Showing papers in "Journal of Aircraft in 2020"
TL;DR: The next generation of self-driving cars will have to contend with the needs of pedestrians, cyclists, and motorcyclists on the roads and in the urban environment.
Abstract: Technological advances in areas such as battery technology, autonomous control, and ride-hailing services, combined with the scale-free nature of electric motors, have sparked significant interest ...
59 citations
TL;DR: Electric and hybrid-electric propulsion offer unique possibilities to improve aircraft efficiency and performance and the potential advantages are fuel savings, lower emissions, and reduced noise.
Abstract: Electric and hybrid-electric propulsion offer unique possibilities to improve aircraft efficiency and performance. The potential advantages are fuel savings, lower emissions, and reduced noise. Bec...
51 citations
TL;DR: This work presents a conceptual design and optimization tool for urban air mobility, using small, autonomous, vertical-takeoff-and-landing, battery-powered electric aircraft, for use in urban areas.
Abstract: Urban air mobility refers to an envisaged air taxi service, using small, autonomous, vertical-takeoff-and-landing, battery-powered electric aircraft. A conceptual design and optimization tool for u...
42 citations
TL;DR: In this article, the propulsion systems of UAVs with distributed electric propulsors were compared with conventional UAV propulsion systems, and the propulsion system of short takeoff and landing (STOL) UAV was evaluated.
Abstract: Compared with conventional unmanned aerial vehicles (UAVs), the propulsion systems of vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) UAVs with distributed electric propuls...
31 citations
TL;DR: Practical aspects of frequency-domain approaches for aircraft system identification are explained and demonstrated and topics related to experiment design, flight data analysis, and dynamic modeling a...
Abstract: Practical aspects of frequency-domain approaches for aircraft system identification are explained and demonstrated. Topics related to experiment design, flight data analysis, and dynamic modeling a...
30 citations
TL;DR: In this paper, the authors show that fully battery-based propulsion is not a viable option to substantially reduce the climate impact of the aviation sector as a whole, unless the mission range is significantly reduced, or unrealistically high battery energy densities are assumed.
Abstract: There has been a surge in research related to hybrid-/ electric propulsion (HEP) over the past decade, since this technology has the potential to reduce the energy consumption and in-flight emissions of commercial aircraft and, therefore, to bring the aviation sector closer to the sustainability targets established by the European Commission [1] and NASA [2]. Previous studies have shown that hybrid-electric [3,4] and fully-electric [5] general-aviation aircraft can lead to a reduction in both emissions and operating costs for short ranges, when compared with fuel-based alternatives. However, due to the enormous energy and power requirements of large passenger aircraft, fully battery-based propulsion is not a viable option to substantially reduce the climate impact of the aviation sector as a whole [6], unless the mission range is significantly reduced, or unrealistically high battery energy densities are assumed [7]. For this reason, hybrid architectures (especially parallel [8–10] and turboelectric [11–14] ones) are often investigated as a potential solution for large passenger aircraft.
30 citations
TL;DR: The combination of combustion engine and electric motor as a hybrid-electric propulsion system seems to be a promis... as discussed by the authors, however, until electric energy storage systems are ready to allow fully electric aircraft, the combination of a combustion engine, electric motor, and a hybrid electric propulsion system is not a promising solution.
Abstract: Until electric energy storage systems are ready to allow fully electric aircraft, the combination of combustion engine and electric motor as a hybrid-electric propulsion system seems to be a promis...
30 citations
TL;DR: A recent consideration in aircraft design is the use of folding wingtips, with the aim of enabling higher-aspect-ratio aircraft with less induced drag but also meeting airport gate limitations as discussed by the authors.
Abstract: A recent consideration in aircraft design is the use of folding wingtips, with the aim of enabling higher-aspect-ratio aircraft with less induced drag but also meeting airport gate limitations. Thi...
26 citations
TL;DR: Folding wingtips have begun to feature on recent aircraft designs, as a solution for compliance with existing airport gate width regulations while enabling high-aspect-ratio wings for lower induced induced wing chord heights.
Abstract: Folding wingtips have begun to feature on recent aircraft designs, as a solution for compliance with existing airport gate width regulations while enabling high-aspect-ratio wings for lower induced...
25 citations
TL;DR: The adoption of conventional “black metal” composites in aircraft structures has lead to an improvement in performance over previous metallic designs, and the maturation of automated fiber placeme...
Abstract: The adoption of conventional “black metal” composites in aircraft structures has lead to an improvement in performance over previous metallic designs. With the maturation of automated fiber placeme...
