xv
CONTENTS (CONTINUED) Paragraph Page
103. Assessment of Human Factors85
a. General85
b. Flight evaluations86
(1) During certification86
(2) Prior to certification86
(3) Credit to establish FGS compliance86
(4) Simulation versus flight tests86
c. Structured subjective evaluations87
d. Pilot training and experience87
e. Evaluating new or unique design features87
f. Certification planning documentation87
104—108 [RESERVED]87
CHAPTER 10. AIRPLANE FLIGHT MANUAL88
109. General88
a. AFM terminology88
b. Low-visibility operations88
110. Information Supporting Operational Use of Autopilot88
a. General88
b. Specifying a MUH88
c. Maximum displacement deviation88
111. Limitations89
112. Non-Normal/Emergency Procedures89
113. Normal Procedures89
a. Documentation of normal procedures89
b. Maximum displacement deviation89
c. Procedures for use of FGS in icing conditions89
d. Aircraft with published FCOMs89
e. Aircraft without published FCOMs89
xvi
CONTENTS (CONTINUED)
APPENDICES Number Page
A Safety AssessmentA-1
1. GeneralA-1
2. Identification of Failure ConditionsA-1
3. Considerations when Assessing the Severity of Failure Condition EffectsA-2
4. Failure Condition ClassificationA-3
B DefinitionsB-1
C AcronymsC-1
TABLES Number Page
1 Related 14 CFR Sections2
2 Related Advisory Circulars3
3 Related SAE Documents4
4 Related RTCA Documents4
2-1 Cross-References for § 25.1329 Paragraphs to AC Chapters8
5-1 Examples of Normal Conditions35
5-2 Examples of Rare Normal Conditions38
5-3 Examples of Non-Normal Conditions40
B-1 Terms and DefinitionsB-1
C-1 Acronyms and DefinitionsC-1
FIGURES Number Page
9-1 Relationship between AC Chapters67
INTRODUCTION
1. Purpose. This advisory circular (AC) describes an acceptable means for showing compliance with certain requirements of Title 14 of the Code of Federal Regulations (14 CFR) part 25, § 25.1329, Flight guidance system. While part 25 contains the airworthiness standards applicable to transport category airplanes, the guidance in this ac pertains to the functions of autopilots, flight directors (FD), and automatic thrust control as well as any interactions with stability augmentation and trim functions.
2. Applicability.
a. The guidance provided in this document is directed to airplane manufacturers, modifiers, operators of certain transport category airplanes, foreign regulatory authorities, and Federal Aviation Administration (FAA) transport airplane type certificate (TC) engineers and their designees.
b. The guidance in this AC is neither mandatory nor regulatory in nature and does not constitute a regulation. It describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. We will consider other methods of showing compliance that an applicant may elect to present. While these guidelines are not mandatory, they are derived from extensive FAA and industry experience in determining compliance with the relevant regulations. If, however, we become aware of circumstances that convince us that following this AC would not result in compliance with the applicable regulations, we will not be bound by the terms of this AC, and we may require additional substantiation or design changes as a basis for finding compliance.
c. The material in this AC does not change or create any additional regulatory requirements, nor does it authorize changes in, or permit deviations from, regulatory requirements.
3. Cancellation. This AC cancels AC 25.1329-1B Change 1, dated October 16, 2012.
4. Related Regulations, ACs, and Industry Documents. The following related documents are provided for information purposes and are not necessarily directly referenced in this AC.
a. Regulations. Table 1 identifies the related 14 CFR regulations that are referenced in this AC. The full text of these regulations can be downloaded from the U.S. Government Publishing Office e-CFR. A paper copy may be ordered from the U.S. Government Publishing Office, Superintendent of Documents, Attn: New Orders, PO Box 371954, Pittsburgh, PA, 15250-7954.
