AMC 25.729 Extending retracting mechanisms

• ED Decision 2016/010/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

AMC 25.729 Extending retracting mechanisms ED Decision 2016/010/R 1. PURPOSE. This Acceptable Means of Compliance (AMC) provides guidance material for use as an acceptable means of demonstrating compliance with the landing gear retracting mechanism requirements of the Certification Specification (CS) for large aeroplanes. 2. RELATED DOCUMENTS. a. Related Certification Specifications. [CS 25.729](#_DxCrossRefBm1709821154) and other paragraphs relating to landing gear extending and retracting mechanisms installations together with their applicable AMCs, if any. Paragraphs which prescribe requirements for the design, substantiation, and certification of landing gear extending and retracting mechanisms include: CS 25.111 Take-off path CS 25.301 Loads CS25.303 Factor of safety CS 25.305 Strength and deformation CS 25.307 Proof of structure CS 25.333 Flight envelope CS 25.471 General [Ground loads] CS 25.561 General [Emergency Landing Conditions] CS 25.601 General [Design and Construction] CS 25.603 Materials CS 25.605 Fabrication methods CS 25.607 Fasteners CS 25.609 Protection of structure CS 25.613 Material strength properties CS 25.619 Special factors CS 25.621 Casting factors CS 25.623 Bearing factors CS 25.625 Fitting factors CS 25.729 Extending and retracting mechanisms CS 25.777 Cockpit controls CS 25.779 Motion and effect of cockpit controls CS 25.781 Cockpit control knob shape CS 25.863 Flammable fluid fire protection CS 25.869 Fire protection: systems CS 25.899 Electrical bonding, etc. CS 25.1301 Function and installation CS 25.1309 Equipment, systems and installations CS 25.1315 Negative acceleration CS 25.1316 System lightning protection CS 25.1322 Warning, caution and advisory lights CS 25.1353 Electrical equipment and installations CS 25.1357 Circuit protective devices CS 25.1360 Precautions against injury CS 25.1435 Hydraulic systems CS 25.1515 Landing gear speeds CS 25.1555 Control markings CS 25.1583 Operating limitations CS 25.1585 Operating procedures b. FAA Advisory Circulars (AC's). AC 20-34D Prevention of Retractable Landing Gear Failures AC 23-17B Systems and Equipment Guide for Certification of Part 23 Airplanes and Airships AC 25.1309-1A System Design and Analysis AC 25-7C Flight Test Guide for Certification of Transport Category Airplanes AC 25-22 Certification of Transport Airplane Mechanical Systems AC 43.13-1B Acceptable Methods, Techniques and Practices - Aircraft Inspection and Repair. c. Federal Aviation Administration Orders. Order 8110.4C Type Certification Process Advisory Circulars and FAA Orders can be obtained from the U.S. Department of Transportation, Subsequent Distribution Office, SVC-121.23, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20785. d. Society of Automotive Engineers (SAE) Documents. SAE AIR-4566 Crashworthiness Landing Gear Design SAE ARP-1311A Landing Gear - Aircraft ISO 7137 Environmental Conditions and Test Procedures for Airborne Equipment (not an SAE document but is available from the SAE) These documents can be obtained from the Society of Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale, Pennsylvania, 15096. e. Industry Documents. (1) EUROCAE ED-14G/RTCA, Inc., Document No. DO-160G, Environmental Conditions and Test Procedures for Airborne Equipment. (2) AMC 20-115, Software Considerations in Airborne Systems and Equipment Certification. These documents can be obtained from EUROCAE, 17 rue Hamelin, 75783 Paris Cedex 15, France f. Military Documents. MIL-STD-810 Environmental Test Methods and Engineering Guidelines This document can be obtained from the Department of Defence, DODSSP, Standardisation Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. 4. DISCUSSION. a. Intent of rule. (Reference [CS 25.729](#_DxCrossRefBm1709821154) Extending and retracting mechanisms) This rule provides minimum design and certification requirements for landing gear actuation systems to address: (1) Structural integrity for the nose and main landing gear, extending and retracting mechanism(s), doors, gear supporting structure for loads imposed during flight; (2) Positive locking of the kinematic mechanisms; (3) Redundant means of extending the landing gear; (4) Demonstration of proper operation by test; (5) Gear up-and-locked and down-and-locked position indications and aural warning; (6) Equipment damage from tyre burst, loose tread, and wheel brake temperatures. b. Demonstration of extending and retracting mechanisms proper functioning. (Reference [CS 25.729(d)](#_DxCrossRefBm1709821154) Operation test) Guidance addressing flight testing used to demonstrate compliance with this paragraph may be found in FAA Advisory Circular (AC) 25-7C, Flight Test Guide for Transport Category Aeroplanes, Chapter 4, Section 4, paragraph 52, dated 16 October 2012. c. Extending and retracting mechanisms indication. (Reference [CS 25.729(e)](#_DxCrossRefBm1709821154) Position indicator and warning device) (1) When light indicators are used, they should be arranged so that- (i) A green light for each unit is illuminated only when the unit is secured in the correct landing position. (ii) A warning light consistent with [CS 25.1322](#_DxCrossRefBm1709821114) is illuminated at all times except when the landing gear and its doors are secured in the landing or retracted position. (2) The warning required by [CS 25.729(e)(2)](#_DxCrossRefBm1709821154) should preferably operate whatever the position of wing leading- or trailing-edge devices or the number of engines operating. (3) The design should be such that nuisance activation of the warning is minimised, for example- (i) When the landing gear is retracted after a take-off following an engine failure, or during a take-off when a common flap setting is used for take-off and landing; (ii) When the throttles are closed in a normal descent; or (iii) When flying at low altitude in clean or low speed configuration (special operation). (4) Inhibition of the warning above a safe altitude out of final approach phase either automatically or by some other means to prevent these situations is acceptable, but it should automatically reset for a further approach. (5) Means to de-activate the warning required by [CS 25.729(e)](#_DxCrossRefBm1709821154) may be installed for use in abnormal or emergency conditions provided that it is not readily available to the flight crew, i.e. the control device is protected against inadvertent actuation by the flight crew and its de-activated state is obvious to the flight crew. d. Definitions. For definitions of VSR and VC, see CS-Definitions Chapter 2, entitled 'Abbreviations and symbols'. [Amdt 25/4] [Amdt 25/12] [Amdt 25/14] [Amdt 25/18]