81 research outputs found
Longitudinal flight control with a variable span morphing wing
The present study focuses on the design of a longitudinal flight controller for an unmanned aircraft equipped with dissymmetric variable-span system (VSMW or Variable-Span Morphing Wing). Its primary role consists in the longitudinal flight stabilization of the aeroplane while in levelled cruise flight, although, it was designed to offer longitudinal flight stabilization for other flight phases as well, such as e.g. take-off and landing. The stabilization algorithm relies on the most up-to-date developments in the state-of-the-art LQR and Batz-Kleinman controller techniques to stabilize the aircraft on its intended longitudinal attitude upon any small atmospheric disturbances inflicted. It was designed for the experimental UAV prototype Olharapo equipped with the VSMW, so it can automatically adjust the VSMW overall wingspan in accordance with the flight speed and stabilize the aircraft in the desired attitude, although, its modular concept allows it to be used for different configurations of the aircraft or even for a different aircraft. The development, simulation and testing of the algorithm were done using the MATLAB® software and the aircraft’s stability and control derivatives previously obtained using the XFLR5® software. Minor adaptations of the flight dynamics equations were performed to allow the compatibilization with the VSMW. The required implementation of imposed flight qualities was also performed to ensure proper scaling the controller weight matrix for optimal values. Finally, the algorithm was tested using three different methods: Classic Disturbances Simulation, Sinusoidal Pitch Variation Test Response and Random Pitch Variation Test Response.O presente trabalho consiste na projeção, programação e teste de um controlador de voo
longitudinal destinado a uma aeronave não-tripulada equipada com um sistema de variação
dissimétrica da envergadura das asas (conhecido como VSMW, asa dissimétrica ou asa
telescópica). Este trabalho tem como principal objetivo desenvolver um controlador capaz de
assegurar a estabilidade longitudinal da aeronave em voo nivelado a velocidade de cruzeiro,
contudo, este foi também projetado para providenciar essa mesma estabilidade noutras fases
de voo tais como a aterragem ou a descolagem. O algoritmo de estabilização baseia-se nas
mais sofisticadas técnicas de controlo de voo atualmente disponíveis, mais concretamente
LQR e Batz-Kleinman, para estabilizar a aeronave na atitude pretendida aquando da
ocorrência de quaisquer pequenas perturbações atmosféricas que afetem a aeronave durante
o voo. A aeronave a que se destina trata-se de um protótipo designado de Olharapo equipado
com uma asa telescópica que permite ajustar a envergadura total das asas de acordo com a
velocidade de voo. No entanto, o conceito modular da estrutura do programa permite que o
controlador possa ser utilizado para diferentes configurações da mesma aeronave, ou até
mesmo com uma aeronave totalmente diferente. Tanto o desenvolvimento como as
simulações e testes do algoritmo foram efetuados com recurso ao software MATLAB®
, tendo
as necessárias derivadas de estabilidade e controlo iniciais sido providenciadas pelo software
XFLR5®
. As equações de voo foram devidamente adaptadas para permitirem uma
compatibilização com o sistema da asa telescópica e a sua integração nos métodos de
controlo LQR e Batz-Kleinman. As qualidades de voo da aeronave foram devidamente
definidas e impostas ao controlador para garantir a afinação da matriz de ponderação para
valores ótimos. Por fim, o algoritmo foi sujeito a três tipos de testes e simulações: Simulação
Clássica por meio de Imposição de Perturbações Atmosféricas, Teste de Resposta a uma
Variação Sinusoidal do Ângulo de Arfagem, e Teste de Reposta a uma Variação Aleatória do
Ângulo de Arfagem
Optimized state feedback regulation of 3DOF helicopter system via extremum seeking
In this paper, an optimized state feedback regulation of a 3 degree of freedom (DOF) helicopter is designed via extremum seeking (ES) technique. Multi-parameter ES is applied to optimize the tracking performance via tuning State Vector Feedback with Integration of the Control Error (SVFBICE).
