DSpace Repository

The ERF

The European Rotorcraft Forum is one of the premier events in the rotorcraft community’s calendar bringing together manufacturers, research establishments, academia, operators and regulatory agencies to discuss advances in research, development, design, manufacturing, testing and operation of rotorcraft.

The ERF International Committee is providing free access to the available papers presented at the past ERF conferences. Two years after each ERF, the conference papers are uploaded to the repository.

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ERF
European Rotorcraft Forum

Recent Submissions

Aeroelastic Optimization of Helicopter Composite Horizontal Stabilizer Using the Superior Damping Properties of Flax Fibers
(2023) John, J.; Gaugelhofer, L.; Hackner, C.; Cumiskey, J.; Yavrucuk, I.
Helicopter structures are heavily influenced by vibration, often forcing structural changes late in the design process. While structural dynamics simulations may not always provide accurate results, flight testing remains often the only method to identify dynamic interactions and excitations. This is particularly relevant for new, innovative designs where practical experience is limited. One potential approach to mitigate design risks is to improve the damping of the aircraft structure. Natural fibers such as flax could be a promising approach. However, additional flax material is required to achieve stiffness and strength comparable to carbon components, resulting in increased weight. The aim of this study is to investigate how this weight increase can be minimized while still achieving optimal damping levels. To accomplish this, knowledge gained from the hybridization of simple specimens and cross-sectional laminates has been extended to a 3D laminate configuration. The goal is to develop structures with matching dynamic properties, minimal weight increase, and significant damping improvement. The influencing parameters of this strategy were first tested on double-T beams. High-strain regions were targeted for extensive hybridization to maximize damping, while low-strain regions received minimal hybridization to avoid excessive weight gain. As a practical demonstration, this approach was applied to a horizontal stabilizer. Emphasis was placed on the critical first bending modes, both asymmetrical and symmetrical. The dynamic properties of the structures, including damping and stiffness, were measured by experimental modal analysis. The results illustrate the feasibility of designing hybrid components with comparable dynamic behavior, demonstrating significantly improved damping properties with only a minor increase in weight. For example, the damping in the first symmetrical bending mode of the horizontal stabilizer was more than quadrupled while maintaining the same natural frequency and adding less than 10% of mass.
Effects of Aero-Propulsive Coupling on High Solidity Electric Ducted Fan Performance for Various Wing Integrations
(2023) Safieh, D.A.; Rauleder, J.
The increase in population in urban areas and their surroundings, combined with inefficient and saturated land routes, have sparked a booming interest in regional and urban air transportation options. Electric Ducted Fans (EDF) are expected to help these new concepts meet the ambitious goals set by the aviation industry. While most boundary layer ingestion propulsion methods, like EDFs, have been extensively studied at a system level, little attention has been given to decoupling EDF forces for various wing integrations. This study focuses on understanding the changes in performance that various aero-propulsive integrations have on the EDF, comparing leading edge and trailing edge EDF integrations to an isolated EDF. For both integration cases, the EDF power loading increased over the isolated case. This increase was greater for the higher advance ratios. The leading edge integration pitching moment showed a growing destabilizing moment similar to that of the isolated thruster for the upper surface integration, but showed a constant destabilizing behavior (independent of angle of attack) for the lower surface. While the pitching moment of the isolated case was destabilizing and increased in magnitude with increased angle of attack, the pitching moment of the trailing edge integrated EDF was mostly constant. For the upper surface this moment is stabilizing while for the lower surface its destabilizing. This shows the importance of understanding the EDF’s aerodynamic characteristics as they might affect the overall lifting system characteristics. A high-frequency analysis using a short-time Fourier transform (STFT) on the system pitching moment and inlet acoustic signature showed similar dominant frequencies for the isolated EDF and leading edge integration for both the loads and acoustic data, but revealed the existence of new high and low frequency transient loads for the trailing edge integration. Both integration methods showed increases in performance and power reduction. The trailing edge integrated EDF required 12% less power (max value) than the isolated EDF, while the leading edge integrated EDF required 8% less power (max value) for the same operational conditions.
Virtual-Pilot-in-the-Loop Simulation Model to assess Helicopter Routes Feasibility
(2023) Roncolini, F.; Quaranta, G.
A virtual-pilot-in-the-loop reference tracking simulation environment is set up in order to analyze the feasibility of candidate trajectories. The helicopter is modeled as a linear state-space dynamics, and the pilot is modeled by means of the revised optimal control pilot model (ROCM). The pilot’s neuromuscular dynamics and processing delay are modeled as second-order dynamics, augmenting the system states from 9 to 25. A guidance logic is implemented to allow the trajectory tracking. The pilot’s workload is assessed by means of the computation of the aggression factor, related to the control input rates. The pilot-in-the-loop simulator performs a good trajectory tracking, even if some adjustments need to be introduced in the guidance logic, and is able to detect some level of criticality in the analyzed trajectories.
Effect of Torsional Flexibility on an Unmanned Helicopter Performance Including Compressibility Effect
(2023) Uzunkaya, A.F.; Yaman, Y.
In this study, torsional deformation of an unmanned helicopter and its effect on the performance characteris-tics are examined. In the analyses, blade-element momentum theory is used for the calculation of the aero-dynamic loads by implementing compressibility corrections. For the interactions between the aerodynamic loads and torsional deformations, an iterative solution procedure is developed. To obtain the trim points of the helicopter, a trim code is written in which blade is modeled as either rigid or elastic in the torsional direc-tion. It is found that there occur some differences between the rigid and elastic blade in terms of the control inputs. However, since the aerodynamic center is close to the shear center of the reference blade, the differ-ence is found to be negligible small. Therefore, effects of the torsional deformations on the helicopter control and performance are minimal.
Convertiplane Control during Transition: the Collective and Throttle Lever (CATL)
(2023) Abà, A.; Pedrioli, A.; Monstein, R.; Hitz, M.; Schneider, G.; Capone, P.
Control of convertiplanes during transition is a challenging task. This work focuses on the development of the interface be-tween the pilot and the flight control thrust axis command. The goal is to provide the pilot with an ergonomically well-designed and intuitive inceptor and thus, minimizing human errors and increasing flight safety. The paper follows the development of the innovative thrust inceptor called the Collective and Throttle Lever (CATL) at the Center for Aviation at the Zurich Uni-versity of Applied Sciences from 2015 to today. The various phases of the CATL development are described starting from the concept phase, continuing with the development of the prototype and its integration with the XV15 simulation model and a real-time simulator and concluding with the description of the preliminary testing and results. The obtained positive results provide some insight into the problem. Further investigations and trials are needed for a more thorough assessment of the inceptor. These will be the subject of future works.