By Andrea Hargraves 
Airbus reports that following the success of its recent “fello'fly” A350 assisted flight demonstration, the European Union (EU) GEESE project within SESAR (Single European Sky ATM Research) and Airbus is now achieving, Led by Airbus, significant progress has been made towards this concept.
By further developing science, technology and processes, in collaboration with its industry partners, it may one day be possible to see passenger aircraft benefiting from the vigilance of others, reducing fuel consumption and associated emissions.
Between 2019 and 2021, as part of its “fello’fly” demonstration project, Airbus developed and flight-tested a concept known as “Wake Energy Retrieval – WER”. This technique involves flying two aircraft in formation, allowing following aircraft to benefit from the lift generated by the vortices of the aircraft in front of them, reducing the power required from their engines. The concept imitates the flight of migratory birds, such as geese.
The campaign culminated, on November 9, 2021, with the first long-distance demonstration of WER flights in transatlantic airspace. It involved two A350 aircraft spaced approximately 1.2 nautical miles (2.2 km) apart, flying from Toulouse, France, to Montreal, Canada. Subsequent analyzes indicate that airlines can save 5 to 10 percent on fuel per flight.
The positive results caught the attention of the industry in general, both in Europe and on the other side of the Atlantic. This has led to the partners of the SESAR-3 Joint Project (SESAR JU) joining forces to further explore WER under a new dedicated industrial research project called GEESE. Although this is an abbreviation for “gaining environmental efficiency through energy savings” (Achieving environmental efficiency by saving energy) is also the English word GOOSE, referring to the fact that flocks of geese use a similar technique when they migrate in formation, flying long distances while taking advantage of each other's wake energy.
International cooperation among stakeholders
Led by Airbus, GEESE is a €10 million project funded by the European Union's Horizon Europe initiative and industry. This brought together a diverse group of stakeholders including Eurocontrol, DSNA, Air France, ON, Indra, ENAC, DLR, AirNav, Bulatsa, CIRA, UAB, Frequentis, Boeing, French Bee, NATS, Virgin Atlantic and Delta Air Lines.
GEESE aims to determine how to enable and expand WER's operations for transatlantic and transcontinental flights across Europe. The project identifies the operational tasks required for pilots to adopt technologies to automatically manage multiple WER locations, including flight management systems and new cockpit functions that capture and track wake vortex.
The campaign is also exploring a “matching assistance” system for dispatchers at flight operations control centers. It is worth noting that the airline partners will work together to update their flight plans to find a suitable aircraft to pair with, taking into account the routes to the meeting point and other considerations.
To this end, the project will carry out a series of simulations to validate the pairing procedures, with the participation of the airlines Air France, French Bee, Delta and Virgin Atlantic. You'll also delve into the science of mats to develop key concepts and consider the effect of formations. This includes determining the impact of the second aircraft in a pair, identifying safe locations behind the pair, and how to ensure the safety of surrounding traffic.
Three operational work packages are under development at GEESE
“Enabling WER Operations from Europe to the North Atlantic”: This package will develop and improve the initial operating concept (CONOPS), assess safety, analyze impacts on existing systems, and develop simulations and tests to evaluate assumptions.
“Expanding the WER concept to continental Europe”: will provide operational solutions to expand WER operations within European domestic airspace.
“Transportation Science Work Package”: will look at other potential benefits unrelated to reducing CO2 emissions from formation flying.
Current situation and next steps
Following project selection by SESAR and preparation of grant funding, which took place at the end of the second quarter of 2023, GEESE received the green light for the three-year implementation phase.
Laura Monteroni, vehicle systems engineer at Airbus Engineering, said:
“Today, one year after the start of the project, we are mainly working on defining the operational processes needed to set up WER operations.
These processes will control how the two aircraft adapt their paths. We will develop these processes with the airlines and controllers, so they can make changes to the flight plan and any adjustments that allow the aircraft to meet each other.
We have made good progress in reaching agreement with stakeholders on operations, paving the way for planning and detailing all the verification activities we will carry out over the next year.
This year we also started security assessments. Therefore, we are currently still in the documentation phase, with the flights themselves scheduled to begin around the second half of 2025.
During the flight tests to be operated by Air France, FrenchB, Delta and Virgin, the paired aircraft will be positioned at different altitudes in accordance with the current minimum vertical separation requirements for ATM.
This limitation is not a problem for GEESE tests, as their goal is not to recreate the physics of WER flight (which has already been demonstrated in flyo'fly), but rather to validate the processes necessary for the aircraft to meet and combine as a pair, from a navigation point of view.
Flexibility to upload flight plan as an advantage
Although this is not a prerequisite in itself, it would be useful if the aircraft allowed the pilot to upload the flight plan directly into the aircraft's flight management system (FMS). This capability, already available on the A350, prevents the pilot from making changes to the flight plan by manually entering all the information using the aircraft's MCDU keypad.
Once uploaded into the FAA system, the new flight plan can be selected as a “Secondary Flight Plan” option, while the original flight plan remains in the FAA system as the primary flight plan.
Operational scenarios
For actual airline operations, it is expected that the new flight plan will be issued and sent by the Flight Operations Center (AOC) to the pilot after consultation and coordination between the AOC and the Air Traffic Controllers (ATC) – who will be affected. Any change in flight plan.
Furthermore, this will be done as part of a Collaborative Decision Management (CDM) workflow, where the relevant air traffic controllers confirm whether or not they can accept the changes – taking into account, for example, aircraft sector load or airspace restrictions. Only after the new flight plan is approved will the pilot be allowed to activate the secondary flight plan in the flight management system.
Furthermore, the fuel load will remain exactly the same as the original flight plan. “The fuel loaded will not be affected as it will be based on a “No WER” scenario.“Laura says. “In fact, what we are suggesting is that the airlines involved will not know whether they will actually form a pair. They will simply state your intention for your trip to be part of WER.“
Aircraft requirements
While WER testing is essentially “independent of aircraft type,” Laura advises some general “aircraft-wide” requirements: “For example, a function capable of automatically locating the “follower” aircraft behind the “leader” aircraft and tracking its vortex. However, what we will not do is dictate how an aircraft capability or functionality should be implemented in a specific aircraft design and how aircraft technology will achieve this.“
Laura ends by saying:
“For Airbus, this is done separately by our fellow engineers at Felo'fly. For other aircraft manufacturers, it will be up to them to decide how they want to implement the technical features.
However, at GEESE we are discussing whether we can expand the testing to include the A330 and some Boeing aircraft.
We do not have significant operational constraints on the aircraft itself, the WER process is primarily a change in flight plan, so we are in discussions with airlines to evaluate the concept with a wide range of aircraft types.
Airbus information