Special Issue "Rotorcraft"

A special issue of Aerospace (ISSN 2226-4310).

Deadline for manuscript submissions: closed (15 January 2019).

Special Issue Editor

Dr. Richard Green
E-Mail Website
Guest Editor
School of Engineering, University of Glasgow, R719 Level 7, Aerospace Sciences, James Watt Building South, Glasgow G12 8QQ, Scotland, UK
Interests: fluid mechanics

Special Issue Information

Dear Colleagues,

Rotorcraft have been in development since the early days of aviation, and were conceived originally as a solution for very low speed flight. Helicopters have the almost unique ability to hover and gain access to difficult locations that are all but impossible with fixed wing aircraft. This makes them ideal for tasks such as search and rescue, emergency support and medical evacuation, observation, supply for offshore platforms, small ship operation, and a multitude of military operations. Rotary wing flight is far more complex than fixed wing flight, however, whether it is for an unpowered rotor in the case of an autogyro, or a powered rotor in the case of a helicopter. Rotorcraft have unique handling and control issues, the aerodynamics and flight mechanics are so closely compounded to the extent that they cannot be considered separately, and the aerodynamics and fluid mechanics are rich with interesting phenomena. They are fascinating from a variety of perspectives. Versatility is the key to the success of rotorcraft as a field of aviation, and future developments promise to extend their speed, range and acceptability. An important class of rotorcraft that has emerged in recent years is in the form of small unmanned aerial vehicles (UAVs) that typically includes quadcopters. These exploit the versatility of rotorcraft in a very low cost platform, and while they have the potential to be very useful devices, their rapid rise in popularity has led to ethical questions and changes in the law about their use. Rotorcraft therefore have a broad appeal from a wide range of perspectives, including basic science, challenging engineering, sophisticated robotics and autonomous guidance. This Special Issue will address this by inviting papers relevant to rotorcraft including computational and experimental aerodynamics, acoustics and vibration, aeromechanics, flight dynamics, handling qualities, operational aspects of rotorcraft, future concepts, and rotary wing UAVs.

Dr. Richard Green
Guest Editor

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Keywords

  • Helicopter
  • rotorcraft
  • tilt rotors
  • compound helicopter
  • rotorcraft aeromechanics
  • rotary wing aerodynamics

Published Papers (3 papers)

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Research

Open AccessArticle
A Simple Model to Assess the Role of Dust Composition and Size on Deposition in Rotorcraft Engines
Aerospace 2019, 6(4), 44; https://doi.org/10.3390/aerospace6040044 - 16 Apr 2019
Abstract
There have been several recorded mishaps of rotorcraft experiencing flame-out due to engine surge as a result of rapid accumulation of sand and dust on nozzle guide vanes. Minerals such as sodium chloride and albite have lower melting points than quartz and are [...] Read more.
There have been several recorded mishaps of rotorcraft experiencing flame-out due to engine surge as a result of rapid accumulation of sand and dust on nozzle guide vanes. Minerals such as sodium chloride and albite have lower melting points than quartz and are found to constitute some of the loose sediment on unprepared landing sites in the Persian Gulf. Despite this, they are not found in great abundance, if at all, in many of the test dusts that are used to qualify engines operating in harsh environments. The consequence is an under-prediction of the time to failure due to vane deposit build-up. In the current work, we use a simple model to demonstrate the sensitivity of accumulation efficiency (the proportion of ingested dust that sticks) to mineral dust physico-chemical properties. We utilise the concept of thermal Stokes number to examine the relationship between time to equilibrate and residence time and how this varies as a function of constituent mineral, as well as particle size. The likelihood of impact increases with momentum Stokes number, while the likelihood of adhesion decreases with thermal Stokes number, yet the two both increase with the square of particle diameter. This leads to a peak in deposition rate at a certain particle size. However, dust mineralogy is shown to influence sticking efficiency more than impact efficiency owing to differences in melting point. Finally, we apply our simple model to estimate the mass of dust deposited during a single brownout landing of a Pave Hawk helicopter, using two different commercially-available test dusts. Full article
(This article belongs to the Special Issue Rotorcraft)
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Open AccessArticle
Non-Linear Dynamic Inversion Control Design for Rotorcraft
Aerospace 2019, 6(3), 38; https://doi.org/10.3390/aerospace6030038 - 18 Mar 2019
Abstract
Flight control design for rotorcraft is challenging due to high-order dynamics, cross-coupling effects, and inherent instability of the flight dynamics. Dynamic inversion design offers a desirable solution to rotorcraft flight control as it effectively decouples the plant model and effectively handles non-linearity. However, [...] Read more.
Flight control design for rotorcraft is challenging due to high-order dynamics, cross-coupling effects, and inherent instability of the flight dynamics. Dynamic inversion design offers a desirable solution to rotorcraft flight control as it effectively decouples the plant model and effectively handles non-linearity. However, the method has limitations for rotorcraft due to the requirement for full-state feedback and issues with non-minimum phase zeros. A control design study is performed using dynamic inversion with reduced order models of the rotorcraft dynamics, which alleviates the full-state feedback requirement. The design is analyzed using full order linear analysis and non-linear simulations of a utility helicopter. Simulation results show desired command tracking when the controller is applied to the full-order system. Classical stability margin analysis is used to achieve desired tradeoffs in robust stability and disturbance rejection. Results indicate the feasibility of applying dynamic inversion to rotorcraft control design, as long as full order linear analysis is applied to ensure stability and adequate modelling of low-frequency dynamics. Full article
(This article belongs to the Special Issue Rotorcraft)
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Open AccessArticle
Process Development for Integrated and Distributed Rotorcraft Design
Aerospace 2019, 6(2), 23; https://doi.org/10.3390/aerospace6020023 - 21 Feb 2019
Abstract
The German Aerospace Center is currently developing a new design environment for rotorcraft, which combines sizing, simulation and evaluation tasks into one toolbox. The complete environment applies distributed computation on the servers of the various institutes involved. A uniform data model with a [...] Read more.
The German Aerospace Center is currently developing a new design environment for rotorcraft, which combines sizing, simulation and evaluation tasks into one toolbox. The complete environment applies distributed computation on the servers of the various institutes involved. A uniform data model with a collaboration and interface software, developed by DLR and open source, are used for exchange and networking. The tools used apply blade element methods in connection with full six degrees of freedom trim, panel methods for aerodynamic loads, different empirical models for sizing, engine properties and component mass estimation and finite element methods for structural design. A special feature is the integration of a higher fidelity overall simulation tool directly into the sizing loop. The paper describes the use of the several tools for the phases of conceptual and preliminary design. A design study is presented demonstrating the sensitivity of the process for a variation of the input parameters exhibiting a broad range for trade-off studies. The possibility to continue for analyzing and sizing of the structural properties is also demonstrated by applying a finite element approach for specific load cases. These features highlight the core of the new design environment and enable the development of goal-oriented design processes for research especially of new and unconventional rotorcraft configurations. The work presented in this paper was conducted throughout the DLR internal project, namely the Technologies for Rotorcraft in Integrated and Advanced Design (TRIAD). TRIAD is a joint project of the institutes of Flight Systems, the institute of Aerodynamics and Flow Technology, the institute of Structures and Design, the System Architectures in Aeronautics and Institute of Aerospace Medicine and receives basic founding. Full article
(This article belongs to the Special Issue Rotorcraft)
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