Malaysian Institute of Aviation TechnologyTopic 5 ELECTROMAGNETIC ENVIRONMENT Introduction Malaysian Institute of Aviation Technology • Any electrical or electronic device creates what is called an electromagnetic (EM) environment as electrons are moved around to make the device work. • In addition, there may be natural phenomena such as lightning occurring in the same location. • Or for one of a variety of reasons, an electrostatic discharge may take place even when a device or system is not in its normal functioning mode. • When engineers first became aware of the effects of such phenomena, in the earliest days of radio, they usually referred to radio frequency interference (RFI). • Electromagnetic effect : .High Intensity Radiated FreqUency (HIRF) .Electrostatic Discharge (ESD) .Electromagnetic Environment Effect Malaysian Institute of Aviation Technology • Today. the term electromagnetic interference (EMI) better reflects the fact that electrical and electronic systems may cause disturbances at any frequency between 0 Hz and the GHz (microwave) range.Electromagnetic Compatibility (EMC) .Electromagnetic Interference (EMI) . Malaysian Institute of Aviation Technology The Electromagnetic Spectrum . Malaysian Institute of Aviation Technology Frequency bands used in EMI measurement . Malaysian Institute of Aviation Technology Electromagnetic Interference (EMI) • Electromagnetic interference (or EMI. also called radio frequency interference or RFI) is a (usually undesirable) disturbance that affects an electrical circuit due to electromagnetic radiation emitted from an external source. such as an electrical circuit or from the Sun. obstruct. • The disturbance may interrupt. or otherwise degrade or limit the effective performance of the circuit. that carries rapidly changing electrical currents. . • The source may be any object. artificial or natural. • These emissions can interfere with the performance of sensitive wireless receivers nearby. you will probably hear RF noise in the receiver that originates in the PC system. • If you have a wireless receiver of any kind and use it at the same time as you operate your personal computer.Malaysian Institute of Aviation Technology • The internal circuits of personal computers generate EM fields in the RF range. • Also. . cathode ray tube (CRT) displays generate EM energy over a wide band of frequencies. contact the manufacturer for technical assistance. . • Before performing any modifications to equipment. if possible. • This is especially important if modifications might void an existing warranty. • Specialized components such as line filters. and inductors can be installed in power cords and interconnecting cables to reduce the EMI susceptibility of some systems. be shielded to keep unwanted RF energy from entering or leaving.Malaysian Institute of Aviation Technology • Problems with EMI can be minimized by ensuring that all electronic equipment is operated with a good electrical ground system. capacitors. cords and cables connecting the peripherals in an electronic or computer system should. and it is imperative with medical devices of any kind. • In addition. Malaysian Institute of Aviation Technology ELECTROMAGNETIC COMPATIBILITY (EMC) • Electromagnetic compatibility (EMC) is the studies of unintentional generation. or EMI) that such energy may induce. • The goal of EMC is ensure the correct operation. transmitter defects such as harmonics are considered in Radio transmitter design. These effects are not due to defects in the transmitter (other than poor RF shielding). propagation and reception of electromagnetic energy with reference to the unwanted effects (Electromagnetic interference. . and the avoidance of any interference effects. of different equipment which use electromagnetic phenomena. in the same electromagnetic environment. • EMC problems can occur when the system which is being adversely affected is subject to a high field strength due to a radio transmitter. . • Susceptibility or immunity issues. • Interference. mitigation and hence electromagnetic compatibility is achieved primarily by addressing both emission and susceptibility issues.e. to the entry of electromagnetic fields is described by the use of the terms susceptibility or immunity. or noise. in the presence of unplanned electromagnetic disturbances.. in contrast. or adjacent devices.Malaysian Institute of Aviation Technology • The sensitivity of a device. quieting the sources of interference and hardening the potential victims. refer to the correct operation of electrical equipment. i. referred to as the victim. Example of EMC situation Malaysian Institute of Aviation Technology • TV reception is garbled whenever someone turns on the vacuum cleaner • computer crashes during a lightning storm or power surge and valuable data is lost. . • overhear a voice conversation in your stereo or there is an annoying hum or buzz that won't go away. • portable radio next to your computer always sounds better when you turn off your computer. system controls that once were operated manually via cables and hydraulics are becoming replaced by digital electronics.Institute ofRadiated Aviation TechnologyFrequency (HIRF) HighMalaysian Intensity • External Disturbance caused by powerful radio transmitter