Discrete multivariable version of ES is developed to minimize a cost function that measures the performance of the controller. The cost function is a function of the error between the actual and desired axis positions. The controller parameters are updated online as the optimization takes place. This method significantly decreases the time in obtaining optimal controller parameters. Simulations were conducted for the online optimization under both fixed and varying operating conditions. The results demonstrate the usefulness of using ES for preserving the maximum attainable performance
Airborne forward pointing UV Rayleigh lidar for remote clear air turbulence (CAT) detection: system design and performance
A high-performance airborne UV Rayleigh lidar system was developed within the
European project DELICAT. With its forward-pointing architecture it aims at
demonstrating a novel detection scheme for clear air turbulence (CAT) for an
aeronautics safety application. Due to its occurrence in clear and clean air at
high altitudes (aviation cruise flight level), this type of turbulence evades
microwave radar techniques and in most cases coherent Doppler lidar techniques.
The present lidar detection technique relies on air density fluctuations
measurement and is thus independent of backscatter from hydrometeors and
aerosol particles. The subtle air density fluctuations caused by the turbulent
air flow demand exceptionally high stability of the setup and in particular of
the detection system. This paper describes an airborne test system for the
purpose of demonstrating this technology and turbulence detection method: a
high-power UV Rayleigh lidar system is installed on a research aircraft in a
forward-looking configuration for use in cruise flight altitudes. Flight test
measurements demonstrate this unique lidar system being able to resolve air
density fluctuations occurring in light-to-moderate CAT at 5 km or moderate CAT
at 10 km distance. A scaling of the determined stability and noise
characteristics shows that such performance is adequate for an application in
commercial air transport.Comment: 17 pages, 19 figures. Pre-publish to Applied Optics (OSA
The use of modern tools for modelling and simulation of UAV with Haptic
Unmanned Aerial Vehicle (UAV) is a research field in robotics which is in high demand in recent years, although there still exist many unanswered questions. In contrast, to the human operated aerial vehicles, it is still far less used to the fact that people are dubious about flying in or flying an unmanned vehicle. It is all about giving the control right to the computer (which is the Artificial Intelligence) for making decisions based on the situation like human do but this has not been easy to make people understand that it’s safe and to continue the enhancement on it. These days there are many types of UAVs available in the market for consumer use, for applications like photography to play games, to map routes, to monitor buildings, for security purposes and much more. Plus, these UAVs are also being widely used by the military for surveillance and for security reasons. One of the most commonly used consumer product is a quadcopter or quadrotor.
The research carried out used modern tools (i.e., SolidWorks, Java Net Beans and MATLAB/Simulink) to model controls system for Quadcopter UAV with haptic control system to control the quadcopter in a virtual simulation environment and in real time environment. A mathematical model for the controlling the quadcopter in simulations and real time environments were introduced. Where, the design methodology for the quadcopter was defined. This methodology was then enhanced to develop a virtual simulation and real time environments for simulations and experiments. Furthermore, the haptic control was then implemented with designed control system to control the quadcopter in virtual simulation and real time experiments.
By using the mathematical model of quadcopter, PID & PD control techniques were used to model the control setup for the quadcopter altitude and motion controls as work progressed. Firstly, the dynamic model is developed using a simple set of equations which evolves further by using complex control & mathematical model with precise function of actuators and aerodynamic coefficients Figure5-7. The presented results are satisfying and shows that flight experiments and simulations of the quadcopter control using haptics is a novel area of research which helps perform operations more successfully and give more control to the operator when operating in difficult environments. By using haptic accidents can be minimised and the functional performance of the operator and the UAV will be significantly enhanced. This concept and area of research of haptic control can be further developed accordingly to the needs of specific applications
The use of modern tools for modelling and simulation of UAV with Haptic
Unmanned Aerial Vehicle (UAV) is a research field in robotics which is in high demand in recent years, although there still exist many unanswered questions. In contrast, to the human operated aerial vehicles, it is still far less used to the fact that people are dubious about flying in or flying an unmanned vehicle. It is all about giving the control right to the computer (which is the Artificial Intelligence) for making decisions based on the situation like human do but this has not been easy to make people understand that it’s safe and to continue the enhancement on it. These days there are many types of UAVs available in the market for consumer use, for applications like photography to play games, to map routes, to monitor buildings, for security purposes and much more. Plus, these UAVs are also being widely used by the military for surveillance and for security reasons. One of the most commonly used consumer product is a quadcopter or quadrotor.
