Microsoft PowerPoint EWIS job aid 2.0.ppt

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1 Aircraft EWIS Practices Job Aid 2.0 Federal Aviation Administration Aircraft Electrical Wiring Interconnect System (EWIS) Best Practices Job Aid Revision: 2.0 This job aid covers a pplicable 14 CFR part 25 aircraft (although it is also widely acceptab le for use with other ty pes of aircraft such d rotorcraft). This job aid as military, small airplanes, an practices; pr imary factors addresses policy; industry EWIS associated with EWIS degradation; informat ion on TC/STC data package requirements; EWIS se lection and protection; routing, splicing and termination pract ices; and EWIS maintenance concepts (including how to perform a EWIS general visual actual aircraft inspection). The job aid also includes numerous EWIS photos and examples. 1 UNCONTROLLED COPY WHEN DOWNLOADED

2 Aircraft EWIS Practices Job Aid 2.0 Additional Notes This presentation contains • additional speaker notes for most slides It’s advisable to read these • notes while viewing the slide presentation Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 2 Administration 2 UNCONTROLLED COPY WHEN DOWNLOADED

3 Aircraft EWIS Practices Job Aid 2.0 Printing the Additional Notes To print the slides and accompanying speaker notes: – Navigate back to the FAA Aircraft Certification job aids web page – Open and print Printable Slides and Notes Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 3 Administration 3 UNCONTROLLED COPY WHEN DOWNLOADED

4 Aircraft EWIS Practices Job Aid 2.0 Background Why the need for EWIS best practices Job • Aid? – Accident/Incident Service History – Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) – Enhanced Airworthiness Program for Airplane System (EAPAS) – EAPAS Rule Making Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 4 Administration Historically, wiring and asso ciated components were installed without much th he aging aspects: ought given to t • Fit and forget. • Unanticipated failure m odes and their severity. - Arc tracking. - Arcing. - Insulation flashover. Maintenance programs often di d not address these aging aspects. Service hi story also indicates that Foreign Object Damage (FOD) such as drill shavin gs, caustic liquid s, etc. does can lead to EWIS faults. cause EWIS degradation that 4 UNCONTROLLED COPY WHEN DOWNLOADED

5 Aircraft EWIS Practices Job Aid 2.0 Introduction • ety concerns raised Late 1980s, wiring saf due to accidents & incidents • Investigations found common degrading factors in airplane el ectrical wiring systems • Investigation into wiring issues done by industry, civil aviation authorities, other government agencies Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 5 Administration The aging issues in wiring s ystems were made known by the following: ncerns were raised due to accidents •In the late 1980s, wiring safety co & incidents •Investigations found co mmon degrading factors in airplane electrical wiring systems •Investigation in to wiring issues done by industry, civil aviation authorities, go vernment agencies 5 UNCONTROLLED COPY WHEN DOWNLOADED

6 Aircraft EWIS Practices Job Aid 2.0 Wiring Investigation Findings Wiring is affected by: Design • • Environment • Maintenance • Awareness • Operation Abuse • Training • • Time Repair • Installation • Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 6 Administration As listed here, the investigation of the aircraft wiring revealed that play a role in there are several factors, together with time, wiring degradation. 6 UNCONTROLLED COPY WHEN DOWNLOADED

7 Aircraft EWIS Practices Job Aid 2.0 Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) • Phase I – Tasked to develop and propose recommendations for airworthiness enhancements to the FAA. Tasks completed and reports appr oved by ATSRAC in January 2001. • Phase II – Tasked to developed and propose airworthiness enhancements based on the re commendations developed in Phase I. Tasks completed and reports appr oved by ATSRAC in January 2003. Phase III • the implementation of the – Tasked to assist FAA with enhancements developed in Phase II. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 7 Administration making Advisory Committee Aging Transport Systems Rule Phase I – The following tasks were undertaken by ATSRAC in this phase for developing and proposing recommendations for airworthiness enhancements to the FAA: Sampling inspection of the fleet Review of fleet service history Improvement of maintenance criteria Review and update standard practice for wiring Review air carrier and repair station in spection and repair training programs Phase II – The following tasks were undertaken by ATSRAC in this phase to develop and propose airworthiness enhanc ements based on the recommenda tions developed in Phase I: Improving wire system cert ification requirements Enhancing wiring maintenance pr ocedures and instructions Enhancing and augment cu rrent training programs Standardizing the format of Stand ard Wiring Practices Manual Study of aging issues in small tran sport airplanes electrical wiring The following tasks are currently undertaken Phase III - by ATSRAC in this phase to assist FAA with the implementation of t he enhancements developed in Phase II: Provide assistance in implementat ion of the airworthiness enhanc ements and, if requested, develop alternatives to rulemaking for impl ementation of training and maintenance enhancements. Assist in review and implement ation of new technologies devel oped for mitigating the aging issues in aircraft wiring systems. Study and develop enhan cements for wiring maintenance procedures for small transport less than 7,500 pound payload). pacity between 6 to 30 and airplanes (with a passenger ca 7 UNCONTROLLED COPY WHEN DOWNLOADED

8 Aircraft EWIS Practices Job Aid 2.0 Routing/Chafing In-Service Examples Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 8 Administration These photos show examples of findings. These examples show the potential for chafing and arcing. 8 UNCONTROLLED COPY WHEN DOWNLOADED

9 Aircraft EWIS Practices Job Aid 2.0 Accumulation of Dirt and Lint Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 9 Administration Accumulation of dirt and lint crea te a potential for smoke and fire, making inspection of the EWIS impossible. 9 UNCONTROLLED COPY WHEN DOWNLOADED

10 Aircraft EWIS Practices Job Aid 2.0 Coil and Stow In-Service Example / Result Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 10 Administration This slide shows an example of improper term ination of unused ation caps and it’s wires. On the left si de, there are no termin improperly stowed. an improper main tenance action. On the right side is a photo of stead of being Coaxial cable was left attached to an antenna in removed in its entirety – at least it should have been detached from the antenna. Consequently, lightning attached to the antenna, traveled along the EWIS , and caused a fire in the cabin. 10 UNCONTROLLED COPY WHEN DOWNLOADED

11 Aircraft EWIS Practices Job Aid 2.0 Bend Radius Problem In-Service Example Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 11 Administration This photo shows an improper bend radius installation of electrical wire. The pro on aircraft should per bend radius for wire be 10 times the outside diameter of the largest diameter wire in the bundle for one side suppor ted (3 times for two sides supported.) Standard industrial pra ctice and is in AC 43.13-1b and Standard Wiring Prac tices Manual (SWPM). 11 UNCONTROLLED COPY WHEN DOWNLOADED

12 Aircraft EWIS Practices Job Aid 2.0 Arcing Event Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 12 Administration These photos illustrate an improper main tenance action caused when The attach screw e was relocated. the airplane’s airworthiness certificat A maintenance insp ector riding on penetrated the power cables. The FA s clothing on fire. the jump seat caught hi The arcing event, whic de the electrical power h originated from insi the hallway (looking center, burned a hole t hrough the left side of forward) between the cockpit and cabin. 12 UNCONTROLLED COPY WHEN DOWNLOADED

13 Aircraft EWIS Practices Job Aid 2.0 Effect of Improper Maintenance Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 13 Administration oto shows failure of wire due to chafing inside a The left side of this ph metallic conduit. Created an arc, wh ich created holes in the fuel line below the conduit. Caus ed by improperly replaci ng an existing power feeder. 13 UNCONTROLLED COPY WHEN DOWNLOADED

14 Aircraft EWIS Practices Job Aid 2.0 Effect of Poor Design Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 14 Administration This shows arcing due to lavat ory servicing li nes leaking on damaged EWIS, creating an arc that caused a fire that led to extensive damage insi de and outside of the airplane. Business class lavatory drip shield not installed – water shorted cannon plug in wire bundle below deck. ning, operations – all need Maintenance, design, trai improvement. 14 UNCONTROLLED COPY WHEN DOWNLOADED

15 Aircraft EWIS Practices Job Aid 2.0 Previous Regulations Inadequate • Previous regulations fell short of providing specific wiring-related requirements. Specific wiring-related requirements • needed to be included in certification and operational regulations. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 15 Administration 15 UNCONTROLLED COPY WHEN DOWNLOADED

16 Aircraft EWIS Practices Job Aid 2.0 Culture Shift: EAPAS Safety Initiative • Recognizing importance of EWIS in safe operation of airplanes leads to being more proactive; FAA is – Treating wiring as a system – Mandating DAH support of the initiative – Integrating FAA lines of business; joint AFS/AIR activity; and cooperation with & between DAHs and operators Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 16 Administration To completely and t horoughly address th e aging issues in aircraft wiring required a cultural shift comprising of: Recognizing importance of electric al wiring in safe operation of airplanes leads to being more proactive; FAA is • Treating wiring as a system of the initiative • Mandating DAH support • Integrating FAA lines of business: th & between joint AFS/AIR activity; and cooperation wi DAHs and operators 16 UNCONTROLLED COPY WHEN DOWNLOADED

17 Aircraft EWIS Practices Job Aid 2.0 Goal of EPAS Rule Enhance safety by improving all aspects of aircraft electrical wiring Goal is based on – – Industry/government committee data-driven recommendations – Maximizing harmonization Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 17 Administration ce safety by improving all The goal of EAPAS was to enhan aspects of aircraft electrical wiring Goal is based on – • Industry/government committee data-driven recommendations • Maximizing harmonization with international authorities So now you hopefully have a better understand ing of the history behind the EAPAS rulemaking and how it came into being. ng to provide a defin ition for an EWIS. We are next goi 17 UNCONTROLLED COPY WHEN DOWNLOADED

18 Aircraft EWIS Practices Job Aid 2.0 EWIS lectrical E W iring nterconnection I S ystem Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 18 Administration Wiring needs to be treated as an important system on airplanes. Wiring Interconnection Wiring is now referred to as the Electrical System (EWIS). 18 UNCONTROLLED COPY WHEN DOWNLOADED

19 Aircraft EWIS Practices Job Aid 2.0 EWIS Definition [per new § 25.1701(a)]: An EWIS • is Any wire, wiring device, or combination of these, including termination devices, installed in any area of the airplane for the purpose of transmitting electrical energy between two or more intended termination points . . . . Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 19 Administration 19 UNCONTROLLED COPY WHEN DOWNLOADED

20 Aircraft EWIS Practices Job Aid 2.0 25.1701(a)] § [ EWIS is not ... • Electrical equipment or avionics qualified to acceptable environmental conditions and testing procedures Portable electrical • devices not part of airplane’s type design • Fiber optics Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 20 Administration 20 UNCONTROLLED COPY WHEN DOWNLOADED

21 Aircraft EWIS Practices Job Aid 2.0 Key Point to Remember . . . Wire and associated components now treated as an airplane system Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 21 Administration 21 UNCONTROLLED COPY WHEN DOWNLOADED

22 Aircraft EWIS Practices Job Aid 2.0 EWIS Degradation Factors Physical Age Properties EWIS Degradation Environment Installation Maintenance Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 22 Administration EWIS degradation • EWIS degradation is a process that is a fu nction of several variables; aging is on ly one of these. Other main factors that influence EWIS d egradation are the: - Environment in which it is installed. - Physical properties of the EWIS. llation of the EWIS. - Actual physical insta - Maintenance (cleaning a nd repair) of the EWIS. Characteristics of aging EWIS • The manner in which EWIS degrades is there fore dependent upon the EWIS type, ho w it was originally installed, the overall time and environment exposed to in servic e, and how the EWIS was maintained. the EWIS is installed” has a • Service history shows that “how direct effect on EWIS degradation . In other words, EWIS that alled properly has an is not selected or inst increased potential to degrade at an accelerated ra te. Therefore, good aircraft requirements for EWIS to EWIS practices are fundamental remain safely intact. 22 UNCONTROLLED COPY WHEN DOWNLOADED

23 Aircraft EWIS Practices Job Aid 2.0 Causes of EWIS Degradation • Vibration • Moisture • Maintenance Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 23 Administration Vibration – High vibration areas tend to accelerate degradation over time, resulting in "chattering" contacts and in bration can also cause tie- termittent symptoms. High vi wraps, or string-ties to dam age insulation. In addition, high vibr ation will exacerbate any existing problem with wire insulation cracking. Moisture – High moisture areas generally accele rate corrosion of terminals, pins, sockets, and conductors. It should be noted t hat EWIS installed in clean, dry areas with moderate temperatures appears to hold up well. Maintenance ties, if done improperly, may – Unscheduled maintenance activi contribute to long term prob that do not meet adation. Repairs lems and EWIS degr minimum airworthi ness standards may have limited dura bility. Repairs that conform ance practices are ge nerally considered to manufacturers recommended mainten require rework if properly maintained. permanent and should not • Metal shavings and debris have been discovered on wire bundles after maintenance or repairs have been conduct ed. Care should be taken to protect wire bundles and connector s during modification wo rk, and to ensure all shavings and debris are cleaned up after work is completed. • As a general rule, EWIS that is undisturbed will have less degradation than e more brittle with EWIS that is reworked. As EWIS becom age, this effect becomes more pronounced. 23 UNCONTROLLED COPY WHEN DOWNLOADED

24 Aircraft EWIS Practices Job Aid 2.0 Causes of EWIS Degradation , cont. Indirect damage • • Chemical contamination Heat • • Installation Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 24 Administration Indirect damage – Events such as pneumatic duct ruptures can cause damage that, while not initially evident, can later cause EWIS problems. When such an event has occurred, surrounding EWIS should be carefully inspected to ensure no damage is evident. Chemical contamination – Chemicals such as hydraulic fluid, battery electrolytes, fuel, corrosion inhibiting compounds, waste system chemicals, cleaning agents, deicing fluids, paint, and soft drinks can contribute to degradation of EWIS. EWIS in the vicinity of these chemicals should be inspected for damage or degradation. Recommended original equipment manufacturer cleaning instructions should be followed. • Hydraulic fluids, for example, require specia l consideration. Hydraulic fluid is very damaging to connector grommet and wire bundle clamps, leading to indirect damage, such as arcing and chafing. EWIS components that may have been exposed to hydraulic fluid should be given special attention during EWIS inspections. Heat – EWIS components exposed to high heat can accelerate degradation, insulation dryness, and cracking. Direct contact with a high heat source can quickly damage insulation. Even low levels of heat can degrade EWIS over long periods of time. This type of degradation is sometimes seen on engines, in galleys, and behind lights. – EWIS not installed properly can further accelerate the EWIS degradation Installation process. Improper routing, clamping, and terminating during initial installation or during a modifications can lead to EWIS damage. 24 UNCONTROLLED COPY WHEN DOWNLOADED

