Automatic Flight Control Research Articles

Progress in the use of automatic flight controls in safety critical applications

High authority automatic flight control systems are now in wide use in both transport and combat aircraft. These have required the development of failure survival system architectures, and techniques in safety assessment to ensure that the risk of fatal accidents attributable to the automatic control aspect is acceptably remote.Most of the current systems are analogue in nature, and employ sufficient redundancy to survive at least one failure during operation. Future systems will employ quadruplex or triplex-monitored architectures, capable of surviving at least two failures, and will be mainly digital in concept. The design and safety assessment techniques developed for analogue systems have been adequate for current systems, but the new digital technology and more extensive use of systems in safety critical applications will demand further development of the various aspects involved.A major contribution to the design and safety assessment of safety critical systems was made during the past two decades in the programmes for the development of automatic landing for civil aircraft, culminating in the system in the Anglo-French Concorde.

The role of simulation in automatic flight control systems research

Of all the branches of engineering, we regard aeronautical engineering as that which most needs simulation as an essential element of its constitution. Not even by choice may an aeronautical engineer be unfamiliar with simulation, for its advantages in the phases of design, production, and operation of aircraft are recognised by every aeronautical organisation, and its effectiveness, either in producing acceptable answers to flight problems, or in demonstrating flight characteristics, is the authority by which academics can insist upon the inclusion of the elements of simulation in their syllabuses. It is our belief that simulation has come to occupy this central position mainly as a result of the fundamental problems of safe flight.

Characteristic frequency-gain design study of an automatic flight control system

Abstract Recent work on the application of complex variable theory to the analysis of linear multivariable systems has led to a design approach that integrates the multivariable frequency-response and root-locus techniques. A brief discussion of a two-stage design method that derives from this approach is first undertaken and its application to an automatic flight control system is then considered. The design starts with the introduction of an inner-loop compensator for which root-locus techniques are employed for the adjustment of closed-loop characteristic frequencies. This is then followed by an outer-loop gain injector design where frequency-response techniques are employed for the adjustment of open-loop characteristic gains. The overall scheme results in a controlled system whose response is fast, non-oscillatory, accurate in the steady state and largely non-overshooting and non-interactive.

Avionics

Sperry Flight Systems' TERN 100 automatic navigation system and the Sperry SPZ‐500 integrated automatic flight control system are now certified for operation in Lockheed‐731 Jet‐Star and JetStar II aircraft.

NASA-CR-2677 : D. E. Johnston, R. H. Klein and R. H. Hoh 1976. Manual and automatic flight control during severe turbulence penetration. (110 pages, 55 figures, 6 tables, 17 references)

NASA-CR-2677 : D. E. Johnston, R. H. Klein and R. H. Hoh 1976. Manual and automatic flight control during severe turbulence penetration. (110 pages, 55 figures, 6 tables, 17 references)

Power utilisation in electronic loads

Most civil and military aircraft developed over the past 10 to 15 years have relied upon increasingly complex avionic systems. Some units in this category have been developed to improve the presentation of information to the crew or to decrease their workloads; others have come to play a vital role in automatic flight control (such as fly-by-wire), so that it may not be possible to fly the aircraft without them (and indeed, in the case of ccv the aircraft may even be unstable without them); others again have been developed to give the crew better communication with each other and the outside world, and more detailed information from the radar system and its display. Figure 1 lists a breakdown of systems in a typical modern military aircraft in each of these categories: information and display, control, communications and radar.

Design of nonlinear automatic flight control systems

A method for the synthesis of nonlinear automatic flight control systems is developed, and the performance of a control system synthesized by use of this method is compared to the performance of control system designed by use of linear quadratic optimal control theory. Comparisons are made on the basis of aircraft dynamic response at high angles of attack. It is found that the nonlinear controller reduces the altitude loss during stall and increases the magnitude of the angle of attack for which the aircraft can recover from stall.

All-Weather Automatic Landing Concepts and Operations: Review of Aerospatiale Experience

This paper reviews Aerospatiale's experience and achievements in the field of all-weather automatic landing and describes the Automatic Flight Control Systems installed on the following aircraft: Caravelle, equipped with a fail-passive system; Airbus, equipped with a double-multiple -type, fail-operational system; and Concorde, equipped with a duplicated monitored-type fail-operational system. The certification conditions are discussed for each of these systems together with a brief description of their design principles and operational limits. Finally, the experience gained by the French domestic airline Air Inter in the field of low-visibility automatic landing with its Caravelles is detailed both as far as the means implemented and the results obtained are concerned.