The research carried out used modern tools (i.e., SolidWorks, Java Net Beans and MATLAB/Simulink) to model controls system for Quadcopter UAV with haptic control system to control the quadcopter in a virtual simulation environment and in real time environment. A mathematical model for the controlling the quadcopter in simulations and real time environments were introduced. Where, the design methodology for the quadcopter was defined. This methodology was then enhanced to develop a virtual simulation and real time environments for simulations and experiments. Furthermore, the haptic control was then implemented with designed control system to control the quadcopter in virtual simulation and real time experiments.
By using the mathematical model of quadcopter, PID & PD control techniques were used to model the control setup for the quadcopter altitude and motion controls as work progressed. Firstly, the dynamic model is developed using a simple set of equations which evolves further by using complex control & mathematical model with precise function of actuators and aerodynamic coefficients Figure5-7. The presented results are satisfying and shows that flight experiments and simulations of the quadcopter control using haptics is a novel area of research which helps perform operations more successfully and give more control to the operator when operating in difficult environments. By using haptic accidents can be minimised and the functional performance of the operator and the UAV will be significantly enhanced. This concept and area of research of haptic control can be further developed accordingly to the needs of specific applications
Development, analysis, and implications of open-source simulations of remotely piloted aircraft
In recent years, the use of Remotely Piloted Aircraft (RPAs) for diverse purposes has increased exponentially. As a consequence, the uncertainty created by situations turning into a threat for civilians has led to more restrictive regulations from national administrations such as Transport Canada. Their purpose is to safely integrate RPAs in the current airspace used for piloted aviation by evaluating Sense and Avoid (SAA) strategies and close encounters. The difficulty falls on having to rely on simulated environments because of the risk to the human pilot in the piloted aircraft.
In the first part of this research, the technical difficulties associated with the development and study of RPA computer models are discussed. It explores the rationale behind using Open-Source Software (OSS) platforms for simulating RPAs as well as the challenges associated with interacting with OSS at graduate student level. A set of recommendations is proposed as the solution to improve the graduate student experience with OSS.
In the second part, particular challenges related to the design of OSS computer models are addressed. Based on: (1) the differences and similarities between piloted and RPA flight simulators and (2) existing Verification and Validation (V&V) approaches, a validation method is presented as a solution to the subject of developing fixed-wing RPAs in OSS environments.
This method is used to design two flight dynamics models with SAA applications. The first computer model is presented in tutorial format as a case study for the validation procedure whereas the second computer model is specific for testing SAA strategies. In the last part, one of the designed RPAs is integrated into a computer environment with a representative general aircraft. From the simulated encounters, a diving avoidance manoeuvre on the RPA is developed. This performance is observed to analyze the consequences to the airspace.
The implications of this research are seen from three perspectives: (1) the OSS challenges in graduate school are wide-spread across disciplines, (2) the proposed validation procedure is adaptable to fit any computer model and simulation scenario, and (3) the simulated OSS framework with an RPA computer model has served for testing preliminary SAA methods with close encounters with manned aircraft
Integrated multi-functional morphing aircraft technologies
In the past years, the development of morphing wing technologies has received a great
deal of interest from the scientific community. These technologies potentially enable an increase
in aircraft efficiency by changing the wing shape, thus allowing the aircraft to fly near its
optimal performance point at different flight conditions. This thesis explores the development,
analysis, building and integration of two new functional Variable-Span Wing (VSW) concepts to
be applied in Remotely Piloted Aircraft Systems (RPAS). Additional studies are performed to
synthesize the mass of such morphing concepts and to develop mass prediction models.
The VSW concept is composed of one fixed rectangular inboard part, inboard fixed wing
(IFW), and a moving rectangular outboard part: outboard moving wing (OMW). An aerodynamic
shape optimization code is used to solve a drag minimization problem to determine the optimal
values of wingspan for various speeds of the vehicle’s flight envelope. It was concluded that, at
low speeds, the original wing has slightly better performance than the VSW and for speeds higher
than 25 m/s the opposite occurs, due to the reduction in wing area and consequently the total
wing drag. A structural Finite Element Model (FEM) of the VSW is developed, where the interface
between wing parts is modelled. Deflections and stresses resulting from static aerodynamic
loading conditions showed that the wing is suitable for flight. Flutter critical speed is studied.
FEM is used to compute the VSW mode shapes and frequencies of free vibration, considering
a rigid or the real flexible interface, showing that the effect of rigidity loss in the interface
between the IFW and the OMW, has a negative impact on the critical flutter speed.