25 Aircraft EWIS Practices Job Aid 2.0 Current FAA Guidance AC 25.1701-1 Part 26 Part 25 EWIS Policy AC 25.27A Practices ANM-01-04 AC 25-10 AC 43.13-1b AC 25-16 Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 25 Administration ractices-related to 14 part 25 and part 26 EWIS p There are direct specific CFR. There are some specific el ectrical power wiring requirements, such as address all aircraft EWIS. § 25.1353 , but they do not specifically requires that instru 14 CFR 25.1729 ctions for continue d airworthiness are developed using analytica l procedures, which woul d include maintenance tasks and intervals for EWIS. A large body of FAA general guidance for Chapter 11 of AC 43.13-1b . wiring practices is in 25 UNCONTROLLED COPY WHEN DOWNLOADED

26 Aircraft EWIS Practices Job Aid 2.0 Part 25 New part 25 requirements for certification of terconnection systems electrical wiring in (EWIS) 1. Revised existing EWIS related certification requirements and relocated some of them 2. Created new EWIS certification requirements and placed them in a new subpart H 3. New EWIS ICA requirements Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 26 Administration 26 UNCONTROLLED COPY WHEN DOWNLOADED

27 Aircraft EWIS Practices Job Aid 2.0 Part 26 • Affects continued airworthiness issues and/or safety improvements for transport airplanes addressed vi a operational rules • Supports to comply the ability of operators rule requirements with the operational • EAPAS Part 26 Requires actions of Design (DAHs), such as: Approval Holders – instructions for continued airworthiness, – distribution of information to affected operators Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 27 Administration 27 UNCONTROLLED COPY WHEN DOWNLOADED

28 Aircraft EWIS Practices Job Aid 2.0 Part 26 Model Applicability Existing airplanes with a maximum type- • certificated passenge r capacity of 30 or more, or • Existing airplanes with a maximum payload capacity of 7,500 pounds or more (reference § 119.3) Existing airplane models with a type • certificate issued on or after January 1, 1958. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 28 Administration 28 UNCONTROLLED COPY WHEN DOWNLOADED

29 Aircraft EWIS Practices Job Aid 2.0 AC 25.1701-1 • This Advisory Circular (AC) provides guidance for certification of electrical wiring interconnection systems (EWIS) on transport category airplanes 14 CFR part 25, subpart H, sections 25.1701 – through 25.1733 H25.4 and H25.5 of Appendix H to part 25. – Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 29 Administration 29 UNCONTROLLED COPY WHEN DOWNLOADED

30 Aircraft EWIS Practices Job Aid 2.0 AC 25.27A • Provides guidance for developing on instructions for maintenance and inspecti EWIS analysis procedure • Uses an enhanced zonal (EZAP). • For airplane models whose maintenance a zonal inspection programs already include ibed here provides program, the logic descr guidance on improving those programs. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 30 Administration 30 UNCONTROLLED COPY WHEN DOWNLOADED

31 Aircraft EWIS Practices Job Aid 2.0 AC 25.27A, cont. For airplanes without a zonal inspection • program, use of this logic will produce zonal inspections for EWIS that can be added to the existing maintenance program. Contains information that can be used by • operators to Improve EWIS maintenance practices. Stresses the importance of inspecting EWIS • and promotes a philosophy of “protect and clean as you go” when performing maintenance, repair, or alterations on an airplane. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 31 Administration 31 UNCONTROLLED COPY WHEN DOWNLOADED

32 Aircraft EWIS Practices Job Aid 2.0 Policy ANM-01-04 Design data should NOT leave the • installation to the discretion of the installer. • Routing of EWIS should follow the criteria established by the FAA in the certification the holder’s original or basis, as reflected in ed type design. subsequently approv Installation drawings / instructions should • completely define the required routing and installation with sufficient detail to allow repeatability of the installation. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 32 Administration 32 UNCONTROLLED COPY WHEN DOWNLOADED

33 Aircraft EWIS Practices Job Aid 2.0 Guidance: AC 43.13-1b AC 43.13-1b: Acceptable Methods, • Techniques, and Practices - Aircraft Inspection and Repair –Flight Standards AC –Chapter 11- Aircraft Electrical Systems NOTE: The guidance provided in AC 43.13-1b is general in nature and is not to be referenced or used as a substitute for EWIS installation drawings and/or EWIS diagrams. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 33 Administration mprehensive wide range of basic AC 43.13-1b covers a fairly co EWIS practices topics. NOTE: The guidance provi ded in AC 43.13-1b is general in nature and is not to be referenced or used as a substitute for EWIS installation drawings and/or EWIS diagrams. 33 UNCONTROLLED COPY WHEN DOWNLOADED

34 Aircraft EWIS Practices Job Aid 2.0 Guidance: AC 25-16 AC 25 -16: Electrical Fault and Fire • Prevention and Protection (4/5/91) – Provides acceptable means to address electrically caused faults, overheat, smoke, and fire in transport category airplanes Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 34 Administration it relates to tices guidance as AC 25-16 provides wiring prac aircraft fire and smoke safe ty with emphas is on wiring flammability, circuit breaker prote ction, wiring near flammable fluids, and associated ac ceptable test methods. This AC is currently bei ng considered for updating. 34 UNCONTROLLED COPY WHEN DOWNLOADED

35 Aircraft EWIS Practices Job Aid 2.0 Guidance: AC 25-10 AC 25 -10: Guidance for Installation of • Miscellaneous, Non-required Electrical Equipment (3/6/87) – Provides acceptable means to comply with applicable 14 CFRs associated with installation of electrical equipment such as galleys and passenger entertainment systems Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 35 Administration AC 25-10 mainly covers non-required equipment installations etc. From a such as galleys, passenger entert ainment systems, should be treated equally, wiring standpoint, all systems regardless of the functi ons criticality because of potential fire and smoke hazards. This AC contains minimal wiring practices specifics, including general load analysis r equirements and circ uit breaker protection requirements, which are more t horoughly covered in AC 43.13-1b covering 25-10 in any and AC 25-16, so we are not going to be detail. 35 UNCONTROLLED COPY WHEN DOWNLOADED

36 Aircraft EWIS Practices Job Aid 2.0 Electrical Load Determination • Load analysis – Ensure that total electrical load can be safely controlled or managed within rated limits of affected components of aircraft’s electrical system (§ 25.1351) – New or additional electrical devices should not be installed without an electrical load analysis (AC 43.13-1b) Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 36 Administration Electrical load determination is to ensure each aircraft electrical bus can safely support a predetermined amount of electrical load that is based on the electrical capacity of the aircraft generators trical distribution system. and the aircraft’s overall elec §25.1351 requirement: ined through analysis It must be determ that all electrical devices can be safely controll ed or managed by the aircraft’s electrical system. AC 43.13-1b: Whenever an electrical device is added, a load analysis should be performed to ens ure that the ne w load on the bus can be powered adequately such that there is adequate electrical power margin to avoid overloading the bus. Where necessary as determined by a load analysis, wire, wire bundles, and circuit pr otective devices having the correct ratings should be added or replaced. 36 UNCONTROLLED COPY WHEN DOWNLOADED

37 Aircraft EWIS Practices Job Aid 2.0 Circuit Breaker Devices Must be sized to open before current rating of attached wire is exceeded, or before cumulative rating of all connected loads is exceeded, whichever is lower ( § 25.1357) Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 37 Administration protective devices be requires that automatic Section 25.1357 used to minimize distress to the electrical system and minimize hazard to the airplane in the event of wiring faults or serious malfunction of the system or connected equipment. 37 UNCONTROLLED COPY WHEN DOWNLOADED

38 Aircraft EWIS Practices Job Aid 2.0 Circuit Breaker Protection • “A circuit breaker must always open before any component downstream can overheat and generate smoke or fire.” (AC 43.13-1b, para. 11-48) • “Circuit breakers are designed as circuit protection for the wire, not for protection of black boxes or components . . .” (AC 43.13-1b, para. 11-51) Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 38 Administration AC 43.13-1b contains some conflicting st atements. The bullets in says that contradictory. The this slide are somewhat first bullet st any downstream component the breaker must protect again failure. The second bullet says breakers are de signed such that they DO NOT protect components or LRUs. otect the aircraft wiring as In reality, breakers are sized to pr the main design constraint . Any further protection of components or LRUs is desirable but not mandatory. Ideally, circuit breakers should protect against any wiring fault that leads to arcing, sparking, flames, or smoke. But as we will learn, thermal circuit breakers do no t always detect arcing events. 38 UNCONTROLLED COPY WHEN DOWNLOADED

39 Aircraft EWIS Practices Job Aid 2.0 , cont. Circuit Breaker Protection Use of a circuit breaker as a • recommended switch is not – Repeated opening and closing of contacts can lead to damage and premature failure of circuit breakers – Most circuit breaker failures are latent Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 39 Administration Most circuit breakers, other than some remote control circuit as switches a nd should not breakers (RCCB), are not designed be used as a switch. Repeate d opening and closing of the contacts can lead to damage and premature failure of the circuit breakers. Also keep in mind th at circuit breaker failures are, for the most part, latent in nature. So you won’t know they have failed until y ou need them. 39 UNCONTROLLED COPY WHEN DOWNLOADED

40 Aircraft EWIS Practices Job Aid 2.0 Wire Selection Size wires so they: • – Have sufficient mechanical strength – Do not exceed allowable voltage drop levels – Are protected by circuit protection devices – Meet circuit current-carrying requirements Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 40 Administration Section 25.1357 protective devices be requires that automatic used to minimize distress to the electrical system and minimize hazard to the airplane in the event of wiring faults or serious malfunction of the system or connected equipment. 40 UNCONTROLLED COPY WHEN DOWNLOADED

41 Aircraft EWIS Practices Job Aid 2.0 , cont. Wire Selection Mechanical strength of wire sizes less than • #20 – Do not use wire with less than 19 strands – Provide additional support at terminations – Should not be used when subject to excessive vibration, repeated bending, or frequent disconnection (ref. para. 11-66(a), page 11-21) Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 41 Administration tor strands must not be used. Wire containing less than 19 conduc Consideration should be given to the use of high-strength alloy increase mechanical strength. conductors in small gauge wires to As a general practice, wires smaller than #20 should be provided with additional clamps and be grouped w ith at least three other wires. They also should have additional support at terminations, such as connector grommets, strain relief clamps, shrinkable sleeving, or telescoping bushings. They should not be used in applicati ons where they will be subjected to excessive vibration, repeated bendi ng, or frequent disconnection from screw termination. 41 UNCONTROLLED COPY WHEN DOWNLOADED

42 Aircraft EWIS Practices Job Aid 2.0 Wire Selection, cont. Conductor stranding • – Minimizes fatigue breakage • Platings for all copper aircraft wiring – Plated because bare copper develops surface oxide film — a poor conductor • Tin < 150° C • Silver < 200° C • Nickel < 260° C Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 42 Administration Elevated temperature degradation of tin- and silver-plated copper conductors will occur if they are exposed to continuous operation at elevated levels. •For tin-plated conductors , tin-copper intermetallics will se in conductor resistance. form, resulting in an increa •For , degradation in the form of silver-plated conductors interstrand bonding, silver migration, and oxidation of the copper strands will occur wi th continuous operation near rated temperature, resu lting in loss of wi re flexibility. Also, due to potential fire hazard, s ilver-plated conductors shall not be used in areas wher contamination by e they are subject to ethylene glycol solutions. • Both tin- and silver-p lated copper conductors will exhibit degraded solderability aft er exposure to c ontinuous elevated temperature . 42 UNCONTROLLED COPY WHEN DOWNLOADED

43 Aircraft EWIS Practices Job Aid 2.0 Determining Current-Carrying Capacity Effect of heat on wire insulation • – Maximum operating temperature – Single wire or wires in a harness – Altitude Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 43 Administration Heating is an important factor affe cting wire insulati on. This must be factored into prop er selection of wire for each particular application. 43 UNCONTROLLED COPY WHEN DOWNLOADED

44 Aircraft EWIS Practices Job Aid 2.0 Determining Wire System Design • AC 43.13-1b, Section 5: tables and figures provide an acceptable method of determining wire system design Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 44 Administration The applicant should ensure that the maximum ambient temperature that the wire bundles will be subjected to, plus the temperature rise due to the wire current load s, does not exceed the maximum conductor temperature rating. In smaller harnesses, the allow able percentage of total current approaches the single wire may be increased as the harness configuration. The continuous current ratings cont ained in the t ables and figures in AC 43.13-1b were derived only for wire application, and cannot be applied directly to associated wire termination devices (e.g., connector contacts, rela ys, circuit breakers, switches). The current ratings for devices are limited by the design characteristics of the de vice. Care should be taken to ensure that the continuous current value chosen for a particular system circuit ent which could shall not create hot spots within any circuit elem lead to premature failure. 44 UNCONTROLLED COPY WHEN DOWNLOADED

