The journey to electric flight

Opinion: The journey to electric flight​

Author: Dr Francisco Montomoli, Department of Aeronautics, Imperial College London​

Date: December 2018​

Aviation is changing, with a global vision for that is cleaner and quieter. Currently, aviation accounts for 2 per cent of carbon emissions globally, while noise around airports is negatively affecting neighbouring communities. In the absence of concerted action, these challenges emissions and noise problems will significantly increase given that passenger traffic is predicted to grow by 4.7% per annum over the next 15 years.​

The Green Aviation Initiative at Imperial College London, led by the Dept of Aeronautics, is addressing these challenges. It is helping to enable a transformation to sustainability in partnership with aircraft engine manufacturers, aircraft manufacturers as well as airport and airspace operations.​

The Advisory Council for Aviation Research and Innovation in Europe (ACARE) was set up to deliver the EU’s ‘European Aeronautics: A vision for 2020’. This set the sector aims to improve fuel efficiency by an average of 1.5% per year until 2020, reduce net CO2 emission by 50% by 2050 (against a 2005 baseline), reduce nitrogen oxides by 80% and reduced perceived noise by 50%.​

In the last 50 years aircraft fuel consumption has reduced by 70% per passenger kilometre through technological advances in both engine and airframe. As a reference point, a 1% structural weight saving can lead to between a 0.5% to 1.5% reduction in fuel consumption and this has been a core area of progress.

In the next few years, a further reduction of 10% in fuel consumption is possible through airframe aerodynamic improvements such as natural or hybrid flow control, advanced riblet techniques and low-drag technology. A reduction of about 20% may be achieved with new engine configurations such as open rotor and ultrafan technology. ​

However, from 2020, new innovative solutions like blended-wing-body configuration will be increasingly needed. They could deliver an estimated further 20% fuel efficiency. Improved operational practices coupled with optimised aircraft deployment across the network has the potential to cut fuel consumption by 5% and as much as a further 12% reduction possible through airspace modernisation.​

Among the technological advances required to achieve a transformational level of carbon reduction are novel propulsion methods such as hybrid or full electrical propulsion. Full electrical propulsion of a passenger plane is not considered to be possible with current battery technology owing to their weight. However, there are many hybrid projects in progress, such as the Airbus Vahana and progress in battery development suggests that a full electric plane may be possible.

Norway has already set a goal to have the first electric passenger flight in 2025, and a similar efforts has been announced in UK with Heathrow announcing free landing charges for a year for the first electric-hybrid service.

​What will we expect to see?​

Configuration and overall aircraft design​

Alternative configurations are necessary there is only so far continuous improvement can be achieved with conventional configurations​

Aircraft engines​

• novel engine architectures (ultra fan)​
  
• electric/hybrid engines (E-Fan)​
• high density batteries​

Aerodynamics and flight performance

• step changes in flow control and drag-reduction​
  
• use of both active and passive systems​

Structures​

• composites (self-repairing, signal carrying, electrical conductance, bio-composites)​
• bio-inspired additive manufactured​

Air traffic management​

• 4D flight planning and execution​
• optimisation of aircraft mission in time and space

For Heathrow, this poses new and exciting questions such as understanding the necessary airport layout to enable electric aircraft and how to capitalise on the opportunity to reduce impact on the local communities through noise and reduced emissions.​

New aircraft will be not only inherently greener and quieter but will look completely different from what we have seen before. We are expecting to see blended wings, with distributed hybrid/electrical propulsion. New solutions and concepts for flights beyond 2050 are already under development. We are seeing extraordinary structures mimicking bones within the airframe, with transparent ceilings that will enable passengers to see into the inner workings of the aircraft. ​

We are rapidly moving towards an era in aviation when passengers will be able to have a radically more sustainable journey allied to a futuristic flying experience. ​