A full-scale prototype is built using composite materials and an electro-mechanical actuation
system is developed using a rack and pinion driven by two servomotors. Bench tests,
performed to evaluate the wing and its actuation mechanism under load, showed that the system
can perform the required extension/retraction cycles and is suitable to be installed on a
RPAS airframe, which has been modified and instrumented to serve as test bed for evaluating
the prototype in-flight. Two sets of flight tests are performed: aerodynamic and energy characterization.
The former aims at determining the lift-to-drag ratio for different airspeeds and the
latter to measure the propulsive and manoeuvring energy when performing a prescribed mission.
In the aerodynamic testing, in-flight evaluation of the RPAS fitted with the VSW demonstrates
full flight capability and shows improvements produced by the VSW over a conventional fixed
wing for speeds above 19 m/s. At low speeds, the original wing has slightly better lift-to-drag
ratio than the VSW. Contrarily, at 30 m/s, the VSW in minimum span configuration is 35% better
than the original fixed wing. In the other performed test, it is concluded that the VSW fitted
RPAS has less overall energy consumption despite the increased vehicle weight. The energy
reduction occurs only in the high speed condition but it is so marked that it offsets the increase
in energy during takeoff, climb and loiter phases.
Following the work on the first VSW prototype, a new telescopic wing that allows the
integration of other morphing strategies is developed, within the CHANGE EU project. The wing
adopted span change, leading and trailing edge camber changes. A modular design philosophy,
based on a wing-box like structure, is implemented, such that the individual systems can be
separately developed and then integrated. The structure is sized for strength and stiffness
using FEM, based on flight loads derived from the mission requirements. A partial span, fullsized
cross-section prototype is built to validate the structural performance and the actuation mechanism capability and durability. The wing is built using composite materials and an electromechanical
actuation system with an oil filled nylon rack and pinion is developed to actuate it.
The structural static testing shows similar trends when compared with numerical predictions.
The actuation mechanism is characterized in terms of actuation speed and specific energy consumption
and it was concluded that it functioned within its designed specifications. A full-scale
prototype is later built by the consortium and the leading and trailing edge concepts from the
different partners integrated in a single wing. Wind tunnel tests confirmed that the wing can
withstand the aerodynamic loading. Flight tests are performed by TEKEVER, showing that the
modular concept works reliably.
From the previous works, it is inferred that morphing concepts are promising and feasible
methodologies but present an undesired mass increase due to their inherent complexity. On
the other hand, mass prediction methods to aid the design of morphing wings at the conceptual
design phase are rare. Therefore, a mass model of a VSW with a trailing edge device is proposed.
The structural mass prediction is based on a parametric study. A minimum mass optimization
problem with stiffness and strength constraints is implemented and solved, being the design
variables structural thicknesses and widths, using a parametric FEM of the wing. The study is
done for a conventional fixed wing and the VSW, which are then combined to ascertain the VSW
mass increment, i.e., the mass penalization of the adopted morphing concept. Polynomials are
found to produce good approximations of the wing mass. Additionally, the effects of various
VSW design parameters in the structural mass are discussed. On one hand, it was found that the
span and chord have the highest impact in the wing mass. On the other hand, the VSW to fixed
wing ratio proved that the influence of span variation ratio in the wing mass is not trivial. It
is found that the mass increase does not grow proportionally with span variation ratio increase
and that for each combination of span and chord, exists a span variation ratio that minimizes
the mass penalty. Using the VSW to fixed wing ratio function, the mass model is derived. To
ascertain its accuracy, a case study is performed, which demonstrated prediction errors below
10%. Although the mass model results are encouraging, more case studies are necessary to prove
its applicability over a wide range of VSWs.
The work performed successfully demonstrated that VSW concepts can achieve considerable
geometry changes which, in turn, translate into considerable aerodynamic gains, despite
the increased weight. They influence all aspects of the wing design, from the structural side to
the actuation mechanisms. The parametric study summarizes the mass penalties of such concepts,
being successful at demonstrating that the mass penalty is not straightforward and that a
careful selection of span, chord and variable-span ratio can minimize the mass increase.Nos últimos anos, o desenvolvimento de asas adaptativas tem sido alvo de um grande interesse
por parte da comunidade científica. Nesta tese explora-se o desenvolvimento, análise,
construção e integração de dois novos conceitos de Asas de Envergadura Variável (VSWs) funcionais
a serem aplicados em Sistemas de Aeronaves Pilotadas Remotamente (RPASs). Estudos
adicionais são levados a cabo para sintetizar a massa desses conceitos e desenvolver modelos
de previsão de massa.