45 Aircraft EWIS Practices Job Aid 2.0 Wire Substitution for Repairs and Maintenance When replacement wire is required, • review aircraft maintenance manual to determine if original aircraft manufacturer (OAM) has approved any substitution – If not approved, then contact OAM for an acceptable replacement Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 45 Administration Most aircraft EWIS designs are to specifications that require rigorous testing of wires before they are manufacturers to pass Products List. Aircraft approved or added to a Qualified manufacturers who ma intain their own wire specifications exercise close control of their approved sources. Therefore, it is maintenance manual or contact important to review the aircraft the original aircraft manufact urer (OAM) when wire substitutions are necessary. The OAM may have special co ncerns regarding shielding, insulation, etc. for certain wiring on the aircraft that perform critical hosen based on functions or wiring that is c a set of unique circumstances. 45 UNCONTROLLED COPY WHEN DOWNLOADED

46 Aircraft EWIS Practices Job Aid 2.0 EWIS Routing Eliminate potential for chafing against • structure or other components Position to eliminate/minimize use as • handhold or support Minimize exposure to damage by • maintenance crews or shifting cargo • Avoid battery electrolytes or other corrosive fluids Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 46 Administration such a manner to ensure In general, EWIS should be routed in reliability and to offer protection from the potential hazards shown in this slide. The next several slides are pi ctures illustrating these hazards. 46 UNCONTROLLED COPY WHEN DOWNLOADED

47 Aircraft EWIS Practices Job Aid 2.0 EWIS Riding on Structure Power cables riding on structure can cause damage to the power cables Improper Proper Example of wire chafing. 47 UNCONTROLLED COPY WHEN DOWNLOADED

48 Aircraft EWIS Practices Job Aid 2.0 EWIS Riding on Other EWIS Wire bundles that cross should be secured together to avoid chafing Improper Proper Example of wire chafing. 48 UNCONTROLLED COPY WHEN DOWNLOADED

49 Aircraft EWIS Practices Job Aid 2.0 tening Hole Edge EWIS Riding on Ligh If the grommet is too short, then there is wire bundle chafing Improper Proper Example of wire chafing. 49 UNCONTROLLED COPY WHEN DOWNLOADED

50 Aircraft EWIS Practices Job Aid 2.0 EWIS as a Handhold Route EWIS so that it is not used as a handhold or as a support for maintenance personnel. In addition, route EWIS so that it avoids: • Damage by personnel movi ng within the aircraft. • Damage by stowage or shifting cargo. • Damage by battery or ac idic fumes or fluids. • Abrasion in wheel wells where exposed to rocks, ice, mud, etc. nal analysis/particular risks analysis Damage from external events (zo • demands). • Harsh environments such as se vere wind and moisture-prone (SWAMP) areas, high temperatures, or areas susceptible to significant fluid or fume concentration. EWIS should be routed to permit fr ee movement of sh ock and vibration mounted equipment, designe d to prevent strain on wires, junctions, and supports, and, the EWIS installation should permit shifting of EWIS and equipment necessary to perform mainte nance within the aircraft. In addition, wire lengths should be chosen to al low for at least two reterminations. 50 UNCONTROLLED COPY WHEN DOWNLOADED

51 Aircraft EWIS Practices Job Aid 2.0 EWIS Routing , cont. Protect EWIS in wheel wells and other • exposed areas Route EWIS above fluid lines, if practicable • • Use drip loops to control fluids or condensed moisture Keep slack to allow maintenance and • prevent mechanical strain Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 51 Administration Ensure that EWIS components are adequately protected in wheel wells and other areas where they may be exposed to mud, etc. (If re-routing of damage from impact of rocks, ice, EWIS is not practicable, protective jacketing may be installed.) This type of installation must be held to a minimum. Where practical, route EWIS s a nd cables above fluid lines. Wires and cables routed within 6 inches of any flammable liquid, fuel, or oxygen line sh ould be closely clamped and rigidly supported. A mini mum of 2 inches must be maintained between wiring and such lines or related ing is positively clamped to equipment, except when the wir maintain at least 1/2-inch separation or when it must be he fluid-carrying equipment. connected directly to t Ensure that a trap or drip loop is provided to prevent fluids or condensed moisture from running into EWIS and other components. EWIS installed in bilges and other locations where fluids may be trapped are routed as far from the lowest point as possible or otherwise provided with a moisture-proof covering. 51 UNCONTROLLED COPY WHEN DOWNLOADED

52 Aircraft EWIS Practices Job Aid 2.0 EWIS Above Fluid Lines Path of exposed end Broken wire shall not make contact with fluid line EWIS above fluid lines. The clamps should be a compression ming a wire break, the type and should be sp aced so that, assu broken wire will not contact hy draulic lines, oxygen lines, pneumatic lines, or ot her equipment whose subsequent failure caused by arcing coul d cause further damage. 52 UNCONTROLLED COPY WHEN DOWNLOADED

53 Aircraft EWIS Practices Job Aid 2.0 Wires improperly tied, riding on hydraulic lines, contaminated with caustic fluid This example shows a number of problems: • Wires in the bundles are not tied properly. • The wire bundle is riding hard on the hydraulic lines. • The wire bundles app ears to be contamin ated with hydraulic fluid residue. 53 UNCONTROLLED COPY WHEN DOWNLOADED

54 Aircraft EWIS Practices Job Aid 2.0 Y Type Wire Bundle Breakouts Figure 8 loop may be located before A f t e B r or after Wire bundle e f o tail of Y r breakout e Head of strap shall not Wire be located in this area bundles or touching anything to cause chafing Plastic mechanical strapping Wire bundle breakouts. There are three basic wire bundle breakout types used in routing airc raft EWIS. They are called the “Y,” “T,” and Complex types. The “Y” type of breakout is used when a portion of EWIS from to be routed in one direction of the wire bundle dep arts the bundle another direction. wraps are used to  Care should be take n when plastic tie provide wire containm ent at the breakout so that the tie wrap mage to the wire bundle at head does not cause chafing da the breakout junction. 54 UNCONTROLLED COPY WHEN DOWNLOADED

55 Aircraft EWIS Practices Job Aid 2.0 T Type Wire Bundle Breakouts Head of strap shall Wire bundle breakout not be located in this area or touching anything to cause chafing Wire Plastic mechanical strapping bundle The “T” type of breakout (also called 90° breakout ) is used when portions of EWIS from both directions in the wire bundle depart the bundle to be rou ted in another direction. 55 UNCONTROLLED COPY WHEN DOWNLOADED

56 Aircraft EWIS Practices Job Aid 2.0 Complex Type Wire Bundle Breakouts A Complex type of breakout is generally used to route certain ndle to a terminal st rip, module block, or wires out of a wire bu other termination. fficient slack in the For all types of breakout s, there should be su wires that are being broken out of the bundle to avoid strain on the wire between the wire bundle and the termination. 56 UNCONTROLLED COPY WHEN DOWNLOADED

57 Aircraft EWIS Practices Job Aid 2.0 Stand-offs Use stand-offs to maintain clearance • between EWIS and structure – Employing tape or tubing is generally not acceptable as an alternative • : Where impossible to install Exception off-angle clamps to maintain EWIS separation in holes, bulkheads, floors, etc. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 57 Administration wire bundles from contacting The EWIS design should preclude be used to ma intain clearance structure. Stand-offs should between EWIS and structure. Employing tape or protective tubing as an alternative to stand- should be avoided offs as a primary means of preventing EWIS contact with structure. Exception : Using tape or tubing is allowed in cases where it is impossible to install off-angl e clamps to maintain EWIS separation in ho les, bulkheads, floors, etc. 57 UNCONTROLLED COPY WHEN DOWNLOADED

58 Aircraft EWIS Practices Job Aid 2.0 Using Stand-offs Improper Proper onal clearance, clamps should not When using standoffs for additi be installed in a ma nner that defeats th e standoff’s purpose of providing additional clearance between EWIS and structure. 58 UNCONTROLLED COPY WHEN DOWNLOADED

59 Aircraft EWIS Practices Job Aid 2.0 Bundle riding on structure lems is chafing due aircraft EWIS prob One of the more common to wire bundles coming into cont act with aircraft structure or other aircraft equipment. 59 UNCONTROLLED COPY WHEN DOWNLOADED

60 Aircraft EWIS Practices Job Aid 2.0 Wire bundle too close to control cable at is in close contact with a This picture shows a wire bundle th control cable. Adequate distan ce between EWIS and control cables should be maintained to account for movement due to slack and maintenance. 60 UNCONTROLLED COPY WHEN DOWNLOADED

61 Aircraft EWIS Practices Job Aid 2.0 Clamping Support wires by suitable clamps, • ces at intervals of grommets, or other devi not more that 24 inches • Supporting devices should be of suitable size and type with wire and/or cables held securely in place without damage to wire or wire insulation Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 61 Administration primary support Clamps and other Wire supports an d intervals. devices should be constructed of are compatible materials that with their installation and environment, in terms of temperature, fluid resistance, exposure to ultraviolet light, and wire bundle mechanical loads. • Generally, clamps should not be spaced at intervals exceeding 24 inches. In hi gh vibration areas or areas requiring routing arou nd structural intrusio ns, the clamping intervals may need to be reduced in order to provide adequate support. 61 UNCONTROLLED COPY WHEN DOWNLOADED

62 Aircraft EWIS Practices Job Aid 2.0 Clamps • Wire bundles should be snug in clamp (no movement) – Cable not able to move axially RF cables: do not crush • Mount clamps with attachment • hardware on top • Tying not used as alternative to clamping Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 62 Administration Clamps on wire bundles should not allow the bund le to move through the clamp when a slight axial pull is applied. Clamps on RF cables must fit without crushing and must be sn ug enough but may allow the through the clamp, to prevent the cable from moving freely cable to slide throug l pull is applied. The cable h the clamp when a light axia or wire bundle may be wrapped with one or more turns of tape or other material suitable for the environment when required to achieve this fit. Plastic clamps or cable ties must not be used where their failure could result • in interference with movable controls, wire bundle contact with movable equipment, or chafing damage to essential or unprotected EWIS. They must not be used on vertical runs where inadvertent slack migration could result in chafing or other damage. • Clamps must be installed with their attachment hardware positioned above them , wherever practicable, so that they are unlikely to rotate as the result of wire bundle weight or wire bundle chafing. Clamps lined with nonmetallic material should be used to su pport the wire bundle along the ru n. Tying may be used between clamps, but should not be considered as a substitu te for adequate clamping. Adhesive tapes are n and, therefore, are not subject to age deterioratio acceptable as a clamping means. 62 UNCONTROLLED COPY WHEN DOWNLOADED

63 Aircraft EWIS Practices Job Aid 2.0 Example of Correct Cable Slack Appropriate slack This is an example of an appro priate amount of cable slack k protects the wires from stress between clamps. Appropriate slac and from contact with inappropriate surfaces. • Too much cable slack can allow the cable to contact which could damage the wire structure or other equipment bundle. Too little slack can cause a pre-load cond ition on the cable • which could cause damage to th e wire bundle and/or clamps as well. • d be left between the last Also, sufficient slack shoul clamp and the termination or electrical equipment to adverse effects prevent strain at the terminal and to minimize of shock-mounted equipment. 63 UNCONTROLLED COPY WHEN DOWNLOADED

64 Aircraft EWIS Practices Job Aid 2.0 Clamp Distortion Proper clamp position Improper clamp position Distortion of rubber on clamp is NOT acceptable the wire bundles are routed As is shown in the top graphic, perpendicular to the clamp. • If wire bundles are not routed perpendicular to the clamp created against the clamp (bottom graphic), stress can be and clamp grommet which can di stort the clamp and/or clamp lamp grommets can cause wire grommet. Distorted clamps/c bundle damage over time. 64 UNCONTROLLED COPY WHEN DOWNLOADED

65 Aircraft EWIS Practices Job Aid 2.0 Clamp Orientation 90±5° Incorrect Correct Incorrect 90±5° Correct This slide further illustrates correct and incorrect clamp orientations. Incorrect clamp or ientation can lead to wire bundle damage. 65 UNCONTROLLED COPY WHEN DOWNLOADED

66 Aircraft EWIS Practices Job Aid 2.0 Example - Clamp Distortion This photograph is a good example of clamp distortion. Note that the wire bundle is not perpendicular to the clamp. 66 UNCONTROLLED COPY WHEN DOWNLOADED

67 Aircraft EWIS Practices Job Aid 2.0 (Tie Mount) Plastic Snap-in Clamp support bracket snap-in tie mount release tail tab Some EWIS designs utilize plas tic snap-in clam ps sometimes mounts.” These types of clamps are not referred to as “tie re bundles and should not be used in high suitable for large wi temperature or hi gh vibration areas. • Any type of plastic clamp or cable tie should not be used where their failure co uld result in interf erence with movable controls, wire bundle contact wi th movable equipment, or chafing damage to esse ntial or unprotected EWIS. 67 UNCONTROLLED COPY WHEN DOWNLOADED

68 Aircraft EWIS Practices Job Aid 2.0 Typical Rubber Clamp All wires contained Rubber cushion in rubber cushion Wedge Clamp tabs No pinching Stand off IS is clamp pinching. This A common problem in aircraft EW occurs when the clamp is improperly installed or the clamp is too small. Clamps on wire bundles shou ld be selected so that they have a snug fit wit hout pinching wires. 68 UNCONTROLLED COPY WHEN DOWNLOADED

69 Aircraft EWIS Practices Job Aid 2.0 Typical Nylon Closed-Face Clamp Installation Do not pinch wire here to an existing wire bundle to It is important when adding wiring evaluate the existing clamp si zing in order to avoid possible clamp pinching. In some cases it may be necessar y to increase the size of the clamps to accommodate t he new wiring. 69 UNCONTROLLED COPY WHEN DOWNLOADED

70 Aircraft EWIS Practices Job Aid 2.0 Engage Clamp Tab in Slot Improper Clamp tab Clamp slot Proper are properly When using clamp tabs, make s ure that the tabs engaged. Otherwise, the tab co uld become loose and cause subsequent wire damage. • During EWIS installation inspec tions, ensure that the clamp is snapped before installing and tigh tening the bolt. 70 UNCONTROLLED COPY WHEN DOWNLOADED

