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Airframe & Powerplant Rating

Oral Exam Prep Guide

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“Quality Without Compromise”

SECTION I—AVIATION MECHANIC GENERAL

ORAL TEST SUBJECT AREA “A” BASIC ELECTRICITY

1. What is the most important law applicable to the study of electricity?
Ohm's Law (E=I*R) (Voltage = Amps*Resistance)

2. What are the elements of Ohm's Law?Voltage (E), current (I), and resistance (R).

3. What are the sources of electrical power?
Mechanical (generator), chemical (battery), photoelectric (light), and thermal (heat).

4. What does an electrical circuit consist of?
A source of electrical pressure or EMF, resistance in the form of an energy consuming electrical device, and conductors, usually in the form of copper oraluminum wires, to provide a path for electron flow. .

5. What represents capacitance in an AC circuit?
A capacitor (condenser).

6. What is the function of a capacitor?
To store electricity.

7. What is inductance?
A voltage that is induced in a coif in an AC circuit. This voltage is opposite in direction to the applied voltage, and opposes any change in thealternating current.

8. What is impedance?
It is the combined effect of resistance, inductive reactance, and capacitive reactance in an AC circuit.

9. What is the unit of measurement of power in a DC circuit?
The watt. Amperes times volts equals watts (P = I x E). 746 watts equals one horsepower.

10. What is a kilowatt?
It is 1,000 watts.

11. In a DC circuit, what occurswhen voltage is increased while resistance remains constant?
There will be an increase in current.

12. What are the three types of DC electrical circuits?
They are series circuits, parallel circuits, and series-parallel circuits.

13. A 24-volt lead-acid battery has how many cells?
It has 12 cells. Each cell is rated at 2 volts.

14. What should be the specific gravityof the electrolyte in a fully charged lead-acid battery?
It should be between 1.275 and 1.300,

15. What instrument is used to determine the specific gravity of electrolyte in a lead-acid battery? A hydrometer.

16. Why can't a hydrometer be used to determine the charge of a nickel-cadmium battery?
The specific gravity of the electrolyte in a nickel-cadmium battery does not changeappreciably during charge or discharge of the battery.

17. When using a hydrometer to check the charge of a lead-acid battery, at what temperatures
must a correction factor be applied to the reading?
Adjustments must be made if temperature of the electrolyte is above 90° F or below 70°F.

18. What is electromagnetic induction?
It is the transfer of electrical energy bymeans of a magnetic field. This is the principle of transformer operation.

19. How are battery compartments protected against corrosion?
They are coated with special corrosion resistant paints such as bituminous paint.

20. What should be the correct electrolyte level in a properly serviced batter?
It should be approximately 3/8 inches above the plates. If thebattery has baffle plates above the cell plates, the electrolyte level should be up to the hole in the baffle plate in each cell.

21. Why should nickel-cadmium batteries and lead-acid batteries not be stored or serviced in the same area?
The electrolyte in nickel-cadmium batteries is chemically opposite to the lead-acid battery electrolyte and the fumes from lead-acid battery cancontaminate the electrolyte in the nickel-cadmium batteries.

ORAL TEST SUBJECT AREA “B” AIRCRAFT DRAWINGS

1. What type of lines are used on aircraft drawings to indicate hidden views, alternate positions, and center lines?
A hidden view line is a medium width line made up of short dashes. It represents an edge that cannot be seen when looking at the part from a specific position....