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  A simplified model for evaluating eVTOL conceptual designs and with example results for three types of eVTOL aircraft configurations

  Yip, S.L.K. ; Hoong, A.K.J. ; Wang, J.

  eVTOL Performance Analysis Tool, known as ePERF is a MATLAB-based analysis developed at NTU specifically for evaluating the performance of different types of eVTOL aircraft and is ideal for eVTOL aircraft conceptual and preliminary design phases. The framework is built to have a modular nature allowing for rapid trade studies of different sizing parameters, and it provides a representative performance evaluation of the eVTOL in all phases of flight. ePERF consists of three main modules: a rotary wing module, a drag estimation module for forward flight and an energy module for range calculation. Momentum theory is used for hover calculations. A component level drag build-up method is used for cruise calculations. The energy model considers the input battery parameters and results from the other two modules to compute the energy requirements of the eVTOL based on a given mission profile. The outputs of ePERF include the power and energy requirements for each flight phase, an estimated attainable range, as well as the velocity for best range. In this paper, the ePERF is explained and then it is used to estimate the performance for three different example eVTOL aircraft: (A) a Lift + Cruise type like Beta Technologies - Alia, (B) a tiltrotor type like Joby Aviation - S4, and (C) a fixed Lift + Tiltrotor type like Vertical Aerospace - VX4. The results show that reducing the structural weight of the eVTOL aircraft is one of the key factors in achieving best performance.
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  Generic eVTOL aircraft preliminary sizing method for AAM/UAM missions

  Kahn, Y.M. ; Balli, M.E. ; Trainelli, L.

  Advanced Air Mobility (AAM) or Urban Air Mobility (UAM) presents many challenges to the aircraft design. The concept not only requires operations over urban airspace but also without the use of traditional airports with long runways. Additionally, the new aircraft designs must do so on electric power as much as possible with low chemical and noise emissions. Hence the term electric vertical takeoff and landing or eVTOL is popularized. This paper presents a novel method for preliminary sizing of eVTOL aircraft of arbitrary architecture. The methodology allows the conceptual analysis and initial trade-off studies independent of the aircraft configuration. Aircraft is considered as the sum of building blocks like rotors, propellers, wings, and several other subsystems contributing to mass, energy, power and drag estimates. Results from this study permit a quick evaluation of configurations and missions with an inevitable degree of approximation. Finally, the main features of the method are discussed in the paper with a relevant validation exercise for various eVTOL aircraft considering mass and other performance metrics.
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  Comparison of optimization based inverse simulation methods for helicopter maneuvers

  Tosun, F. ; Kalkan, U.

  In a helicopter certification process, aviation safety agencies want to be sure that the helicopter can safely fly all maneuvers defined in its usage spectrum. Therefore, loads engineers carry out all these maneuvers for each appropriate combination of weight and center of gravity. Moreover, this maneuvering and load analysis process should be performed in the most efficient way. For this reason, this article works on two different algorithms, the gradient-based Symmetric Rank-One (SR1) and commercial optimization tool Siemens HEEDS, to perform desired helicopter maneuvers. In this study, helicopter pushover maneuver is carried out and the results for each algorithm are compared as an example. However, different maneuver results are also added to show applicability of the solution algorithms. Furthermore, rotorcraft simulation and modelling software FLIGHTLAB is used to simulate the maneuver. Rotorcraft is modeled as rigid and uniform inflow is used for the calculation of rotor aerodynamic loads.
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  Manufacturing of a variable chord extension concept for helicopter rotor blades with a flexible EPDM skin

  Kalow, S. ; Riemenschneider, J. ; Balzarek, C. ; Mendrock, T.

  In the SABRE project a new morphing concept, the so-called linear variable chord extension, has been devel-oped. Here, the blade chord length in the root area is changed with the help of an elastic skin to adapt it to the respective flight condition. This paper focuses on the manufacturing process of the technology demonstrator and give a detailed overview about the advantages and disadvantages of handling with EPDM material. This also addresses the challenge of reinforcing the EPDM with CFRP fibers.
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  JAXA-ONERA-DLR cooperation: results from rotor optimization in forward flight

  Kimura, K. ; Wilke, G. ; Bailly, J. ; Tanabe, Y.

  This paper presents the results of a cooperative study by JAXA, DLR, and ONERA on the optimal design of helicopter blades for high-speed forward flight. Optimizations and simulations are carried out by each agency with their own analysis codes using both blade element theory-based methods and computational fluid dynamics. These results are cross-compared and show common trends identified for optimum rotor blades obtained by each agency and the mechanism for improving forward flight performance are discussed. From the effective drag distributions, it is confirmed that, in order to improve forward flight performance, it is first important to reduce drag on the advancing side, and that a blade with a relatively small twist angle and planforms with a smaller chord length at the root and tip compared to the mid-span section is generally a suitable blade.