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

A simplified model for evaluating eVTOL conceptual designs and with example results for three types of eVTOL aircraft configurations
(2022) 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.
Aerodynamics of small rotors in hover and forward flight
(2022) Lossle, F.; Kostek, A.A.; Schwarz, C.; Schmid, R.; Gardner, A.D.; Raffel, M.
A wind tunnel test of eleven two- and three-bladed small-scale rotors was conducted in an open-jet, lowspeed wind tunnel. The goal was to study the influence of number of blades, blade pitch and geometry on the hover performance. Two rotors were also studied in forward flight with varying rotational speeds, rotor tilt angles and flow velocities covering a wide range of operating conditions. The experimental results were used to develop a simple, empirical model of the studied rotor based on dimensionless quantities. The model can be used in the preliminary design of multicopters. The performance measurements were supplemented with optical background-oriented schlieren (BOS) measurements to visualize the blade tip vortices in the rotor wake in order to gain a better understanding of the flow state. Simulations with DLR’s free wake unsteady panel code (UPM) were carried out for comparison.
JAXA-ONERA-DLR cooperation: results from rotor optimization in forward flight
(2022) 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.
Are eVTOL aircraft inherently more susceptible to the vortex ring state than conventional helicopters?
(2022) Brown, R.E.
There is currently extensive interest worldwide in developing small, lightweight, electrically powered, multi-rotor vertical takeoff and landing aircraft. The aim is to use these new vehicles to carry a small number of passengers on short-range intra-urban missions, for instance as part of a passenger ferry service between an airport and a downtown commuter hub. The concern is that these aircraft might have certain characteristic design features that, in combination with the environmental conditions that they will experience, will render them particularly susceptible to a potentially hazardous operating regime, known as the Vortex Ring State, especially during their descent and landing. This paper extends our classical understanding of the basic physics that underpins the Vortex Ring State in order to assess the likely impact of this phenomenon on the safety and operational characteristics of this new class of vehicle.
Hybrid propulsion benefit in optimal power-off landings of light multi-role helicopters
(2022) Scorcelletti, F.; Mauri, F.; Kranich, F.; Merlo, F.
The present paper focuses on the simulation of helicopter Power-Off maneuvers. These complex dynamic flight conditions are here formulated as trajectory optimization problems. Our numerical procedures can be conceptually used with any blackbox flight mechanics simulators, with minimal assumptions on the functionalities of such third-party software components, and can cater to a wide range of vehicle models of varying complexity. The Maneuver Optimal Control Problem is solved through a direct approach, by means of Direct Transcription techniques or Multiple Shooting methods depending on the model complexity and problem characteristics. By considering a model similar to the Kopter AW09 single-engine helicopter, three main applications are here addressed, i.e. the Autorotation Entry, the Flare, and the full Power-Off Landing. A specific effort of this work is focusing on the effects of an extra electrical power supply following the failure of the thermal engine to enhance safety in critical conditions (”1.5 engine” concept). The delicate trade-off between the additional weight of the electrical power kit and the energy booster available in case of an emergency is addressed for typical Power-Off Landing procedures in proximity of the ground.