Demand For Aircraft Research Articles

Nonlinear adaptive control for high angle of attack flight

This paper presents a nonlinear methodology for the control of a high angle of attack aircraft, in particular, a modified F-18 aircraft. As a modern combat aircraft demands better maneuverability and performance over domains which include high angles of attack, research in high angle of attack is presently at an advanced stage. An adaptive controller is developed to maneuver an aircraft at a high angle of attack even if the aircraft is required to fly over a highly nonlinear flight regime. The adaptive, controller presented in this paper is based on nonlinear prediction models, and can be constructed to minimize the given cost function or the difference of a described Lyapunov function with respect to the control input at each step. A controller uses system identification parameters to calculate a command signal so that the output of system follows the reference trajectory. The control is calculated to let system follow the reference trajectory under some constraints. This paper shows that nonlinear adaptive control can be utilized effectively to control high performance aircraft such as the F-18 aircraft for rapid maneuvers with large changes in angle of attack.

Integration of high bypass ratio engines on modern transonic wings for regional aircraft

AbstractChanging airline scenarios and aggravated congestion have led to an increasing demand for new regional aircraft which will cover ranges of more than 1500 nm and accommodate 80 to 130 passengers. These far exceed the capability of today's commuter types. In the required thrust range of 15-5-20 klb only a very limited number of older engines with high SFC is available. Recently the manufacturers have begun offering new turbofans based on modern core technology and internal mixing (long duct) with lower SFC.The underwing turbofan installation aspects are well understood from earlier wide and narrowbody aircraft but installing a long-duct nacelle on such a small aircraft means a significant increase in interference problems which may lead to close coupling and new methods for minimisation of the mutual interference.After a survey of installation problems on previous jet transports up to the Airbus family the state of the art of experimental and theoretical methods for interference analysis is discussed. By means of an inverse design method a local lofting change on a given wing design confined to 20% span area was derived in order to sustain the isobar pattern of the clean wing with the pod/pylon on.The design modification was checked by means of a 3D-Euler code and verified on a large half-model in the NLR-HST wind tunnel. From the analysis of the resulting conclusions concerning the feasibility of such a lofting change, further improvements are made.

Separation of ownership from control and the demand for corporate aircraft

Evidence is offered on the relationship between separation of ownership from control and management's profit-maximizing behavior. Various regression models, built around managerial equity holdings, are specified to capture management's consumption behavior via the ownership of executive aircraft. These aircraft are widely perceived as being the ultimate in managerial perquisites. The results indicate that both the probability of possessing a corporate executive fleet and the value of existing fleets decline as managerial equity holdings increase. These findings are consistent with the convergence of interests hypothesis, wherein managerial equity holdings strengthen the incentives for managers to maximize profit.

Landing Gear—the Aircraft Requirement

The trends of major landing gear design parameters are presented reflecting the developments in aircraft performance over the last two decades. These trends illustrate the likely requirements for the future and identify the differences between civil and military landing gears. The aircraft manufacturer will inevitably demand a lower mass landing gear, increased service life and lower support costs of the product, the latter now becoming increasingly important. The method of achieving lower support costs, known as integrated logistic support, is summarized, highlighting the relevance to landing gear design. A number of likely changes required to meet future aircraft demands are discussed and how they will test the innovation and ingenuity of the landing gear designer. Key areas include, (a) stringent turn-round requirements demanded by aircraft operators, (b) computer control of actuation, nose wheel steering and wheel brake control systems and (c) the advent of advanced suspension systems, particularly for military STOVL and repaired runway operations.

Takeoff and landing in a downburst

Investigations into landing and takeoff in a downburst are made with a simple wind model based on the flow toward a flat plate. Approaches along a given nominal glide path are analyzed. The influence of the changing wind on the aircraft's demand for energy is calculated. The results are given in energy height errors. Computer simulations of an aircraft with fixed controls show the well-known flight-path pattern of accidents in manual flight. As far as the demand for energy is concerned, approaching through a downburst is not a problem. This can be pointed out by computer simulations with a modern autopilot and autothrottle control system. The energy situation of an aircraft in a downburst is more dangerous for takeoff than for landing. Heavy thunderstorms can produce wind conditions under which a takeoff is not possible. Gentle downbursts can be crossed by a simple escape maneuver. The acquired knowledge of landing and takeoff in a downburst contains some important aspects for the go-around.

The Naval Aircraft Factory, the American Aviation Industry, and Government Competition, 1919–1928

The economics of the American aircraft manufacturing industry have been determined in large measure by government aviation policies and the market for military airplanes. This was most apparent in the 1920s, when the industry suffered from sharply reduced military orders and an almost nonexistent demand for civilian aircraft. Struggling for survival, manufacturers singled out the Naval Aircraft Factory, a large navy-owned and run facility in Philadelphia, as at least partially responsible for the dislocation of their industry; they insisted that it and other forms of “government competition” be eliminated. Professor Trimble explores in this article how the ensuing controversy caused naval and civilian officials in the 1920s to develop policies that integrated the factory into naval aircraft procurement and helped to ameliorate the problems of private aircraft contractors.

The future world demand for civil aircraft

In 1972 civil sales formed some 30% of the US aerospace industry. Although in 1973 there was a swing back to defence products, civil sales retain an important position. Not surprisingly, aerospace industries without sizeable civil projects on hand, such as Britain's and Canada's, are looking with concern at their future prospects.Such increasing dependence brings its own problems, for civil sales have been characterised by large fluctuations in the past. Predictions have often been wrong and costly, yet accuracy is a prerequisite of the industry's steady development. The heavy research and development and expenditure involved in a major civil programme necessitates a forecasting horizon of up to a decade.

