Browsing by Author "Gautrey, Jim"
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Item Open Access The aircraft spin - a mathematical approach and comparison to flight test(American Institute of Aeronautics and Astronautics, 2017-06-09) Bennett, Christopher J.; Lawson, Nicholas J.; Gautrey, Jim; Cooke, AlastairA Scottish Aviation Bulldog light aircraft operated by the National Flying Laboratory Centre (NFLC) at Cran eld University, modi ed with research equipment including bre optic sensors for wing strain and fuselage pressure measurements, is used to investigate the dynamics of a fully developed spin. A theoretical model is developed to compare with existing ight test data. In particular, the frequency of the aircraft spin is analysed as a function of the mass distribution of the aircraft to determine the e ect of the fuel load. It is found that the spin frequency is minimally a ected by the fuel load since the moments of inertia corresponding to the engine, for example, are far more signi cant. However, it is con rmed that the yawing e ect of the propeller causes the aircraft to spin faster to the right than to the left.Item Open Access Flight control system architecture analysis and design for a fly-by-wire generic regional aircraft(1996) Gautrey, JimFly-by-wire systems are becoming increasingly common in civil transport aircraft due to the economic and technological benefits that this technology provides. These fly-by-wire systems are comprised of two major components; the flight control laws, which govern the aircraft’s handling characteristics, and the flight control system architecture, or the hardware, which is used to implement the control laws. This report will primarily consider the design of the flight control hardware, although control laws will be briefly examined for current civil fly-by-wire aircraft. The background to the architecture is presented, along with relevant issues such as processing distribution and the requirements for system synchronisation. The flight control systems for current civil aircraft are described in detail, and these systems are compared to detailed certification, maintenance and functional requirements. The findings of the analysis are used to propose a fly-by-wire flight control system architecture for a Generic Regional Aircraft. This architecture is not complex, only uses existing technology and meets the requirements previously determined. It has a capability for deferred maintenance sing it is shown that the aircraft can be dispatched with one flight control computer failed and still meet the mandatory reliability requirements defined by the national airworthiness authorities. Control laws are not proposed.Item Open Access Flying qualities and flight control system design for a fly-by-wire transport aircraft(Cranfield University, 1998-09) Gautrey, Jim; Cook, M. V.Fly-by-wire flight control systems are becoming more common in both civil and military aircraft. These systems give many benefits, but also present a new set of problems due to their increased complexity compared to conventional systems and the larger choice of options that they provide. The work presented here considers the application of fly-by-wire to a generic regional transport aircraft. The flying qualities criteria used for typical flying qualities evaluations are described briefly followed by analysis of several past transport aircraft flying qualities programmes against these criteria. From these results, some control law independent design requirements are formulated for a civil aircraft for the approach and landing task. These control law independent flying qualities criteria are intended to be used with any generic rate-like control law for a transport aircraft and enabled a number of different control laws to be designed. The results of a number of flying qualities evaluations are presented. Both an ILS approach task and a formation flying task were used. The effects of windshear were also considered. It was found that control laws which maintain flight path are suitable for the ILS approach task, while most rate-like response characteristics give good flying qualities for the formation flying task. Finally, the conclusions drawn from these evaluations are presented, and both the Civil and Military current airworthiness requirements are assessed. In addition to the flying qualities work, a study is made of the management issues associated with fly-by-wire design. A fly-by-wire aircraft design programme was proposed and the project management issues associated with this were considered. A timescale was proposed for the design process for a generic regional aircraft, and the critical path for this process is presented.Item Open Access Generic regional aircraft flying qualities for the approach and landing task(Cranfield University, 1997-08) Gautrey, JimMany changes have occurred in the past 20 years in aircraft manufacture and development. New technologies have appeared, spanning the entire aircraft design environment, such as new production methods, new materials and new avionics systems. These new methods have been developed for two reasons. For military aircraft, they have arisen through the need to improve performance. However, for civil aircraft they have arisen through the need to reduce the overall cost. This report considers one aspect of these technologies for civil aircraft: