7.7.3 EWIS Flashcards
What is becoming increasingly important for aircraft operation?
The safe and economic operation of an aircraft is becoming ever more dependent on electrical and electronic systems.
What must be treated as an integral part of the aircraft?
Electrical wires and cables must be treated as an integral part of the aircraft, requiring careful installation.
What are Line Replaceable Units (LRUs)?
In all modern aircraft, individual systems and computers are housed in Line Replaceable Units (LRUs), modules, and card files.
What is the main consideration for an aircraft wiring system?
The main consideration for an aircraft wiring system is reliability.
What does the performance and safety of the aircraft depend on?
The performance and safety of the aircraft, its crew, and its passengers depend on the correct functioning and integrity of an electrical circuit under all flight conditions.
What is done to ensure maximum reliability of aircraft wires and cables?
Stringent tests are applied to ensure that they are all of maximum reliability.
How are electrical power supplies routed in aircraft?
Electrical power supplies, as well as system inputs/outputs, are routed and distributed to the LRU racks and fed with information from their respected sensors or power busses.
What factors define the specifications of wires and cables in aircraft?
Specifications are defined by the type of power, current, signal, voltage environment, and use.
What are some typical uses and considerations for aircraft wiring?
Power supplied, analogue voltage output environment, sensor output resistance changes, discrete ground inputs, formatted data exchange, HIRF protection, RF energy inputs, size and miniature connection, high-temperature areas, environmental considerations, rack and panel connections, fire-wire.
What must be checked during maintenance of interconnected wiring?
Each of the individual requirements and specifications of all the cables, wiring, and connections involved in that wiring network or system need to be checked.
What can cause overheating of wires and cables?
Wires and cables must be protected from overload conditions that can lead to overheating, causing the release of toxic fumes and possibly leading to a fire.
What has been realized about current maintenance practices?
Regulators and industry groups have realized that current maintenance practices cannot be adequate to address the ageing of non-structural systems.
What factors can increase the probability of wire degradation?
Inadequate maintenance, contamination, improper repair, or mechanical damage can increase the probability of degradation.
What were some findings from reviews of service history regarding electrical installations?
Concerns about in-service continuing airworthiness of electrical installations were revealed, partly due to a lack of rigorous design and certification code.
What were the major contributory factors in the TWA Flight 800 and Swissair 111 accidents?
Wiring was found to be a major contributory factor in both accidents.
What contaminants were found on wiring during inspections?
Wiring was contaminated with dust, dirt, metal shavings, lavatory wastewater, coffee, soft drinks, and napkins.
What is a potential risk from dust found on wire bundles?
Dust can provide combustible material and increase the risk of a fire.
What can cause collateral damage to wiring?
Maintenance performed on other aircraft systems or repairs to the structure can cause collateral damage to wiring.
What committee was tasked with examining ageing aircraft systems?
The Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) was tasked with this examination.
What is EWIS?
EWIS covers areas of the build, maintenance practices, inspection, cleaning, and repair of electrical cables and the interconnecting system.
What must each EWIS component be designed for?
Each EWIS component must be of a design appropriate to its intended function.
What are the three documents issued by EASA for EWIS maintenance?
AMC 20-21, AMC 20-22, and AMC 20-23.
What is the purpose of wire separation in aircraft?
The purpose of wire separation is to prevent hazards of interference between wires or between electrical and non-electrical systems.
What must EWIS be designed to minimize?
EWIS must be designed and installed to minimize damage and the risk of damage to EWIS by passengers, crew members, baggage, and maintenance personnel.
What must all EWIS components meet?
All EWIS components must meet strict fire and smoke protection requirements.
How must EWIS components be identified?
EWIS components must be labelled or otherwise identified by a consistent method.
What are the two commonly used manuals for electrical installations on aircraft?
Airbus Industries Electrical Standard Practices Manual (ESPM) and Boeing D6-54446 Standard Wiring Practices Manual (SWPM).
