AC 25.1329-1C CHG 2
CONTENTS (CONTINUED) Paragraph Page
b. Vertical speed47
c. Flight path angle47
d. Indicated Airspeed/Mach Hold (speed on elevator)47
e. Indicated Airspeed/Mach Select (speed on elevator)47
f. Flight level change (speed on elevator)47
g. Altitude capture47
(1) Mode transition47
(2) Guidelines for Altitude Capture mode48
h. Altitude hold49
(1) Entering mode49
(2) Mode transition annunciation49
(3) Barometric pressure adjustment49
i. VNAV49
(1) FMS path49
(2) Climb or descent49
65. Multi-Axis Modes50
a. Takeoff mode50
(1) Vertical guidance50
(2) Lateral guidance50
(3) Rotation guidance50
(4) Autothrust50
(5) Operation and performance50
b. Go-around mode51
(1) Vertical elements51
(2) Speed51
(3) Autothrust51
(4) Engagement52
(5) All engine and engine out capability52
c. Approach mode52
(1) Final approach path52
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CONTENTS (CONTINUED) Paragraph Page
(2) Mode annunciations52
(3) Sub-modes52
(4) Mode engagement sequence52
66. Autothrust Modes52
a. Thrust mode52
b. Speed mode53
c. Retard mode53
67. Special Considerations for VNAV Approach Operations Related to Selecting a Target
Altitude53
a. Approach operations53
b. VNAV path operations53
68. Control Wheel Steering (Control Steering through the Autopilot)53
a. General53
b. Design53
(1) Control forces53
(2) Bank and pitch attitudes53
(3) Control behavior54
(4) Stall and stall recovery54
(5) Adjustments to trim54
(6) Takeoff and landing54
(7) Automatic reversion to CWS mode54
c. Terminology and application of advisory material54
(1) Touch control steering55
(2) Supervisory override55
69. Special Considerations for the Integration of Fly-by-Wire Flight Control Systems
and FGS55
a. Speed protection55
b. System degradation55
70—74 [RESERVED]55
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AC 25.1329-1C CHG 2
CONTENTS (CONTINUED) Paragraph Page CHAPTER 7. FGS INTEGRATION ........
.56
75. General56
76. System Integration Issues56
a. Common and cascading failure modes56
b. Risk of error56
c. System safety analysis56
77. Functional Interfaces56
a. Interfacing sensors56
b. Potential inconsistencies between systems57
c. Function and performance57
78—82 [RESERVED]57
CHAPTER 8. SAFETY ASSESSMENT58
83. General58
a. Basic safety requirements58
b. Safety assessment58
c. Validation of safety assessment58
d. Coordination with the FAA58
84. FGS Failure Conditions58
a. Functionality58
b. Effect of failure condition59
85. Type and Severity of Failure Conditions59
a. Types of failure conditions59
(1) Loss of function59
(2) Malfunction59
b. Cause59
c. Severity60
d. Assessment of failure conditions60
(1) Functional failures60
(2) Airframe loads60
(3) Assessing total effect of failure60
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86. Mitigation of Failure Conditions60
a. General60
b. Identification of methods61
c. FGS de-selection61
87. Validation of Failure Conditions61
a. General61
b. Validation options61
c. Validation methodology61
88. Specific Considerations62
a. FGS action during ground operations62
b. FGS operations in close proximity to the ground62
(1) Takeoff62
(2) Approach63
c. Cruise operations64
d. Asymmetric thrust during autothrust operation64
89. Failure to Disengage the FGS65
90—97 [RESERVED]65
CHAPTER 9. COMPLIANCE DEMONSTRATION USING FLIGHT TEST AND SIMULATION 66
98. General66
a. Methods of compliance demonstration66
b. Criteria for establishing compliance66
c. Elements of certification flight test66
d. Pilot-in-the-loop evaluation66
e. Other applicable guidance material for FGS takeoff and/or approach modes66
(1) Criteria to consider66
(2) Procedures to show compliance67
f. Relationship of AC chapters67
99. Performance Demonstration (Fault Free): § 25.130167
a. General67
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(1) Certification plan67
(2) Evaluating performance68
(3) Evaluating compatibility of mode controls, indications, and alerts68
b. Normal performance68
(1) Demonstration68
(2) Evaluation68
(3) Expected errors68
c. Performance in “other than normal” conditions68
(1) Test program68
(2) Evaluation of FGS69
(3) Additional guidance for windshear69
d. Specific performance conditions69
(1) Icing considerations69
(2) Low-speed protection70
(3) High-speed protection70
(4) Go-around70
(5) Steep approach (special authorization)71
(6) Indication of and response to an out -of-trim condition72
e. Flight director/head up display72
(1) General72
(2) Specific demonstrations for HUD73
(3) Simulator demonstration for HUD74
f. Flightcrew override of the FGS75
(1) Autopilot override75
(2) Autothrust override75
(3) Pitch trim system evaluation during autopilot override75
100. Failure Conditions Requiring Validation: § 25.130976
a. General76
(1) Safety assessment76
(2) Evaluation of failure conditions76
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CONTENTS (CONTINUED) Paragraph Page
b. Validation elements76
(1) Assessment76
(2) Failure condition76
(3) Pilot recognition77
(4) Pilot reaction time78
(5) Pilot recovery79
c. Takeoff79
(1) Worst-case failure condition79
(2) Failures to be evaluated79
(3) On runway guidance79
d. Climb, cruise, descent, and holding79
e. Maneuvering79
f. Approach79
(1) Approach with vertical path reference80
(2) Approach without vertical path reference81
(3) Steep approach81
g. Specific conditions81
(1) Failure conditions to be evaluated81
(2) Failure to disengage81
101. Criteria Supporting Operational Use of Autopilot81
a. Typical flight operations81
b. Operations in close proximity to the ground82
(1) General82
(2) Considerations82
(3) Autopilot engagement altitude/height after takeoff82
(4) Autopilot engagement during approach83
(5) Circling approach85
c. Climb, cruise, descent, and holding85
d. Maneuvering85
102. Automatic Disengagement of the Autopilot85
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AC 25.1329-1C CHG 2
CONTENTS (CONTINUED) Paragr aph 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
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AC 25.1329-1C CHG 2
CONTENTS (CONTINUED)
APPENDI CES 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
D Advisory Circular FeedbackD-1
TABLES Number Page
1-1-1 Related 14 CFR Sections2
1-1-2 Related Advisory Circulars3
1-1-3 Related SAE Documents4
1-1-4 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
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AC 25.1329-1C CHG 2
INTRODUCTION
1. Purpose. This AC describes an acceptable means for showing compliance with certain requirements of 14 CFR 25.1329, Flight guidance systems. 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 s), 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, Federal Aviation Administration (FAA) transport airplane type certificate engineers , and FAA designees.