71 Aircraft EWIS Practices Job Aid 2.0 Clamp Pinching Improper Do not pinch wires here Proper This slide further illustrates how wires can be pinched and damaged due to improper clamp installation. 71 UNCONTROLLED COPY WHEN DOWNLOADED

72 Aircraft EWIS Practices Job Aid 2.0 cont. Clamp Pinching, Improper Proper Too much wiring in a clamp or improperly installed clamps can lead to pinching of the wires. 72 UNCONTROLLED COPY WHEN DOWNLOADED

73 Aircraft EWIS Practices Job Aid 2.0 Open-faced nylon clamp with cable build-up (missing hardware) This picture was taken during a genera l visual EWIS inspection of a wide-body transport aircraft. No te the missing clamp hardware. Also note that the blac k cable used a tape bu ild-up at the clamp. Some manufacturer’s EWIS specif ications allow for wire cable build-up under certain circumstances. 73 UNCONTROLLED COPY WHEN DOWNLOADED

74 Aircraft EWIS Practices Job Aid 2.0 Wire Bend Radii • Minimum bend radius - 10 times the outside diameter of the largest wire or cable in the group — unsupported Exceptions – ction in bundle (supported at • Terminations/reversing dire both ends of loop) - 3 times the diameter • RF cables - 6 times the diameter • Thermocouple wire - 20 times the diameter Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 74 Administration The minimum radius of bends in wire groups or bundles must not be less th an 10 times the outside diameter of the largest wire or cable, except that at th where wires break e terminal strips erse direction in a bundle. out at terminations or rev Where the wire is suitably supported , the radius may be 3 times the diameter of the wire or cable. to install wiring or cables within the radius Where it is not practical requirements, the bend should be enclosed in insulating tubing. The radius for thermocouple wire is 20 times the diameter. (This is very delicate wire.) Ensure that RF cables, (for example, coaxia l and triaxial, are no less than 6 times bent at a radius of the outside diameter of the cable. 74 UNCONTROLLED COPY WHEN DOWNLOADED

75 Aircraft EWIS Practices Job Aid 2.0 Minimum Bend Radii No support at Min. bend radius - 10 x end of bend parameter of wire or cable Min. bend radius 3 x diameter of wire Diameter of Support at both wire or cable ends of wire bend This illustration shows the proper bend radii for th ree different scenarios. 75 UNCONTROLLED COPY WHEN DOWNLOADED

76 Aircraft EWIS Practices Job Aid 2.0 Bend radii okay- Greater than 3 times diameter (secured at both ends of loop) at both ends of the a wire loop secured This photograph shows loop. In this case, the bend radius should be no le ss than 3 times the diameter of the larges t wire in the wire bundle. 76 UNCONTROLLED COPY WHEN DOWNLOADED

77 Aircraft EWIS Practices Job Aid 2.0 Bend radii problem- Less than 3 times the diameter end of the loop, this does not Also supported at each wire bundle meet bend radius standar ds due to the large wires in the bundle. 77 UNCONTROLLED COPY WHEN DOWNLOADED

78 Aircraft EWIS Practices Job Aid 2.0 Unused Wires Secured • – Tied into a bundle or secured to a permanent structure Individually cut with strands even with • insulation Pre-insulated, closed-end connector or 1- • inch piece of insulating tubing folded and tied back Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 78 Administration Ensure that unused wires are individually dead-ended, tied into a permanent structure. a bundle, and secured to • Each wire should have strands cut even wi th the insulation ed end connector or and a pre-insulated clos a 1-inch piece of its end folded back insulating tubing placed over the wire with and tied. 78 UNCONTROLLED COPY WHEN DOWNLOADED

79 Aircraft EWIS Practices Job Aid 2.0 Spare Connector Contact: Preparing Single Contact Tubing Contact Wire 3 times length of contact This slide and the next two d epict an acceptable method of insulating and physi cally securing a spare connector contact within a wire bundle. 79 UNCONTROLLED COPY WHEN DOWNLOADED

80 Aircraft EWIS Practices Job Aid 2.0 Spare Connector Contact: Folding Tube and Tying Single Contact 0.75 ± 0.15 in. Tying tape Fold 80 UNCONTROLLED COPY WHEN DOWNLOADED

81 Aircraft EWIS Practices Job Aid 2.0 Spare Connector Contact: Single Contact Attachment to Wire Bundle Wire Tying tape bundle 81 UNCONTROLLED COPY WHEN DOWNLOADED

82 Aircraft EWIS Practices Job Aid 2.0 Spare Wire Termination Using Endcap Install end cap over wire Wire and end cap end. Shrink in place. in position Wire Adhesive tape bundle End caps Fiberglass tying tape ive method of are an effect Installing prefabricated end caps protecting unused wires wi th exposed conductors.  This slide depicts a typica l example of the use of a prefabricated end cap. 82 UNCONTROLLED COPY WHEN DOWNLOADED

83 Aircraft EWIS Practices Job Aid 2.0 Unused wiring - Improper termination with exposed conductor (should be properly insulated and secured to bundle) ual inspection, this example Found during a general EWIS vis shows two unused wires that have been cu t and the conductors are unprotected. In add ition, the unused wire s are not se cured to the wire bundle. 83 UNCONTROLLED COPY WHEN DOWNLOADED

84 Aircraft EWIS Practices Job Aid 2.0 Coil and Stow Methods Wire Wire bundle bundle ties Clamp Coil and stow short wire bundles in low vibration areas Coil and stow methods are often used to secure excess length of a wire bundle or to secure wire bundles that are not connected to any equipment, such as wiring provisioning for a future installation. 84 UNCONTROLLED COPY WHEN DOWNLOADED

85 Aircraft EWIS Practices Job Aid 2.0 Coil and Stow Methods , cont. Wire bundle ties Clamp Excess wire Wire bundle Coil and stow long wire bundles in low vibration areas ng and stowing wiring The key objective to coili is to safely secure the wire bundle to prevent excess ive movement or contact with other equipment that co uld damage the EWIS. 85 UNCONTROLLED COPY WHEN DOWNLOADED

86 Aircraft EWIS Practices Job Aid 2.0 , cont. Coil and Stow Methods Wire Wire bundle Teflon bundle tape ties Adjacent wire bundle Coil and stow in medium and high vibration areas Coil and stow in medium and high vibration areas requires additional tie straps , sleeving, and support. 86 UNCONTROLLED COPY WHEN DOWNLOADED

87 Aircraft EWIS Practices Job Aid 2.0 Stowing Unused Wires Improper Proper These photos show improper and proper stowing of unused wires. 87 UNCONTROLLED COPY WHEN DOWNLOADED

88 Aircraft EWIS Practices Job Aid 2.0 EWIS Replacement EWIS components should be replaced • when: – Chafed or frayed – Insulation suspected of being penetrated – Outer insulation is cracking – Damaged by or known to have been exposed to electrolyte, oil, hydraulic fluid, etc. – Evidence of overheating can be seen Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 88 Administration EWIS needs to be replaced un der a number of circumstances: • Wiring that has been subjected to chafing or fraying, that has primary insulation is suspected of been damaged, or that being penetrated. tion is brittle when slight • Wiring on which the outer insula flexing causes it to crack. • Wiring that has weather-crack ed outer insulation. NOTE: some wire insulation types ap pears to be wrin kled when the wire is bent and may not be damaged. • Wiring that is known to electrolyte or to have been exposed on which the insulation appears to be, or is suspected of being, in an initial stage of deterioration due to the effects of electrolyte. mage due to • There is visible evidence of insulation da overheating. 88 UNCONTROLLED COPY WHEN DOWNLOADED

89 Aircraft EWIS Practices Job Aid 2.0 Heat Discoloration This photograph shows an exampl e of heat discoloration on protective sleeving wh ich is part of the wire bundle. The large In this case, the the difference in color. clamp was moved to see wiring that is not covered in sleeving shows no signs of heat bulb was radiati distress. An adjacent light ng enough heat to cause discoloration over time to t he protective slee ving. Although deal, it is acceptable. this condition is not i 89 UNCONTROLLED COPY WHEN DOWNLOADED

90 Aircraft EWIS Practices Job Aid 2.0 Wire Replacement Wire should be replaced when: • – Wire bears evidence of being crushed or kinked – Shield on shielded wire if frayed and/or corroded – Wire shows evidence of breaks, cracks, dirt, or moisture in plastic sleeving – Sections of wire have splices occurring at less than 10-ft intervals Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 90 Administration Continuing, these are additiona l circumstances that warrant replacing EWIS: having been crushed or • EWIS that bears evidence of severely kinked. • Shielded EWIS on which the meta llic shield is frayed and/or corroded. Cleaning agents (w hich can cause wire damage) or preservatives should not be used to mini mize the effects of tion of wire shields. corrosion or deteriora • EWIS showing evidence of breaks, cracks, dirt, or moisture in the plastic sleeves placed over wire splices or terminal lugs. • Sections of wire in which splice s occur at less than 10-foot intervals, unless specifically authorized, due to parallel connections, locations, or inaccessibility. 90 UNCONTROLLED COPY WHEN DOWNLOADED

91 Aircraft EWIS Practices Job Aid 2.0 , cont. Wire Replacement • Shielding requirements – Replacement wires must have the same shielding characteristics as the original wire, such as shield optical coverage and resistance per unit length – Replacement wires should not be installed outside the bundle shield Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 91 Administration shielding have the same Replacement wires should as shield optical original wires, such characteristics as the coverage and resistance per unit length. a shielded wire If any wires are going to be replaced inside bundle, the replacement wires should not be installed outside the bundle shield. For more information on shielding, the Lightning/HIRF Video and is available. (To obtai Self-study Guide n, see your Directorate training manager.) 91 UNCONTROLLED COPY WHEN DOWNLOADED

92 Aircraft EWIS Practices Job Aid 2.0 Adding or Replacing Wires on a Bundle Chafing Improper procedure Proper procedure When adding or repla cing wires on or in a wire bundle, the in the same manner re should be routed replacement or added wi in the wire bundle. as the other wires  Wire bundle clamps and/or ti es may need to be loosened or removed in order to properly add or rep lace wires.  When the new wire is installed, the ties and clamps should be excessive disass opened one at a time to avoid embly of the wire bundles. 92 UNCONTROLLED COPY WHEN DOWNLOADED

93 Aircraft EWIS Practices Job Aid 2.0 Adding Wires on a Bundle Improperly routed outside of the tie wrap that secures the clamp Properly routed Proper and improperly rou ted wires in a bundle 93 UNCONTROLLED COPY WHEN DOWNLOADED

94 Aircraft EWIS Practices Job Aid 2.0 Wire Splicing • Keep to a minimum • Avoid in high vibration areas Locate to permit inspection • • Stagger in bundles to minimize increase in bundle size splice connector, Use self-insulated • if possible Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 94 Administration Splicing is permitted on EWIS as long as it does not affect the reliability and the electro-mechanical characteristics of the EWIS. Splicing of power wires, co-axial cables, multiplex bus, and large gauge wire should be avoided. If it can’t be avoided, then the power wire splicing must have approved data. Splicing of electrical wire should be kept to a minimum and • avoided entirely in locations subject to extreme vibrations. Splicing of individual wires in a group or bundle should have engineering approval and the splice(s) should be locate d to allow periodic inspection. Many types of aircraft splice connectors are available for use when splicing individual wires. • Use of a self-insulated splice connector is preferred; however, a non-insulated splice co nnector may be used pr ovided the splice is covered with plastic sleeving that is secured at both ends. • Environmentally-sealed splices that conform to MI L-T-7928 provide a reliable means of splicing in SWAM P areas. However, a non-insulated splice connector may be us ed, provided the splice is covered with dual a suitable material. wall shrink sleeving of 94 UNCONTROLLED COPY WHEN DOWNLOADED

95 Aircraft EWIS Practices Job Aid 2.0 Staggered Splices Splices in bundles should be staggered so as to minimize any increase in the size of the bundle that would: • Prevent bundle from fittin g into designated space. • Cause congestion adversel y affecting maintenance. • Cause stress on the wires. 95 UNCONTROLLED COPY WHEN DOWNLOADED

96 Aircraft EWIS Practices Job Aid 2.0 Overheated wire at the splice Splices that are not crimped properly (under or over) can cause increased resistance lead ing to overheat conditions. 96 UNCONTROLLED COPY WHEN DOWNLOADED

97 Aircraft EWIS Practices Job Aid 2.0 Ganged wire splices f should be per strain relie If splices are not staggered, pro provided in order to avoi d stress on the wires. In this particular installation, strain re lief was applied to avoi d stress on the wires. 97 UNCONTROLLED COPY WHEN DOWNLOADED

98 Aircraft EWIS Practices Job Aid 2.0 Ganged wire splices, cont. The top two wires in this photo are experiencin g stress due to a preload condition. Also note th at the wire bundle is not properly clamped. 98 UNCONTROLLED COPY WHEN DOWNLOADED

99 Aircraft EWIS Practices Job Aid 2.0 Terminals Tensile strength of the wire-to-terminal • joint should be at least the equivalent tensile strength of the wire Resistance of the wire-to-terminal joint • should be negligible relative to the normal resistance of the wire Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 99 Administration Tensile strength terminals are attached to the ends of electrical wires to facilitate con nection of the wires to terminal strips or items of equipment. The tensile wire-to-terminal strength of the joint should be at least equivalent to the tensile strength of the wire itself. Resistance of wire-t o-terminal joint should be negligible, relative to the normal resistance of the wire. • Selection of wire terminals. The following should be considered in the select ion of wire terminals. - Current rating. - Wire size (gauge) and insulation diameter. - Conductor material compatibility. - Stud size. - Insulation material compatibility. - Application environment. - Solder/solderless. 99 UNCONTROLLED COPY WHEN DOWNLOADED