Microwave Landing System Requirements for STOL Operations

The operational/functional requirements for the new Microwave Landing System (MLS) are examined for STOL operations. The study utilizes a nonlinear six-degree-of-freedom simulation of a De Havilland Buffalo C-8A aircraft and automatic flight control system to assess the MLS/STOL accuracy, coverage, and data rate requirements for the azimuth, DME, primary elevation, and flare elevation functions. The aircraft performance is statistically determined for representative curved flight paths through touchdown. A range of MLS errors and coverages, environmental disturbances, and navigation filtering are investigated. The study indicates that STOL applications do not place any unique requirements on the MLS.

Use of Fiber Optics in Digital Automatic Flight Control Systems

The availability of digital MSI and LSI has made digital flight control systems more cost effective than analog systems for all but the simplest systems. The organization of a digital flight control system is concerned not only with implementation of the control laws and associated logic but also with the management of the data used in these computations and the organization of the computation. The configuration taken by a digital flight control system is dominated by the integrity and data handling requirements. This paper considers the impact of these factors on the design and operation of digital flight control systems with particular emphasis on the use of fiber optics for transmission of data between lanes.

Digital Automatic Flight Control is the Answer - What is the Question?

Beginning with process controls in the mid fifties, digital control systems have seldom met all the claimed advantages and in many cases have been outright failures. Airborne digital computers have just begun to appear in the commercial jet transport market after several years of experimental and military development. The success of these systems in meeting user expectations has not been overwhelming, which leads to the question: Why change from known analog flight control technology to digital? This paper examines that question by reviewing the state of the art in analog flight control system technology and evaluating this against current airline problems. A realistic means of evaluating claimed advantages for new technology is thus established. The advertised solutions of digital technology to analog problems are examined and, in some cases, debunked. However, consideration of the real problems and the capabilities of digital systems leads to the conclusion that there is a real payoff. Evidence from background studies at Boeing is offered to support this conclusion. A description of the digital flight control system electronics (FCSE) development program for the new Boeing 7×7 airplane is also provided. This program is currently in progress, and its specific objective is to assure that the real payoff is achieved for the subsequent production system.

Digital Computation Makes AFCS More Reliable

In airline service the reliability of a system is more than the confirmed failures for the system; it is the total removal experience of the system. Thus, the reliability of a system lies not only in the piece part failure rates, but also in the capability to verify and isolate failures. The application of digital technology brings several significant reliability improvements to automatic flight control systems (AFCS) when compared to contemporary analog systems. These advantages are demonstrated by the experience of the digital air data computer (DADC) of the DC-10 and the digital AFCS of the JA-37 Viggen. Experience with this equipment is reviewed, and the results are interpreted in terms of projections for airline DAFCS reliability. The digital system built-in test implemented by a stored program and the central processor gives a system integrity and dispatch reliability unequaled by analog systems. This high-integrity self-test reduces removal rates by giving line personnel a trustworthy tool and more complete automatic test processes for verifying maintenance actions. Digital circuit technology is directly suitable to largescale integrated circuits (LSIC) which reduce piece part counts and improve LRU reliability. Digital circuits are less subject to drift and the attendant difficulty to detect failures. These factors, coupled with the inherent high-integrity self-test, provide the basis for a significant improvement in reliability by the use of a digital automatic flight control system.

Architecture Considerations for Digital Automatic Flight Control Systems

Functional partitioning, redundancy structure, internal communications, and software modularization define the architecture of a digital automatic flight control system (DAFCS). Selection of a suitable system architecture for commercial transports involves such factors as the functional scope, growth provision and flexibility requirements, sensor interfaces, the aircraft's actuator and control surface redundancy, and the dispatch reliability requirements. Trade-offs concerning these various factors are discussed, and it is shown that a very versatile and almost universal DAFCS can be configured to meet the general and peculiar needs associated with each aircraft application. Specific results associated with this system's recent demonstration flights in the DC-10 aircraft, as well as examples from several other transport aircraft applications of the same DAFCS architecture, are used to illustrate the design concepts.

