0 U.S. Department Advisory of Transportation Federal Aviation Circular Administration Subject: Approval of Flight Guidance Systems Date: 10/27/14 AC No: 25 .1329-1C Initiated By: ANM-11 0 This advisory circular (AC) describes an acceptable means for showing compliance with certain requirements of Title 14, Code of Federal Regulations (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, and automatic thrust control as well as any interactions with stability augmentation and trim functions. 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. If you have suggestions for improving this AC, you may use the feedback form at the end ofthis AC. Michael Kaszycki Acting Manager, Transport Airplane Directorate Aircraft Certification Service 10/27/14 AC 25.1329-1C CONTENTS Paragraph Page INTRODUCTION ....................................................................................................................... 1 1. Purpose ............................................................................................................................. 1 2. Applicability .................................................................................................................... 1 3. Cancellation ..................................................................................................................... 1 4. Related Regulations, ACs, and Industry Documents ....................................................... 1 a. Regulations ................................................................................................................ 1 b. Advisory Circulars ..................................................................................................... 2 c. Related Industry Standards ........................................................................................ 4 d. Other FAA documents ............................................................................................... 4 5—10 [RESERVED] ............................................................................................................ 5 CHAPTER 1. BACKGROUND ................................................................................................... 6 11. General ............................................................................................................................. 6 a. AC 25.1329-1C .......................................................................................................... 6 b. Scope .......................................................................................................................... 6 12. Evolution of FGS ............................................................................................................. 6 a. Complexity ................................................................................................................. 6 b. Guidance considerations ............................................................................................ 6 13—16 [RESERVED] ............................................................................................................ 6 CHAPTER 2. OVERVIEW OF FLIGHT GUIDANCE SYSTEMS ................................................ 7 17. Purpose of FGS ................................................................................................................ 7 18. Components ..................................................................................................................... 7 a. Included in definition ................................................................................................. 7 b. Excluded from definition ........................................................................................... 7 19. FGS Functions ................................................................................................................. 7 a. Elements of FGS ........................................................................................................ 7 b. Approach and landing system .................................................................................... 7 c. Flight management system ........................................................................................ 7 d. Design philosophy ..................................................................................................... 8 e. Description of FGS behavior and operation .............................................................. 8 ii 10/27/14 AC 25.1329-1C CONTENTS (CONTINUED) Paragraph Page 20. Compliance with § 25.1329 ............................................................................................. 8 a. General ....................................................................................................................... 8 b. Relevant paragraphs ................................................................................................... 8 21—26 [RESERVED] .......................................................................................................... 13 CHAPTER 3. FGS ENGAGEMENT, DISENGAGEMENT, INDICATIONS, AND OVERRIDE .. 14 27. Autopilot Engagement, Disengagement, and Indications .............................................. 14 a. Autopilot engagement .............................................................................................. 14 (1) Single switch action ........................................................................................ 14 (2) Engagement status of autopilot ....................................................................... 14 (3) Multiple autopilots .......................................................................................... 14 (4) Acceptable transients ...................................................................................... 14 (5) FD not engaged ............................................................................................... 14 (6) FD engaged ..................................................................................................... 14 b. Autopilot disengagement ......................................................................................... 15 (1) General ............................................................................................................ 15 (2) Autopilot disengagement alerts....................................................................... 16 (3) Quick disengagement control ......................................................................... 16 (4) Alternative means of autopilot disengagement ............................................... 17 (5) Flightcrew pitch trim input ............................................................................. 17 28. FD Engagement, Disengagement, and Indications ........................................................ 18 a. FD engagement ........................................................................................................ 18 (1) General ............................................................................................................ 18 (2) Guidance cue(s) .............................................................................................. 19 (3) Reactive windshear guidance system.............................................................. 19 b. FD disengagement ................................................................................................... 19 29. Autothrust Engagement, Disengagement, and Indications ............................................ 19 a. Autothrust engagement ............................................................................................ 19 (1) Indication ........................................................................................................ 19 (2) Accessibility of controls ................................................................................. 19 iii 10/27/14 AC 25.1329-1C CONTENTS (CONTINUED) Paragraph Page (3) Inadvertent engagement/disengagement ......................................................... 19 (4) Automatic engagement ................................................................................... 19 b. Autothrust disengagement ....................................................................................... 20 (1) Indication of disengagement ........................................................................... 20 (2) Inadvertent disengagement ............................................................................. 20 (3) Consequence of disengagement ...................................................................... 20 (4) Autothrust quick disengagement control ........................................................ 20 30. Override of the FGS ....................................................................................................... 21 a. General ..................................................................................................................... 21 b. Autopilot override .................................................................................................... 21 (1) With automatic disengagement ....................................................................... 21 (2) Without automatic disengagement .................................................................