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(4) Automatic Disengagement 40
46. FGS Considerations for Head Up Displays (HUD) 41
a. General 41
b. Characteristics of HUD Guidance 41
(1) Supplemental Use Display System 41
(2) External Visual References 41
(3) Interference and Occlusion 41
(4) Display Criteria 42
(5) Conformal Symbology 42
(6) Low Visibility Approach 42
(7) Clutter 42
c. HUD/Head Down Display (HDD) Compatibility 42
(1) General 42
(2) Consistency and Compatibility 42
d. Alerting Issues 43
(1) Alerts Displayed on HUDs 43
(2) Monochrome HUDs 44
(3) Mulit-Color HUDs 44
(4) Single HUD Installation 44
(5) Dual HUD Installations 44
(6) Ground Proximity Warning System (GPWS)/Traffic Alert and Collision Avoidance System (TCAS) Alerts On HUD 44
e. Upset/Unusual Attitude Recovery Guidance 44
(1) Guidance Cues 44
(2) Orientation Cues 45 47 – 51. [RESERVED] 45
Chapter 5. Performance of Function
52. General 47
a. Intended Function 47
b. Effect of System Tolerances 47
53. Normal Performance 47
a. General 47
b. Conditions to Consider 47 Table 5.1 Examples of Normal Conditions 48
c. Level of Performance 49
(1) Significant Characteristics 49
(2) Configuration Changes 49
(3) Compliance Evaluation 49
(4) Prescribed Levels of Performance 49
(5) Equivalence of Performance 49
(6) Autopilot 49 4
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(7) Flight Director (FD) 49
(8) Autothrust 49
(9) Automatic Trim 49
54. Performance in Rare Normal Conditions 50
a. General 50
(1) Range of Conditions 50
(2) Effect on Performance 50
b. Conditions to Consider 50 Table 5-2 Examples of Rare Normal Conditions 51
c. Level of Performance 52
(1) Performance Standard 52
(2) Autopilot Authority Limit 52
(3) Masking of Potential Hazard 52
55. Icing Considerations in Normal and Rare Normal Conditions 52
a. Effect on Performance 52
b. Alerts 52
c. Effect on Speed Protection 53
56. Performance in Non-Normal Conditions 53
a. General 53
b. Considerations to Consider 53 Table 5-3 Examples of Non-Normal Conditions 54
c. Level of Performance 55
(1) Performance Standard 55
(2) Autopilot Authority Limit 55
(3) Masking of Potential Hazard 55
57. Speed Protection 55
a. General 55
(1) Speed Excursions 55
(2) Compliance with § 25.1329(h) 55
(3) Design Standard 56
b. Low Speed Protection 57
(1) General 57
(2) Factors to Consider 57
(3) Low Speed Protection During Approach Operations 57
(4) Windshear Recovery Guidance 59
c. High Speed Protection 59
(1) General 59
(2) Factors to Consider 59 58 – 61. [RESERVED] 60
Chapter 6. Characteristics of Specific Modes
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62. General 61
63. Lateral Modes 61
a. Heading or Track Hold 61
b. Heading or Track Select 61
c. Lateral Navigation (LNAV) Mode 61
(1) Lateral Flight Path 61
(2) Automatic Mode Transitions 61
(3) Takeoff or Go-Around (TOGA) 62
64. Vertical Modes 62
a. Target Altitude Selection 62
b. Vertical Speed 62
c. Flight Path Angle 62
d. Indicated Airspeed (IAS)/Mach Hold [speed on elevator] 62
e. Indicated Airspeed (IAS)/Mach Select [speed on elevator] 62
f. Flight Level (FL) Change [speed on elevator] 63
g. Altitude Capture 63
(1) Mode Transition 63
(2) Guidelines for Altitude Capture Mode 63
h. Altitude Hold 64
(1) Entering Mode 64
(2) Mode Transition Annunciation 64
(3) Barometric Pressure Adjustment 64
i. VNAV 65
(1) FMS Path 65
(2) Climb or Descent 65
65. Multi-Axis Modes 66
a. Takeoff Mode 66
(1) Vertical Guidance 66
(2) Lateral Guidance 66
(3) Rotation Guidance 66
(4) Autothrust 66
(5) Operation and Performance 66
b. Go-Around Mode 67
(1) Vertical Elements 67
(2) Speed 67
(3) Autothrust 67
(4) Engagement 68
(5) All Engine and Engine Out Capability 68
c. Approach Mode 68
(1) Final Approach Path 68
(2) Mode Annunciations 68 6
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(3) Sub-Modes 68
(4) Mode Engagement Sequence 68
66. Autothrust Modes 68