b. This is a guidance document. Its content is not legally binding in its own right and will not be relied upon by the Department as a separate basis for affirmative enforcement action or other administrative penalty. Conformance with this guidance document is voluntary only.
Nonconformity will not affect rights and obligations under existing statutes and regulations. This document is intended only to provide information to the public regarding existing requirements under the law or agency policies. The guidan ce 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 . If the FAA becomes aware of circumstances in which following this AC would not result in compliance with the applicable regulations, the FAA may require additional substantiation or design changes as a basis for finding compliance.
3. Cancellation. This AC cancels AC 25.1329-1C Change 1, d ated May 24, 2016.
4. Related Regulations, ACs, a nd Industry Documents. The following related documents are provided for information purposes and are not necessarily directly referenced in this AC.
a. Regulations. Table 1-1 i dentifies 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 Bookstore website.
AC 25.1329-1C CHG 2 Table 1-1. Related 14 CFR Sections Controllability and Maneuverability —General Control Systems—General Trim systems Motion and effect of cockpit controls Installation Function and installation Equipment, systems, and installations Supercooled large drop icing conditions Airplane Flight Manual—Operating limitations Title Section Loads Stability augmentation and automatic and power -operated systems § 25.143 § 25.301 § 25.671 § 25.672 § 25.677 § 25.777 § 25.779 § 25.781 § 25.901 § 25.903 § 25.1301 § 25.1303 § 25.1309 § 25.1322 § 25.1420 § 25.1581 § 25.1583 § 25.1585 Cockpit controls Cockpit control knob shape Engines Flight and navigations instruments Flightcrew alerting Airplane Flight Manual—General Airplane Flight Manual—Operating procedures
b. Ad visory Circulars. Table 1-2 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 website.
AC 25.1329-1C CHG 2 Table 1-2. Related Advisory Circulars AC 20-115D Airborne Software Development Assurance Using July 21, 2017 EUROCAE ED-12( ) and RTCA DO-178( ) AC 20-152A RTCA, Inc., Document RTCA/DO-254, Design October 7, 2022 Assurance Guidance for Airborne Electronic Hardware AC 20-191 Airworthiness Approval of Airborne Systems used TBD for Takeoff, Precision Approach, Landing, and Rollout in Low-Visibility Conditions AC 25-7D Flight Test Guide for Certification of Transport May 4, 2018 Category Airplanes AC 25-12 Airworthiness Criteria for the Approval of Airborne November 2, 1987 Windshear Warning Systems in Transport Category Airplanes AC 25.1322-1 Flightcrew Alerting December 13, 2010 AC 120-118 Criteria for Approval/Authorization of All Weather July 2, 2018 Operations (AWO) for Takeoff, Landing, and Rollout Number Title Date AC 20-138D Airworthiness Approval of Positioning and April 7, 2016 Change 2 Navigation Systems AC 20-174 Development of Civil Aircraft and Systems September 30, 2011 AC 21-16G RTCA Document DO-160 versions D, E, F, and G, June 22, 2011 “Environmental Conditions and Test Procedures for Airborne Equipment” AC 25-11B Electronic Flight Displays October 7, 2014 AC 25.1309-1B System Design and Analysis August 30, 2024 AC 25.1581-1 Airplane Flight Manual July 14, 1997 Change 1 AC 120-41 Criteria for Operational Approval of Airborne Wind November 11, 1983 Shear Alerting and Flight Guidance Systems (cancelled) 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.
AC 25.1329-1C CHG 2
c. Related Industry Standards.
(1) The following documents are available from the Society of Automotive Engineers (SAE). You can pur chase 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 website.
Table 1-3. Related SAE Documents SAE ARP4761A Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment SAE ARP5366 Autopilot, Flight Director, and Autothrust Systems Number Title SAE ARP5288 Transport Category Airplane Head Up Display (HUD) Systems SAE AS8055A 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 from the RTCA website.
Table 1-4. Related RTCA Documents RTCA DO-178C/ Software Considerations in Airborne Systems and EUROCAE ED-12C Equipment Certification RTCA DO-254/ Design Assurance Guidance for Airborne Electronic EUROCAE ED-80 Hardware Number Title RTCA DO-160G/ Environmental Conditions and Test Procedures for EUROCAE ED-14G Airborne Equipment
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 website.