Advisory Circular
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Advisory Circular Subject: Dynamic Evaluation of Seat Date: 01/10/06 AC No: 25.562-1B Restraint Systems and Occupant Initiated by: ANM-110 Protection on Transport Airplanes 1. PURPOSE. This advisory circular (AC) provides information and guidance regarding acceptable means of compliance with the requirements of 14 CFR part 25 applicable to dynamic testing of seats. The AC provides background and discussion of the reasoning behind the test procedures. It also describes the test facilities and equipment necessary to conduct the tests. 2. APPLICABILITY. a. The guidance provided in this document is directed to airplane manufacturers, modifiers, foreign regulatory authorities, Federal Aviation Administration (FAA) transport airplane type certification engineers, and FAA designees. b. This material 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. The FAA will consider other methods of demonstrating 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. On the other hand, if 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. This material does not change or create any additional regulatory requirements nor does it authorize changes in, or permit deviations from, existing regulatory requirements. 3. CANCELLATION. Advisory Circular 25.562-1A, dated 01/19/96, is canceled. 01/10/2006 AC 25.562-1B 4. RELATED REGULATIONS. Sections 25.562, 25.785, 25.787, and 25.789 of Title 14, Code of Federal Regulations. Ali Bahrami Manager Transport Airplane Directorate Aircraft Certification Service ii AC 25.562-1B 01/10/2006 CONTENTS SECTION PAGE 1. DEFINITIONS 1 2. DISCUSSION 2 a. Intent of Tests 2 b. Standardized Test Procedures—Reasons and Practicalities 2 c. Standardized Test Procedures—Relationship to Design 2 3. TEST CONDITIONS 4 a. General 4 b. Consideration of Test Criteria 7 4. TEST ARTICLES 8 a. General 8 b. Critical Components 8 c. Family of Seats 9 5. TEST ARTICLE SELECTION AND RELATED TEST SETUP 10 a. General 10 b. Criteria for Selection 11 c. Family of Seats 11 d. Structural Tests 11 e. Injury Criteria 16 f. Deformation for Egress 20 6. TEST FACILITIES 21 a. General 21 b. Deceleration Sled Facilities 21 c. Acceleration Sled Facilities 22 d. Impact-with-rebound Sled Facilities 23 e. Drop Towers 23 7. ANTHROPOMORPHIC TEST DEVICES 24 a. General 24 b. Modification to Measure Pelvic/Lumbar Load 24 c. Other ATD Modifications 25 d. Equivalent ATDs 26 8. INSTRUMENTATION 26 a. General 26 b. Electronic Instrumentation 27 c. Photographic Instrumentation 28 iii 01/10/2006 AC 25.562-1B 9. TEST FIXTURES 29 a. General 29 b. Floor Deformation 29 c. Other Mounting Configuration Constraints 31 d. Side-facing Seats 38 e. Multiple Row Test Fixtures 38 f. Other Fixture Applications 39 10. TEST PREPARATION 39 a. Preparation for the Tests 39 b. Use of Anthropomorphic Dummies 39 c. Seat Adjustment 40 d. Installation of Instrumentation 40 e. Restraint System Adjustment 41 f. Floor Requirement 42 g. Seat Components 42 11. DATA REQUIREMENTS 45 12. DATA ANALYSIS 45 a. General 45 b. Impact Pulse Shape 45 c. Total Velocity Change 46 d. Head Injury Criterion (HIC) 47 e. Upper Torso Restraint System Load 47 f. Compressive Load Between the Pelvis and Lumbar Column 48 g. Retention of Upper Torso Restraint Straps 48 h. Retention of Pelvic Restraint 49 i. Femur Load 49 13. PASS/FAIL CRITERIA 49 14. TEST FAILURES VS. RETEST 50 15. TEST DOCUMENTATION 51 a. General 51 b. Test Description 52 16. COMPUTER MODELS 53 iv AC 25.562-1B 01/10/2006 APPENDICES APPENDIX 1 – PROCEDURE FOR EVALUATING PULSE SHAPES 54 APPENDIX 2 – SEAT DEFORMATION 59 APPENDIX 3 – SEAT FAMILY DEFINITION 63 APPENDIX 4 — DEMONSTRATING COMPLIANCE WITH HIC FOR REPETITIVE SEAT ROWS 83 APPENDIX 5 — SUBSTANTIATING RETENTION OF ITEMS ATTACHED TO SEATS 91 FIGURES Figure 3-1 – Seat/Restraint System Dynamic Tests 6 Figure 5-1 – Decision Chart – 16g Test 13 Figure 5-2 – Structural Test Article Decision Tree for Seat Family 14 Figure 5-3 – Restraint Trailing Occupant 18 Figure 7-1 – Installation of Pelvic-Lumbar Load Cell in Part 572B ATD 25 Figure 9-1 – Schematic Floor Deformation Fixture – Seat Legs Attached at Floor Level 30 Figure 9-2 – Floor Warpage Multiple Leg Seat 32 Figure 9-3 – Floor Warpage Multiple Leg Seat 33 Figure 9-4 – Schematic Floor Deformation Fixture – Seat Legs Attached at Side Wall 36 Figure 9-5 – Seats Mounted in an Aisle 37 Figure 10-1 – Measurement of 1g Pre-load 43 Figure 10-2 – Test Orientation, 1g Position 44 v 01/10/2006 AC 25.562-1B THIS PAGE INTENTIONALLY LEFT BLANK vi AC 25.562-1B 01/10/2006 1. DEFINITIONS. The following definitions apply to the terms used in this AC. These terms may be used in other documents with different meanings and should, therefore, be verified in the context