Assessment of an aircraft’s environmental performance must be based on more than just exhaust emissions and should also consider how it is built, argues Professor Iain Gray.

I have been in the industry for 40 years and I still do not always know the difference between the overall environmental impact of one type of aircraft design and another. I could make a subjective call but not a quantitative one – at this stage, who could?

The industry knows the only workable business models for the future will be built on low environmental impact. The whole sector has been galvanised, investing billions. But what makes aviation genuinely sustainable; what kind of definition is being used? For the moment it is looking like a very important but narrow version: a matter of reducing carbon dioxide emissions in flight.

Iain Gray of Cranfield University

Source: Cranfield University

Gray says a ‘holistic view’ of manufacturing process in aviation is required

We need to take a far more detailed and holistic view – not just the one rating around the type and level of fuel use. Maybe that means a second rating that demonstrates an understanding – and accountability – for an aircraft’s entire lifecycle.

Fuel burn and emissions are always going to be important, but they should not be the only measure. There are many other factors across the life of an aircraft that could leave a heavy footprint on the environment.

Every choice made from the beginning of the design process matters in terms of long-term efficiency and overall sustainability. Which materials are used for a design has implications: will there be a need for rare earth metals, where are they coming from, and what is the impact of the mining operations involved? It is an issue which is becoming more problematic for the automotive sector as the demand for electric vehicles grows and the pressures build on rare earth metals – notably lithium and cobalt – needed for battery production.

What is the footprint from using composites? Is there potential to reduce wasted materials by using an additive rather than the traditional subtractive manufacturing? A typical airframe panel starts with ten or more times material than finally goes onto the actual aircraft. Cranfield University research around additive manufacturing projects in the aerospace and oil and gas industries has suggested savings of up to 80% in terms of the quantity needed of an energy-intensive material such as titanium; along with 70% lower manufacturing costs.


Then there is the supply chain. Aircraft tend to be built as a jigsaw of elements and materials flown and shipped in from different parts of the world, raising questions over how far this is necessary, and whether there could be smarter, local sourcing and manufacture.

Different aircraft designs necessitate different maintenance requirements through their life, meaning there is potential for looking at ways to minimise the demand for more new materials – as well as thinking about end-of-life and disposal of the aircraft, and how more elements can be re-used or at least recycled.

These are some of the issues that will be addressed in the 2022 National Manufacturing Debate on 29 November, as part of Manufacturing and Materials Week in the UK, gauging the latest thinking across sectors including aerospace, and setting out best practice and next steps.

Compared with many other sectors, aviation is working with a more rigid set of parameters. Introducing changes to designs, materials and manufacturing processes is not easy – and nor should it be. Design cycles are long and expensive and need to continue to be backed up with demonstration and certification phases. The sector’s reputation for safety based on the careful introduction of incremental change is long-established and needs to be protected.

What that means is that senior industry managers need to start building sustainability and environmental impact into their thinking, and at every decision point.

Passengers need to be part of the education process around genuine sustainability. How long is it before the flight-booking process involves looking at an aircraft rating for all-round environmental performance, just like we would when buying a home or electrical appliance?

Professor Iain Gray is Director of Aerospace at Cranfield University.

Manufacturing and Materials Week events will run between 28-30 November 2022 at Cranfield University: