Flight Guidance System Requirements Specification
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NASA/CR-2003-212426 Flight Guidance System Requirements Specification Steven P. Miller, Alan C. Tribble, Timothy M. Carlson, and Eric J. Danielson Rockwell Collins, Cedar Rapids, Iowa June 2003 The NASA STI Program Office . in Profile Since its founding, NASA has been dedicated to the • CONFERENCE PUBLICATION. Collected advancement of aeronautics and space science. The papers from scientific and technical NASA Scientific and Technical Information (STI) conferences, symposia, seminars, or other Program Office plays a key part in helping NASA meetings sponsored or co-sponsored by NASA. maintain this important role. • SPECIAL PUBLICATION. Scientific, The NASA STI Program Office is operated by technical, or historical information from NASA Langley Research Center, the lead center for NASA’s programs, projects, and missions, often scientific and technical information. The NASA STI concerned with subjects having substantial Program Office provides access to the NASA STI public interest. 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NASA Center for AeroSpace Information 7121 Standard Drive Hanover, MD 21076-1320 NASA/CR-2003-212426 Flight Guidance System Requirements Specification Steven P. Miller, Alan C. Tribble, Timothy M. Carlson, and Eric J. Danielson Rockwell Collins, Cedar Rapids, Iowa National Aeronautics and Space Administration Langley Research Center Prepared for Langley Research Center Hampton, Virginia 23681-2199 under Cooperative Agreement NCC1-01001 June 2003 Available from: NASA Center for AeroSpace Information (CASI) National Technical Information Service (NTIS) 7121 Standard Drive 5285 Port Royal Road Hanover, MD 21076-1320 Springfield, VA 22161-2171 (301) 621-0390 (703) 605-6000 Abstract This report describes a requirements specification written in the RSML¡e language for the mode logic of a Flight Guidance System of a typical regional jet aircraft. This model was created as one of the first steps in five-year project sponsored by the NASA Langley Research Center, Rockwell Collins Inc., and the Critical Systems Research Group of the University of Minnesota to develop new methods and tools to improve the safety of avionics designs. This model will be used to demonstrate the application of a variety of methods and techniques, including safety analysis of system and subystem requirements, verification of key properties using theorem provers and model checkers, identification of potential sources mode confusion in system designs, partitioning of applications based on the criticality of system hazards, and autogeneration of avionics quality code. While this model is representative of the mode logic of a typical regional jet aircraft, it does not describe an actual or planned product. Several aspects of a full Flight Guidance System, such as recovery from failed sensors, have been omitted, and no claims are made regarding the accuracy or completeness of this specification. 2 Contents 1 Introduction 5 1.1 How Requirements Analysis Relates to Aircraft Safety ................ 5 1.2 Overview of a Flight Guidance System ......................... 9 1.3 Fundamentals of the Mode Logic ............................ 12 2 The FGS Requirements Specification 15 2.1 Overview of the FGS Specification ........................... 16 2.2 Prioritization of Events ................................. 20 2.3 Basic Definitions ..................................... 23 2.4 Flight Director (FD) ................................... 25 2.5 Pilot Flying (PF) ..................................... 29 2.6 Independent Mode .................................... 30 2.7 Flight Modes ....................................... 32 2.7.1 Lateral Modes .................................. 35 2.7.1.1 Roll Hold (ROLL) Mode ....................... 37 2.7.1.2 Heading Select (HDG) Mode ..................... 40 2.7.1.3 Navigation (NAV) Mode ....................... 44 2.7.1.4 Lateral Approach (LAPPR) Mode .................. 50 2.7.1.5 Lateral Go Around (LGA) Mode ................... 56 2.7.2 Vertical Modes .................................. 60 2.7.2.1 Pitch Hold (PITCH) Mode ...................... 62 2.7.2.2 Vertical Speed (VS) Mode ...................... 65 2.7.2.3 Flight Level Change (FLC) Mode .................. 69 2.7.2.4 Altitude Hold (ALT) Mode ...................... 73 2.7.2.5 Altitude Select (ALTSEL) Mode ................... 77 2.7.2.6 Vertical Approach (VAPPR) Mode .................. 85 2.7.2.7 Vertical Go Around (VGA) Mode .................. 91 2.8 Flight Control Laws ................................... 95 2.9 Flight Control Panel (FCP) ............................... 103 2.10 Navigation Sources .................................... 127 2.11 Air Data System ..................................... 128 2.12 References ......................................... 129 3 4 2.13Autopilot(AP)......................................130 2.14 Offside FGS ........................................ 133 2.15 FGS Inputs ........................................ 152 2.16 FGS Outputs ....................................... 156 References ............................................ 161 Index .............................................. 163 Chapter 1 Introduction This report describes a requirements specification written in the RSML¡e [8, 6] language for the mode logic of a Flight Guidance System of a typical regional jet aircraft. This model was created as one of the first steps in a project sponsored by the NASA Langley Research Center, Rockwell Collins, Inc., and the Critical Systems Research Group of the University of Minnesota to develop new methods and tools to improve the safety of avionics designs. This model will be used to demonstrate the application of a variety of methods and techniques, including: ² Safety analysis of system and subsystem requirements ² Verification of key properties using theorem provers and model checkers ² Identification of potential sources mode confusion in system designs ² Partitioning of applications based on the criticality of system hazards ² Autogeneration of avionics quality code While this model is representative of the mode logic of a typical regional jet aircraft, it does not describe an actual or planned product. Several aspects of a full Flight Guidance System, such as recovery from failed sensors, have been omitted, and no claims are made regarding the accuracy or completeness of this specification. The report is organized as follows. In this chapter, Section 1.1 discusses why the modeling and analysis of requirements is important to aircraft safety, Section 1.2 provides an overview of a modern Flight Guidance System, and Section 1.3 discusses the the fundamentals of the mode logic found in the FGS. Chapter 2 deals with the requirements specification itself. Section 2.1 describes how the specification is organized. The remaining sections of Chapter 2 are the specification itself. 1.1 How Requirements Analysis Relates to Aircraft Safety Aircraft safety has improved steadily over the last few decades and much of this improvement can be attributed to the introduction of advanced automation in the cockpit. The predicted 5 6 Accident Category Fatalities Accidents Controlled Flight Into Terrain 2111 28 Loss of Control in Flight 2011 29 In Flight Fire 600 3 Midair Collision 506 2 Fuel Tank Explosion 238 2 Landing »200 14 Takeoff »144 3 Ice/Snow »60 3 Fuel Exhaustion »40 5 Wind Shear »30 2 Runway Incursion »10 4 Misc. Fatality »10 3 On Ground »10 3 Refused Takeoff »10 1 Turbulence »10 3 Unknown 482 7 Total 6465 112 Table 1.1: Fatal Accidents - Worldwide Commercial Jet Fleet, 1990-1999 - From [14] ten-fold increase in air traffic by 2016 will force much greater reliance on automated systems. New technologies, such as: Communication, Navigation, and Surveillance for Air Traffic Manage- ment (CNS/ATM); Global Air Traffic