Since 2000, passenger and freight air travel has more than doubled. The International Energy Agency (IEA) has found the global aviation industry is not on track to meet the targets set in the IEA’s 2030 Sustainable Development Scenario.
Improving fuel efficiency on the ground and in the air is the easiest way to save energy and reduce greenhouse gas emissions.
There are several ways to make aircraft lighter and improve their fuel efficiency, such as:
- ensuring the right amount of extra fuel is carried for each flight
- fitting carbon brakes
- redesigning for lighter engines, fittings and composite-fibre component.
New data analytics techniques make more accurate predictions of fuel requirements, helping to avoid the weight and waste of excess reserve fuel.
Combining multiple small weight reductions can add up to significant savings. There might also be other benefits. For example, using electronic flight bags (EFBs) on a tablet instead of paper flight manuals saves around 16kg per aircraft. Tablets are also searchable and can be instantly updated, which eliminates paper and printing costs. The Civil Aviation Safety Authority has rules around using EFBs in Australia.
Lightweight seating can also save hundreds of kilograms of weight meaning significant potential fuel savings.
The way an aircraft is loaded can significantly affect the fuel efficiency of a flight. If the load is not balanced, the pilot will need to trim the aircraft continually throughout the flight to compensate. Operating an aircraft in trim mode uses more fuel.
The two main sources of drag for aircraft are skin-friction drag and lift-induced drag. For a typical long-range flight at cruise conditions, these make up approximately 50% and 33% of the total drag, respectively.
Reducing aircraft drag can result in significant fuel savings. The following are shown to have the largest effects:
- Large eddy break-up devices.
- Hybrid laminar flow technology.
- Innovative wing-tip devices.
- Trailing-edge optimisation.
- Control of the shock boundary layer interaction and of the boundary layer separation, for example, special aerodynamic coatings can be applied to the nose cone and other key regions of the craft.
Electrical energy efficiency
Although it may not show as a major component of total costs, electrical efficiency in aircraft can bring substantial savings across a fleet.
Electricity used in-flight, such as for data, lighting, audio and TV systems, can be made more energy-efficient and cost-effective.
Aircraft are usually powered by an auxiliary power unit, which tends to use a relatively inefficient gas turbine run on expensive jet fuel. More energy-efficient auxiliary power units are available, but they do have substantial up-front costs.
When aircraft are docked, it can be preferable to source electricity from the airport than from the plane’s own power unit.
Technology allows flight path optimisation in real time in response to changing weather patterns. In-flight re-routing can save a lot of fuel on international long-haul flights, where upper-level winds and jet streams can change quickly.
Flying at higher altitudes can also reduce drag and increase fuel efficiency.
Using jet streams is vital in aviation, as they can save flight time and fuel. In Australia, flights from west to east can take advantage of tailwind jet streams, while flights in the opposite direction need to avoid the jet stream as much as possible.
Airlines can improve fuel efficiency for international flights by forecasting jet streams better. New technology is also available to help pilots avoid clear air turbulence, which improves fuel efficiency and passenger safety.
Descent paths, scheduling and taxiing aircraft
Jet airliners have usually approached a runway by ‘stepping down’ rather than making a smooth, steady descent. So, at each step, the pilots adjust engine thrust, which uses more fuel. New technology means airlines can work with air traffic control for a much smoother descent, thereby improving fuel efficiency.
Airlines can also work with air traffic control to reduce fuel use while in holding patterns. Adjusting the flight times so aircraft have shorter holding periods can also save fuel.
You can also save fuel by using one engine to taxi the aircraft. 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.
New engines and aircraft
Investing in lighter, more efficient engines will improve fuel efficiency. You can purchase aircraft engines that are up to 15% more fuel efficient than what was available 15 years ago. Similarly, upgrading airline fleets to more efficiently designed aircraft can bring significant fuel savings.
Technologies required for significant engine weight reductions include:
- improved materials, especially composites
- improved aerodynamics, to reduce the number of turbine and compressor stages
- increased turbine entry temperatures, to reduce airflow and core engine size needed to produce power.
Combining these measures can result in huge energy efficiency gains in the short and long terms.
Biofuels can have substantially lower emissions than standard jet fuel. Jet biofuel has also been found to be slightly more fuel efficient.
Bio-derived jet fuel blends are proven to meet safety, technical and quality standards for the aviation industry.
Ground operations could take advantage of electric options for equipment such as aircraft tugs and baggage and cargo transportation. Upgrading this equipment will increase efficiency, reduce pollution and reduce the overall cost of company operations.
Electric plane engines
MagniX, an aviation tech company founded on the Gold Coast, aims to transform commercial passenger planes with the development of an electric propulsion system.
Led by a former Boeing executive, MagniX believes they are on the way to replacing the turbo propellor engines found on the small, workhorse planes that service remote areas around the world.
The startup, announced in September 2018, has successfully tested an all-electric version of one of the world’s best-known small utility airplanes, the Cessna 208B Grand Caravan. The plane was powered by MagniX’s 750-horsepower Magni500 propulsion system.
MagniX predicts electric long-haul flights are at least 20 to 30 years away, but the company aims to have an all-electric motor ready to install in a commercial plane by 2022.
To read more about the MagniX electric plane engines, see the ARENA website.
Until fully electric planes become capable of longer flights, hybrid planes are an interim solution. High-energy liquid fuels can be used for take-off, when most of the energy is required, and batteries used for cruising. To read more, see the Advanced Science News website.
Biofuel trial flights
In 2018, Qantas operated the world's first dedicated biofuel flight between the US and Australia. The 15-hour Melbourne to Los Angeles flight used 24,000 litres of blended biofuel (50%) derived from mustard seed oil, abating 18 tonnes of CO2 emissions.
Qantas also announced it will purchase blended biofuel derived mainly from used cooking oil, helping to reduce its carbon emissions by around 10% for its flights from London. This marks the first time an Australian airline will purchase biofuel for regular scheduled services.
Hydrogen fuel has the benefit of reducing the carbon footprint of the aviation industry as well as reducing noise. One of the significant drawbacks of hydrogen fuel is the lack of infrastructure to make it a viable alternative to fossil fuels.
If used directly, hydrogen power requires fewer alterations to aircraft since it would not need a hydrogen fuel cell. A hydrogen fuel cell is more efficient, however it would require significant changes to aircraft fuel storage as well as heavier take-off weight. Either way, adjustments would need to be made to ensure that aircraft could still operate their regular schedules and capacity.
Europe’s first commercial plant for hydrogen-based aviation fuel is in the planning stage. The project is being led by Norsk e-Fuel, a consortium of four companies looking to develop the technology to fit with existing infrastructure. The joint venture plans to be in operation by 2023.
Clean energy and infrastructure: Pathway to airport sustainability (PDF 5.4MB) (Clean Energy Finance Corporation) Australian Government
Industry directory Australian Industry and Skills Committee
Aviation biofuels Qantas
Fuel efficiency Qantas
Technology Roadmap International Air Transport Association
Aviation – tracking clean energy progress International Energy Agency