25 citations
TL;DR: This Paper describes how flight simulation has been used to investigate helicopter recovery operations to the deck of HMS Queen Elizabeth, the United Kingdom’s new aircraft carrier.
Abstract: This Paper describes how flight simulation has been used to investigate helicopter recovery operations to the deck of HMS Queen Elizabeth, the United Kingdom’s new aircraft carrier A helicopter fl
TL;DR: Boundary-layer ingestion promises increased aircraft efficiency, but excessive inlet distortion must be avoided to prevent fans that are too heavy or structurally infeasible.
Abstract: Boundary-layer ingestion (BLI) promises increased aircraft efficiency, but excessive inlet distortion must be avoided to prevent fans that are too heavy or structurally infeasible. We propose a new...
TL;DR: In this paper, the unsteady effects present in a ship airwake are further analyzed in the context of helicopter launch and recovery operations under a real ship air wake scenario, and the results were used for simulation of helicopter landing and recovery.
Abstract: In the present work, unsteady effects present in a ship airwake are further analyzed. The effort is performed in the context of simulation of helicopter launch and recovery operations under a reali...
TL;DR: This work proposes to enrich the procedure for the conceptual design of hybrid aircraft found in literature through the definition of a multidisciplinary design optimization (MDO) framework aimed at handling design problems for such kinds of aircraft.
Abstract: Hybrid-electric aircraft are a potential way to reduce the environmental footprint of aviation Research aimed at this subject has been pursued over the last decade; nevertheless, at this stage, a full overall aircraft design procedure is still an open issue This work proposes to enrich the procedure for the conceptual design of hybrid aircraft found in literature through the definition of a multidisciplinary design optimization (MDO) framework aimed at handling design problems for such kinds of aircraft The MDO technique has been chosen because the hybrid aircraft design problem shows more interaction between disciplines than a conventional configuration, and the classical approach based on multidisciplinary design analysis may neglect relevant features The procedure has been tested on the case study of a single-aisle aircraft featuring hybrid propulsion with distributed electric ducted fans The analysis considers three configurations (with 16, 32, and 48 electric motors) compared with a conventional baseline at the same 2035 technological horizon To demonstrate the framework’s capability, these configurations are optimized with respect to fuel and energy consumption It is shown that the hybrid-electric concept consumes less fuel/energy when it flies on short range due to the partial mission electrification When one increases the design range, penalties in weight introduced by hybrid propulsion overcome the advantages of electrified mission segment: the range for which hybrid aircraft have the same performance of the reference conventional aircraft is named the “breakdown range” Starting from this range, the concept is no longer advantageous compared to conventional aircraft Furthermore, a tradeoff between aerodynamic and propulsive efficiency is detected, and the optimal configuration is the one that balances these two effects Finally, multiobjective optimization is performed to establish a tradeoff between airframe weight and energy consumption
TL;DR: In this paper, the noise emissions of a full-scale nose landing gear (NLG), measured in a wind tunnel and obtained from computational simulations, are compared with those of three regional aircraft types recorded in flyover measurements.
Abstract: The noise emissions of a full-scale nose landing gear (NLG), measured in a wind tunnel and obtained from computational simulations, are compared with those of three regional aircraft types recorded in flyover measurements. A comparison is made with the noise prediction models of Fink, Guo, and German Aerospace Center (DLR). A good agreement was found between all the spectra. The noise emissions up to 1.2 kHz were found to scale with the sixth power of the flow velocity, as usual; however, the spectra at higher frequencies collapsed better when scaled to the seventh power, confirming the fact that high-frequency noise is radiated from the turbulent flow surrounding small features of the NLG. Microphone arrays showed that the main noise sources were located in the middle of the wheel axle. For the flyovers and computational simulations, strong tonal peaks (at around 2200 Hz) were found, which are likely to be caused by open cavities in the NLG. This phenomenon is not accounted for in prediction models. Removing these tones would result in noise reductions of up to 2 dB. Thus, it is highly recommended to include cavity-noise estimations in the current prediction models, or to simply eliminate such cavities where possible with the use of cavity caps.
TL;DR: In this paper, Cai et al. used surface dielectric barrier discharge (SDBD) plasma actuation for anti-icing in an aircraft and achieved an effective flow control with an inflow velocity at a Ma 0.4 and a Reynolds number of 2.3.