O conceito da VSW é constituído por uma parte interna retangular fixa, Asa Fixa Interna
(IFW), e por uma parte externa retangular móvel, Asa Móvel Externa (OMW). Um código de
otimização aerodinâmica é utilizado para minimizar a resistência ao avanço, determinando os
valores ótimos de envergadura para várias velocidades de voo do veículo. Concluiu-se que, a
baixas velocidades, a asa original apresenta um desempenho ligeiramente melhor que a VSW,
enquanto que a velocidades superiores a 25 m/s, a VSW apresenta um desempenho melhor
devido à redução da área das asas e, consequentemente, à redução da resistência total das
asas. Para levar a cabo um estudo estrutural, foi desenvolvido um Modelo de Elementos Finitos
(FEM) estrutural da VSW, no qual se modelou a interface entre a IFW/OMW. As deflexões e
tensões resultantes dos carregamentos aerodinâmicos estáticos mostraram que a asa é capaz de
suportar as cargas em voo. A velocidade de flutter é também investigada, sendo o FEM utilizado
para calcular as formas dos modos de vibração da VSW e respetivas frequências de vibração livre.
Considerou-se uma interface colada ou flexível, confirmando-se que o efeito da perda de rigidez
na interface IFW/OMW, tem um impacto negativo sobre a velocidade de flutter.
Um protótipo da VSW é construído, utilizando materiais compósitos, e um sistema de atuação
eletromecânico é desenvolvido usando um sistema de pinhão e cremalheira movido por
dois servomotores. Os testes de bancada, realizados para avaliar a asa e o mecanismo de atuação,
mostraram que o sistema é capaz de realizar a extensão/retração da asa, sendo adequado
para ser instalado num RPAS. Este RPAS foi modificado e instrumentado para servir de banco de
ensaio para avaliação do protótipo em voo. São realizados dois conjuntos de testes de voo: caracterização
aerodinâmica e energética. O primeiro incide na determinação da razão de planeio
para diferentes velocidades e o segundo é levado a cabo para determinar a energia propulsiva
e de manobra ao executar uma missão típica. Nos testes aerodinâmicos ficou comprovado que
o RPAS equipado com a VSW é capaz de uma normal operação e ainda que mostra melhorias
sobre uma asa fixa convencional para velocidades acima de 19 m/s. A velocidades mais reduzidas,
a asa original tem um desempenho ligeiramente melhor do que a VSW. Por outro lado, a
30 m/s, a VSW na configuração de envergadura mínima é 35% melhor do que a asa fixa original.
No outro ensaio realizado, conclui-se que o RPAS de envergadura variável tem menos consumo
de energia global, apesar do aumento de peso do veículo. A redução de energia ocorre apenas
na fase de cruzeiro de alta velocidade, mas foi tão acentuada que compensou o aumento da
energia durante as fases de descolagem, subida e espera.
Na sequência do trabalho anterior e no âmbito do projeto europeu CHANGE, é desenvolvida
uma nova VSW que permite a integração de outras estratégias adaptativas. A nova
asa adotou a mudança de envergadura, e a mudança de curvatura nos bordos de ataque e de
fuga. Esta adotou uma filosofia de projeto modular, baseada numa caixa de torção, permitindo
o desenvolvimento das diferentes tecnologias adaptativas separadamente. A estrutura é divmensionada para resistência e rigidez usando FEM, com base em cargas de voo derivadas dos
requisitos da missão. Um primeiro protótipo é construído para validar o desempenho estrutural
e a funcionalidade do mecanismo de atuação. A asa é construída usando materiais compósitos e
utiliza um sistema de pinhão e cremalheira e um servomotor, para variar a envergadura. Testes
estruturais estáticos mostram que as deflexões corroboram as previsões numéricas. O mecanismo
de atuação é caracterizado em termos de velocidade de atuação e consumo de energia
específica, concluindo-se que funciona dentro do previsto. O segundo protótipo é construído
pelo consórcio e os conceitos de bordo de ataque e de fuga são integrados. Testes em túnel de
vento confirmaram que a asa suporta o carregamento aerodinâmico. Os testes de voo, realizados
pela TEKEVER, mostram que o conceito modular funciona de forma fiável.
