CoA. Reports

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Open Access
Aircraft parameter identification using Matlab
(2000)
System identification techniques are routinely used in experimental stability and control studies throughout the aerospace industry. Over the years, various researchers at the College of Aeronautics have contributed to this field; most recently some of the latest methods have been employed to estimate the stability and control derivatives of a variety of aircraft types. Although the more recent investigations provide a useful insight into the capabilities and characteristics of several up-to-date methods, they have not resulted in tools which may be used on a routine basis. Consequently, the purpose of this report is to describe a set of procedures which are straightforward to apply, and produce reasonable solutions to the type of linear parameter identification problems which are often found in aerospace work. Recordings of the short period and phugoid modes from Handley-Page Jetstream G-NFLC are used throughout as examples. Firstly, those characteristics of the aircraft’s instrumentation system which influence the quality of the signals - sample rate, antialiasing filters, time delays - are considered. This information is used in conjunction with standard signal processing techniques to ensure that the data is of sufficient quality to be used in the parameter estimation process. Next, a basic Fourier analysis and a least squares algorithm are employed to produce non- parametric and parametric models respectively. The results thus obtained are comparable to those generated using more sophisticated techniques. In conclusion, standard signal processing methods combined with relatively simple estimation theory offer an adequate solution to the linear parameter estimation problem.
Open Access
An analysis of the flight dynamics of a second generation SST aircraft
(1999) Steer, Anthony J.
This interim report covers an initial overview of delta-wing aircraft static, dynamic and control characteristics, collated from publications within the public domain and the authors related research. This is to give the reader an overall understanding how a delta-winged supersonic transport aircraft’ s characteristics differ to those of a conventional civil transport aircraft. This is followed by identifying the aircraft’s static and dynamic stability, with the effect of speed and CG location on the aircraft dynamic modes specifically addressed. Following this, a comprehensive investigation and analysis of the open loop response of a SCT baseline aircraft, in both low-speed cruise and approach and landing conditions, has been carried out. Both time and frequency domain techniques have been utilised. Finally, conclusions are made based on the results of the work presented.
Open Access
The application of a C* flight control law to large civil transport aircraft
(1993) Field, Edmund
The work contained in this report is part of an on-going programme of research into handling qualities of fly-by-wire civil transport aircraft currently being undertaken within the Flight Dynamics Group of the College of Aeronautics . Although much work has been undertaken into handling qualities of military aircraft over the last 30 years, civil aircraft have received considerably less attention. Over the last decade civil transport aircraft incorporating fly-by-wire flight control systems have been introduced into commercial operation, the latest including some modified aerodynamic designs. However the civil arena lacks the supporting research into handling qualities that the military side has enjoyed. More recently the civil side is beginning to receive the attention it deserves with work in Europe by Fokker and the Group for Aeronautical Research and Technology in EURope (GARTEUR), for example. In the United States much work has been done by the manufacturers such as Boeing and McDonnell Douglas, and as ever work supported by the US Air Force and NASA. The primary aim of this current programme is to design flight control laws to give fly-by-wire civil transport aircraft excellent flying qualities at all flight conditions, but especially in piloted flight phases. The most critical flight phase of a civil transport is that of the landing approach, and, as with other studies of this type, this phase receives the greatest attention in this study. This report concerns an analysis of the C* parameter. The C* criterion was one of the first handling qualities criteria designed to take account of advanced aerodynamic designs of modern aircraft and higher order systems introduced by flight control systems. Several aircraft have since employed control laws based around the C* parameter. A proportional feedback C* controller was applied to a Boeing 747-100 in landing approach configuration, and assessed against the C* criterion and the US military specification MIL-STD- 1797A.
Open Access
The applications of computational fluid dynamics to problems in rotorcraft aerodynamics:
(1995) Shaw, Scott
The flowfield around a helicopter rotor in forward flight is intrinsically unsteady and contains many complex interacting flow phenomena. As a consequence experimental investigations are difficult to perform, difficult to interpret and costly. There is a clear need for reliable computational methods whose uncertainties are less than those of experiment. In this paper computational methods currently available for the solution of problems in rotor aerodynamics are examined and the current direction of research in this field identified.