Abstract: I CING is regarded as a severe safety issue for the industry, such as aviation and wind energy in cold weather, because it will degrade the performance when supercooled water droplets impinge and freeze onto the surface of the airfoil and rotating blades. The contamination of the streamlined profile will cause serious degradation of the aerodynamic efficiency and unbalance the whole rotor system. Therefore numerous studies have focused on this icing phenomenon and various anti-/de-icing technologies have been developed in the past few decades [1–5]. However, the current anti/ de-icing technology is not sufficient to address the ever-evolving requirements in aerodynamics, materials and energy consumption [6]. As a result, the novel methods and techniques for extended durability and efficient anti-/deicing performance are considered desirable [7–13]. Plasma flow control has received growing research attention in the past few decades for its unique features, such as nomoving parts, fast response, and exceptional ease of installation on the surface without changing the shape. One such significant development is the use of surface dielectric barrier discharge (SDBD) plasma actuators, which are composed of two electrodes separated by a dielectric material arranged in an asymmetric fashion [14–17]. The most common SDBD plasma flow control methods include alternative-current surface-dielectric-barrier-discharge (AC-SDBD) and nanosecond-pulse surface-dielectric-barrier-discharge (NS-SDBD) plasma actuations. The mechanism of AC-SDBD plasma flow control has been studied by different researchers in recent years [14,16]. The results for different researchers are consistent, i.e., application of a sufficiently high-voltage ac signal between the electrodes weakly ionizes the air over the dielectric covering the encapsulated electrode. The ionization of the air is a dynamic process within the ac cycle. The ionized air, in the presence of the electric field, results in a body force vector. Such induced airflow can impart momentum to the flow, just like flow suction or blowing, but without mass injection. For the NS-SDBD plasma actuator, it has great potential in highspeed flow control; however, its different aerodynamic effects at different timescales make its mechanism in the flow control much more complicated. In addition, because the input is a high-voltage signal of the nanosecond level, its electromagnetic interference is much stronger than that of the AC-SBDB, causing serious interference to the control and measurement equipment of the icing wind tunnel. Recently, researchers have achieved effective flow control results at higher wind speeds and Reynolds numbers through the optimization of the actuator geometry, substrate materials, and other parameters [18–20]. Using AC-SDBD plasma actuation, Zhang et al. [19] showed the effective flow control over an airfoil with an inflow velocity of 100 m/s using a symmetrically arranged encapsulated electrodes actuator; Kelley et al. [18] achieved effective flow control with an inflow velocity at a Ma 0.4 and a Reynolds number of 2.3 × 10 using 3.175-mm-thick ceramics as the insulatingmaterials. Using NS-SDBD plasma actuation, Nishihara et al. [20] demonstrated effective bow shock perturbations with an incoming flow Mach number of five. However, the drawback of plasma flow control is its low efficiency of energy conversion (the surface discharge-induced kinetic efficiency versus the discharge current is only several percent) [14]. The part of the electrical energy which is converted to heat remains useless as far as flow control applications are concerned [21–24]. Meng et al. [25,26] and Cai et al. [27] proposed a researchmethod for icing control using AC-SDBD plasma actuation, which can make full use of the aerodynamic and thermal effects of SDBD plasma discharge. Meng et al. [26] and Cai et al. [27] showed the feasibility of SDBD plasma icing control on a cylinder model. The anti-/deicing performance of the AC-SDBD plasma actuator was evaluated based on visualization and thermal images in an icing wind tunnel. Compared with the traditional anti-/de-icing system, AC-SDBD plasma almost satisfies all the icing control requirements of the nextgeneration aircraft design. First it can be flush mounted on the surfaces without interfering with the flow to keep the natural laminar flow, and it can be used for flow control when the aircraft is not in the icing condition during flight. Second, it can fully use the discharge energy of the AC-SDBD, i.e., both the thermal and aerodynamic effects. Besides, the self limiting nature of the discharge limits the rise in temperature of the AC-SDBD plasma thereby protecting the composite structures from over-heating during anti-/deicing. Lastly, with the development of the model battery technology, the AC-SDBD actuator can be powered by battery-driven pocket highvoltage generators, which have been installed on unmanned aerial vehicles in several field tests as electronic rudders [28]. Therefore, the AC-SDBD actuators can be comfortably mounted on an all-electric aircraft as a full electric-based icing control technique. Received 8 August 2019; accepted for publication 7 October 2019; published online 13 February 2020. Copyright © 2020 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. All requests for copying and permission to reprint should be submitted to CCC at www .copyright.com; employ the eISSN 1533-3868 to initiate your request. See also AIAA Rights and Permissions www.aiaa.org/randp. *Graduate Student; currentyDoctorate, IowaStateUniversity, Iowa 50011. Professor; mxsbear@nwpu.edu.cn (Corresponding Author). Professor; jcai@nwpu.edu.cn. Assistant Professor; zhouww@sjtu.edu.cn. Assistant Professor; liuya19@ecu.edu. **Professor; huhui@iastate.edu.
