It was just one year ago when I last spoke to Eric Ferreira da Silva, head of engineering of urban air mobility (UAM) at Airbus Helicopters.
In the fast-paced world of UAM, a lot has changed since. The CityAirbus demonstrator has completed its flight test campaign, and the data from this program adds to what Airbus learned from the A3 Vahana eVTOL aircraft. The recently revealed CityAirbus NextGen can be seen as a blend of these two vehicles. I decided to check back with Eric to learn more.
Alex Scerri: Eric, when we spoke last year, you were very clear that the CityAirbus you were flight testing was a demonstrator. Can you be as emphatic today that CityAirbus NextGen represents the aircraft that you will be marketing?
Eric Ferreira da Silva: Yes, this will be the aircraft that will go to market.
Alex Scerri: If you look at the CityAirbus demonstrator and the A3 Vahana, how much of each has made its way into CityAirbus NextGen?
Eric Ferreira da Silva: The obvious change in the CityAirbus NextGen from the demonstrator is the wing, which will increase cruise efficiency. This comes from Vahana. From the CityAirbus demonstrator, we have retained the relative simplicity of a multicopter with fixed pitch rotors that control the aircraft by varying the revolutions per minute (RPM).
Unlike the Vahana, there is no wing tilting nor moveable flight control surfaces. This is consistent with our objective to reduce complexity. We have also tilted the aft two rotors at a specific fixed angle to generate most of the forward thrust in cruise, but also produce a lift component such that they can be used for redundancy.
Alex Scerri: How much load does the wing carry during cruise flight?
Eric Ferreira da Silva: At cruise speed, about half the weight of the aircraft is supported by the lift generated by the wing with the other half generated by the rotors. In our design, all six rotors continue working during cruise flight.
Alex Scerri: What other specifications can you share with us for CityAirbus NextGen?
Eric Ferreira da Silva: For now, we can say that the cruise speed will be 120 kilometers per hour (75 miles per hour) with an operational range of 80 km (50 mi). The aircraft can carry three passengers and a pilot.
Alex Scerri: How will you counter any noise issues that may arise because of the variable RPM thrust control system?
Eric Ferreira da Silva: This is something we have studied in detail. The rotors themselves are designed to minimize the emitted sound. One important parameter is the tip speed, but not only. The mix of frequencies and how this is perceived in the human ear is another factor.
We are also involved in other related projects, such as with the French Civil Aviation Authority (DGAC), to understand how sound is perceived in an urban environment. In this case, there are other effects, such as sound reflection off buildings, which will be a different case to a fly-over scenario in open landscape.
Alex Scerri: As for the quoted noise level of less than 65 dB(A) during fly-over, at what height above ground are you assuming the aircraft will fly in cruise?
Eric Ferreira da Silva: That’s a good question. I will not give you a number, but when you compare it to other noise sources in a city, such as ground vehicles, we can say that the distance to an eVTOL can be assumed to be at an order of magnitude greater than from a ground source. Just as an example, if the sound level from a motorbike is measured at 15 meters (49 feet), we would assume that the eVTOL is at 150 m (492 feet).
Alex Scerri: Since our last conversation, there have been several special condition for VTOL and means of compliance (MoC) documents published by the European Union Aviation Safety Agency. How have these shaped CityAirbus NextGen?
Eric Ferreira da Silva: Yes, we took these MoCs into account to have the CityAirbus NextGen comply with the requirements for an enhanced category VTOL.It works both ways as we are also actively feeding back our development studies into the rulemaking activity to help define the standards.
Alex Scerri: Will the full-size prototypes of the CityAirbus NextGen fly in early or late 2023?
Eric Ferreira da Silva: For now, we’ll just say 2023. That is just two years away, which in engineering terms can be a short or a long time. As work progresses, we will be able to refine our estimate.
Alex Scerri: Are you waiting for any technology bricks to reach maturity to be incorporated in the CityAirbus NextGen, or could you source all components today?
Eric Ferreira da Silva: I would say the main subject that still needs some work is battery technology. We are planning to use some cells that are still at prototype phase, but they should be available for commercial aerospace applications by the time the aircraft arrives to market. As the aircraft will initially have a pilot, we will not be held back by the various systems that will be needed for fully autonomous flight. Nonetheless, we are actively working in that area as well.
Alex Scerri: When do you expect to certify the CityAirbus NextGen?
Eric Ferreira da Silva: We expect to enter the certification phase in 2025.
Alex Scerri: Will you offer the CityAirbus NextGen to private clients, or will sales be limited to commercial urban air taxi operators?
Eric Ferreira da Silva: We expect that most customers will be private or public companies providing airport to city shuttles, sightseeing flights, etc. There is also a demand for airborne emergency and security services. Although nothing would exclude a customer from buying these aircraft for private use, we don’t expect that to be our main market.
Alex Scerri: When do you expect to put the CityAirbus NextGen in the Airbus catalogue and start taking orders?
Eric Ferreira da Silva: We are in discussions with many interested parties, but we will not divulge any more details at the present time.
Alex Scerri: Do you have any estimate on the catalogue price?
Eric Ferreira da Silva: For now, we cannot share the catalogue price. However, one important target that we want to achieve is that UAM services are accessible as widely as possible. This is driven not only by the acquisition cost but also the operational costs which need to be affordable. This is a pivotal factor behind our design choices. Going back to one of your questions, batteries will be an important part of this operating cost, which we are working to keep as low as possible.
Alex Scerri: Do you expect to market the aircraft as CityAirbus NextGen, or can we expect a change in name like how the A3XX became the A380?
Eric Ferreira da Silva: What I can tell you is that we are keeping the CityAirbus name as it has become a well-known brand. We used the NextGen tag to differentiate it from the demonstrator.
Alex Scerri: Can we expect to see the CityAirbus demonstrator flying at Pontoise in France?
Eric Ferreira da Silva: The demonstrator had its last flight in July this year, so the answer is no. We will participate in a holistic way in the Pontoise sandbox. This testing will cover all facets of UAM operations, not only test flights. Depending on how the timelines develop, we will be there with CityAirbus NextGen.
Alex Scerri: Besides Pontoise and Manching in Germany, are you planning any other test flight locations, for example, to test in different environmental conditions like what was done for other Airbus programs?
Eric Ferreira da Silva: We have the same approach to the CityAirbus NextGen as for all our aircraft. When you see the flight envelopes we want to test and demonstrate, we do not need to go to the extremes that would be required for our other airplanes and helicopters. This is reflecting the environment where the CityAirbus NextGen will operate. The environmental range we find in Europe will be enough to cover the complete test program.
Alex Scerri: Is there anything else you would like to share with us?
Eric Ferreira da Silva: I would like to reiterate Airbus’ commitment to UAM. There are big teams and resources sustaining the project, and all people involved were proud to see this new aircraft presented to the public. This gives everyone more energy and motivation to continue working to see the program proceed successfully. We are confident of seeing the UAM ecosystem gaining public acceptance and becoming a reality.
We have also signed a trilateral agreement with Thales and Diehl Aerospace for the joint development of the flight control computers for CityAirbus NextGen. To give you an example, the computing power that used to be housed in a flight computer the size of shoebox has now been shrunk to the scale of a smartphone, with the same or better level of reliability. These and other technological steps that we are developing will bring gains beyond UAM.