Baseado nos trabalhos anteriores, conclui-se que os conceitos adaptativos são promissores
e viáveis, mas apresentam um aumento de massa indesejável devido à sua inerente complexidade.
Por outro lado, os métodos de previsão de massa para auxiliar o projeto de asas adaptativas
na fase de projeto conceitual são raros. Deste modo, um modelo de massa da VSW com um
dispositivo de borda de fuga é proposto. A previsão de massa estrutural é baseada num estudo
paramétrico. Um problema de minimização de massa com constrangimentos de rigidez e resistência
é implementado e resolvido, sendo as variáveis de projeto espessuras e larguras estruturais.
Para o levar a cabo, um FEM paramétrico da VSW é desenvolvido. O estudo é feito para
uma asa fixa convencional e para a VSW, os quais são combinados para determinar o incremento
de massa da VSW. Aproximações polinomiais das massas da asa são produzidas, mostrando serem
capazes de produzir uma adequada representação. Adicionalmente, são discutidos os efeitos
dos vários parâmetros de design da VSW na massa estrutural. Por um lado, verificou-se que a
envergadura e a corda têm o maior impacto na massa da asa. Por outro lado, a razão de massas
da VSW e da asa fixa provou que a influência da razão de variação de envergadura na massa das
asas não é trivial. Verifica-se que o aumento de massa não cresce proporcionalmente com o
aumento da razão de variação de envergadura e que para um dado conjunto de envergadura e
corda existe uma razão de variação de envergadura que minimiza o aumento de massa. O modelo
de massa é derivado usando a aproximação polinomial da razão da VSW com a asa fixa. Para
verificar a precisão do modelo, é realizado um caso de estudo que demonstrou erros de previsão
abaixo dos 10%. Embora os resultados do modelo de massa sejam encorajadores, mais casos de
estudo são necessários para provar a sua aplicabilidade a uma ampla gama de VSW.
O trabalho realizado demonstrou com sucesso que os conceitos de VSW podem alcançar
consideráveis mudanças de geometria, que se traduzem em ganhos aerodinâmicos consideráveis,
apesar do aumento de peso. Estes influenciam todos os aspetos do projeto da asa, desde a parte
estrutural até aos mecanismos de atuação. O estudo paramétrico tentou resumir a penalização
de massa de tais conceitos, sendo bem sucedido em demonstrar que esta penalização não é
simples e que uma seleção cuidadosa de envergadura, corda e razão de variação de envergadura
pode minimizar o aumento de peso.This thesis and the associated research was partially funded by the European Community’s
Seventh Framework Programme (FP7) under the Grant Agreement 314139
Control system development for autonomous soaring
Thermal and dynamic soaring are two techniques commonly used by birds to extract energy from the atmosphere. This enables them to reduce, energy used during flight and increases their endurance. The thermal soaring technique involves extraction of energy from thermal updrafts and in dynamic soaring energy is extracted from wind shear. These techniques are investigated in this thesis using point mass and non-linear 6DoF models of an unmanned powered sailplane. The key challenges of autonomous thermal soaring are the ability to identify remote thermal activity using on-board sensors and to position correctly in a thermal. In dynamic soaring, a real-time fuel saving trajectory generation technique along with a trajectory following control system is needed. A hand held IR camera was used to assess the feasibility to observe hot spots associated with thermals. The thermal positioning capability was demonstrated in a 6DoF model using a positioning algorithm. The inverse Dynamics Virtual Domain (IDVD) technique was used to generate real-time trajectories for dynamic soaring applications using a point mass model of a powered unmanned sailplane and the fuel saving trajectories were validated using a high fidelity 6DoF model and a classical controller. An important outcome of the research is the fact that energy saved during dynamic soaring flight was also realized due to a sinusoidal manoeuvre using reduced thrust. In this manoeuvre the kinetic energy is converted into potential energy by gaining altitude and by reducing airspeed. Then initial values of altitude and speed are gained by loosing the altitude. In this process a horizontal distance is travelled by using reduced thrust.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Aeronautical engineering: A continuing bibliography with indexes (supplement 272)
This bibliography lists 719 reports, articles, and other documents introduced into the NASA scientific and technical information system in November, 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics
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