a. Thrust Mode 68
b. Speed Mode 68
c. Retard Mode 69
67. Special Considerations for VNAV Approach Operations Related to Selecting a Target Altitude 69
a. Approach Operations 69
b. VNAV Path Operations 69
68. Control Wheel Steering (CWS) [control steering through the autopilot] 69
a. General 69
b. Design 69
(1) Control Forces 69
(2) Bank and Pitch Attitudes 70
(3) Control Behavior 70
(4) Stall and Stall Recovery 70
(5) Adjustments to Trim 70
(6) Takeoff and Landing 70
(7) Automatic Reversion to CWS Mode 70
c. Terminology 71
(1) Touch Control Steering (TCS) 71
(2) Supervisory Override 71
69. Special Considerations for the Integration of Fly-by-Wire Flight Control Systems and FGS 71
a. Speed Protection 71
b. System Degradation 71 70 – 74 [RESERVED] 71
Chapter 7. FGS Integration
75. General 73
76. System Integration Issues 73
a. Common and Cascading Failure Modes 73
b. Risk of Error 73
c. System Safety Analysis 73
77. Functional Interfaces 74
a. Interfacing Sensors 74
b. Potential Inconsistencies Between Systems 74
c. Function and Performance 74 78 – 82 [RESERVED] 74
Chapter 8. Safety Assessment
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83. General 75
a. Basic Safety Requirements 75
b. Safety Assessment 75
c. Validation of Safety Assessment 75
d. Coordination with the FAA 75
84. FGS Failure Conditions 75
a. Functionality 76
b. Effect of Failure Condition 76
85. Type and Severity of Failure Conditions 76
a. Types of Failure Conditions 76
(1) Loss of Function 76
(2) Malfunction 77
b. Cause 77
c. Severity 77
d. Assessment of Failure Conditions 77
(1) Functional Failures 77
(2) Airframe Loads 77
(3) Assessing Total Effect of Failure 78
86. Mitigation of Failure Conditions 78
a. General 78
b. Identification of Methods 78
c. FGS De-Selection 78
87. Validation of Failure Conditions 78
a. General 78
b. Validation Options 79
c. Validation Methodology 79
88. Specific Considerations 79
a. FGS Action During Ground Operations 79
b. FGS Operations in Close Proximity to the Ground 79
(1) Takeoff 80
(2) Approach 81
c. Cruise Operations 82
d. Asymmetric Thrust During Autothrust Operation 82
89. Failure to Disengage the FGS 83 90 – 97 [RESERVED] 83
Chapter 9. Compliance Demon stration Using Flight Test and Simulation
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98. General 85
a. Methods of Compliance Demonstration 85
b. Criteria for Establishing Compliance 85
c. Elements of Certification Flight Test 85
d. Pilot–in–the–Loop Evaluation 85
e. Other Applicable Guidance Material for FGS Takeoff and/or Approach Modes 86
(1) Criteria to Consider 86
(2) Procedures to Show Compliance 86
f. Relation of AC Chapters 86 Figure 9-1, Relationship Between AC Chapters 87
99. Performance Demonstration (Fault Free): § 25.1301 88
a. General 88
(1) Certification Plan 88
(2) Evaluating Performance 88
(3) Evaluating Compatibility of Mode Controls, Indications, and Alerts 88
b. Normal Performance 88
(1) Demonstration 88
(2) Evaluation 88
(3) Expected Errors 89
c. Performance in “Other Than Normal” Conditions 89
(1) Test Program 89
(2) Evaluation of FGS 89
(3) Additional Guidance for Windshear 89
d. Specific Performance Conditions 89
(1) Icing Considerations 89
(2) Low-Speed Protection 90
(3) High-Speed Protection 91
(4) Go-Around 91
(5) Steep Approach [special authorization] 92
(6) Indication Of and Response To an Out Of Trim Condition 93
e. Flight Director (FD) /Head Up Display (HUD 93
(1) General 93
(2) Specific Demonstrations for HUD 94
(3) Simulator Demonstration for HUD 95
f. Flightcrew Override of the FGS 96
(1) Autopilot Override 96
(2) Autothrust Override 97
(3) Pitch Trim System Evaluation During Autopilot Override 97 9
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100. Failure Conditions Requiring Validation: § 25.1309 97
a. General 97
(1) Safety Assessment 97
(2) Evaluation of Failure Conditions 97
b. Validation Elements 98
