Aircraft Technology Roadmap to 2050
Executive Summary
Goals and timeline In 2009, all stakeholders of the aviation industry committed to a set of ambitious climate action goals, namely:
• improving fuel efficiency by 1.5% per annum between 2009 and 2020;
• reaching net carbon-neutral growth from 2020;
• reducing global net aviation carbon emissions by 50% by the year 2050 relative to 2005.
Meeting these goals is one of the major challenges for today’s aviation sector. The industry is well on track for the short-term fuel efficiency goal, and ICAO has put in place the CORSIA system (Carbon Offset and Reduction Scheme for International Aviation) to achieve the mid-term carbon-neutral growth goal. The long-term 50% carbon reduction goal requires the combined efforts of all aviation stakeholders (aircraft and engine manufacturers, airlines, airports, air navigation service providers, and governments).
Since the aviation industry committed to this set of goals in 2009, an impressive number of technological solutions contributing to the 2050 goal have been proposed and many related projects have been initiated. These consist of numerous aircraft (airframe and engine) technologies as well as sustainable aviation fuels, operational and infrastructural measures.
This roadmap focuses on the technologies and the design of future aircraft. In the short-to-mid-term, i.e. until about 2035, new commercial aircraft will still be “evolutionary” developments with a traditional tube-and-wing configuration and turbofan engines powered by conventional jet fuel (or a sustainable drop-in equivalent). From 2035 onwards, one can expect “revolutionary” new aircraft configurations and propulsion systems to be ready for entry into service, provided the economic framework conditions are favorable to their implementation. These radically new aircraft designs include, among others, blended wing bodies, strut-braced wings, and hybrid and battery-electric aircraft.
Current and planned new aircraft models
Numerous new aircraft models in most seat categories have recently entered commercial service or are imminent in the next few years. Under favorable conditions, their fuel burn per available seat-km is typically 15 to 25% less than that of the aircraft models they replace. When considering everyday operational conditions, improvements are usually a few percent lower. Typically, a new aircraft generation replaces older models in the same seat category every 15 to 20 years or so. With the introduction of many new models in the current period (2014 – 2020), this might result in an innovation gap in the second half of the 2020s, before demand for a follow-on of the current new aircraft generation will arise. This could lead to a noticeable slowdown in the average fuel efficiency improvement.
Evolutionary aircraft technologies
Continuous progress is being achieved in all areas of evolutionary technologies, namely aerodynamics, materials and structures, propulsion, and aircraft equipment systems. Some examples of technologies that have recently made noticeable progress are natural and hybrid laminar flow control, new high-bypass engine architectures as well as aircraft systems such as electric landing gear drives and fuel cells for onboard power generation. By applying combinations of evolutionary technologies, fuel efficiency improvements of roughly 25 to 30% compared to today’s aircraft still appear possible. However, further improvements of the tube-and-wing configuration powered by turbofans are becoming more and more difficult to conceive around 2035.
Revolutionary aircraft technologies
In the longer term towards 2050, radically new aircraft configurations will be required to reduce fuel burn and carbon intensity significantly. The novel airframe configurations that are currently seen as most promising are the strut-braced wing, the blended wing body, the double-bubble fuselage, and the box-wing aircraft. While for a long time blended wing bodies were thought to be a solution optimized for very large aircraft of several hundred seats, it has recently become realistic to design small blended wing bodies of 100 to 200 seats. On the one hand, they do not have the same drawbacks as their large counterparts in terms of airport compatibility and passenger acceptance. On the other hand, they allow improved boarding time and passenger comfort.
The most promising propulsion technologies are open rotors, boundary layer ingestion, and electric aircraft propulsion. Due to their large weight per unit of stored energy, batteries as primary energy storage for aircraft propulsion place limitations on the size and range of fully battery-powered aircraft. Various categories of hybrid-electric aircraft propulsion exist as well, which use liquid fuel as a primary energy source. They benefit from the high energy efficiency of electric motors and use batteries as an additional energy source for peak loads. Today, several electrically-powered general aviation aircraft types are already in operation. Specialized start-up companies work on 15 to 20-seaters for the next decade and 50 to 100- seater regional aircraft, announced for entry into service around 2035. Even though this time scale seems optimistic, it shows the stepwise scalability of electric aircraft technology, which helps reduce its development risk. While today about 65% of electricity generation comes from fossil sources and produces significant amounts of CO2, it is likely that the share of renewable electricity will increase noticeably in the next decades, thanks to governments’ and industries’ current focus on climate action throughout all sectors.
Operational aspects
Most radically new aircraft configurations yield additional benefits beyond fuel efficiency, such as lower maintenance costs for electric motors compared to combustion engines, or better aircraft utilization over a day thanks to the shorter airport turnaround time for small blended wing bodies. However, new challenges arise for the implementation and operation of these aircraft. Such challenges could be the required adaptation of the airport infrastructure for large blended wing bodies, the need for a high-power electricity supply for recharging electric aircraft, and issues with higher noise levels and lower flight speeds for open rotors.
Economic aspects
The additional operational benefits and potential challenges have to be considered together with fuel savings when establishing a business case for radically new aircraft. If the direct operating costs (DOC) for a new aircraft type are significantly lower than for comparable models, a higher purchase price can be justified. However, a very high aircraft price, even if linked to high DOC savings, may present a prohibitive risk for airlines as customers. Manufacturers need to consider these aspects when setting their prices and determining the number of aircraft to be sold to reach the break-even point.
The development of a radically new aircraft type represents a very high investment for aircraft manufacturers, which may be considered too risky as long as incremental developments building upon existing aircraft concepts could offer a similar degree of improvement. On the other hand, radically new aircraft is a good opportunity for newcomers in the aerospace market with specialized skills.
Estimated carbon reductions
The impact of new technologies on future CO2 emissions of the global aviation fleet is modeled for different scenarios describing various degrees of air traffic growth and technology implementation. Three air traffic growth scenarios, which were developed in the IATA 20-year passenger forecast, were combined with five technology implementation scenarios. Compared to the reference case with no new aircraft models introduced after the imminent ones, the most optimistic scenario with the introduction of electric aircraft over 150 seats before 2050 achieves a reduction of typically 25% of CO2 emissions. After a peak in the current years with annual fuel efficiency improvements well above 1.5% until shortly after 2020, a slowdown of improvement below 1.0% p.a. in the late 2020s is observed (which does not consider entry into service of a fully new 210–300-seater in the mid-2020s, as its development has not yet been announced officially). After 2035, the improvement rate strongly depends on the scenario chosen and reaches values in the order of 3% p.a. for the most optimistic electrification scenario.
Disruptive technologies
Finally, a short outlook is given on two disruptive transport types that might partially replace subsonic commercial flight in the near future: For short-haul traffic, Hyperloop is a ground-based passenger and cargo transport system currently in the test phase, reaching similar travel speeds as commercial aircraft. For long-haul connections, new supersonic aircraft, which are currently under development, is expected to see a revival in the 2020s, first for business and later for commercial travel. However, the environmental challenges related to supersonic aircraft are higher than for subsonic aircraft
Recommendations
Recommendations for a seamless implementation of radically new aircraft are given. In particular, close cooperation between all aviation stakeholders, including newcomers specialized in single categories of novel aircraft, is required with sufficient lead time to prepare adaptations of airport and airspace infrastructure and to develop necessary standards and regulations. Airlines should proactively show their interest in new fuel-efficient aircraft contributing to the Industry’s climate action goals, to give manufacturers more certainty about the expected demand, which is needed to launch a new aircraft program.
by IATA
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