100 Aircraft EWIS Practices Job Aid 2.0 Bending of Straight Copper Terminals Brazed joint Position of tongue before bending If bending of a terminal is necessary, care should be taken to avoid over bending the termin al which can cause damage to t he terminal. Also, a terminal can only be bent once si nce any additional bendi ng can cause damage. Pre-insulated crimp-type ring-tongue termin als are preferred. The strength, size, and supporting means of studs and bind ing posts, as well as the wire size, should be considered when determining the number of terminals to be attached to any one post. lications, the te e rating must be In high-temperature app rminal temperatur mperature plus current related temperature rise. Use greater than the ambient te of nickel-plated terminals and of unins ulated terminals with high-temperature insulating sleeves should be considered. Terminal blocks should be provided with adequate electrical clearance or insulation strips between mounting hardware and conductive parts. Terminals are sensitive to bending at the junction between the terminal ring and the terminal crimp barrel. Bending the terminal more than once or exceeding pre-determined terminal bend limits will usually result in mechanical weakening or damage to the terminal. limits established by the This slide is an example of OAM with regard to bending the terminal prior to installation. 100 UNCONTROLLED COPY WHEN DOWNLOADED

101 Aircraft EWIS Practices Job Aid 2.0 Terminal Strips Barriers to prevent adjacent studs • from contacting each other Current should be carried by terminal contact • surface and not by stud Studs anchored against rotation • Replace defective studs with studs • of same size and material, mount securely, tighten terminal securing nut Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 101 Administration Wires are usually joined at terminal strips. A terminal strip fitted be used to prevent the terminals on adjacent with barriers should studs from contacting each other. • Studs should be anchored agai nst rotation. When more than four terminals are to be c onnected together, a small metal bus should be mounted across tw o or more adjacent studs. carried by the terminal In all cases, the c urrent should be by the stud itself. contact surfaces and not • Defective studs should be rep laced with studs of the same size and material since termin al strip studs of the smaller sizes may shear due to over tightening the nut. The replacement stud should be secure ly mounted in the terminal ring nut shou ld be tight. strip and the terminal secu 101 UNCONTROLLED COPY WHEN DOWNLOADED

102 Aircraft EWIS Practices Job Aid 2.0 , cont. Terminal Strips Mount strips so loose metallic objects cannot • fall across terminal – Provide spare stud for breaks and future expansion – Inspect terminal periodically for loose connections, metallic objects, dirt, and grease accumulation • Can cause arcing, resulting in fire or systems failure Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 102 Administration ted in such a manner that loose Terminal strips should be moun fall across the terminal s or studs. It is metallic objects cannot good practice to provide at least one spare st ud for future circuit expansion or in case a stud is broken. • Terminal strips shou ld be inspected for loose connections, metallic objects that may have fall en across the terminal strip, dirt and grease accu mulation, etc. Th ese conditions can cause arcing which may result in a fire, or system failures. 102 UNCONTROLLED COPY WHEN DOWNLOADED

103 Aircraft EWIS Practices Job Aid 2.0 Terminals on circuit breakers Connectors and terminals in aircra ft require special attention to ensure a safe and satisfactory in stallation. Every possibility of terminals not being torqued properly , due to misinstallation, poor maintenance, and servic e life, should be addre ssed in the design. • Electrical equipment malfunct ion has frequently been traced to poor terminal connecti ons at terminal boards. produce localized heating that • Loose contact surfaces can may ignite nearby combustible materials or overheat adjacent wire insulation. Note the green torque st ripes painted on the t erminal fasteners in this picture. This is an excellent method to quickly determine if a terminal fastener is still to rqued to its original value. 103 UNCONTROLLED COPY WHEN DOWNLOADED

104 Aircraft EWIS Practices Job Aid 2.0 Power feeder terminals Again, you can see th e red colored torque stri pes applied to these high current power feeder terminat ions. High current terminals are more sensitive to increased to a improperly resistance due torqued terminal. • As a side note, the power feeder cables should not be touching each other without be ing suitably tied with spacers or other securing device. 104 UNCONTROLLED COPY WHEN DOWNLOADED

105 Aircraft EWIS Practices Job Aid 2.0 Terminal Lugs • Connect wiring to terminal block studs No more than 4 lugs, or 3 lugs and • a bus bar, per stud Lug hole size should match stud diameter • – Greatest diameter on bottom, smallest on top – Tightening terminal connections should not deform lugs Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 105 Administration Wire terminal lugs shou ld be used to co nnect wiring to terminal block studs or equipment terminal studs. No more than four terminal lugs or three termin al lugs and a bus should be connected to any one stud. • Total number of terminal lugs per stud includes a common bus bar joining adjacen t studs. Four terminal lugs plus a permitted on one stud. common bus bar thus are not Terminal lugs should be selected with a stud hole diameter that the stud. However, when the terminal matches the diameter of lugs attached to a stud vary in diameter, the greatest diameter should be placed on t he bottom and the smallest diameter on top. Tightening terminal co nnections should not deform the terminal lugs or the studs. Terminal lu gs should be so positioned that bending of the terminal lug is not required to remove the fastening screw or nut, and movement of the terminal lugs will tend to tighten the connection. 105 UNCONTROLLED COPY WHEN DOWNLOADED

106 Aircraft EWIS Practices Job Aid 2.0 Terminal Lugs , cont. • Aluminum lugs – Crimped to aluminum wire only • Special attention needed to guard against excessive voltage drop at terminal junction contact area – Inadequate terminal – Stacking errors – Improper torquing – Use calibrated crimp tools Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 106 Administration Aluminum terminal lugs should be crimped to aluminum wire only. The tongue of the aluminum terminal l ugs or the total number of tongues of aluminum terminal lugs when stacked, should be sandwiched between two flat washers (cadmium plated) when terminated on terminal studs. Spacers or washers should not be used bet ween the tongues of like material terminal lugs. Special attention should be given to al uminum wire and cable installations to age drop and high guard against conditions that would resu lt in excessive volt resistance at junctions that may ultima tely lead to failure of the junction. Examples of such conditions are im proper installation of terminals and  n (“torquing” of nuts), an d inadequate terminal washers, improper torsio contact areas. sizes of 10 gauge and larger to carry Note that aluminum wire is normally used in electrical power in large transport category aircraft in order to save weight. Although not as good a conductor as copp er, aluminum is lighter when compared to copper and the weight sa vings can be significant fo r a large aircraft that may have several hundred feet of power feeder cable. Because aluminum is used primarily for high current power applications, the sensitive to conditions le terminal junctions are more ading to increased junction resistance which can cause arcing and localized heat distress. 106 UNCONTROLLED COPY WHEN DOWNLOADED

107 Aircraft EWIS Practices Job Aid 2.0 Terminal Nut Stacking (like materials) Lock washer Flat washer Copper terminal lugs Terminal stud Terminal stacking mate rials and methods • Multiple wires often terminate onto a single terminal stud. Care should be taken to inst all the terminal properly. The materials that the terminals are constructed of will impact the Dissimilar metals , when in type of stacking methods used. can produce electrolysis contact , that can cause corrosion, thus degrading the terminal ju nction resistance and causing arcing or hot spots. • For stacking terminals that are ma de of like materials , the terminals can be stacked dire ctly on top of each other. 107 UNCONTROLLED COPY WHEN DOWNLOADED

108 Aircraft EWIS Practices Job Aid 2.0 Nut Terminal Stacking (unlike materials) Lock washer Flat washer Copper terminal Aluminum terminals Flat washers Terminal stud stacking unlike materials together When (for example, aluminum and copper), a cadmium-pl ated flat washer is usually needed to isolate th e dissimilar metals. 108 UNCONTROLLED COPY WHEN DOWNLOADED

109 Aircraft EWIS Practices Job Aid 2.0 Terminal Nut Lock Stacking washer Methods Flat washer Crimp barrel (belly up) Crimp barrel (belly down) One-Sided Entry With Two Terminals stalled on one side of the terminal When two terminals are in strip, care should be taken to ensure th at the terminal crimp barrels do not interfere with one another. One method to avoid terminals with the barrels “back to this problem is to install the back.” 109 UNCONTROLLED COPY WHEN DOWNLOADED

110 Aircraft EWIS Practices Job Aid 2.0 Nut Terminal Lock washer Stacking Flat washer , cont. Methods Crimp barrel (belly up) in center of “V” Crimp barrel (belly down) in “V” split One-Sided Entry With 3 Terminals This illustration depicts a t erminal installation with three . terminals entering on one side 110 UNCONTROLLED COPY WHEN DOWNLOADED

111 Aircraft EWIS Practices Job Aid 2.0 Nut Terminal Lock washer Stacking Flat washer Methods , cont. Crimp barrel (belly up) in “V” split Crimp barrel (belly down) in “V” split One-Sided Entry With 4 Terminals four terminals erminal installation with This illustration depicts a t entering on one side . The stacking method us ed to connect terminal s to terminal strips should cause no interference between terminals that could compromise the integrity of the terminal junction. 111 UNCONTROLLED COPY WHEN DOWNLOADED

112 Aircraft EWIS Practices Job Aid 2.0 Terminal Tightening Hardware Improper Proper Space Nut Lock washer Flat washer Lock washer not compressed Lock washer compressed Service history has sh own that hardware stac k up at terminals is Omission of lock wa shers, incorrect prone to human error. washers, improper sizing has been a definite of washers, etc. problem. It is important to use the correct ti ghtening hardware and install it correctly for a given installation. This illustration shows a typical flat washer/lock washer/nut insta llation. It is important to ensure the locking washer is fully compre ssed and is adjac ent to the nut. After the terminal is completely assembled, there should be a minimum of two to three thread s showing on the stud when the nut is properly torqued. 112 UNCONTROLLED COPY WHEN DOWNLOADED

113 Aircraft EWIS Practices Job Aid 2.0 Washer Size Selection Improperly sized Raised portion of terminal Split lock washer Non-self locking nut Aluminum Steel washers terminal Properly sized Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 113 Administration size washers in any and use the correct It is important to select termination. Undersized or over sized washers can lead to and localized hea increased junction resistance t or arcing. This illustration shows how an improperly sized washer can lead to insufficient contact between the terminal and terminal lug. 113 UNCONTROLLED COPY WHEN DOWNLOADED

114 Aircraft EWIS Practices Job Aid 2.0 Lock Washers In this photograph, the lock was her is missing from the terminal on the left. 114 UNCONTROLLED COPY WHEN DOWNLOADED

115 Aircraft EWIS Practices Job Aid 2.0 Grounding: Definition • Grounding is the process of electrically connecting conductive objects to either a conductive structure or some other conductive return path for the purpose of safely completing either a normal or fault circuit. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 115 Administration Grounding. One of the more important factors in the design and ft electrical systems maintenance of aircra is proper bonding and grounding. Inadequate bonding or grounding can lead to unreliable operation of systems, such as EMI, electrostatic discharge damage to sensitive el ectronics, personnel shock hazard, or damage from lightning strike. 115 UNCONTROLLED COPY WHEN DOWNLOADED

116 Aircraft EWIS Practices Job Aid 2.0 Grounding • Types of grounding – AC returns – DC returns – Others • Avoid mixing return currents from various sources – Noise will be coupled from one source to another and can be a major problem for digital systems Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 116 Administration Grounding types: AC returns, DC returns, and others. Mixing return currents. If wires carrying return currents from different types of sources, such as sign als or DC and AC generators, are connected to the same ground point or have a common connection in the return paths, an interaction of the currents will occur. This interaction may not be a problem, or it could be a major non-repeatable anomaly. • To minimize the interaction bet ween various return currents, be identified and used. As a different types of grounds should minimum, the design should use three ground types: (1) AC returns, (2) DC returns, and (3) all others. • For distributed power systems, the power return point for an alternative power source would be separated. - For example, in a two-AC ge nerator system (one on the right side and the other on the left side ), if the right AC generator were supplying backup power to equipment located in the left side, (left equipment rack) the ba ckup AC ground return should be labeled “AC Right.” The return currents for the left generator should be connected to a ground point labeled “AC Left.” 116 UNCONTROLLED COPY WHEN DOWNLOADED

117 Aircraft EWIS Practices Job Aid 2.0 Grounding , cont. • Design of ground path should be given as much attention as other leads in the system Grounding should provide a constant • impedance Ground equipment items externally even • when internally grounded – Avoid direct connections to magnesium structure for ground return Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 117 Administration Design of ground paths. The design of the ground return circuit should be given as much attention as the other leads of a circuit. Constant impedance. A requirement for proper gr ound connections is that they maintain an impedance t hat is essentially constant. Ground return circuits should have and voltage drop • a current rating adequate for satisfactory operation of the connected electrical and electronic equipment. • EMI problems, that can be caused by a system’s power wire, can be reduced substantially by locating t he associated ground return near the origin of the power wiri ng (e.g., circuit breaker panel) and routing the power wire and its ground return in a twisted pair. Special care should be exercise • d to ensure replacement on ground return leads. The use of numbered s instead of bare insulated wire lead grounding jumpers may aid in this respect. External grounding of equipment items. In general, equ ipment items should have an external gr ound connection, even wh en internally grounded. Direct connections to a magnesium structure (which may create a fire be used for ground return. not hazard) must 117 UNCONTROLLED COPY WHEN DOWNLOADED

118 Aircraft EWIS Practices Job Aid 2.0 Grounding , cont. • Heavy current grounds – Attach to individual grounding brackets attached to aircraft structure with a proper metal-to-metal bond – Accommodate normal and fault currents of system without creating excessive voltage drop or damage to structure – Give special attention to composite aircraft Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 118 Administration Heavy current grounds. Power ground connections for generators, transforme r rectifiers, batteri es, external power receptacles, and other heavy-current loads mu st be attached to individual grounding brackets th at are attached to aircraft nding attachment. structure with a proper metal-to-metal bo • This attachment and the surrou must provide nding structure adequate conductivity to ac commodate normal and fault currents of the system withou t creating excessive voltage drop or damage to the structure. • At least three fasteners, locate d in a triangula r or rectangular pattern, must be used to secure such brackets in order to minimize susceptibility to loosening under vibration. • If the structure is fabr icated of a material such as carbon fiber composite (CFC), which has a higher resistivity than aluminum or copper, it will be necessary to provide an alternative ground path(s) for power return current. 118 UNCONTROLLED COPY WHEN DOWNLOADED

