Chap 8: electromagnetic environment

Question 1

what is EMI and its description

Answer 1

electromagnetic interference

disruption of operation of an electronic device in the vicinity of an EM field that is emitted by another device

Question 2

what is EMC and its description

Answer 2

electromagnetic compatibility

ability of a device to function normally in its EM environment without introducing big EM disturbances

Question 3

what is high intensity radiated fields

Answer 3

HIRF is radio frequency field that is strong enough to affect living things and performance of devices

Question 4

design considerations for EMC

Answer 4

place sensitive circuit or receiver away from electrical noise
orientation of receiver (minimise unwanted signals)
install grounding shield from noisy sources or receiver
minimise potential electrical noise
design highly selective receivers (only pick up certain frequencies)

Question 5

how can EMI be solved?

Answer 5

making sure all electronic equipment and systems on aircraft has a good electrical ground system

electrical shield for wires and cables

install electronic filters and transient-absorbers

Question 6

ways to implement EMC

Answer 6

all electronic equipments on aircraft is operated with a good electrical ground system.

Wire harnesses and cables electrically- shielded

line electronic filters and transient-absorbers can be installed in power lines and circuits

Question 7

ways to test EMC

Answer 7

conducted susceptibility: RF interference coupled into the equipment under test interconnecting cables and power leads using injection probe

radiated susceptibility: EUT and its interconnecting cables and power leads are exposed to RF radiated fields (100MHz - 18 GHz)

Question 8

what can happen electrically during flight?

Answer 8

electrical energy build on the structure of aircraft by precipitation static (static charges) and by charges due to electrostatic induction

resultant is the potential difference between aircraft and the atmosphere

Question 9

how to protect against electrical charges

Answer 9

having a continuous low-resistance link between all the parts of a/c in the form of electrical bonding which will connect to electrical ground eventually

Question 10

how to discharge electricity from aircraft

Answer 10

1) nose-wheel or tail-wheel tyre that contains a special compound providing the tyre with good electrical conductivity
2) short flexible steel wire is used to secure the nose wheel axle members to earth or ground point

Question 11

what does faraday’s cage do for aircrafts

Answer 11

traditional aircraft had largely metallic structures which faraday’s cage shielded the a/c against effects on lightning strikes