fly-by-wire. This technology uses electrical signalling in place of conventional heavy mechanical control runs. In addition, flyby- wire generally permits improvements to be made in aircraft flying and handling qualities. This requirement has originated from two main sources; a need to make improvements in the light of an increasing amount of experience, and a requirement to cope with aerodynamic modifications which have been implemented to improve aerodynamic efficiency, but which have a deleterious effect on the aircraft's flying and handling qualities. Both of these adverse effects have come about from a desire to reduce costs for the end aircraft user, i.e. the airlines. The aircraft used for these evaluations is a Generic Regional Aircraft, of about 100 seats and a weight of 90,000 lbs. Only a limited portion of the flight envelope was considered since these evaluations primarily concentrate on the approach and landing flight phase. These evaluations are being carried out as part of a joint Avro International Aerospace — Cranfield University Engineering Doctorate programme researching advanced flight control system design for a Generic Regional Aircraft. The overall aim of this programme is to produce a control law design which gives aircraft in question excellent handling qualities. The evaluations described here comprise the first in a series of three planned studies, and consider solely the approach and landing flight phase.Item Open Access Generic regional aircraft flying qualities for the windshear and formation flying tasks(1998) Gautrey, JimThis report describes a series of flying qualities investigations designed to look at flying qualities issues associated with fly-by-wire control laws for civil transport aircraft. It follows on from a previous study which considered flying qualities for the reconfiguration, approach and landing tasks. Issues raised during this previous study were followed up and design improvements made to the control laws in order t o improve them for this subsequent series of evaluations. Two different tasks are considered for this series of evaluations for the following reasons. Firstly, the control laws were only evaluated between airspeeds of 140 knots and 121 knots for the approach and then to approximately 115 knots in the flare during the previous set of evaluations. This obviously does not cover the entire aircraft airspeed range, but since the approach and landing task is generally accepted t o be the most critical task for a civil aircraft, it is deemed a suitable task for evaluating the control laws under consideration. However, civil aircraft manufacturers generally use other tasks for the evaluation of control laws since there is a requirement t o test the laws over the full flight envelope. For example, several different tasks were used for evaluation during the design of the Boeing 777, including a variety of approach tasks, en-route tasks, and in-flight tracking type tasks. A formation flying task was therefore proposed as a suitable task for evaluating control law performance at altitude for the generic regional aircraft. It was initially thought t o be a tight flight path control task, and this was quickly confirmed from a brief trial prior t o the main evaluations. In addition, this task is one which is the most demanding for a large military aircraft since it requires precision control of both flight path and airspeed. Finally, it is becoming more and more common to use modified civil aircraft in either the military transport or in-flight refuelling roles, with the Vickers VC-10 and Lockheed L-1101 being used as in-flight refuelling receivers and tankers and the Nimrod (Military Comet) as a receiver in the Royal Air Force alone. It was also decided t o consider atmospheric effects. Initially, it was proposed t o consider the effects of both windshear and turbulence, but evaluations in turbulent conditions were later dropped since its main effect is in the longitudinal (airspeed) axis, with effects in the longitudinal (pitch) axis being limited by the effects of the control laws. In addition it did not give repeatable results. However windshear, which here is taken to represent a decreasing headwind, is a flight path control problem since it causes an effective change in aircraft flight path angle, and it was found to be a much more suitable task.Item Open Access Undercarriage drag prediction for a fixed undercarriage light aircraft(AIAA, 2017-06-09) Bennett, Christopher J.; Gautrey, Jim; Lawson, Nicholas J.The following paper presents undercarriage drag predictions for a light aircraft with fixed landing gear. A Scottish Aviation Bulldog 120, operated by the National Flying Laboratory Centre (NFLC) at Cranfield University, is considered as the test case for this study. Taking advantage of a recently developed laser scanned model, computational fluid dynamics (CFD) techniques are exploited to investigate the undercarriage drag. Results via standard theoretical and empirical methods are compared to the CFD results. It is found that the established empirical methods matched the CFD predictions to within the stated error bands for moderate angles of attack. However, due to the aircraft flow field at higher angles of attack, some discrepancies in the level of drag predicted are observed. Further flight test data is recommended to confirm these findings