TL;DR: Exploration of design tradeoffs for aerodynamic surfaces requires solving of multi-objective optimization (MOO) problems and the major bottleneck here is the time-consuming evaluations of the computations.
Abstract: Exploration of design tradeoffs for aerodynamic surfaces requires solving of multi-objective optimization (MOO) problems. The major bottleneck here is the time-consuming evaluations of the computat...
TL;DR: A comparison of computational and experimental ice accretions generated on three swept-wing models in the NASA Glenn Icing Research Tunnel is presented in this paper, where the wind tunnel models span floor to ceiling.
Abstract: A comparison of computational and experimental ice accretions generated on three swept-wing models in the NASA Glenn Icing Research Tunnel is presented. The wind tunnel models span floor to ceiling...
TL;DR: In this article, the application of riblets on a typical regional turboprop configuration is discussed and the effect of the riblet is modeled as a singular roughness problem by a proper boundary condition.
Abstract: The application of riblets on a typical regional turboprop configuration is discussed in this paper. The effect of the riblets is modeled as a singular roughness problem by a proper boundary condit...
TL;DR: In this article, an advanced potential flow method is used to study the aerodynamic interactions between small rotors of quadrotor configurations and the impact on the overall flight performance of the quadrotors.
Abstract: An advanced potential flow method is used to study the aerodynamic interactions between small rotors of quadrotor configurations and the impact on the overall flight performance. The aerodynamic an...
TL;DR: An experimental study was performed in a water tunnel to evaluate the effects of continuous and pulsed blowing jets on the counter-rotating vortices generated by the afterbody of a slanted base cyl....
Abstract: An experimental study was performed in a water tunnel to evaluate the effects of continuous and pulsed blowing jets on the counter-rotating vortices generated by the afterbody of a slanted base cyl...
TL;DR: A 10%-scale high-lift versions of the Common Research Model and an active flow control (AFC) version of the model equipped with a simple-hinged flap were successfully tested.
Abstract: A 10%-scale high-lift version of the Common Research Model and an active flow control (AFC) version of the model equipped with a simple-hinged flap were successfully tested. The main objective of t...
TL;DR: Three flutter-suppression designs for a flexible flying-wing research drone are discussed, along with the modeling and flight-test results.
Abstract: Three flutter-suppression designs for a flexible flying-wing research drone are discussed, along with the modeling and flight-test results. The drone, with wing span of 10 feet, aspect ratio of alm...
TL;DR: The development of faster computing power and nonintrusive experimental techniques has allowed for the advancement in computational fluid dynamics (CFD) validation and the greater understanding of the fluid dynamics as mentioned in this paper.
Abstract: The development of faster computing power and nonintrusive experimental techniques has allowed for the advancement in computational fluid dynamics (CFD) validation and the greater understanding of ...
TL;DR: In this article, an accurate calculation of fatigue life of aircraft lugs is proposed to evaluate the impact of cyclic loads on the fatigue life, considering the thermal load on the aircraft.
Abstract: Cyclic loads have a significant impact on the fatigue life of aircraft lugs. To evaluate fatigue life of aircraft lugs, an accurate calculation of fatigue life is essential. Therefore, thermal stre...
TL;DR: Beyond aerodynamic stall, the analysis of aircraft flight requires models accurately representing nonlinearities and instabilities and previous bifurcation analysis studies therefore had a priori know-nothing about these models.
Abstract: Beyond aerodynamic stall, the analysis of aircraft flight requires models accurately representing nonlinearities and instabilities. Previous bifurcation analysis studies therefore had a priori know...
TL;DR: In this paper, a hingeless proprotor whirl flutter in cruise flight is investigated using comprehensive rotorcraft analysis codes CAMRAD II and RCAS, using a conventional soft-in...
Abstract: Hingeless proprotor whirl flutter in cruise flight is investigated using comprehensive rotorcraft analysis codes CAMRAD II and RCAS. Generic hingeless proprotor designs include conventional soft-in...
TL;DR: In this paper, a vortex-based aerodynamic solver is employed to investigate the tandem rotor/ground-obstacle interference problems that occur during landing operations, which produces high pilot workloads.
Abstract: The tandem rotor/ground-obstacle interference problems that occur during landing operations produce high pilot workloads. In this study, a vortex-based aerodynamic solver is employed to investigate...