of those documents. Anthropomorphic Test Device (ATD)—A device—sometimes called a test “dummy”— used to provide realistic dynamic response representing that of a human. Baseline Testing—The initial series of tests performed as part of the original certification to substantiate that a family of seats meets regulatory requirements. Energy Absorbing Device—An energy dissipating element of a seat which is load-rate or peak-load sensitive. Energy Absorber “Bottom-Out”—The energy absorber “bottoms out” when it reaches its maximum stroke and no longer provides an energy absorption function. Energy Absorber Rating—The load required to actuate the energy-absorbing device. The “highest rated” energy-absorbing device would be the device that requires the highest load to initiate. Family of Seats—A group of seat assemblies, regardless of the number of seat places, built from equivalent components in the primary load path. See paragraph 4c and Appendix 3 for an expanded discussion. Instability Failure—An instantaneous loss of the load-carrying capability of a structural member (for example, the collapse of a column). Occupant Position—The static relationship of the occupant relative to fixed points on the seat. This is assessed using the Seat Reference Point (SRP), as defined in Society of Automotive Engineers Aerospace Standard AS8049 Revision A. Rational Analysis—An analysis based on good engineering principles, judgment, and/or accepted methodology. This can include, but is not limited to, static/dynamic load comparison, static strength analysis, comparative static/dynamic strength analysis, linear static and non-linear finite element analysis, and inspection. Seat Primary Load Path—The components within the seat that carry the load from the point of load application to the structure that reacts the load from the seat system or sub- system. The primary load path may be segmented into its discrete elements, depending on the parameter being evaluated, as follows: • Structural: from seat belt to fittings which attach the seat system to the airplane structure. • Lumbar: from bottom cushion to fittings which attach the seat system to the airplane structure. 1 01/10/2006 AC 25.562-1B • Row-to Row Head Injury Criterion (HIC): from point of ATD head contact to the attachment of seat primary structure. • Head Path (for example, front row or large pitch seats): same as structural. Similar Design Philosophy - A design which uses the same: • Method of construction and manufacturing process (for example, machined part versus built-up part), • Detail part materials (for example, alloys or heat treat), • Load path, • Geometry, including section properties, except for minor differences resulting from space limitations within the seat or aircraft interface, and • Attachment method, except for minor differences resulting from space limitations within the seat Typically—to be considered “minor”—differences to the geometry and attachment method must be shown to be equivalent to or less critical than the seat tested during “baseline testing” with regard to strength, stiffness, and seat permanent deformation. 2. DISCUSSION. a. Intent of Tests. The intent of the tests is to evaluate airplane seats, restraints, and related interior systems in order to demonstrate their structural strength and their ability to protect an occupant from serious injuries in a survivable crash. For example, the potential for serious head injury, which is influenced by head strike envelopes and seat pitch, is assessed in the tests. A standardized methodology for making head impact injury assessments is provided in Appendix 4. This methodology should minimize the amount of testing required. b. Standardized Test Procedures—Reason and Practicalities. The tests described in this AC are standardized procedures generally regarded as the minimum necessary to demonstrate compliance. Standardized procedures seek to obtain consistent results between different test facilities. These facilities may be of varying types, as described in paragraph 6. Often they are not under the direct control of the designer or manufacturer of the article under test, and they may be primarily dedicated to testing which is not related to the aerospace industry. To foster industry standardization, this AC describes many of the procedures and evaluations that are already accepted as standards by government and commercial test facilities. These procedures have been modified only as necessary for the specific testing of civil airplane systems. c. Standardized Test Procedures—Relationship to Design. As stated above, the tests are standardized by necessity. However, the seat/restraint should be designed to protect the occupant under all conditions within the impact envelope specified in § 25.562.