1、AEROSPACE INFORMATION REPORTAIR5575Issued 2002-06Hot Stamp Wire Marking Concerns for Aerospace Vehicle ApplicationsFOREWORDHot stamp ink marking of aircraft electrical wiring for circuit identification was initially introduced in the 1940s. At that time the process was well matched to the physical c
2、haracteristics of the wire insulation, which was thick enough to withstand the indentation of the marking process. However, as wire insulation has become markedly thinner over the intervening years, problems have arisen with damage to wiring as a result of excessive penetration by hot stamp marking.
3、 The frequent need for adjustments in temperature, pressure and dwell time inherent to achieving legible hot stamp wire marking provides numerous opportunities for error. The controls, methods, and guidance necessary to achieve satisfactory performance with hot stamp marking are often not made avail
4、able to operators in smaller wire shops.In recent years, non-impact marking processes have been developed that can mark virtually all of the common wire types used in aerospace interconnect applications. Given the availability and cost effectiveness of these processes and the associated equipment, t
5、he time has come for military services and civil regulatory agencies to accelerate the phase-out of hot stamping in aircraft applications. Full conversion to non-impact marking processes is needed in order to enhance the safety and reliability of todays air vehicles.Modern aircraft electrical and av
6、ionics systems depend heavily on their interconnecting wiring to function properly. To carry signals and power between components, thousands of feet of airframe wiring are routed through nearly every cubic foot of an aircrafts volume. Although some of this wiring is carefully installed and located i
7、n the pristine environment of pressurized interior sections, much of it is subjected to operational stresses. These stresses are created by operation in compartments that experience repeated cycles at extreme temperatures, vibration, fluids of various types, and potential damage induced during maint
8、enance activities in adjacent areas. The ability of such wiring to resist failure under these circumstances is not only dependent on its materials and construction, it is largely dependent upon the application of the best available fabrication, assembly and installation practices during the manufact
9、uring cycle.SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement ari
10、sing therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2009 SAE International All rights reserved. No part of this pub
11、lication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (ou
12、tside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedbackon this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5575Reaffirmed 2009-019Copyright SAE International Provided by IHS under license wit
13、h SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5575- 2 -TABLE OF CONTENTS1. SCOPE .31.1 Purpose.31.2 Field of Application32. REFERENCES .32.1 Applicable Documents 32.1.1 SAE Publications 32.1.2 U.S. Government Publications32.1.3 ASTM Publications42.1.4
14、 Other Publications.42.1.5 Technical Papers.43. DISCUSSION43.1 Failure Investigation43.2 Determining the Cause of Wiring Failures 43.2.1 United States Air Force Findings 53.3 Implications for Wire Marking Technology 63.4 Hot Stamp Quality Control 73.5 Long Term Insulation Failures.83.6 Arcing Effect
15、s on Aircraft Systems93.7 Government/Industry Actions - Wire Identification Marking Process 93.7.1 Excerpts from FAA AC43.13-1B, Acceptable Methods, Techniques, andPractices - Aircraft Inspection and Repair, Chapter 11 .103.7.2 Excerpt from UK Civil Aviation Authority Note 11-22 Appendix 24-3 113.7.