Open Access
An approximate method for estimating the lifting characteristics of thin bodies of non-circular cross-section
(Cranfield Institute of Technology; College of Aeronautics, 1990) Christopher, P. A. T.
Open Access
Arbitrary-order high resolution schemes for model hyperbolic conservation laws
(1992) Shi, Jian
This report investigates the general theory and methodology of high resolution numerical schemes for one-dimensional hyperbolic conservation laws. The Universal Formula from which 2-level explicit conservative arbitrary-order numerical methods can be derived is developed. This report also explores the issue of linear stability. A new approach to linear stability analysis is presented. The generalized formulation for TVD methods with stable region of -1 ≤ c ≤ 1 proposed. To demonstrate the theories, some third order and fourth order TVD methods are generated.
Open Access
Arbitrary-order numerical schemes for linear hyperbolic systems
(1992) Shi, Jian
This report is an extension of the work carried out in [16]. In [16] we defined arbitrary-order numerical methods for model scalar hyperbolic equation. In this report we extended these methods to linear hyperbolic systems where waves can propagate in both directions. First, we define a generalized numerical formula which can accommodate arbitrary wave speeds for scalar advection equation. Then to illustrate its application, we derive three, four, and five point generalization numerical schemes. Finally, according to the theory of linear systems, we extend the generalized schemes to linear hyperbolic systems in a straight forward manner.
Open Access
Arbitrary-order numerical schemes for model parabolic equation
(1992) Shi, Jian
This report investigates the general theory and methodology of high order numerical schemes for one-dimensional model parabolic equation. The Universal Formula from which a 2-level explicit arbitrary-order numerical methods for diffusion equation can be derived is developed. Using the Universal Formula some high order numerical methods are constructed. Some important features of numerical methods are revealed through the construction of high order numerical methods and stability analysis. Subject to the limitation of diffusion number, d, being positive, only the method that satisfies positive stable region is relevant.
Open Access
ASTOVL combat aircraft design synthesis and optimization
(1992) Kehayas, N.
This report presents the development of a Baseline Configuration for an Advanced Short Take-Off and Vertical Landing (ASTOVL) Combat Aircraft, the Design Synthesis and coding of this Baseline Configuration (Code VERTI), the interfacing of the Design Synthesis Code VERTI with the Optimizer code RQPMIN and the optimization of the Baseline Configuration. The background and the objectives of this Research Programme are initially examined. The evaluation of the ASTOVL Combat Aircraft Baseline Configuration is then described, including all the problems, assumptions, choices and compromises that led to the specific configuration. The development of the Design Synthesis and the Code VERTI then follow, where the methodology used, the techniques adopted and the code operation are explained. A full description of the Design Synthesis is included as an appendix. Finally, the interfacing of Code VERTI with the optimizer RQPMIN and the optimization of the Baseline Configuration are presented. The problems and difficulties of the RQPMIN operation are thoroughly discussed. The RQPMIN- VERTI code is used to optimize the initial Baseline Configuration and an optimization example is provided in appendix form. The optimized Baseline Configuration is partly validated against two ASTOVL combat aircraft designs. In addition to the optimization with the aircraft empty mass as objective function, a search for a better objective function is attempted.
Open Access
A beginners guide to literature in the field of aeroelasticity
(1997) Battoo, R. S.
This document is meant primarily for students (or readers) who may not be familiar with the field of aeroelasticity. The main objective of this paper is to point the reader to some important texts and papers that have been published in the areas which embrace aeroelasticity, using which the reader may gain sufficient knowledge about the subject to make informed decisions. It is hoped that by drawing the readers attention to these salient papers the more interested readers will be able to increase their knowledge on many aspects related to aeroelasticity. This paper is not meant to be exhaustive, rather it is meant to be a preliminary exposition which will assist readers in locating/selecting other relevant references or texts. This paper does not attempt to be an expert guide nor direct the reader to publications in a specific area. What it does attempt to do is hopefully generate interest and illuminate areas related to the field of aeroelasticity which readers can explore to their desire. A modestly comprehensive list of references is included, however it must be emphasized that there are a very extensive number of papers published each year, in all related fields of aeroelasticity. Inclusion of all these would not be appropriate in a paper of this kind. Never-the-less the more interested reader will find sufficient information to utilize the given citations for locating further material.