2 Table 1. Related 14 CFR sections Section Title § 25.143 Controllability and Maneuverability—General § 25.301 Loads § 25.671 Control Systems—General § 25.672 Stability augmentation and automatic and power-operated systems § 25.677 Trim systems § 25.777 Cockpit controls § 25.779 Motion and effect of cockpit controls § 25.781 Cockpit control knob shape § 25.901 Installation § 25.903 Engines § 25.1301 Function and installation § 25.1303 Flight and navigations instruments § 25.1309 Equipment, systems, and installations § 25.1322 Flightcrew alerting § 25.1420 Supercooled large drop icing conditions § 25.1581 Airplane Flight Manual—General § 25.1583 Airplane Flight Manual—Operating limitations § 25.1585 Airplane Flight Manual—Operating procedures
b. Advisory Circulars. Table 2 identifies the ACs that are related to the guidance in this AC. The table lists the latest version of each AC at the time of publication. If any AC is revised after publication of this AC, you should refer to the latest version for guidance. You can find the latest version at the FAA Web site.
3 Table 2. Related Advisory Circulars Number Title Date AC 20-115C Airborne Software Assurance July 19, 2013 AC 20-138D Airworthiness Approval of Positioning and October 10, 2014 Change 1 Navigation Systems AC 20-152 RTCA, Inc., Document RTCA/DO-254, July 5, 2005 Design Assurance Guidance for Airborne Electronic Hardware AC 20-174 Development of Civil Aircraft and Systems September 30, 2011 AC 25-7C Flight Test Guide for Certification of Transport October 16, 2012 Category Airplanes AC 25-11B Electronic Flight Displays October 7, 2014 AC 25-12 Airworthiness Criteria for the Approval of Airborne Windshear Warning Systems in November 2, 1987 Transport Category Airplanes AC 25.672-1 Active Flight Controls November 15, 1983 AC 25.1309-1A System Design and Analysis October 3, 2011 AC 25.1419-2 Compliance with the Ice Protection Requirements of §§ 25.1419(e), (f), (g), and October 27, 2009
(h) AC 25.1581-1 Airplane Flight Manual July 14, 1997 Change 1 AC 120-28D Criteria for Approval of Category III Weather July 13, 1999 Minima for Takeoff, Landing, and Rollout AC 120-29A Criteria for Approving Category I and August 12, 2002 Category II Weather Minima for Approach AC 120-41 Criteria for Operational Approval of Airborne November 11, 1983 Wind Shear Alerting and Flight Guidance Systems Note: This table identifies the latest version of each AC at the time of publication.
If any AC is revised after publication of this AC, you should refer to the latest version for guidance.
c. Related Industry Standards.
(1) The following documents are available from the Society of Automotive Engineers (SAE). You can purchase these documents by mail from SAE Customer Service, 400 Commonwealth Drive, Warrendale, PA, 15096; by faxing your order information to
(724) 776-0790; or from the SAE Web site.
Table 3. Related SAE Documents Number Title SAE ARP4754A Guidelines for Development of Civil Aircraft and Systems SAE ARP4761 Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment SAE ARP5288 Transport Category Airplane Head-Up Display (HUD) Systems SAE ARP5366 Autopilot, Flight Director, and Autothrust Systems SAE AS8055 Minimum Performance Standard for Airborne Head-Up Display (HUD)
(2) The following documents are available from RTCA, Inc. (formerly the Radio Technical Commission for Aeronautics). You can purchase these documents by mail from RTCA Inc., 1150 18th Street NW, Suite 910, Washington, DC 20036; by faxing the Document Order Form to (202) 833-9434; or from the RTCA Web site.
Table 4. Related RTCA Documents Number Title RTCA DO-178B/ EUROCAE ED-12B Software Considerations in Airborne Systems and Equipment Certification RTCA DO-160E/ EUROCAE ED-14D Environmental Conditions and Test Procedures for Airborne Equipment RTCA DO-254/ EUROCAE ED-80 Design Assurance Guidance for Airborne Electronic Hardware
d. Other FAA documents.
(1) Federal Aviation Administration Human Factors Team Report on: The Interfaces Between Flightcrews and Modern Flight Deck Systems, dated June 18, 1996, is available at the FAA Web site.
(2) FAA Order 8260.3, United States Standard for Terminal Instrument Procedures (TERPS), Changes 1 – 19, is available at the FAA Web site.
