opportunities exist to reduce weight and improve the fuel efficiency of aircraft. They include ensuring the optimal amount of fuel carried is sufficient for each flight, so as to minimise weight and drag, to exploring options to retrofit and redesign aircraft using lighter engines and composite-fibre components.

Some examples of opportunities in this area are outlined below.

Improve aerodynamics

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.

Changes to reduce drag can offer significant fuel efficiency savings.

Improve electrical energy efficiency

Although it may not show up as a major component of total costs, electrical efficiency in aircraft makes a difference. 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 gas-powered auxiliary power units are available on the market, but they do have substantial up-front costs and the energy efficiency dividend is not great. 

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 is also more efficient to source electricity from the airport itself than from the plane’s own power unit. 

Invest in new engines and aircraft

Investing in new, 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.

Some examples of opportunities in this area are outlined below.

Retrofit engines

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).