The Potential and Development of a V/S.T.O.L. Inter‐city Airliner

IN a previous article (Ref. 1, 1966), Chichester‐Miles of H.S.A. discussed some of the advantages and opportunities offered by the use of V.T.O.L. aircraft in short haul air transport. In a more recent article (Ref. 2, 1969), Boorer and Davey of B.A.C. reviewed the characteristics and some of the operational problems of V/S.T.O.L. aircraft, and argued in favour of initial civil S.T.O.L. aircraft leading to V.T.O.L. developments as an effective part of the overall ground and air transport system of the 1970s, on the basis of a foreseeable market demand for such aircraft at ranges between 50 and 300 miles. Quoting from their conclusions: ‘S.T.O.L. commercial operations appear therefore to be just around the corner. V.T.O.L. commercial operations may be a decade or so away but, as and when a S.T.O.L. inter‐city transport system develops, the improvement of S.T.O.L. performance toward V.T.O.L. may well become attractive and perhaps even necessary.’

Demand for intercity passenger transportation by VTOL aircraft.

Aircraft demand and cost functions were estimated for six types of VTOL aircraft. From these functions total aircraft profit or loss as a function of the number of aircraft produced was calculated.

The Interaction of Demand and Supply

In the Introduction to the second paper in this series (September 1965 IOURNAL), a simple flow diagram illustrates the relationship between demand and supply for aircraft and air transport which is shown in Fig. 1.Manufacturers supply airlines with aircraft from which a fleet is built. The airlines are thus faced with problems of capital investment and procurement programmes, which were discussed under the heading of fixed costs in the second paper.The discussion of problems of fleet effectiveness and optimal utilisation begun in the second paper, and elaborated in the third (October 1965 JOURNAL), is continued in Section A of the present one.Attention is then switched in Section B to the demand for air transport. On the basis of demand for transport of passengers and freight, airlines must determine routes, allocate frequencies to these routes, and prepare time-tables.The paper concludes the discussion of Operational Research applied to airlines by summarising the models used in the series in the light of the aims specified in the first paper (August .1965 JOURNAL).

The Demand for Aircraft and the Aircraft Industry, 1907–1958

The invention of the airplane by Wilbur and Orville Wright in 1903 marked the beginning of an industry which has grown to be the largest single manufacturing employer in the United States. Once the airplane was invented, there was wide-spread expectation that producing aircraft would be a very profitable business.

Problems and Progress in Aircraft Design

IF variety is the spice of life, then aircraft engineers have little to complain of in their experience of the last twenty years. It is true that most of the hopes of a sane world, with which we set out after the first war—a world in which aircraft would be a powerful influence for good —were wearing a bit thin in 1929. It was becoming clear that only the few could afford to fly. There was little prospect of a demand for aircraft as private or public transport vehicles on a scale which would provide a healthy basis for a free competitive industry. Possibly the most surprising phenomenon of those times of depression was the survival of so many aircraft concerns. In the succeeding years—Mr Churchill's ‘locust years’ 1931–35—darkened by the shadow of coming catastrophe, the meagre defence requirements provided a means of existence. Research, fostered by a few brave spirits, not only lived but made notable strides. Above all, the creative genius of engineers contrived to find means of producing the vital advances upon which, from 1936 onwards, rearmament in the air was founded.

The Aviation Psychologist

AERONAUTICAL psychology has been haphazardly applied in the past, but the increased complexity of modern aircraft demands a scientific approach to the problems. Psychiatrists are mainly concerned with curing abnormal conditions of patients and are mostly drawn from the medical profession, but the psychologist has to apply his specialized knowledge to the normal person who is living and working under a given set of conditions whether it be piloting an aircraft or riveting the skin of the Brabazon I. Indeed, the person inserting rivets may have been ‘studied’ by a time and motion engineer who is in fact applying a part of the technique of the psychologist. Wherever the human being has to operate mechanical equipment there is scope for the psychologist to contribute towards increased efficiency.

Standardized Control Rods

MASS production methods in the construction of modern aircraft demand far‐reaching standardization of such component parts as can be used in various types of aeroplane. Such standardization has, for instance, been applied to the power plant control rods of the Ju 52 where a unified design of welded steel levers is found together with standardized shafts. That type of construction has given very satisfactory results on the whole though improvements have been made here and there to keep abreast of the general advance in aircraft design and of the development of fabricating methods. The standardized rigging thus evolved responds to practical requirements in that the number of parts has been reduced to a minimum so as to allow of a maximum of combinations and to cut down the number of spares to be kept in store. Such demands were chiefly made by the German Air Force since interchangeability of parts is, of course, a factor of primary importance to ensure simplification of supply services and ease of maintenance of the first line fleet in case of an emergency. Moreover, plain bearings for moving parts had proved unsatisfactory in service as they necessitated frequent inspection and lubrication. The only way out of that difficulty was to employ ball bearings through‐out to reduce friction to an absolute minimum and to eliminate lubrication altogether.

Carburation Practice in Aero‐Engines

THE progress in the practice of aero‐engine carburation up to the year 1914, and the improvement in performance which resulted have been briefly traced in the April issue. The Great War (1914–1918) created an unprecedented demand for aircraft for the special purposes of warfare, and it will be appreciated that this demand resulted in rapid development on certain lines dictated by the urgency of the situation.