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Interview with

Michael Shamiyeh

Systems and Aircraft Technologies

NOISE EMISSIONS COULD PLAY AN IMPORTANT ROLE AS A DESIGN DRIVER IN THE DESIGN PROCESS OF EVTOLS.
Michael Shamiyeh

Michael Shamiyeh has been employed at Bauhaus Luftfahrt since September 2015. The 31-year-old aerospace engineer is a member of the research focus area “Systems and Aircraft Technologies” as well as an expert in the field of aircraft design and power train integration.

What is your current research focus, Mr. Shamiyeh?

I am exploring the design space and characteristics of eVTOLs, i.e. electrically or hybrid-electrically powered vertical take-off aircraft, usually designed for one to five passengers. The electrical distribution of energy opens up numerous new possibilities for engine integration and thus a large number of fundamentally different aircraft types. In addition to simple multicopters, tilt-wing or tilt-rotor aircraft or so-called lift+cruise configurations with two separate drive trains for take-off and cruise flight are conceivable. Most concepts for the implementation of vertical take-off capability have already been implemented and tested as prototypes in the past. However, due to the complex mechanical construction or the considerable weight disadvantage, they were not able to prevail. The low power-to-weight ratio, high efficiency, and good scalability of the electrical components have changed the situation fundamentally at this point, so that the concepts must be re-evaluated. In addition, the distributed electric power trains are expected to greatly reduce maintenance efforts and noise emissions during flight. This potentially expands the application spectrum of the classic vertical take-off aircraft, the helicopters. To identify the right fields of application for the various aircraft types, not only fundamental performance characteristics and energy efficiencies have to be assessed, but also operating and maintenance costs or noise emissions are to be quantified. The latter could also play an important role as a design driver in the design process.

What is the relevance of your work for the future of aviation?

The attractive characteristics of eVTOLs open up potentially new markets for aviation with new boundary conditions, most of which have yet to be defined. Probably the most popular example here is the currently much-discussed topic of urban air mobility. Numerous companies and start-ups around the world are currently working on the vision of connecting the surrounding countryside quickly and reliably through the air on a grand scale. It remains to be seen whether, when, and how such a transport system can become a meaningful and sustainable reality. Many fundamental aspects like an appropriate station network, suitable ground infrastructure, realistic business scenarios, or operator models currently require more detailed considerations and analyses. In order to enable the right decisions at these points, it is important to know what is technically feasible and ultimately certifiable.

Which methods and tools are you using?

A combination of preliminary design methods for helicopters and conventional fixed-wing aircraft is used for the design and performance analysis. This includes a blade element method for rotors and propellers as well as an extended lifting line method for wings, fins, and stabilisers. In addition, there are numerous empirical methods and heuristics derived from existing data for mass estimation. A larger module is responsible for the design of the hybrid-electric drive trains. In order to estimate noise emissions of the rotors, a comprehensive aeroacoustics package has also been implemented. The majority of the methods were developed internally in Java and can thus be flexibly extended to reflect new design aspects.

What are the results of your work?

When designing an air taxi, the trade-off between high energy efficiency during hover and efficient cruise flight is crucial. Due to the relatively short mission ranges, the hovering phases and a possibly steep climb-out of the city have large impact on the overall mission performance. Depending on the underlying design mission, the decision may be made in favour of one or the other configuration type. This suggests a fleet mix of multicopters and fixed-wing concepts in the longer term.

The performance data currently published for the various all-electric powered air taxis are clearly too optimistic. Considering the necessary reserves, realistic flight profiles, and reasonable operating assumptions, immense progress is still needed in the area of energy storage and battery technologies to meet these requirements. Until then, hybrid-electric propulsion systems could be an option for longer missions.

In what way does Bauhaus Luftfahrt provide the best environment for your research?

As indicated above, the questions regarding urban air mobility are complex and manifold; an analysis from different perspectives is necessary to develop consistent scenarios to draw the right conclusions. Although eVTOL configurations can be designed and evaluated independently, their performance within a representative overall transport system is much more meaningful. The interdisciplinary way of working and the wide range of disciplines at Bauhaus Luftfahrt enable such a holistic assessment. In our studies, discussions, and daily work, we really benefit from the versatility of our team. In addition, the close exchange with our partners in industry provides valuable insights that we can directly include in our work.