119 Aircraft EWIS Practices Job Aid 2.0 Bonding Equipment bonding • – Low impedance paths to aircraft structure required for electronic equipment to provide radio frequency return circuits – Facilitates reduction in EMI for most electrical equipment produce EMI should be • Cases of components that grounded to structure Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 119 Administration . Low impedance paths to aircraft structure Equipment bonding red for electron ic equipment to provide radio are normally requi frequency return circuits and for most electr ical equipment to The cases of components that facilitate reduction in EMI. produce electromagnetic energy s hould be grounded to structure. • To ensure proper operati on of electronic equipment, it is particularly important to conform the syst em’s installation specification when inter-conne ctions, bonding, and grounding complished. are being ac 119 UNCONTROLLED COPY WHEN DOWNLOADED

120 Aircraft EWIS Practices Job Aid 2.0 , cont. Bonding Metallic surface bonding • – Electrically connecting conductive exterior airframe components through mechanical joints, conductive hinges, or bond straps arges and lightning strikes • Protects against static ch Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 120 Administration Metallic surface bonding . All conducting obje cts on the exterior ally connected to the airframe of the airframe must be electric ints, conductive hing es, or bond straps through mechanical jo capable of conducting static charges and lightning strikes. for some objects such as • Exceptions may be necessary antenna elements, whose func tion requires t hem to be electrically isolated from the airf rame. Such it ems should be provided with an alternative m eans to conduct static charges urrents, as appropriate. and/or lightning c 120 UNCONTROLLED COPY WHEN DOWNLOADED

121 Aircraft EWIS Practices Job Aid 2.0 Bonding , cont. • Static bonds – Required for all isolated conducting parts with 2 area greater than 3 in and a linear dimension over 3" subjected to appreciable electrostatic charging due to precipitation, fluid, or air in motion han 1 ohm when clean and dry • Resistance of less t ipation on larger objects usually ensures static diss Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 121 Administration parts inside and outside Static bonds . All isolated conducting 2 area greater than 3 in the aircraft, having an and a linear dimension over 3 inches, that are subjected to appreciable electrostatic charging due to precipi tation, fluid, or air in motion, lly secure electrical connection to the should have a mechanica aircraft structure of sufficient conductivity to di ssipate possible static charges. • A resistance of less than 1 ohm when clean and dry will generally ensure such dissipati on on larger obj ects. Higher ible in connecting resistances are permiss smaller objects to airframe structure. 121 UNCONTROLLED COPY WHEN DOWNLOADED

122 Aircraft EWIS Practices Job Aid 2.0 EWIS Identification • Necessary for: – Safety of operation – Safety to maintenance personnel – Ease of maintenance • To identify performance capability, use wire material part number and five digit/letter code identifying manufacturer Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 122 Administration Purpose. The proper identification of EWIS components with their circuits and voltages is necessary to provide safety of operation, safety to maintenance personnel, and ease of maintenance. Common manufacturer marking process. Each wire and cable should be marked with a part number. It is common practice for wire manufacturers to follow the wire material part number with the five digit/letter code identifying the wire manufacturer. Using this code, C.A.G.E. existing installed wire that needs replacement can be identified as to its performance capabilities. This helps to prevent the inadvertent use of lower performance and unsuitable replacement wire. • NOTE: Special care should be taken when hot stamping wire. Service history has shown problems associated with hot stamping due to insulation damage caused during the process. The method of identification • should not impair the characteristics of the EWIS. • Original wire identification. To facilitate installation and maintenance, retain the original wire-marking identification. The wire identification marks should consist of a combination of letters and numbers that identify the wire, the circuit it belongs to, its gauge size, and any other information to relate the wire to a EWIS diagram. All markings should be legible in size, type, and color. The wire identification • Identification and information related to the EWIS diagrams. marking should consist of similar information to relate the wire to a EWIS diagram. 122 UNCONTROLLED COPY WHEN DOWNLOADED

123 Aircraft EWIS Practices Job Aid 2.0 EWIS Identification , cont. Wire identification marks identify wire, • circuit, and gauge size • Markings should be legible in size, type, and color at 15-inch ma ximum intervals along the wire (directly on wire or indirect [sleeve/tag]) Less than 3 inches needs no marking • – Readable without removing clamps, ties, or supporting devices Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 123 Administration Marking EWIS in aircraft. Identification markings generally are placed at each end of the wire and at 15-inch maximum interv als along the length of the wire. • Wires less than 3 inches lo ng need not be identified. • Wires 3 to 7 inches in length should be identified approxima tely at the center. sleeves should be located so that ties, clamps, or • Added identification marker supporting devices need not be re-moved in order to read the identification. The wire identification code mu st be printed to re ad horizontally (fro m left to right) or • vertically (from top to bottom). The two methods of marking wire or cable are as follows: - (1) Direct marking is accomplished by printing the cable’s outer covering. - (2) Indirect marking is accomplished by printing a heat-shrinkable sleeve and installing the printed sleeve on the wire or cables outer covering. Indirect- marked wire or cable should be identified with printed sleeves at each end and at intervals not longer than 6 feet. T he individual wires inside a cable should be identified within 3 inch es of their termination. • The marking should be permanent such that environmental stresses during adversely affect legibility. operation and maintenance do not 123 UNCONTROLLED COPY WHEN DOWNLOADED

124 Aircraft EWIS Practices Job Aid 2.0 Marking a Wire Bundle No marking Proper indirect marking repercussions when there is a situation in There can be serious which a number of unma rked cables are disc onnected. When the cables reconnected, the chances are high that they will be connected incorrectly, thus causing numerous problems. 124 UNCONTROLLED COPY WHEN DOWNLOADED

125 Aircraft EWIS Practices Job Aid 2.0 Connectors • Many types, however crimped contacts generally used –Circular type – Rectangular – Module blocks • Selected to provide maximum degree of safety and reliability given electrical and environmental requirements onnectors to prevent moisture – Use environmentally-sealed c penetration Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 125 Administration Connectors. The number and complexity of EWIS have resulted in an increased use of electrical connectors. The proper choice and application of connectors is a significant part of the aircraft EWIS system. Connectors should be kept to a minimum, selected, and installed to provide the maximum degree of safety and reliability to the aircraft. For the installation of any particular connector assembly, the specification of the manufacturer should be followed. The connector used for each application should be selected only after a careful Purpose and types. determination of the electrical and environmental requirements. Consider the size, weight, tooling, logistic, maintenance support, and compat ibility with standardization programs. For ease of assembly and maintenance, connectors • using crimped contacts are generally chosen for all applications except those requiring a hermetic seal. A replacement connector of the same basic type and design as the connector it replaces should • be used. • With a crimp type connector for any electrical connec tion, the proper insertion, or extraction tool should be used to install or remove wires from such a connector. Refer to manufacturer or aircraft instruction manual. • After the connector is disconnected, inspect it for loose soldered connections to prevent unintentional grounding. • Connectors that are susceptible to corrosion difficulties may be treated with a chemically inert waterproof jelly or an environmentally-sealed connector may be used.  NOTE: Although not required by AC 43.13-1b, moisture -proof connectors should be used in all areas of the aircraft, including the cabin. Service history indicates that most connector failures occur due to some form of moisture penetration. Even in the pressurized, environmentally- controlled areas of the cockpit and cabin, mois ture can occur due to “rain in the plane” type of condensation that generally is a problem in all modern transport category aircraft. 125 UNCONTROLLED COPY WHEN DOWNLOADED

126 Aircraft EWIS Practices Job Aid 2.0 Circular Connectors Although AC 43.13-1b does not address pin layout design aspects, consideration should be given to the design of the pin arrangement to avoid situations where pin-to-pin shorts could result in mu ltiple loss of functions and/or power supplies. For example, you would avoid 115 Vac, 400Hz being located adjacent to low power wires, such as 28 and 5 Vdc. A wide variety of circular environment-resistant connectors are used in applications where they will probably be subjected to fl uids, vibration, thermal, ve elements, etc. In addition, firewall class mechanical shock, corrosi hese same features should be able to prevent the connectors incorporating t penetration of the fire through the aircraft firew all connector opening and continue to function withou t failure for a specified perio d of time when exposed to fire. Hermetic connectors pro vide a pressure seal for maintaining pressurized areas. • When EMI/RFI protection is required, special attention should be given to the termination of individual and overall shields. Backshell adapters designed for shield termin ation, connectors with conductive finishes, and ailable for this purpose. EMI grounding fingers are av 126 UNCONTROLLED COPY WHEN DOWNLOADED

127 Aircraft EWIS Practices Job Aid 2.0 Circular Connectors , cont. In medium or high vibrat necessary to provide ion areas it may be a locking device to keep the connectors from loosening. 127 UNCONTROLLED COPY WHEN DOWNLOADED

128 Aircraft EWIS Practices Job Aid 2.0 Improper Lock Wire Installation This slide shows a lock wire improper ly installed. The lock wire is installed on the "loose ning” side of the connect or; it should be on the “lightening” side. 128 UNCONTROLLED COPY WHEN DOWNLOADED

129 Aircraft EWIS Practices Job Aid 2.0 Proper Lock Wire Installation This is an example of a pr operly installed lock wire. 129 UNCONTROLLED COPY WHEN DOWNLOADED

130 Aircraft EWIS Practices Job Aid 2.0 Rectangular Connectors Rectangular connectors are typically used in applications where a very large number of circuits are accommodated in a single mated pair. They are available with a great variety of contacts, which can include a mix of standar d, coaxial, and large power types. Coupling is accomplished by various means. hold their flange • Smaller types are sec ured with screws that together. • Larger ones have integra l guide pins that ensure correct rews that both al alignment, or jacksc ign and lock the connectors. • Rack and panel connectors use in tegral or rack-mounted pins box mounting hardware for couplings. for alignment and 130 UNCONTROLLED COPY WHEN DOWNLOADED

131 Aircraft EWIS Practices Job Aid 2.0 Module Blocks (Terminal Blocks) Module blocks accept crimped contacts similar to those on connectors. Some use internal bu sing to provide a variety of circuit arrangements. blocks) are useful where a • Module blocks (or terminal number of wires are c onnected for power or signal distribution. When used as grounding modules, they save installation on the aircraft. and reduce hardware • Standardized modules are available wi th wire-end grommet tions and are track-mounted. seals for environmental applica 131 UNCONTROLLED COPY WHEN DOWNLOADED

132 Aircraft EWIS Practices Job Aid 2.0 Terminal Block Grommet Distortion A wire  View A  Acceptable View A Unacceptable grommet For complex wire breakouts that are terminated into terminal taken to allow eno ugh slack to prevent blocks, care must be the terminated wires that are excessive forces from pulling inserted into the terminal block. • This condition can lead to term inal block gromm et distortion, or a wire that will be pulled which can lead to wire damage free from the terminal block. 132 UNCONTROLLED COPY WHEN DOWNLOADED

133 Aircraft EWIS Practices Job Aid 2.0 Grommet Distortion grommet Improper: distortion due to tight wires; not enough slack Proper: no excessive tension on wires; enough slack to avoid grommet distortion 133 UNCONTROLLED COPY WHEN DOWNLOADED

134 Aircraft EWIS Practices Job Aid 2.0 Conduits • Purpose – Mechanical protection of wires and cables – Grouping and routing wires Standards • – Absence of abrasion at end fittings – Proper clamping – Adequate drain holes free of obstructions – Minimized damage from moving objects – Proper bend radii Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 134 Administration Purpose . Primarily the purpose of conduits is for mechanical protection of cables or wires. Secondarily, conduits are used for environmental protection and grouping of wires by signal type. Standards Conduit should be inspected for : proper end fittings; absence of • abrasion at the end fittings; proper cl amping; distortion; adequate drain other obstructions; and freedom from holes that are free of dirt, grease, or abrasion or damage due to moving obje cts, such as aircraft control cables or shifting cargo. Size of conduit . Conduit size should be sele cted for a specific wire • bundle application to allow for ease in maintenance, and possible future circuit expansion, by specifying the conduit inner diameter (I.D.) about 25 percent larger than the maximum diameter of the wire bundle. • Conduit fittings. Wire is vulnerable to abrasion at conduit ends. Suitable fittings should be affixed to conduit ends in such a manner that a smooth surface comes in contact with the wire. When fittings are not used, the end of the conduit should be flared to prevent wire insulation damage. Conduit should be suppor ted by use of clamps along the conduit run. 134 UNCONTROLLED COPY WHEN DOWNLOADED

135 Aircraft EWIS Practices Job Aid 2.0 Conduit Installation Guidelines Do not locate conduit where service or • maintenance personnel might use as handhold or footstep Provide inspectable drain holes at the • lowest point in conduit run — remove drilling burrs carefully Support conduit to prevent chafing against • structure and avoid stressing end fittings Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 135 Administration Conduit installation. n be avoided by Conduit problems ca following these guidelines: • Do not locate conduit wh ere service or maintenance footstep. personnel might use it as a handhold or • Provide inspectable drain hole s at the lowest point in a conduit run. Drilli ng burrs should be c arefully removed. ructure and to • Support conduit to prevent ch afing against st avoid stressing its end fittings. 135 UNCONTROLLED COPY WHEN DOWNLOADED

136 Aircraft EWIS Practices Job Aid 2.0 Conduit Covering Damaged conduit covering Acceptable conduit covering FOD is a big problem with damaged conduit covering. 136 UNCONTROLLED COPY WHEN DOWNLOADED