5—10 [RESERVED]
6 CHAPTER 1. BACKGROUND
11. General.
a. AC 25.1329-1C. This revision incorporates minor changes associated with issuance of the final rule for Airplane and Engine Certification Requirements in Supercooled Large Drop, Mixed Phase, and Ice Crystal Icing Conditions (79 Federal Register (FR) 65508, November 4, 2014). Specifically, in this AC, we added a reference to § 25.1420, Supercooled large drop icing conditions, in Table 1; excepted “large drop icing” as an icing normal condition in Table 5-1;
and added “large drop icing” as a rare normal condition in Table 5-2.
b. Scope. This advisory material provides information for Flight Guidance Systems (FGS), which include any autopilot functions, FD functions, and automatic thrust control functions as well as any interactions with stability augmentation and trim functions.
12. Evolution of FGS.
a. Complexity. There have been dramatic changes in technology and system design, which have resulted in much higher levels of integration, automation, and complexity. These changes have also redefined the allocation of functions and interfaces between systems.
Relatively simple, dedicated systems have been replaced with digital multifunction systems with more modes and automatic changes in modes of operation. The introduction of fly-by-wire flight control systems has created new interface considerations for the FGS.
b. Guidance considerations. These new systems are capable of providing better performance, increased safety, and decreased workload. But, if designed without consideration for the criteria in this AC, these systems could also be confusing and not immediately intuitive for the flightcrew. Significant operational experience has been gained on new generation systems, and this guidance material is provided based on that experience.
13—16 [RESERVED]
7 CHAPTER 2. OVERVIEW OF FLIGHT GUIDANCE SYSTEMS
17. Purpose of FGS. The FGS is primarily intended to assist the flightcrew in the basic control and tactical guidance of the airplane. The system may also provide workload relief to the pilots and provide a means to fly a flightpath more accurately to support specific operational requirements, such as Reduced Vertical Separation Minimum (RVSM) or Required Navigation Performance (RNP).
18. Components.
a. Included in definition. For the purpose of this AC, the term “FGS” includes all the equipment necessary to accomplish the FGS function, including the sensors, computers, power supplies, servo-motors/actuators, and associated wiring. It includes any indications and controllers necessary for the pilot to manage and supervise the system.
b. Excluded from definition. Any equipment or component that remains mechanically connected to the primary flight controls or propulsion controls when the FGS is not in use is regarded as a part of the primary flight controls and propulsion system, and the provisions for such systems are applicable.
19. FGS Functions.
a. Elements of FGS.
(1) Flight guidance and control (for example, autopilot, FD displayed head down or head up).
(2) Autothrottle/autothrust systems. The term “autothrust” is generic in nature and includes power control systems for propeller driven airplanes.
(3) Interactions with stability augmentation and trim systems.
(4) Alerting, status, mode annunciation, and situation information associated with flight guidance and control functions.
b. Approach and landing system. The FGS includes those functions necessary to provide guidance and control in conjunction with an approach and landing system, such as the following:
(1) Instrument landing system (ILS).
(2) Ground-Based Augmentation System (GBAS) Landing System (GLS).
c. Flight management system (FMS). The FGS also includes those functions necessary to provide guidance and control in conjunction with an FMS. The FGS does not include the flight planning and the generation of flightpath and speed profiles tied to
8 waypoints and other flight planning aspects of the FMS. However, it does include the interface between the FMS and FGS necessary for the execution of flightpath and speed commands.
d. Design philosophy. The applicant should establish, document, and follow a design philosophy that supports the intended operational use regarding FGS behavior, modes of operation, and the pilot interface with controls, indications, alerts, and mode functionality.
e. Description of FGS behavior and operation. A description of the FGS behavior and operation should be addressed from flightcrew and maintenance perspectives in appropriate documentation and training material.
20. Compliance with § 25.1329.
a. General. Subsequent chapters of this advisory material provide acceptable means of compliance with § 25.1329 and the applicability of other part 25 rules to FGS (for example, §§ 25.1301 and 25.1309). The demonstrated means of compliance may include a combination of analysis, laboratory testing, flight testing, and simulator testing. The applicant should coordinate with the FAA early in the certification program via a certification plan to reach agreement on the methods to be used to demonstrate compliance.