What is the focus of typical analytical methods for maintenance programmes?
They have not provided a focus on wiring, leading to inadequate addressing of EWIS deterioration.
What are the three types of inspections defined by regulatory authorities?
- Stand-alone General Visual Inspections (GVI)
- Detailed (DET) inspections
- Zonal Inspections
What is a General Visual Inspection (GVI)?
A visual examination of an area, installation, or assembly to detect obvious damage, failure, or irregularity.
What are the key considerations when performing a GVI?
- Inspection is made from within touching distance.
- A mirror may be necessary for visual access.
- Conducted under normally available lighting conditions.
- May require removal of access panels.
- Cleaning must minimize the risk of hiding conditions.
What should be considered regarding dust and debris contamination during a GVI?
Potential effects on adjacent systems, particularly wiring, must be considered.
What distinguishes a Detailed Inspection (DET) from a Detailed Visual Inspection (DVI)?
A DET includes tactile assessment in addition to visual inspection, while a DVI is solely visual.
What is a zonal inspection?
A collective term for selected GVIs and visual checks applied to each zone to detect obvious unsatisfactory conditions.
What are typical EWIS degradation items to be detected in a zonal inspection?
- Wire harnesses issues
- Connector integrity
- Wiring protection sheath deformities
- Dust and lint accumulation
- Signs of overheating
What are the areas of concern for wire raceway and bundles?
Adding wires can cause wear and chafing, particularly in wing leading and trailing edges.
What should be checked at grounding points?
- Security
- Condition of the termination
- Cleanliness
- Corrosion
What are the risks associated with power feeder cables?
They are susceptible to installation errors and splice degradation.
What is the significance of drip loops in wiring?
Drip loops must be maintained to prevent water from entering connectors and causing damage.
What are common issues with connectors?
- Worn environmental seals
- Loose connectors
- Missing strain relief
- Contamination leading to corrosion
What should be inspected regarding terminations?
They are susceptible to mechanical damage, corrosion, heat damage, and contamination.
What is the importance of maintaining cleanliness in terminal blocks?
They must be kept free of combustibles to prevent fire hazards.
What are the concerns for wiring near access panels?
Wiring can receive accidental damage due to repetitive maintenance access.
What must be periodically checked in fluid drain plumbing?
Drain paths must be free of obstructions to prevent liquid contamination of wiring.
What is the risk associated with wiring in the cargo bay underfloor?
Wiring can be damaged due to maintenance activities and must be inspected regularly.
What must EWIS damages be repaired in accordance with?
EWIS damages must be repaired in accordance with the Manufacturer’s Wiring Practices manual.
What should be done in case of discolouration of electrical items?
Replace the electrical item.
What is the procedure for cracks in electrical items?
Replace the electrical item.
What action is required for expansion of sealing grommets?
Replace the electrical item.
What should be done if supplier marks are erased?
Replace the electrical item.
What is the procedure for loss of label adhesion?
Replace the electrical item.
What action is needed if functional item numbers are erased on labels?
Replace the electrical item.
What is the Enhanced Zonal Analysis Procedure (EZAP) designed for?
EZAP is designed to permit appropriate attention to be given to electrical wiring installations.
What does EZAP help identify?
EZAP helps identify applicable and effective maintenance tasks to minimise the accumulation of combustible materials.
What is required if wiring is installed in a zone with combustible materials?
Some level of inspection of the wiring in the zone is required.
What characteristics are included in the inspection level rating system?
Zone size, density of installed equipment, and potential effects of fire on adjacent wiring and systems.
How is zone size assessed?
Zone size is assessed relative to the size of the aircraft, identified as small, medium, or large.
What is a General Visual Inspection (GVI)?
A GVI is a required inspection for all wiring in the zone at a common interval.
What are the possible inspection tasks for programmes with a Zonal Inspection Programme (ZIP)?
Zonal GVI, Stand-alone GVI, Detailed Inspection (DET).
What are the principal causes of wiring degradation?