(1) Assessment 98
(2) Failure Condition 98
(3) Pilot Recognition 98
(4) Pilot Reaction Time 100
(5) Pilot Recovery 100
c. Takeoff 101
(1) Worst Case Failure Condition 101
(2) Failures to be Evaluated 101
(3) On Runway Guidance 101
d. Climb, Cruise, Descent, and Holding 101
e. Maneuvering 101
f. Approach 101
(1) Approach With Vertical Path Reference 101
(2) Approach Without Vertical Path Reference 103
(3) Steep Approach 103
g. Specific Conditions 103
(1) Failure Conditions to be Evaluated 103
(2) Failure to Disengage 103
101. Criteria Supporting Operational Use of Autopilot 103
a. Typical Flight Operations 103
b. Operations in Close Proximity to the Ground 104
(1) General 104
(2) Considerations 104
(3) Autopilot Engagement Altitude/Height After Takeoff 104
(4) Autopilot Engagement During Approach 105
(5) Circling Approach 107
c. Climb, Cruise, Descent, and Holding 107
d. Maneuvering 107
102. Automatic Disengagement of the Autopilot 108
103. Assessment of Human Factors 108
a. General 108
b. Flight Evaluations 108
(1) During Certification 108
(2) Prior to Certification 108
(3) Credit to Establish FGS Compliance 109
(4) Simulation Versus Flight Tests 109
c. Structured Subjective Evaluations 109
d. Pilot Training and Experience 110
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e. Evaluating New or Unique Design Features 110
f. Certification Planning Documentation 110 104 – 108 [RESERVED] 110
Chapter 10. Airplane Flight Manual
109. General 111
a. AFM Terminology 111
b. Low-Visibility Operations 111
110. Information Supporting Operational Use of Autopilot 111
a. General 111
b. Specifying a Minimum Use Height (MUH) 111
(1) Takeoff 111
(2) Cruise 111
(3) Approach 111
c. Maximum Displacement Deviation 112
111. Limitations 112
112. Non-Normal/Emergency Procedures 112
113. Normal Procedures 112
a. Documentation of Normal Procedures 112
b. Maximum Displacement Deviation 112
c. Procedures for Use of FGS in Icing Conditions 112
d. Aircraft With Published Flightcrew Operation Manuals (FCOM) 112
e. Aircraft Without Published FCOMs 113
Appendices
1 Safety Assessment A1-1
1. General A1-1
2. Identification of Failure Conditions A1-1
3. Considerations When Assessing The Severity of Failure Condition Effects A1-2
4. Failure Condition Classification A1-3 2 Definitions A2-1 3 Acronyms A3-1
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Tables
Number Page 2-1 Cross-References § 25.1329 Paragraphs to AC Chapters 17 5-1 Examples of Normal Conditions 48 5-2 Examples of Rare Normal Conditions 51 5-3 Examples of Non-Normal Conditions 54
Figures
Number Page 9-1 Relationship Between AC Chapters (Chapter 9) 87
1 — 10 [Reserved]
Chapter 1 Background
11. General.
a. Advisory Circular (AC) 25.1329-1B. This advisory material replaces material previously provided in AC 25.1329-1A for autopilots. The automatic control and guidance systems in current aircraft have evolved to a level that dictates a revision to current advisory material.
b. Scope. This advisory material provides information for flight guidance systems (FGS), which include any autopilot functions, flight director (FD) functions, and automatic thrust control functions as well as any interactions with stability augmentation and trim functions.
12. Evolution of FGSs.
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 multi–function 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]
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15 Chapter 2 Overview of flight guidance systems (FGS)
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 flight path more accurately to support specific operational requirements, such as reduced vertical separation minimum (RVSM) or required navigation performance (RNP).
18. FGS 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 exam ple, 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) Microwave landing system (MLS)