137 Aircraft EWIS Practices Job Aid 2.0 08/15/99 Wire Insulation Selection Chose characteristics based on • environment – Abrasion resistance – Flame resistant – Arc resistance – Mechanical strength – Corrosion resistance – Smoke emission – Cut-through strength – Fluid resistance – Dielectric strength – Heat distortion Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 137 Administration Environmental characteristics. As shown in this slide, there are many insulation materials and combinations used in aircraft wiring. Wire insulati on characteristic shoul d be chosen based on smoke emission requirements meeting FAA flame resistance and ich the wire is to be installed. (25.869) and the environment in wh 13 137 UNCONTROLLED COPY WHEN DOWNLOADED

138 Aircraft EWIS Practices Job Aid 2.0 Flame Resistant Insulating Materials Mil Spec Polymer 22759/12 PTFE 22759/16 ETFE 81381 Aromatic polyamide Composite 22759/80-92 Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 138 Administration pes of insulation materials These are the four most common ty used in aircraft today. All of the wire insu lating materials in this slide meet the minimum FAA sm oke and flammability standards. 138 UNCONTROLLED COPY WHEN DOWNLOADED

139 Aircraft EWIS Practices Job Aid 2.0 Selecting Insulating Materials FACT: There is no “perfect” insulation system for aerospace wire and cable The designer’s task: Consider trade-offs to secure best • balance of properties Consider influence of design, • installation and maintenance ...for each application! Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 139 Administration 139 UNCONTROLLED COPY WHEN DOWNLOADED

140 Aircraft EWIS Practices Job Aid 2.0 How to Choose Wire Insulation Seek the best balance of properties: • – Electrical – Mechanical – Chemical – Thermal Plus – Nonflammability and low smoke Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 140 Administration 140 UNCONTROLLED COPY WHEN DOWNLOADED

141 Aircraft EWIS Practices Job Aid 2.0 Comparative Properties of Wire Insulation Systems Most desirable Least 1 2 4 Relative Ranking 3 ETFE PTFE PI COMP Weight COMP PI Temperature PTFE ETFE PI ETFE COMP PTFE Abrasion resistance PI COMP Cut-through resistance PTFE ETFE Chemical resistance ETFE COMP PI PTFE PTFE PI ETFE Flammability COMP PI COMP Smoke generation ETFE PTFE Flexibility PTFE ETFE COMP PI Creep (at temperature) PI COMP PTFE ETFE Arc propagation resistance PTFE COMP PI ETFE - (mil spec 81381) PI [Aromatic Polyimide (KAPTON)] Desirable properties : abrasion/cut-through, low-smoke/non-flame, • weight/space Limitations • : arc-track resistance, flexibility ETFE (TEFZEL) - (mil spec 22759/16) • Desirable properties : chemical resistance, abrasion resistance, ease of use C)  • Limitations : high temperature, cut-through, thermal rating (150 - (mil spec 22759/80-92) Composite (TKT) • Desirable properties : high temperature rating (260  C), cut-through resistance, arc-track resistance • : outer layer scuffing Limitations PTFE (TEFLON) - (mil spec 22759/12) • Desirable properties : 260  C thermal rating, low-smoke/non-flame, high flexibility : Cut-through resistance, “creep” at temperature Limitations • 141 UNCONTROLLED COPY WHEN DOWNLOADED

142 Aircraft EWIS Practices Job Aid 2.0 Conclusion on Insulation • Aircraft designer can choose among many polymeric materials • Physical and chemical properties are equally important Safest system combines “balance of • properties” with inherent flame and/or smoke resistance Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 142 Administration 142 UNCONTROLLED COPY WHEN DOWNLOADED

143 Aircraft EWIS Practices Job Aid 2.0 AC 25-16: Electrical Fault and Fire Detection Supplements existing guidance provided • in AC 43.13-1b Should apply to new airplanes, • as well as modifications Not intended to take the place of • instructions or precautions provided by aircraft/equipment manufacturers Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 143 Administration The purpose of AC 25-16, “Electrica l Fault And Fire Prevention,” ion on electrically ca used faults, overheat, is to provide informat smoke, and fire in transport ca tegory airplanes. Acceptable e potential for these conditions means are provided to minimize th to occur, and to minimize or co ntain their effects when they do occur. An applicant may elect to use any other means found to be acceptable by the FAA. This AC is currently being rev iewed and will be revised based on recent service history and ATSRAC recommendations. 143 UNCONTROLLED COPY WHEN DOWNLOADED

144 Aircraft EWIS Practices Job Aid 2.0 AC 25-16: Circuit Protection Devices (CPDs) Circuit breaker resets • – Can significantly worsen an arcing event – Crew should only attempt to reset a tripped breaker if function is absolutely required • Information should be provided in AFMs or AFM revisions or supplements Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 144 Administration Information should be provided in FAA-approved Airplane Flight Manuals (AFM) or AFM revisions or supplements that the crew should only attempt to restore an auto matically-disconnected power source or reset or replace an automa tically-disconnected at affects fli ght operations or circuit protection device (CPD) th safety. NOTE: It is strongly re commended that circuit breakers for • non-essential systems not be reset in flight. Most transport OA Ms and operators are revi sing their procedures to not flight following a circuit allow circuit breaker resets in breaker trip event. Service hi story has shown that resetting a circuit breaker can greatly influe nce the degree of arcing damage to the EWIS. Each successi ve attempt to restore an progressively automatically-disconnected CPD, can result in worsening effects from arcing. 144 UNCONTROLLED COPY WHEN DOWNLOADED

145 Aircraft EWIS Practices Job Aid 2.0 Arc Tracking and Insulation Flashover (Caused by multiple circuit breaker resets) breaker resets. multiple circuit This picture shows the effects of In this case, the original ar cing event was not able to be determined due to th e severe secondary da mage following the circuit breaker resets. 145 UNCONTROLLED COPY WHEN DOWNLOADED

146 Aircraft EWIS Practices Job Aid 2.0 EWIS Separation Regulatory requirements • – Sections 25.1707, 25.1709, 25.903(d), 25.631 Manufacturers’ standards • – Power/signal wire separation • EMI concerns Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 146 Administration EWIS separation/segregation is a fundamental design technique used to isolate failure effects such that certain single failures that EWIS separation is can compromise redundan cy are minimized. s of EMI in aircraft EWIS. also used to control the effect • From a regulatory standpoint, we have regulations in place that may influence EWIS design with respect to separation/segregation. • In addition, manufacturers may have company design standards which establish EW IS separation requirements with respect to power and sig nal routing which are usually driven from a EMI standpoint. • The next few slides briefly present the primary regulations associated with EWIS separation/segregation. 146 UNCONTROLLED COPY WHEN DOWNLOADED

147 Aircraft EWIS Practices Job Aid 2.0 System Separation: EWIS § 25.1707 Applies to each EWIS on airplane • Requires adequate physical separation • between EWIS and certain airplane systems known to have potential for creating a hazardous condition, for example: – Fuel systems – Hydraulic systems – Oxygen systems – Water/waste systems Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 147 Administration 147 UNCONTROLLED COPY WHEN DOWNLOADED

148 Aircraft EWIS Practices Job Aid 2.0 , cont. System Separation: EWIS § 25.1707 • Adequate physical separation must be achieved by separation distance that provides or by a barrier protection equivalent to that separation distance “Hazardous” -- must perform a qualitative • design assessment of installed EWIS – Use engineering & manufacturing judgment – Evaluate relevant service history to decide whether an stem, or any structural EWIS, any other type of sy component could fail so that a condition affecting the airplane’s ability to continue safe operation could result Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 148 Administration 148 UNCONTROLLED COPY WHEN DOWNLOADED

149 Aircraft EWIS Practices Job Aid 2.0 System Safety: EWIS § 25.1709 1. EWIS be designed and installed so each catastrophic failure condition is extremely improbable, – and does not result from a single failure, and each hazardous failure condition – is extremely remote failures and physical 2. Both functional of EWIS must be assessed when demonstrating compliance with this rule to fully assess effect of EWIS failures Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 149 Administration 149 UNCONTROLLED COPY WHEN DOWNLOADED

150 Aircraft EWIS Practices Job Aid 2.0 EWIS Separation from a 25.903(d) Standpoint Turbine engine installations: Minimize • hazards in case of rotor failure – Project debris path through aircraft • Determine vulnerable areas where redundancy can be violated – May need to separate certain critical systems components including EWIS, s, fly-by-wire control paths e.g., electrical power feeder Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 150 Administration Recently, the JAA requirements with respect to uncontained engine failure assessment were harmonized with the FAA and 20-128A. AC 20-128A provides specific were issued as AC ating compliance with 25.903(d). methods for demonstr • The primary requirem ent relative to uncontained engine failure is to use prac tical design precautio ns to minimize the risk of catastrophic damage due to non-contained engine rotor debris. - An element of difficulty is introduced when the fuselage diameter is exposed to the relatively large diameter fan rotors of modern high-bypass-ratio t urbofan engines. - Separation of critical syst ems EWIS may be a primary hing compliance. factor in establis 150 UNCONTROLLED COPY WHEN DOWNLOADED

151 Aircraft EWIS Practices Job Aid 2.0 EWIS Separation from a 25.631 Standpoint • Continued safe flight and landing after impact with 8-lb. bird – Consider protected location of control system elements • If impact can effect redundant system EWIS, may need additional physical protection of EWIS or wiring separation – E.g.: Impact brow area above windshield could affect electrical power redundancy in some aircraft Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 151 Administration The birdstrike impact area s of the aircraft shou ld be assessed for their structural strength by test and/or approved analysis methods. Any penetr ations or deformations of the aircraft effect of systems rther analyzed for the structure should be fu installation. test on the cockpit overhead • For example, if a birdstrike eyebrow area indicates an elasti c deformation of 2 inches, then the deformation should be analyzed or superimposed on whatever systems may be installed in the overhead cockpit area at that particular deformatio n location. In many aircraft, electrical and/or hydraulic control panels and associated EWIS are installed in the overhead cockpi t area (this is a relatively small area). • The effect of the birdstrike ca n be analyzed with respect to a common cause failure standpoint. EWIS separation aspects ance to this rule. an element in compli of the design may be 151 UNCONTROLLED COPY WHEN DOWNLOADED

152 Aircraft EWIS Practices Job Aid 2.0 Post-TC EWIS Separation Maintain EWIS separation requirements • throughout life of aircraft – STC applicants may not be aware of separation or other EWIS requirements (i.e., do not have needed design data) – EWIS added or moved as part of the STC should satisfy original separation requirements and EWIS standards – FAA policy letter ANM-01-04 Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 152 Administration A potential problem with STCs and other modifications to transport aircraft is that the applicants may not analyze their proposed EWIS installation with respect to the OAM’s EWIS separation requirements and other OAM EWIS design standards. Added or modified EWIS could possibly defeat the OAM EWIS philosophy and create unsafe conditions. The FAA is currently in the process of drafting policy. The draft policy letter will clarify FAA’s policy to require that type design data packages for multiple approvals include the following: • A drawing package that completely defines the configuration, material, and production processes necessary to produce each part in accordance with the certification basis of the product. • Any specifications referenced by the required drawings. Drawings that completely define the location, installation, and routing, as appropriate, of all equipment in accordance with the certification basis of the product. • Examples of such equipment are wire bundles, plumbing, control cables, and other system interconnecting hardware. • If the modification being approved is a change to a type certificated product, the modification must be equivalent to and compatible with the original type design standards. Instructions for Continued Airworthiness (ICA) prepared in accordance with the requirements of 21.50 (“Instructions for continued airworthiness and manufacturer’s maintenance manuals having airworthiness limitations sections”). 152 UNCONTROLLED COPY WHEN DOWNLOADED

153 Aircraft EWIS Practices Job Aid 2.0 Instructions for Continued Airworthiness (ICAs) EWIS ICAs are developed using Enhanced Zonal Analysis Procedure (EZAP): • Each zone of airplane Each zone with EWIS • • Each EWIS zone with combustible materials • Each EWIS zone close to both primary and back-up flight controls and lines • Tasks, intervals, and procedures to reduce combustibles (i.e. clean-as-you-go) Instructions for protections & caution information • Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 153 Administration 14 CFR 25.1729 requires applicants to subm it Instructions for se known as the maintenance Continued Airworthiness, otherwi requirements, for the tion as part of the proposed EWIS installa compliance data package . Historically, EW IS has been thought of as “fit and f orget” and typically ha s not been properly addressed in the ICA data package submitt ed to the FAA for approval. In light of ATSRAC recomm endations, the FAA requires applicants to submit EWIS-relat ed maintenance requirements to the FAA ACO and AEG offices for appro val to satisfy the intent of 25.1729. This slide shows some of the issues th at need to be addressed for wire repla cements instructions. 153 UNCONTROLLED COPY WHEN DOWNLOADED

154 Aircraft EWIS Practices Job Aid 2.0 Why EZAP? • EZAP used to develop ICA to prevent the possibility of smoke and fire by – Minimizing accumulation of combustibles on and around EWIS – Detecting EWIS degradations This leads to fewer EWIS and other airplane • systems failures and to safer operation Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 154 Administration 154 UNCONTROLLED COPY WHEN DOWNLOADED

155 Aircraft EWIS Practices Job Aid 2.0 3 EWIS Inspection Types • General Visual Inspection (GVI) Stand-Alone GVI • • Detailed Inspection (DET) Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 155 Administration 155 UNCONTROLLED COPY WHEN DOWNLOADED

156 Aircraft EWIS Practices Job Aid 2.0 General Visual Inspection (GVI) • A visual examination of an interior or exterior mbly to detect obvious area, installation, or asse egularity. This level of damage, failure, or irr inspection is made from within touching distance unless otherwise specified. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 156 Administration For General Visual Inspection, a mirror may be necessary to enhance visual access to all exposed surfaces in the is level of inspect ion is made under inspection area. Th normally available lighting cond itions such as daylight, droplight and may require hangar lighting, flashlight, or removal or opening of access panels or doors. Stands, quired to gain proximity to ladders, or platforms may be re the area being checked. 156 UNCONTROLLED COPY WHEN DOWNLOADED