16、3 Excerpt from MIL-W-5088L, Wiring Aerospace Vehicles 113.7.4 Quote from AECMAs prEN3838 Aerospace Series Requirements and Testson User-Applied Markings on Aircraft Electrical Cables .113.7.5 Quotes from British Standard G:244 1989 Code of Practice for Installation/Repair of Aircraft Electrical Inte
17、rconnection Systems .113.7.6 Quote from SAE AS50881A, Wiring Aerospace Vehicles.113.7.7 Quote from SAE ARP5369, Guidelines for Identification Marking Using the HotStamp Process123.7.8 Industry Technical Experts 124. CONCLUSIONS13Copyright SAE International Provided by IHS under license with SAENot f
18、or ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5575- 3 -1. SCOPE:This SAE Aerospace Information Report (AIR) discusses the often overlooked relationship between hot stamp marking and the environmental conditions that contribute aircraft wiring problems and discu
19、sses current beliefs of military service experts, regulatory agencies and industry standard writing bodies about the potential hazards imposed by the hot stamping process.1.1 Purpose:Although prominent members of the aerospace community are taking aggressive measures to phase out the hot stamping of
20、 interconnecting wire, the process lingers on, particularly within the operations of smaller manufacturers, modification shops, and operator maintenance facilities. In recent years, non-impact marking processes have been developed that can mark virtually all of the common wire types used in aerospac
21、e interconnect applications. The purpose of this document is to encourage full conversion to non-impact marking processes in order to reduce the probability of causing damage to the wire insulation.1.2 Field of Application:Todays civil aircraft are relied upon by airlines to perform safely for at le
22、ast 50,000 flight hours and 20 or more years of operation. Military aircraft are typically in service for a comparable period under more severe conditions, but do not experience as many flight hours. Extending the life of the current fleet to meet these requirements depends heavily on the processes
23、used for original manufacture, system upgrade modifications and life extension refurbishment programs. Improvement in the manufacturing techniques supporting these activities is essential to guaranteeing acceptable levels of performance throughout the life of the vehicle.2. REFERENCES:2.1 Applicable
24、 Documents:2.1.1 SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.AS50881 Wiring Aerospace VehiclesARP5369 Guidelines for Wire Identification Using the Hot Stamp ProcessARP5607 Legibility of Print on Aerospace Wires and Cables2.1.2 U.S. Government Publications:
25、 Available from DOSDSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.MIL-W-5088L Wiring, Aerospace VehiclesAC43.13-1B Advisory Circular, Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair, U.S. Department of Transportation, Fed
26、eral Aviation AdministrationWL-TR-95-4004 Aircraft Mishap Investigation Handbook for Electronic Hardware, Materials Directorate, Wright Laboratory, U.S. Air Force Material CommandCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted w
27、ithout license from IHS-,-,-SAE AIR5575- 4 -2.1.3 ASTM Publications: Available from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM D 3032 Hookup Wire Insulation, Standard Methods of Testing2.1.4 Other Publications:UK Civil Aviation Authority Note 11-22 Appendix 24-3, Electrical C
28、able Failure, June 22 1998prEN3838 AECMA Standard, Aerospace Series, Requirements And Tests On User-Applied Markings On Aircraft Electrical Cables, September 1995G244 British Standard Aerospace Series Code of Practice For: Installation/Repair of Electrical Interconnection Systems, 1989Handbook Slens
29、ki G. and Galler D., Electronic Failure Analysis Handbook, McGraw-Hill, 19992.1.5 Technical Papers:John W. DeHart, DuPont Company, Carbon Arc Tracking Tests, May 17, 1985John Brooks, International Aero, Gary Scott, Square D Company, Arc-fault Circuit Interrupters for Aerospace Applications, 1999Dr.
