UAM and design: No one size fits all

Monday August 10, 2020

"There is, for example, no great advantage in flying from London to Manchester in three quarters of an hour if one has to spend an hour at each end travelling from and to the centres of those cities by airport bus. The answer to this problem will probably be found in the helicopter, but not in its present form. It is as yet too costly and too small. We have to look into the future for some form of air bus which will take us from Waterloo to the Place de la Concorde in an hour or less…" - Major-General D. Wade, (1955). Civil aviation—progress and problems.

An eVTOL is an electric-powered vertical take-off and landing vehicle that is seen to revolutionise human mobility in the third dimension. We see Urban Air Mobility (UAM) vehicles as an outcome of the synergy between aviation and road transportation and believe that UAM has the potential to become the future of highways in the skies.

As the industry is very new and keeps rapidly evolving, a lot of questions remain unanswered, including the full potential of UAM vehicles. Currently, there are over 300 eVTOL designs registered in the Vertical Flight Society's eVTOL Aircraft Directory.

While all vehicles have different design features, is there a distinct solution that is set to be the winner of the race to market? And where will those aircraft be used?

A variety of options

Today we see many different configurations being developed depending on the manufacturer and their targeted mission profile. Out of the vehicles currently being developed, a majority have multi-rotor or tilt-wing configurations.

Other configurations that are seen include fixed-wing, rotorcraft, hover bikes and a small representation of electrical super short take-off and landing (eSSTOL) concepts. The vehicles are built and tested across all continents with many designs set to accommodate only one passenger on board, but some aim to carry up to and over 3 people.

Roland Berger electric aircraft architectures
An overview of some most common electric aircraft architectures. Credit: Roland Berger

According to Andreas Thellmann, Airbus, multicopter designs are great at providing hovering stability and efficiency. They are also the least noisy configuration which makes them favoured by the public.

However, to their disadvantage, they are not well-suited for high speeds. In terms of market implementation, multicopters can be seen as one of the easiest and fastest to achieve vehicle certification. This is largely due to the low technical complexity as well as multiple layers of redundancy offered by back-up systems.

Contrastingly, tilt-rotor/tilt-wing convertible aircraft are good providers of forward speed, but are more complex from a technological point of view and less energy-efficient for hovering.

The basic technology behind this vehicle architecture is already available and is predicted to provide good time savings and moderate operational costs driving commercial success.

The vehicles capable of operating at highest speeds possible are fixed-wing aircraft. The primary disadvantage is that they are considered the loudest and most susceptible to sudden gusts.

Currently, the underlying technology is not considered to be mature enough to conduct passenger transportation in unfavourable weather conditions and requires further development to satisfy safety requirements.

Overall, the design architecture of the eVTOL is largely dependent on what the company envision its aircraft mission to be. Each design has its pros and cons in terms of market implementation, travel speed, potential routes, efficiency and market size and as a result, for example, inner- or inter-city missions will most probably be served by different vehicles.

Roland Berger electric aircraft architectures analysis
Strengths, weaknesses and potential applications of five electric aircraft architectures. Credit: Roland Berger

One of the uniting aspects for all designs is the ability of the vehicle to take-off vertically and be independent of a runway or road. The industry largely positions itself as one requiring the smallest possible space on the ground, aiming to provide a striking contrast to the amount of investment required in the case of ground mobility as well as traditional aviation infrastructure development.

It is also planned that regardless of the design, eVTOLs will provide enhanced performance and a cheaper solution to the existing vertical mobility. When compared to the traditional helicopters, eVTOLs are predicted to be about 4x quieter, 2x safer and 10x less expensive based on the research conducted by Porsche Consulting.

So where will we see these vehicles being used?

Addressing the needs

Several business models are being developed by manufacturers in terms of how they want for the vehicle to operate. The use case for air taxis, for example, would be inner-city point-to-point service. This type of mission is most likely to be served by multicopters and quadcopters.

Airport shuttles, on the other hand, would provide suburban to urban services covering longer distances, mainly served by either of the tilt-wing/convertible, hybrid, or the fixed-wing vectored thrust concepts

Another possible scenario, intercity flights, will be delivering the longest distance interregional services and will need to be served by eVTOLs capable of developing fastest forward speed, like the fixed-wing aircraft.

A variety of different vehicle architectures
A variety of different vehicle architectures, left to right, represented by Volocopter, EHang, Lilium and Uber Air. Credit: Volocopter, EHang, Lilium, Uber

Aside from the above-mentioned flight missions envisioned for UAM operations, we believe there are even more important roles eVTOL aircraft can play in our daily life. To give an example, potential future business models could include rapid response scenarios such as an ambulance, police, firefighting, natural disaster or armed conflict response.

Also, vehicles could be used in real estate and construction for inspections and surveys of assets and building maintenance. Last, but not least, UAM can be used for entertainment purposes supporting sightseeing and film/TV/radio industries.

In our view, for Urban Air Mobility not to become yet another source of noise, visual pollution and a luxurious alternative to already existing modes of transport available only to the wealthy elite, it is vital for vehicle manufacturers, government and industry supporters to communicate clearly about how the adoption of UAM services can have a positive impact on society and serve a more meaningful purpose in addressing global issues in an urban environment.

Blog cover image credit: Vertical Aerospace

References

https://www.evtol.news/aircraft

https://www.rolandberger.com/publications/publication_pdf/Roland_Berger_Urban_Air_Mobility.pdf

https://www.porsche-consulting.com/us-en/press/insights/detail/study-the-future-of-vertical-mobility-1/