157 Aircraft EWIS Practices Job Aid 2.0 Stand-Alone GVI ection that is not • A general visual insp performed as part of a zonal inspection. Even in cases where the interval coincides with the stand-alone GVI remains zonal inspection, the the work card. an independent step on Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 157 Administration 157 UNCONTROLLED COPY WHEN DOWNLOADED

158 Aircraft EWIS Practices Job Aid 2.0 Detailed Inspection (DET) • An intensive examinatio n of a specific item, ly to detect damage, installation, or assemb . DET is discussed in failure, or irregularity greater detail in section 14b(1) of AC 25.27A. Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 158 Administration 158 UNCONTROLLED COPY WHEN DOWNLOADED

159 Aircraft EWIS Practices Job Aid 2.0 EWIS Inspection Focus Areas Connectors Clamping • • points – Worn seals – Loose connectors – Improper installation – Lack of strain relief – Clamp/wire damage – Drip loops – Clamp cushion – Tight wire bends migration Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 159 Administration - Wire chafing is aggravat ed by loose clamps, Clamping points n migration, or improper clamp damaged clamps, clamp cushio installations. Connectors - Worn environmental seal s, loose connectors, excessive corrosion, missing seal plugs, missing dummy relief on connector grommets can contacts, or lack of strain compromise connector integrity and allow co ntamination to enter the connector, leading to corrosion or grommet degr adation. Drip loops should be main tained when connector s are below the level connectors shou of the harness and tight bends at ld be avoided or corrected. 159 UNCONTROLLED COPY WHEN DOWNLOADED

160 Aircraft EWIS Practices Job Aid 2.0 , cont. EWIS Inspection Focus Areas • Grounding points Terminations • – Tightness – Lugs/splices – Cleanliness • Backshells – Corrosion – Improper build-up – Lack of strain relief • Damaged sleeving and conduits Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 160 Administration Terminations - Terminal lugs and spli ces are susceptible to corrosion, heat dama ge and chemical mechanical damage, contamination. Also t torque on large-gauge , the build up and nu wire studs is critical to their performance. Backshells - Wires may break at backsh ells, due to excessive flexing, lack of strain relief, or improper build- up. Loss of backshell bonding may also occur due to th ese and other factors. Damaged sleeving and conduits - Damage to sleeving and conduits, if not corrected, will often lead to wire damage. Grounding points - Grounding points should be checked for security (i.e. tightness) , condition of the termination, cleanliness, and corrosion. Any grounding poin ts that are c orroded or have ating should be repaired. lost their protective co 160 UNCONTROLLED COPY WHEN DOWNLOADED

161 Aircraft EWIS Practices Job Aid 2.0 EWIS Inspection Locations: Examples • Wings – Exposed EWIS on leading/trailing edges during flap/slat operation Engine/APUs/pylon/nacelle • – Heat/vibration/chemical contamination – High maintenance area • Landing gear/wheel wells – Environmental/vibration/chemical Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 161 Administration EWIS inspection locations . Available data indica te that the locations shown on the slide should receive special attent ion in an operator’s EWIS inspection program. Wings - The wing leading and trailing edges are areas that experience stallations. The wing leading and difficult environments for EWIS in trailing edge EWIS is exposed on odels whenever the some aircraft m flaps or slats are extended. Other potential damage sources include slat torque shafts and bleed air ducts. Engine, pylon, and nacelle area - These areas ex perience high requent maintenance, vibration, heat, f and are susceptible to chemical contamination. APU - Like the engine/nacelle area, th e APU is susceptible to high maintenance, and chem vibration, heat, frequent ical contamination. Landing gear and wheel wells - This area is exposed to severe vibration and chemical external environmental cond itions in addition to contamination. 161 UNCONTROLLED COPY WHEN DOWNLOADED

162 Aircraft EWIS Practices Job Aid 2.0 , cont. EWIS Inspection Locations • Electrical panels/line replacement units (LRU) – High density areas – High maintenance activity – Prone to broken/damaged EWIS • Batteries – Chemical contamination/corrosion • Power feeders – Feeder terminations – Signs of heat distress Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 162 Administration Electrical panels and line replaceable units (LRUs) - Panel EWIS is particularly prone to bro ken wires and damaged insu lation when these high density areas are distu rbed during troubleshooti ng activities, major modifications, and refurbishment. One repair facility ha s found that wire dowels. This reduced tying EWIS to wooden damage was minimized by wire disturbance during modification. mmended to remove It is also reco entire disconnect brackets, when possible, instead of remov ing individual receptacles. Batteries - Wires and EWIS hardware in the vi cinity of all aircraft batteries should be inspected for corrosion and discoloratio n. Discolored wires or serviceability. Corroded should be inspected f wires and/or EWIS hardware should be replaced. - Operators may find it adva ntageous to inspect splices Power feeders If any signs of and terminations for signs of overheat ing and security. overheating are seen, the splice or term ination should be replaced. This applies to galley power feeders, in addition to the main and APU generator retorquing power feeder power feeders. The desi rability of periodically terminations should be evaluated. 162 UNCONTROLLED COPY WHEN DOWNLOADED

163 Aircraft EWIS Practices Job Aid 2.0 EWIS Inspection Locations , cont. • Under galleys and lavatories – Susceptible to fluid contamination – Fluid drainage provisions • Cargo bay/underfloor area – High maintenance activity Surfaces, controls, doors • – Moving and bending wire harnesses Near access panels • – Prone to accidental damage Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 163 Administration Under galleys and lavatories - Areas under the galleys, ainers are particularly susceptible lavatories and other liquid cont to contamination from coffee, food nks and lavatory , water, soft dri fluids, etc. Fluid drain provision s should be periodically inspected and repaired as necessary. Cargo bay/under floor - Cargo can damage EWIS. Damage to EWIS in the cargo bay under floor can occur due to maintenance activities in the area. Surfaces, contro ls, and doors - Moving or bending harnesses should be inspected at these locations. Access panels - Harnesses near access panels may receive accidental damage and shou ld have special emphasis inspections. 163 UNCONTROLLED COPY WHEN DOWNLOADED

164 Aircraft EWIS Practices Job Aid 2.0 25.1703 Requirements for preemptive maintenance New rule assures EWIS components selection • carried out safely, consistently, & standardized What does it require? • 1. EWIS Components must function properly when installed qualified for airborne use 2. EWIS components must be • Household wire or wire used on consumer electronics not acceptable unless shown to meet all part 25 certification requirements 3. Expected service life must be addressed Limitations must be part of the ICA (H25.4) • 4. Must consider known characteristics in relation to each specific application • Includes wire’s insulation susceptibility to arc tracking Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 164 Administration 164 UNCONTROLLED COPY WHEN DOWNLOADED

165 Aircraft EWIS Practices Job Aid 2.0 Use of Grommets Improper Proper The grommet should cover the en tire edge and co me together at the top of the hole. 165 UNCONTROLLED COPY WHEN DOWNLOADED

166 Aircraft EWIS Practices Job Aid 2.0 Potential Foreign Object Damage Metallic Shavings These photographs show foreign obj ect damage (FOD) that can s. Metallic shaving pose a cause damage to EWIS component serious threat which can damage wire insulation and cause subsequent arcing and fire damage. This is one of the reasons for the clean-as-you-go ma intenance philosophy. 166 UNCONTROLLED COPY WHEN DOWNLOADED

167 Aircraft EWIS Practices Job Aid 2.0 Tie Wrap Ends tie wrap Improper: ends have not been cut. Proper It is important to cut the tie wrap ends after securing the wires in order to avoid possible interference with other EWIS components. 167 UNCONTROLLED COPY WHEN DOWNLOADED

168 Aircraft EWIS Practices Job Aid 2.0 Clamp Cushion Damaged clamp cushion Undamaged clamp cushion Damaged clamp cushions can caus e EWIS damage that can lead to arcing. 168 UNCONTROLLED COPY WHEN DOWNLOADED

169 Aircraft EWIS Practices Job Aid 2.0 Sleeving Installation Improperly installed sleeving Properly installed sleeving Protective sleeving s hould overlap at least 30% to ensure 100% coverage of the wire bundle. 169 UNCONTROLLED COPY WHEN DOWNLOADED

170 Aircraft EWIS Practices Job Aid 2.0 Part 25 and 26 Required Compliance Documentation Project Specific Certification Plan (PSCP) • (EWIS/EZAP aspects) – Load analysis – EWIS Installation Drawings and EWIS Diagrams (25.1701,including identification of EWIS components per 25.1711) – EWIS separation requirements (25.1707) – Systems Safety Analysis (25.1709) – ICA for EWIS including any airworthiness limitations (25.1729 and 25.1703, respectively) Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 170 Administration 170 UNCONTROLLED COPY WHEN DOWNLOADED

171 Aircraft EWIS Practices Job Aid 2.0 EWIS Diagrams • Wire selection – Gauge/breaker size – Insulation – EWIS Identification – Environmental considerations • Connectors – Pin/socket ratings – Pin arrangement (best practices) – Environmental considerations Grounding • Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 171 Administration The engineer or designee should revi ew the EWIS diagrams and verify the following points. This informat ion should be availa ble on the EWIS diagrams or referenc ed to the source. The wires must be size d properly and the circuit Wire selection - breaker sized to adequately protect the wire considering the ambient temperature of the envi ronment. The circuit brea ker protecting the wire should open bef ore the circuit breaker prote cting the upstream bus. • The wire insulation and conductor pl ating must be suitable for the environment plus any further temper ature rise due to dissipated power. Connectors - are suitable for the Ensure that the connectors environment and the pins and socket d to handle the s are properly rate power demands of the circuit. • As we discussed earlier, pin ar rangements should minimize the possibility of shorts between power, gr ound, and/or signals. Verify that separation requirements from the safety assessment process are addressed. Also, ensure unused pins are properly protected. have proper grounding. Ensure circuits Grounding - 171 UNCONTROLLED COPY WHEN DOWNLOADED

172 Aircraft EWIS Practices Job Aid 2.0 EWIS Installation Drawings Clamps • – Proper size, type, and material – Spaced appropriately for environment – Mounted correctly Feed throughs/pass throughs • – Grommets used when necessary – Wire bundles properly supported Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 172 Administration It is important to note that installation drawings gene rally do not provide the necessary detail to ensure proper clampi ng, routing, and termination of EWIS for a given installation. ee to perform a first-of-a-model or It is advisable for the engineer or design first-of-a-design general EWIS complianc e inspection in addition to reviewing the EWIS diagrams and EWIS installation drawings. Consideration should be given to the complexity of the EWIS in determining the appropriate depth of the compliance inspection. The engineer or designee should ensure that adequate installation drawings exist and review the drawings and perfor m the compliance inspection to verify the items noted on the following slides (w hich we discussed in detail earlier). Clamps must be suitable with respect to size, type, and material. Also ensure that an adequate number of clamps are us ed to properly support the wire bundle. Clamps should be mounted correctly with proper orientation. Feed throughs/pass throughs - Grommets suitable fo r the environment must be used when the wire bundle passes th rough pressure bulkhead, firewall, the structure. and other openings in 172 UNCONTROLLED COPY WHEN DOWNLOADED

173 Aircraft EWIS Practices Job Aid 2.0 EWIS Installation Drawings , cont. • Routing –Chafing – Location with respect to fluid lines, lavs, and galleys on (component marking) – EWIS Identificati – Drip loops – Bend radius – Coil, cap, and stow methods – Human factors (hand/step holds) – Protected against cargo/maintenance Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 173 Administration EWIS routing should be reviewed to ensure proper clearance from aircraft structure, fluid lines, and other equipment. to the effects on EWIS from • Consideration should be given maintenance, shifting cargo, and passen gers. Proper bend and proper coil and stow methods radius, use of drip loops, should be verified. EWIS that could be used as hand or step holds should be mi nimized or placarded. 173 UNCONTROLLED COPY WHEN DOWNLOADED

174 Aircraft EWIS Practices Job Aid 2.0 , cont. EWIS Installation Drawings • Routing , cont. – Accessible for maintenance, repairs, and inspection – Proper slack – Segregation and separation • Compatible with OAM standards • Does not violate any regulatory safety requirements Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 174 Administration Connectors, clamps, splices, and terminations should be ce, repairs, and inspec tion. Ensure that accessible for maintenan the EWIS is secure yet not pre loaded and that enough slack mounted equipment, maintenance, exists to account for shock- and breakouts to term inals, as appropriate. For EWIS modifications to existing aircraft, the routing should be compatible with safety re quirements and the OAM EWIS and segregation philosophy with respect to ex isting separation standards. 174 UNCONTROLLED COPY WHEN DOWNLOADED

175 Aircraft EWIS Practices Job Aid 2.0 , cont. EWIS Installation Drawings Conduits • – Sized properly – Appropriate for environment – Conduit ends are terminated – Bend radius – Drain holes – Metallic - Are EWIS components properly protected inside? Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 175 Administration are sized properly and Ensure that conduits Conduits. environment. appropriate for the • Pay particular attention to the conduit end poin ts to ensure proper termination. hould be suitable for • Conduit bend radii s both the conduit and wire bundle inside the conduit. • Ensure that low spots in the c onduit have drain holes that can be maintained and inspected. llic conduit is protected in a • Also, ensure that EWIS in meta suitable manner. 175 UNCONTROLLED COPY WHEN DOWNLOADED

176 Aircraft EWIS Practices Job Aid 2.0 Aircraft EWIS Practices Points of Contact: • Brett Portwood: [email protected] FAA Technical Specialist, Safety and Integration Los Angeles ACO; ANM-130L (562)627-5350 Massoud Sadeghi: • [email protected] Aging Systems Program Manager Transport Airplane Directorate; ANM-114 (425)227-2117 Aircraft EWIS Best Practices Job Aid 2.0 Federal Aviation 176 Administration 176 UNCONTROLLED COPY WHEN DOWNLOADED

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