Note 1: This AC uses the terminology “should” and “should not” when discussing compliance to the AC itself, as the AC represents one, but not the only, method of complying with § 25.1329.
Note 2: This AC uses the terminology “must” and “may not” when discussing compliance to § 25.1329 and other specific rules, as compliance to a rule is not optional.
In these cases, the AC text supplies a reference to the specific rule being discussed.
b. Relevant paragraphs. Table 2-1 lists the relevant paragraphs of § 25.1329 and indicates where acceptable means of compliance with each paragraph can be found within this AC.
Table 2-1. Cross-References for § 25.1329 Paragraphs to AC Chapters 14 CFR Section AC Chapter/Paragraph Reference § 25.1329(a) Quick disengagement controls for the autopilot and autothrust functions must be provided for each pilot. The autopilot quick disengagement controls must be located on both control wheels (or equivalent). The autothrust quick disengagement controls must be located on the thrust control levers. Quick disengagement controls must be readily accessible to each pilot while operating the control wheel (or equivalent) and thrust control levers.
Chapter 3 Flight Guidance System Engagement, Disengagement, Indications, and Override Paragraph 27, Autopilot Engagement, Disengagement, and Indications Paragraph 29, Autothrust Engagement, Disengagement, and Indications
9 14 CFR Section AC Chapter/Paragraph Reference § 25.1329(b) The effects of a failure of the system to disengage the autopilot or autothrust functions when manually commanded by the pilot must be assessed in accordance with the requirements of § 25.1309.
Chapter 3 Flight Guidance System Engagement, Disengagement, Indications, and Override Paragraph 27, Autopilot Engagement, Disengagement, and Indications Paragraph 29, Autothrust Engagement, Disengagement, and Indications Paragraph 30, Override of the FGS Chapter 8 Safety Assessment Paragraph 89, Failure to Disengage the FGS § 25.1329(c) Engagement or switching of the flight guidance system, a mode, or a sensor may not cause a transient response of the airplane’s flight path any greater than a minor transient, as defined in paragraph (n)(1) of this section.
Chapter 3 Flight Guidance System Engagement, Disengagement, Indications, and Override Chapter 8 Safety Assessment § 25.1329(d) Under normal conditions, the disengagement of any automatic control function of a flight guidance system may not cause a transient response of the airplane’s flight path any greater than a minor transient.
Chapter 3 Flight Guidance System Engagement, Disengagement, Indications, and Override Chapter 4 Controls, Indications, and Alerts Paragraph 45, FGS Alerting, Warning, Caution, Advisory, and Status Chapter 8 Safety Assessment
10 14 CFR Section AC Chapter/Paragraph Reference § 25.1329(e) Under rare normal and non-normal conditions, disengagement of any automatic control function of a flight guidance system may not result in a transient any greater than a significant transient, as defined in paragraph (n)(2) of this section.
Chapter 3 Flight Guidance System Engagement, Disengagement, Indications, and Override Chapter 4 Controls, Indications, and Alerts Paragraph 45, FGS Alerting, Warning, Caution, Advisory, and Status Chapter 8 Safety Assessment § 25.1329(f) The function and direction of motion of each command reference control, such as heading select or vertical speed, must be plainly indicated on, or adjacent to, each control if necessary to prevent inappropriate use or confusion.
Chapter 4 Controls, Indications, and Alerts Paragraph 43, FGS Controls § 25.1329(g) Under any condition of flight appropriate to its use, the flight guidance system may not produce hazardous loads on the airplane, nor create hazardous deviations in the flight path. This applies to both fault-free operation and in the event of a malfunction, and assumes that the pilot begins corrective action within a reasonable period of time.
Chapter 4 Controls, Indications, and Alerts Paragraph 45, FGS Alerting, Warning, Caution, Advisory, and Status Chapter 5 Performance of Function Chapter 8 Safety Assessment Chapter 9 Compliance Demonstration Using Flight Test and Simulation