The proper symbiosis of the human pilot and automatic flight control

It is indeed a great honour and a particularly pleasing experience for me to have been invited to give the 18th Lanchester Memorial Lecture. Pleasing because it enables me to recall before such a distinguished audience, one of Lanchester's outstanding achievements in the field of aircraft stability, his phugoid theory. This slow oscillation problem has often been neglected but its implications can be vital as the Vulcan crash in 1956 emphasises, and the development of STOL with high lift has forced designers to turn again to a serious consideration of the phugoid as I will show presently in the first part of this lecture.

Airborne Equipment

THE progress of avionic systems in aircraft over the past few years has been characterised by dramatic developments in miniaturisation and in the capability of such equipment to perform the most complex tasks with a very small possibility of error. An area in which advances have been most rapid is in automatic flight control systems (AFCS) and a recent development concerned that produced for the Westland Lynx helicopter (Fig 1) for the British and French Services.

Synthesis of a Separate Surface Wing Leveler

THE purpose of this synoptic is to present a method for sizing and for synthesizing a separate surface wing leveler for general aviation aircraft. The method can be readily extended to more general separate surface automatic flight control systems. Unlike large airplanes which use electromechanical or hydraulic devices to drive the control surfaces, light plane control surfaces are driven mechanically by the pilot alone. Thus any attempt to drive these surfaces automatically results in feedback directly to the pilot's controls. To overcome this problem a separate surface stability augmentation (SSSA) concept has been evolved: see Fig. 1 for a general arrangement. A small control surface is devoted to automatic controls while the pilot controls a larger, similar surface. When properly designed, such a system would not feed back to the pilot and, if the system failed, the pilot could still fly the airplane. No redundancy being needed, the system is also a low cost system. The feasibility of such systems was first discussed in detail in Ref. 1.

Development of the F-12 Aircraft Flight Control System

This paper presents a description of the manual and automatic flight control system of the F-12 series aircraft, the first supersonic cruise vehicles. The impact of the aircraft configuration and flight regime on the design philosophy is reviewed and the development process from initial analog computer analysis to first flight is described. Flight experience including reliability of the tripleredundant, fail-operational stability augmentation is presented. Differences from conventional flight control practice are noted and justified. The inadequacy of certain conventional pilot presentations is discussed. Finally, the control problems encountered in high-speed, high-altitude flight are identified and treated.

Automatic flight controls in fixed wing aircraft–The first 100 years

In 1973, automatic flight controls is one of the most exacting fields of technology, requiring a balanced combination of art, science and human understanding, and the efforts of large project management teams backed by adequate resources to bring any new concept to fruition.Today's systems derive almost entirely from the technology of the past 25 years, and hence it is little known that there was some activity in automatic flight control for fixed wing aircraft as long ago as 1873, some 30 years before the world-changing events at Kittyhawk and when mechanical flight was still confined to balloons and a few rudimentary gliders.

A self-organizing adaptive aircraft control system.

SELF-ORGANIZING system may be defined as one which changes its basic structure as a function of its experiences and environment, to evolve toward some desired output behavior or mode of operation. Such a system can be described as having the ability to learn, and can therefore be designed to handle situations which rigidly programed systems are not particularly adept in handling. A report by Gibson, Fu, et al., 1 gives a good introduction to learning control systems. A more recent introduction to the subject may be obtained from a report by Mendel.2 Almost all present aircraft use some type of air-data scheduling as the method of accommodating their automatic flight control systems to variations in the dynamic characteristics encountered over the full flight envelope of the aircraft. Such systems rely on measurements of dynamic pressure or Mach number. Also, each system must be tailored for the particular aircraft in which it will be deployed, with resulting extensive design changes from system to system, and expensive flight testing for final adjustments to ensure adequate performance. With the rapid increase in technology in the field of electronics, many new electronic techniques have appeared and have proven to be almost indispensable in the safe operation of aircraft. These techniques, available and in use, can provide the necessary mechanization for an adaptive flight control system. Such a system would depend only on measurements of dynamic performance to provide the necessary gain-programing. This should give improved system performance compared to a scheduled-gain system. It should be possible to make such a system almost universally applicable, requiring only a change in the model and a few parameter adjustments for each different aircraft. The method of approach used in this study is to extend that used for the North American SIDAC controller developed by Shipley and his associates.3-4 This was modified by Rang, 5 from the observation that the equation for the handling qualities given by the C*-Criterion, which was developed by Tobie, Elliot, and Malcom,6 is very similar to the basic short-period equation of motion of the air

Automatic Guidance Concept for VTOL Aircraft

V/STOL aircraft automatic flight control, guidance and navigation by onboard computer, discussing mathematical model and simulation results