Open Access
Cardiovascular and subjective measures of task demand in a low workload monitoring task : summary report
(Cranfield Institute of Technology; College of Aeronautics, 1987) Braby, Carole D.
Open Access
Comparison if the convergence behaviour of three linear solvers for large, sparse unsymmetric matrices
(1995) Shaw, Scott
Implicit methods for the calculation of unsteady flows require the solution of large, sparse non-symmetric systems of linear equations. The size of such systems makes their solution by direct methods impractical and consequently iterative techniques are often used. A popular class of such methods are those based upon the conjugate gradient method. In this paper we examine three such methods, CGS, restarted GMRES and restarted GMRESR and compare their convergence properties.
Open Access
Comparison of the time vector method and the state-space method (Eigenvector analysis) for aircraft parameter identification
(1996) Baek, Y.
Many methods for aircraft parameter identification have been developed and are currently in use. Prior to the development of computer methods the graphical Time Vector Method (TVM) was introduced during 1950’s (ref.1,2). Basically the TVM is based on the mechanical vibration theory. When the aircraft responses have oscillatory modes they can be considered as vibrations even though the typical frequency of these may be higher than those of the mechanical vibrations. Because of the graphical approach, the TVM may produce inaccurate results. But it gives use thorough understanding of the physical system. Owing to the rapid development of computers and sophisticated parameter identification algorithms, the rather limited graphical method has fallen into disuse and the other have emerged to replace it. They are, typically, the output error methods, the equation error methods, the Kalman filter estimator, the maximum likelihood technique, and so on (ref. 3~6). The damping angle, natural frequency, relative magnitude and phase angle of each dynamic mode are the basis of the TVM. In this respect the state-space models can provide the same information. In particular the eigenvalues and eigenvectors which involve all the response information of the system, have the same properties as the time vectors. So, the objective of this report is to shown the relationship between the TVM and the state-space method of an analysis and hence to facilitate the state-space method (eigenvector analysis) for aircraft parameter identification.
Open Access
Compressible Flow Produced by Distributed Sources of Mass: An Exact Solution
(Aerodynamics, Cranfield Institute of Technology, 1987-07) Clarke, J. F.
The paper considers the case of a one-dimensional isentropic unsteady compressible flow that is driven entirely by a distribution of sources in the left-hand half space of an unbounded domain. The right-hand half-space contains no sources, so that source-strength drops discontinuously to zero as one crosses from left to right-hand space. Exact solutions are obtained for those parts of the flow that remain isentropic.
Open Access
Computer-aided conceptual aircraft design (CACAD) for transport aircraft
(1996) Vaziry-Zanjany , Mohammad Ali (F)
CACAD is capable to optimise the size, and configurations of turbofab-powered transport aircraft. The synthesis sizes aircraft from the low-capacity short range Fokker F-100 class to the long range medium-capacity Airbus A-340 class. It has an optimisation capability, with the objective function being direct operating cost in which, maintenance costs is extensively sub-divided according to ATA chapters. The objective of this report is to present the listing, the user's guide on how to run the program, as well as the description of the formulation used within the program. There are flow charts, table of nomenclatures included in this report. The floppy disc that contains the programme listings will be made available on request from the office of Department of Aerospace Technology, College of Aeronautics, Cranfield University, Cranfield, Bedford, UK, MK43 0AL
Open Access
Control jet-slender body performance characteristics at hypersonic speeds
(1995) Kontis, Konstantinos
The jet control effectiveness of a 5 deg semi-angle cone has been tested at hypersonic speeds. The study has been carried out in the Cranfield hypersonic gun tunnel facility at a Mach number of 8.2, and a Reynolds number based on base diameter of 3.788 x 10(5). Under those conditions, the initial boundary layer in the absence of the jet was laminar. The jet was injected normal to the cone surface at sonic speed. Both sharp and blunted cones were used. The Jet/flowfield interaction, including boundary-layer separation and its influence upon aerodynamic coefficients was determined. Pressure and force measurements were made in the incidence range of -15 deg to 15 deg. The forces were measured with a 3-component balance equipped with semi-conductor strain gauges. The flow structure was studied using high speed schlieren photography. Jet penetration distances have been compared with theoretical estimates.