or lightning • In modern aircraft equipment. • The susceptibility of flight-critical systems to external radio frequency interference is a real concern and as a result. . High Intensity Radiated Fields testing (HIRF) will play an important role in the future of aviation. • In the future. commercial aircraft will have primarily electronic systems that stabilize the aircraft and will have computerassisted controls for all functions that allow the plane to stay in the air. The reduced electromagnetic shielding afforded by some composite materials used in various applications and designs . especially above the 1 gigahertz (GHz) level .Malaysian Institute of Aviation Technology • Reason why need to protect the electrical and electronic systems in aircraft from HIRF : . and a general greater sensitivity of electronic equipment .An increased susceptibility of electrical and electronic systems to HIRF due to increased data BUS or processor operating speeds.A greater dependence on electrical and electronic systems to perform functions required for continued safe flight and landing of aircraft . higher-density integrated circuits and cards.An expanded frequency range usage. Example .HIRF Generation Malaysian Institute of Aviation Technology . – Proper shielding of wiring systems to prevent interference caused by stray electromagnetic energy – Use fiber optic data buses which are not subjected to interference such as EMI .Malaysian Institute of Aviation Technology Method to minimize HIRF effects • Protection of critical electronics system residing the same area. the following method are carried out – Metal boxes – can prevent entry of EMI waves to interface with systems components. Malaysian Institute of Aviation Technology Electronic components inside the LRU LRU is protected by Metal Box from Electromagnetic field Electromagnetic Field . ii)The braided shield carry effecting any induced EMI directs to ground thus preventing system inaccuracies or failure 2. (Electromagnetic compatibility) . Shielding assist in eliminating EMI by i)Protecting the primary conductor with an outer conductor called the shield by grounding both ends of the shield. Shielding is also used when one unit is to be protected from the effects of HF current in an adjacent unit or protection from HIRF generated by airborne or found equipment.Malaysian Institute of Aviation Technology 1. sockets. plugs. • The inspections are normally visual but will require bonding testing where necessary and the use of specialist test equipment where specified in the AMM. and screening on the aircraft should be inspected as laid down in the maintenance schedule and the AMM.Maintenance Practices Malaysian Institute of Aviation Technology • All wiring. . security. contamination. etc. broken screening.Visual Inspections Malaysian Institute of Aviation Technology • To check for damage. broken strands. correct assembly. locking. chafing. • All wires shields. ground leads. . deterioration. correct torque of plugs/sockets. open circuits. sign of burning. screen jumpers are to be intacted. corrosion. as the charge builds. • Beneath the cloud. . eventually a circuit is created and discharges takes place between the cloud and the ground. often associated with the vertical movement and collision of ice particles. which result in a negative charge at the base of the cloud and a positive charge at the top of the cloud. or between the cloud and another cloud. a "shadow" positive charge is created on the ground and.LIGHTNING Malaysian Institute of Aviation Technology • Lightning is an atmospheric discharge of electricity • Lightning occurs as a result of a build up of static charges within a Cumulonimbus cloud. as well as noise. • Damage is usually confined to aerials. . • Lightning is accompanied by a brilliant flash of light and often by the smell of burning.Malaysian Institute of Aviation Technology • An aircraft passing close to an area of charge can initiate a discharge and this may occur some distance from a thunderstorm. compasses. • Lightning strikes on aircraft commonly occur within 5. avionics.000 feet of the freezing level. and the burning of small holes in the fuselage. • A lightning strike can be very distressing to passengers but physical damage to an aircraft is rare and is not likely to threaten the safety of the aircraft. there have been many incidents of lightning strikes leaving puncture holes in the radomes and tail fins of aircraft (entry and exit holes) and damage to control mechanisms and surfaces. particularly compasses.Transient airflow disturbance associated with lightning to cause engine shutdown on both FADEC and non-FADEC engines with close-spaced engine pairs.A lightning strike can effect avionics systems.Structural damage to aircraft from Lightning strikes is rare and even more rarely of a nature that threatens the safety of the aircraft. .EFFECT Malaysian Institute of Aviation Technology • Aircraft Damage . is not uncommon. Nevertheless. • Interference with Avionics . especially at night. • Crew Incapacitation .Momentary blindness from the lightning flash. • Engine Shutdown . Malaysian Institute of Aviation Technology . Malaysian Institute of Aviation Technology METAL PROTECTED AREAS –B777 . Malaysian Institute of Aviation Technology The End .