Avionics Maintenance (2018) Flashcards
What are the two broad categories of maintenance?
Preventive
corrective maintenance.
Describe preventive maintenance.
maintenance performed to reduce the likelihood of future troubles or malfunctions.
What is the first step you should take when receiving a discrepancy?
Determine if the equipment in question is actually faulty.
Describe the use of continuity tests.
To check for opens or to see if a circuit is complete or continuous.
Describe the major method for testing shorts in transformers, motor windings, and capacitors.
to take resistance measurements and compare them with schematics, MIMs, or identical operational equipment.
What is the proper color code for a 100-ohm resistor with a 10-percent tolerance?
1st Digit: Brown; 2nd digit: Black; Multiplier: Brown; Tolerance: Silver;
What must you consider when substituting a resistor to ensure it is a proper sub- stitution?
You must consider ohmic value, wattage rating, tolerance, physical dimensions, and type of construction.
Who can make microelectronic repairs?
Only certified microminiature component repair (MMCR) personnel.
Describe the causes of component damage during maintenance.
usually results from excess heat during repair, reversed polarity of ohmmeters while checking for continuity, excessive voltage application or signal strength during testing, rough handling, or using the wrong tools or materials.
What manual should you refer to for further information on procedures for desoldering components?
NAVAIR 01-1A-23.
To what NAVAIR manual should you refer for detailed instructions on potting or sealing operations?
NAVAIR 01-1A-505.
What are the three major factors to consider when you have to determine the correct conductor you need for a job?
- Conductor size
- insulation
- the environment for the conductor
When may you use a cable splice (other than one made with the crimp-on splice or con- nector) and to what manual should you refer?
- As an emergency measure only.
- NAVAIR 01-1A-505.
Why should you install cable clamps so the screws are above a wire bundle?
The weight of the cable may bend and break the clamp.
Describe the difference between a wire group and wire bundle.
A wire group is two or more wires tied or laced together to give identity to an individual system. A wire bundle is two or more wires or groups tied or laced together to provide easier maintenance.
When should you NOT use nylon cable straps?
over wire bundles containing coaxial cable or in areas where failure of the strap would allow the strap to fall into moveable parts.
Describe the primary aim of bonding.
to provide an electrical path of low dc resistance and low RF impedance.
What causes arcing at high altitudes?
At high altitudes, arcing is caused by the reduced dielectric strength of the air as it becomes thinner.
How do we reduce the possibility of arcing?
Pressurization of the equipment case.
ESD-sensitive devices can be damaged by electrostatic voltages as low as
20 volts
When handling ESDS devices, personnel and their apparel should be connected to
ground
What is the minimum resistance for personnel ground straps?
250,000 ohms
What color is a symbol of material that is antistatic?
pink
Name the two types of electrical noise interference that enter aircraft receivers.
natural
man-made interference
Of the three types of natural interference, which is caused by radiation of stars?
cosmic noise
Why are rotating electrical machines a major source of receiver interference?
because there are so many electric motors used in the aircraft.
Does the size of an electric dc motor determine its interference capability?
no. the smallest motor could be the worst offender
Name the types of equipment that can cause pulse interference.
radar
beacons
transponders
coded-pulse equipment
Describe rectification ripple frequency.
its twice the power frequency times the number of phases
In aircraft wiring, the effect of induction fields is reduced by using proper spacing and coupling angle between wires. When is interference coupling at its least?
interference coupling is least when the space between active and passive leads is maximum and when the angle between the leads approaches a right angle
What methods may be used to reduce radio interference at the source?
short circuiting
dissipation
open circuiting
combination of all three
Capacitors and capacitive filter circuits make good filters for reducing and elimi- nating noise. What characteristics are used in selecting capacitors for filtering circuits in aircraft?
physical size
high temperature
humidity tolerances
physical ruggedness
How does an RC filter reduce interference?
- by changing the waveform of transients
- dissipating transient energy
How can you distinguish filter classes?
frequency characteristics
