The idea to fly in formation and allow aircraft to effectively ride on the coattails of each other could bring an up to 10% saving on fuel, lowering costs, as well as lowering carbon emissions. It is not new and others have looked at its introduction, but it would represent a fundamental change to air traffic management.
Migrating birds fly in a ‘V’ shape to save energy - a flying technique known as wake-energy retrieval. When a bird flaps its wings, air flows over the wings and swirls upwards behind the wingtips. This flow creates a wake, which is a swirling movement of air containing kinetic energy. When the energetic core of the wake drags surrounding air, it creates smooth currents known as ‘upwash,’ or air that moves upwards. When another bird enters the upwash, it immediately benefits from free lift, which enables it to stay aloft and expend a lot less energy.
The advantages of ‘wake-energy retrieval’ - the technical term for flying in upwash - have been written about for decades. However, given the aviation industry’s commitment to reduce aircraft emissions, Airbus is now taking a fresh look at how this flight technique – under its fello’fly project - could provide aircraft with free lift, enabling them to reduce engine thrust and fuel consumption.
Just like birds, every aircraft creates a wake while flying. Flying together could thus help aircraft to retrieve the lost kinetic energy by positioning a follower aircraft in the air upwash of one of the lead aircraft’s wakes.
This concept has already moved from the air to the ground and is often seen in cycle races where riders will often follow behind one another and enjoy the slipstream of the person out in front.
Several years ago, Airbus first began investigating the benefits of wake-energy retrieval for commercial aircraft. In fact, in 2016, a series of flight tests demonstrated that the highlighted significant fuel savings could be achieved when two aircraft fly approximately three kilometres apart without compromising passenger comfort. However, at this time Airbus said “air traffic management technology was not mature enough to enable aircraft to fly so close together in airspace”.
Alongside the rise of the ‘flight shaming’ movement, what has changed just a few years later? A lot, according to Airbus. Significant technology improvements - including real-time flight tracking - are now being made and “have paved the way” for the development of the fello’fly flight demonstrator project within Airbus UpNext.
The goal of fello’fly is to prove the technical, operational and economic viability of wake-energy retrieval for commercial aircraft. “Safety is our top priority at Airbus,” says Nick Macdonald, demonstrator leader of the project. “We’re working to develop the functions necessary to assist pilots to safely stay in position behind the leader during a long-haul flight.”
The next stage of the project will see Airbus test the technology within the next six months flying two of its A350 prototypes in formation. A trial using two passenger aircraft flying in formation on long-haul routes across the Atlantic could take place with an airline partner as early as 2021 and could become industry standard during the second half of this decade.
If the fuel-reduction technology behind fello’fly proves viable, the aviation industry will benefit from a collaborative activity that demonstrates a clear commitment - between manufacturers, airlines, air navigation service providers, regulators and authorities - to reduce fuel consumption and CO2 emissions.
This would be a tremendous step on the road to sustainability. But, while Airbus is sure of the safety aspects, it will still take a lot to convince passengers. After all, we have all heard gasps from passengers in window seats when they see another aircraft more then the safe separation distance away. That could be the biggest hurdle to adopting flock flying.