The Airbus fello’fly demonstration project is bringing the wake energy retrieval (WER) concept to the test, as a method of reducing CO2 emissions — between 3 and 4 million tons a year — on wide-body operations. Yet operating two big passenger aircraft close together creates different operational problems for the aviation industry, and even creates a need for the discovery of new innovative procedures. Therefore, Airbus has signed deals with two airline customers and three air navigation service providers (ANSPs) to resolve these problems.
Since time immemorial, migrating geese have benefited from the flight strategy of wake-energy retrieval — or surfing a leading bird ‘s air upwash. And the results are obvious: free lifting means remaining aloft for longer periods with lesser energy costs — rational factors that prompted Airbus engineers to take a closer look at applying the similar strategy to aircraft to help airlines reduce fuel consumption.
This project at Airbus is named fello’fly. But though initial flight testing yielded the possibility of fuel savings of 5-10 per cent per journey, many wondered: how can two aircraft fly close together to conduct a fello’fly procedure safely?
The biggest problem for airlines is recognising the two aircraft that are best suited to this collaborative task on provided day, as well as adjustments to the role of the pilot in the implementation of a new method of flight. The main focus for ANSPs is to help controllers securely integrate two aircraft into a joint system when implementing new criteria for air traffic control (ATC). Airbus will collaborate with Frenchbee and SAS Scandinavian Airlines, as well as France’s DSNA (Direction des Services de la Navigation Aérienne), UK’s NATS and EUROCONTROL to illustrate the project’s technical viability and define procedures for transatlantic operations.
Ensuring safe flights.
Aircraft fly in controlled airspace along established paths, based on flight plans authorised by ANSPs in advance. This air traffic control scheme functions successfully to stop accidents and to coordinate passage of air traffic.
In oceanic airspace, according to existing rules, two aircraft usually need to be 30 to 50 nautical miles (55 to 90 kilometres) apart. However, this range would need to be lowered to 1.5 nautical miles (3 kilometres) during fello’fly activities, in order to gain the full benefits of wake-energy retrieval. Although this sounds difficult, a pair of fello’fly aircraft would stay lengthwise ten times farther apart than the 1,000-feet vertical distances that have been safe in use for more than two decades.
“In the aviation industry, achieving our emission-reduction targets will require implementing innovative new ways to use aircraft in the skies. Our collaboration with our airline partners and ANSPs on fello’fly shows that we’re making good efforts towards these goals,” said Nick Macdonald, fello’fly Demonstrator Leader.
In today’s operations, aircraft are guided by ATC via a fixed ocean clearance point to reach transatlantic routes at a specified time and altitude. Then, pilots use a flight management feature to guide the aircraft to arrive at the stated time and altitude at the assigned location. In the case of two fello’fly aircraft, ATC would allow them to land at the same clearance point but separated by 1000 feet on two different flight levels. Under the rules and regulations of today’s airspace this is the only aircraft that can fly together.
According to Nick Macdonald, the fello’fly Demonstrator Leader, the collaboration’s aim is to place safe and realistic procedures that allow aircraft produced wakes to minimise emissions.
“In the aviation industry, achieving our emission-reduction targets will require implementing innovative new ways to use aircraft in the skies,” Nick Macdonald explains. “Our collaboration with our airline partners and ANSPs on fello’fly shows that we’re making good progress towards these goals.”
Initial flight testing has already started. The fello’fly team and their flight research colleagues are evaluating pilot assistance technology — designed to ensure that safety conditions are optimum when two aircraft are flying close together — in a project that will lead to flight tests in an oceanic airspace in 2021, including airlines and ANSPs and a controlled Entry-Into-Service by 2025.
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