As part of the design process, structural assessment represents an important aspect in the development of new airand rotorcraft. It plays a critical role in supporting the weight of the aircraft, transmitting loads from the rotors to the airframe, and ensuring the overall safety and integrity of the vehicle. The conceptual design phase is characterized by exploration and evaluation of broad design concepts, with minimal detail regarding structural design. In contrast, the preliminary design phase involves refining the chosen design concept and conducting more detailed structural analysis and optimization to prepare for the subsequent detailed design phase. In order to evaluate the airframe, the opensource based design environment PANDORA has been developed at DLR. This paper presents an overview of model generation, topology optimization, sizing, and crashworthiness aspects in PANDORA using validation examples and generic rotorcraft models.

Most of the introduced eVTOL models in the UAM market utilize electrically driven rotors with fixed pitch blades, controlled by their rotational speed. This design approach brings new features and challenges that need to be considered during the conceptual design stage, taking new aspects into account, among them the rotor dynamic response. This paper presents an initial parameterization of the rpm-controlled rotors along with the electric motor, based on the conducted literature research. Several isolated rotor variants are modeled and analyzed in terms of performance, and the dynamic response of the rotor rotational speed. The relations between aerodynamics and inertia are discussed, and their effects on the rotor dynamic response are elaborated on.

High-speed configurations are among the new emerging concepts that are currently expanding the scope of rotorcraft design. Especially in the field of defense technology research, the capability of a substantial increase in maximum velocity becomes more interesting. For instance, NATO project NGRC is considering this capability for a new medium utility rotorcraft. DLR supports these activities by its continuing defense technology research. In this study the benefits and drawbacks of a high-speed capability for a given mission scenario are analyzed. For that purpose, a contemporary configuration has been modeled, featuring a maximum velocity of 82 m/s (160 KTAS). The high-speed configuration meets with the same mission requirements, but with an increase of about 50% of maximum speed to 125 m/s (242 KTAS). All tasks in this study are conducted with DLRs integrated design environment IRIS. The high-speed configuration features an off-loaded main rotor, a wing, a propeller and a reduction of the rotational speed of the drive train for the extended flight envelope. The reference configuration as well as the high-speed rotorcraft were compared with the focus on flight performance.

At the Institute of Flight Systems at DLR, studies have been performed to understand the flight characteristics of novel eVTOL configurations. As part of these studies, previously conducted handling qualities assessments on a two-passenger generic quadrotor configuration had revealed major deficiencies about its yaw axis. Based on this result, the quadrotor model has been modified by differential torsional canting to improve its yaw characteristics. This paper analyzes the resulting impacts of such modification on the flight performance, dynamic stability and handling qualities. A piloted simulator test campaign was conducted to assess predicted and assigned handling qualities levels in compliance with the quantitative and qualitative performance standards of ADS-33E. The results show an improvement in midterm yaw response at the expense of increase in total required power. The pilot ratings and comments confirm the improvement on the yaw response upon the flown MTEs.

The popularity of the electric vertical take-off and landing (eVTOL) aircraft in the Urban Air Mobility (UAM) market has significantly increased over the last decade. Many institutes and companies around the globe are conducting research in this field to translate the theory into practice by developing novel eVTOL configurations. At the German Aerospace Center, the Institute of Flight Systems has been developing processes not only to model novel configurations, but also to asses them qualitatively with real pilots. In this regard, a study concerning the Handling Qualities (HQs) assessments of a two passenger quadrotor configuration with variable blade pitch and variable rotor rotational speed control was conducted. The simulation tests were performed in DLR?s Air VEhicle Simulator (AVES), where the HQs were assessed through Mission Task Elements (MTEs) taken from ADS-33E-PRF. Results from the study showed critical HQs issues regarding the control sensitivity, vehicle stability and yaw bandwidth.