Vibration, moisture, maintenance, metal shavings, repairs, indirect damage, contamination, heat, ageing.
How does high vibration affect wiring?
High vibration areas accelerate degradation over time, causing ‘chattering’ contacts and intermittent symptoms.
What effect does moisture have on wiring?
High moisture areas accelerate corrosion of terminals, pins, sockets, and conductors.
What should be done to protect wire bundles during maintenance?
Care must be taken to protect wire bundles and connectors during all work.
What is the recommended method for repairing wires?
Repairing a wire with an environmental splice is recommended.
What does wire contamination refer to?
The presence of a foreign material likely to cause degradation of the wiring or sustain combustion.
What special consideration is needed for hydraulic fluid contamination?
Hydraulic fluids can damage connector grommets and require special attention during inspections.
What happens to wiring exposed to high heat?
Exposure to high heat can accelerate degradation of wiring, causing insulation dryness and cracking.
What does ageing refer to in the context of wiring?
Ageing refers to the health of the wire’s insulation and is related to the conditions it is exposed to.
What are EWIS components adjacent to waste/water systems prone to?
Contamination due to fluids like water.
Water is a conductor and can cause electrocution or short-circuiting of electrical components.
What should be done to prevent fluids from entering electrical components during servicing of waste/water systems?
Cover exposed electronic components and wiring.
Switch off all unnecessary electronic equipment in proximity to water.
What maintenance practice can enhance operational reliability in lavatory systems?
Flushing a weak acid solution periodically.
The system must be confirmed to be free of leaks before using such solutions.
What are EWIS components adjacent to oil and hydraulic systems prone to?
Contamination from oil and hydraulic fluids.
Oil can emit flammable fumes that may ignite from live wires.
What precautions should be taken when entering or working on an aircraft?
Prevent damage to adjacent or hidden electrical components and wiring.
Use protective boards or platforms for support.
What should not be used as handholds when working on aircraft?
Wiring and wire bundles.
Work lights must not be hung or supported by wiring.
What must be avoided when applying Corrosion Preventative Compounds (CPC)?
Prevent CPC from entering wires, wire harnesses, and components.
Application must follow the aircraft manufacturer’s recommendations.
Why must EWIS components meet specified requirements in areas with flammable fluids?
To minimize the probability of ignition of fluids and vapours.
They are potential ignition sources if leakage occurs.
What are the two types of contamination to EWIS components?
Natural and Accidental contamination.
What is Natural contamination?
Natural contamination comes from identified materials used in aircraft systems such as hydraulic fluid, fuel, or dust.
What is Accidental contamination?
Accidental contamination comes from unknown external sources such as chemical spillages or cargo compartment spillages.
What are the mandatory safety practices to follow?
Read safety data sheets, obey local regulations, follow aircraft manufacturers’ instructions, wear protective clothing, ensure proper ventilation, and avoid smoking or ingesting solvents.
What should you do if your skin or eyes become irritated?
Seek medical help.
What materials should be used for cleaning natural contamination?
Aircraft hydraulic fluid, fuel and oil/grease, de-icing fluid, and Isopropyl Alcohol (Material No. 11-010) or equivalent.
How should accidental contamination be treated?
It must be treated on a case-by-case basis, depending on the chemical nature of the material.
What should be done in the event of aggressive contamination?
The wiring must be released from its installation to avoid undue stress.
What are the steps to follow for liquid contamination?
Stop the contamination source, make a sealed barrier, and remove the contamination with a cloth or vacuum cleaner.
What are the steps to follow for powder, granular, or dust contamination?
Ensure there are no draughts and remove the contamination with a vacuum cleaner.
What should be done if contamination is accidental?
Find the characteristics of the contamination agent, evaluate the risk, refer to the AMM table, and visually examine the area.
What is the cleaning method for contaminated areas?
Start cleaning from top to bottom and from the outside to the center, using approved cleaning agents and ensuring a clean, dry, lint-free cloth.
