Electrical Wiring Interconnect System (EWIS) Review Questions with Verified Solutions Latest Update 2024

Electrical Wiring Interconnect System (EWIS) Review Questions with Verified Solutions Latest Update 2024 What is EWIS? - Answers It is any wire, wiring device or termination device installed in any area of aircraft for the purpose of transmitting electrical energy between two or more intended termination points. What are the things EWIS does not include? - Answers It does not include electrical equipment for testing procedures, portable electrical devices not part of airplane's type design and fibre optics. What are the things EWIS does include? - Answers Wires, cables, bus bars, connectors, clamps, electrical grounding and bonding devices, electrical splices, wire insulation, labels, pressure seals. What are the two fundamental properties of insulation materials? - Answers Insulation resistance and dielectric strength. What is insulation resistance? - Answers It is the resistance to current leakage over and through the surface of insulation. Which device is used to measure insulation resistance? - Answers A megohm-meter insulation tester. This device does not damage the insulation. What is dielectric strength? - Answers It is the ability of the insulator to withstand potential difference and is expressed in terms of the voltage at which the insulation fails. How are the maximum dielectric strength values measured? - Answers By raising the voltage of a test sample until the insulation breaks down. Which type of insulation materials are no longer used for new aircraft designs? - Answers PVC and nylon. What are the substances used to make the insulation materials for new aircraft designs? - Answers Teflon, Kapton, PTFE. What are some of the consequences of poor bonding and grounding of aircraft electrical systems? - Answers Electromagnetic interference (EMI), personnel shock hazard or electrostatic discharge damage to sensitive electronics. What is grounding? - Answers It is a process of electrically connecting conductive objects to either a conductive structure or some other conductive return path to safely complete a normal or fault circuit. What is the consequence of mixing return currents from various sources? - Answers It could cause a major problem to digital systems. How is the interaction of various return currents minimised? - Answers By identifying and using different types of ground. As a minimum, the design should use three ground types, AC returns, DC returns and all others. What are the two important aspects of ground return circuits? - Answers They should have a current rating and a voltage drop adequate for satisfactory operation of the connected electrical equipment. How can EMI problems be reduced? - Answers EMI problems caused by a system's power wire can be reduced by twisting the power wire with its ground return. How should the power ground connections of generators, transformer rectifiers, batteries and other heavy-current loads be assembled? - Answers They must be attached to individual grounding brackets that are attached to aircraft structure with a proper metal-to-metal bonding attachment. Which currents are the highest flowing in the aircraft structure? - Answers Power return fault currents. Which materials should not be used in power return paths? - Answers Low-resistive materials such as, carbon fibre composite (CFC). Which areas are not suitable for power return or fault current ground connections? - Answers Flammable vapour areas. What safety precautions should be considered with ground connections. - Answers - Regular inspection and maintenance - special attention to material heating and material degradation - the use of common ground connections for more than one circuit should be avoided. What is bonding? - Answers It is the electrical connecting of two or more conducting objects not otherwise adequately connected. What are some bonding requirements? - Answers - Low impedance paths to the aircraft structure to reduce EMI - conducting objects on the exterior of the airframe must be electrically connected to the airframe through conductive hinges or bond straps to conduct static charges or lightning strikes. What is the general value of resistance of most bond and ground connections? - Answers It should normally not exceed 0.003 ohms. What is the preferable length of bonding jumpers? - Answers As short as possible. What are the precautions taken when installing bonding jumpers. - Answers To prevent their