30、Armin M. Bruning, Lectromechanical Design Company, Aging Measurements of Operating Aircraft: Implications for Specification Writing and A/C Reliability, 19973. DISCUSSION:3.1 Failure Investigation:It is very difficult to determine the initial cause of some types of failures that may involve an aircr
31、afts wiring system. Given the usual condition of affected aircraft sections, it is normally very difficult to determine exactly where the failure occurred and whether wiring was the victim or the cause of the damage.3.2 Determining the Cause of Wiring Failures:Wire arcing failures are sometimes foll
32、owed by insulation destruction, in which the subject wire(s) and much of the surrounding materials are destroyed. It is usually very difficult under such circumstances to determine the exact cause of the event that resulted in such a failure. However numerous efforts have been made to replicate some
33、 of these incidents in a laboratory environment and occasional successes have been achieved.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5575- 5 -3.2.1 United States Air Force Findings: The
34、 United States Air Force Material Directorate of Wright Laboratory at Wright Patterson Air Force Base has undertaken numerous investigations of aircraft mishaps in recent years. Their approach is analytical in that they conduct extensive collection of materials from each subject aircraft and employ
35、laboratory examination and sometimes, incident reconstruction. Their conclusions are not anecdotal - they typically can demonstrate scientifically that any conclusion reached is supported by logical investigation and technical analysis. As the result of these efforts, this organization gained a comp
36、rehensive understanding of wiring failure mechanisms. Their WL-TR-95-4004 Aircraft Mishap Investigation Handbook for Electronic Hardware provides guidance and an appropriate methodology for conducting such investigations. The Wiring Section of this handbook includes several statements regarding arci
37、ng failures of aircraft wiring including the following: “Arc tracking resistance is a fundamental property related to insulation failure and flashover. In the early stages of insulation breakdown, low current discharges occur between the conductor and other energized components. These may occur at p
38、inhole flaws in the insulation or at sites where chemical contamination has compromised the insulation. Tracks develop along the discharge path on the surface of the insulation. The tracks are generally more conductive than the virgin insulation. The material is said to have poor arc-tracking resist
39、ance if these tracks carbonize quickly into significant conducting paths.” “Aromatic polyimide films have this structure and are susceptible to flashover.”“At bends in the wire, radial cracks may develop from manufacturing defects or chafe damage and propagate completely through the insulation mater
40、ial to the conductor. The bare conductor is thereby exposed rather quickly, catastrophically accelerating arc breakdown. Environmental factors can greatly accelerate insulation mechanical property degradation. Examples are sunlight (ultra-violet radiation), moisture and various aircraft fluids.”“Pre
41、caution: Insulation failures in Polyimide insulated wire are difficult to diagnose because of the rapid, catastrophic failures that can occur.” “The problem is especially severe in moist environments. Initially the conduction occurs in small, non-uniform areas which become carbonized quickly.” “Insu
42、lation failure is generally an initiating event and is accompanied by arcing.”A typical example of the United States Air Force Material Directorates findings is shown in Figure 1. The resultant conclusions are similar to those of extensive counterpart studies conducted by the Naval Research Laborato
43、ry, in which several different arc-tracking mechanisms were replicated in a series of laboratory experiments. These tests have lent themselves to gaining a more comprehensive understanding of the types of failures that have occurred and to understanding the underlying causes. They have played a very
44、 important role in determining the types of wire insulation material and construction that will be authorized for future production aircraft. They have also led to the addition of specific qualification tests to verify the resistance of new wire types to wet and dry arc tracking failures. The arc tr
45、acking characteristics are associated with the insulations ability to carbon track or to burn intensively when exposed to a high temperature arc. Carbon tracking and high temperature arcs occur only when the insulation has been penetrated. This new focus on how wire might react to mechanical damage
46、and impact on its surrounding area will be an important contribution to future improvement in wire insulation types.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5575- 6 -FIGURE 1 - Electric
47、al Arcing Damage Caused by Exposure of Hot StampDamaged Conductors in a High Moisture Aircraft Environment3.3 Implications for Wire Marking Technology:The pre-requisite observation that conductors must be exposed in order to initiate failures has also resulted in guidelines that are intended to mini
48、mize the likelihood that manufacturing processes used to mark identification codes on the subject wires contribute to this exposure.For many decades, the use of hot stamping for the marking of such codes was almost universally applied in the aircraft industry. However, experience has shown this proc
49、ess to be operator sensitive. Typically, machinery used for hot stamping is equipped with operator-controlled adjustments for the pressure, temperature and dwell time used to apply each mark. Variations in insulation material properties, marking foil quality and marking equipment condition can result in the need to make numerous adjustments to the process to achieve durable markings of sufficient legibility, as currently