Open Access
Cranfield situation awareness scale: Users Manual
(1997) Dennehy, K
Training to enhance situation awareness depends upon having satisfactory quantitative methods for measuring situation awareness. Until the development of the Cranfield-SAS, there was no direct subjective rating scale to measure the situation awareness of student (ab initio) civil pilots (see appendix 4 for an overview of the measurement guidelines for an overview of the measurement guidelines for scale development). The development of the scale was part requirement for a Ph.D. at Cranfield University. The benefits of such a technique is that a pilot’s progress in developing the skills necessary for situation awareness can be monitored. Instructors specifically can enhance the situation awareness of ab initio civil pilots in terms of: • Workload • Decision making • Design and Performance • Training The “Cranfield-Situation Awareness Scale (SAS)” is based on pilot actions and knowledge that the aviation community considered important to maintaining situation awareness. In general situation awareness refers to pilots knowledge and understanding of the situation in relation to the requirements of the flight task. The “Cranfield-SAS” is a subjective assessment technique and was developed as either an observer-rating (i.e. by instructors) or as a self-rating (i.e. by student pilots) during different predefined flight tasks (see appendix 3 for overview of observer/self-ratings). It is intended that this technique should ultimately be used during flight, flight simulation, or in the debriefing session. This users manual outlines how to use the Cranfield-SAS and has been distributed to instructors at flight schools (i.e. Great Britain and Canada) and to a major airline. The scale remains ownership of Cranfield University buy may be photo-copied (or requests for additional copies) and used freely by both instructors and students (for self-evaluation). As the scale is still under evaluation, we would request that the registration form (presented on a green page in the last page of the manual) be returned to: Dr. C.D. Deighton at the Applied Psychology Unit, Cranfield University. A short questionnaire will then be sent to you to obtain your comments on the structure and content of the scale.
Open Access
Descriptions of Cranfield Aircraft Group design projects (1979-96)
(1996) Fielding, J. P.
This report is a compilation of reprints of papers and articles describing the aircraft design group projects for the period between 1979 to 1996. In Crdeld projects, each student takes responsibility for part of the design of a project aircraft, which is used as a design case study for the whole group of students of the course. This teamwork exercise, with specified individual tasks, is organised on the lines of a project as carried out in industry. It is undertaken over eight months, in parallel with the lectures and individual research studies. It is assisted by displays of aircraft components and manufacturing processes, and field visits are made to aircraft manufacturers and operators. The nature of the course and the future occupations of the students, give guidance to the choice of subject aircraft. The aim is to ensure industrial relevance, but also to include a significant research element in each project. The size of the course usually precludes the design of light aircraft. It is usual to alternate between civil and military aircraft, and each project has a unique configuration.
Open Access
The Design of Michell Optimum Structures
(Cranfield College of Aeronautics, 1960-12) Chan, A. S. L.
The fundamental problem of structural design is the determination of structures of minimum weight which safely equilibrate a given system of external forces. The classical theorem of Michell gave basic requirements for such a structure. The first part of this paper analyses the geometrical layout of two-dimensional structures which satisfy these requirements, making use of the analogy with the theory of plane plastic flow. Expressions for the calculation of sizes and the total volume of the structural members are developed. Method of graphical construction of the structural layout is also given.
Open Access
Design Synthesis for Canard-Delta Combat Aircraft (Optimization)
(Cranfield Institute of Technology; College of Aeronautics, 1988-10) Serghides, V. C.