A&P General Oral

what is the basic unit of voltage?

volt

what is the basic unit of current?

The amp

What is the basic unit of resistance?

the Ohm

Which law of electricity is the most important for an aircraft mechanic to know?

Ohms law

what are the three elements in Ohms law?

Voltage (Volts), current(Amps), and resistance(Ohms).

what are five sources of electrical energy?

Magnetism, chemical energy, light, heat, and pressure.

what four thing's affect the resistance of an electrical conductor?

The material, the cross sectional area, the length and the temperature.

How can you tell the resistance of a composition resistor?

by the series of colored bands around one end of the resistor

what three things must all electrical circuits contain?

A source of electrical energy, a load to use the energy, and conductors to join the source and the load

what is the purpose of a capacitor?

To store electrical energy in electrostatic fields

what is the basic unit of capacitance?

Farad (F)

Why should electrolytic capacitors not be used in an AC circuit?

They are polarized. An electrolytic capacitor will pass current of one polarity, but will block current of the opposite polarity.

what is meant by inductance?

The ability to store electrical energy in electromagnetic fields.

what is the basic unit of inductance?

Henry (H)

what is meant by impedance?

The total opposition to the flow of alternating current. It is the vector sum of resistance capacitive reactance, and inductive reactance.

How can you find the polarity of an electromagnet?

Hold the electromagnet in your left hand with your fingers encircling the coil in the direction electrons flow (from negative to positive). Your thumb will point to the north pole of the electromagnet.

in what units is impedance measured?

Ohms

what is the basic unit of electrical power in a DC circuit?

the Watt

what is meant by a kilowatt?

1,000 watts

What happens to the current in a DC circuit if the voltage is increased but the resistance remains the same?

the current increases

what are the three types of DC circuits, with regard to the placement of the various circuit components?

series, parallel, and series-parallel

how many cells are there in a 24volt lead-acid battery?

12 cells (2v per cell)

what is the specific gravity of the electrolyte in a fully charged lead-acid battery?

between 1.275-1.300

what is the range of temperatures of the electrolyte in a lead-acid battery that does not require that you apply a correction when measuring its specific gravity?

between 70 degrees and 90 degrees Fahrenheit

what instrument is used to measure the specific gravity of the of the electrolyte in a lead-acid battery?

A hydrometer

How is a lead-acid battery compartment treated to protect it from corrosion?

paint it with a asphaltic (tar base) paint or with polyurethane enamel

What is used to neutralize spilled electrolyte from a lead-acid battery?

a solution of bicarbonate of soda and water

How high should the electrolyte level be in a properly serviced lead-acid battery?

only up to the level of the indicator in the cell

what precautions should be taken in a maintenance shop where both lead-acid and nickel-cadmium batteries serviced?

the two types of batteries should be kept separate, and the tools used in one type should no be used on the other

Why is a hydrometer not used to measure the state of charge of a nickel-cadmium battery?

the electrolyte of a nickel-cadmium battery does not enter into the chemical changes that occur when the battery is charged or discharged. its specific gravity does not change appreciably

what is used to neutralize spilled electrolyte from a nickel-cadmium battery?

a solution of boric acid and water

what is meant by electromagnetic induction?

The transfer of electrical energy from one conductor to another that is not electrically connected

how many ohms are in a megaohm

one million ohms (1,000,000)

what part of a amp is a milliamp?

one thousandth of an amp (0.001 amp)

what is meant by tolerance on an aircraft drawing?

The allowable plus or minus variation from the dimension given on the drawing.

what is meant by clearance on an aircraft drawing?

The amount of space, or separation, that is allowed between two components or parts.

what information is given in the title block of an aircraft drawing?

the name and address of the company who made the part, the name of the part, the scale of the drawing, the name of the draftsman, the name if the engineer approving the part and the number of the part

How are dimensions shown on an aircraft drawing?

By numbers shown in the break of a dimension line.

How can you know that the aircraft drawing you are using is the most current version of the drawing?

by the number in the revision block and by the log of the most recent drawings

how many views can there be in an orthographic projection?

six

how many views are used to show most objects in an aircraft drawing?

three

what is the purpose of a center line on an aircraft drawing?

this is the line that shows the center of the object in the drawing

What is a fuselage station number?

The distance in inches from the datum, measured along the longitudinal axis of the fuselage.

where is the title block normally located on an aircraft drawing?

in the lower right-hand corner of the drawing

what is the purpose of a cutting plane on an aircraft drawing?

it shows where an object has been cut to allow an axillary drawing to be made. the arrows on a cutting plane show the direction the auxiliary drawing is viewed

how is the alternate position of a part shown on an aircraft drawing?

by a thin line made up of a series of long dashes separated by two short dashes

Where must a record be kept of the current empty weight and the current center of gravity of an aircraft?

in the aircraft flight manual or weight and balance records required by 14 CFR 23.1583

what is meant by the datum that is used for weight and balance computations?

a readily identified reference chosen by the aircraft manufacture from which all longitude locations on the aircraft are referenced

Why are the distances of all the items installed in an aircraft measured from the datum when computing weight and balance?

this makes it possible to find the point about which the aircraft would balance (the center of gravity)

what are two reasons weight and balance control are important in an aircraft?

for safety of flight and for most efficient performance of the aircraft

*** what is meant by moment in the computation of weight and balance?

a force that tends to cause rotation. it is the product of the weight of an object in pounds and the distance of the object from the datum in inches

*** how do you find the moment of an item that is installed in an aircraft?

multiply the weight of the item in pounds by its distance from the datum in inches

*** what is meant by the arm of an item that is installed in an aircraft?

the distance, in inches, between the center of gravity of the item and the datum

Why must we consider the category under which an aircraft is licensed when we compute its weight and balance?

the different categories under which an aircraft can be licensed have deferent maximum gross weights and different center of gravity ranges

where can you find the leveling means that are specified for a particular aircraft?

in the type certificate data sheet for the aircraft

Where is the arm of an item installed in an aircraft recorded?

in the type certificate data sheet for the aircraft

what must be done to find the empty weight of an aircraft if it has been weighted with fuel in its tanks?

the weight of the fuel and its moment must be subtracted from the weight and moment of the aircraft as it was weighed

what is meant by the tare weight that is used in a weight and balance computation?

the weight of the chocks and other items that are used to hold the aircraft on the scales

what must be done to the tare weight when an aircraft is weighed?

it must be subtracted from the scale reading to find the weight of the aircraft

what is meant by minimum fuel is used in the computation of aircraft weight and balance?

no more fuel than the quantity necessary for one-half hour of operation at rated maximum continuous power. it is the maximum amount of fuel used in weight and balance computations when low fuel may adversely affect the most critical balance conditions

what is meant by the maximum zero fuel weight of an aircraft?

the maximum permissible weight of a loaded aircraft (passengers, crew, cargo) less its fuel

what is meant by undrainable fuel?

The fuel that is left in the tank, lines and components when the aircraft is placed in level flight position and the fuel drained at the main fuel strainer. This is also called residual fuel.

describe what way you would find the empty weight and empty weight center of gravity of an airplane if there are no weight and balance records available?

the aircraft is weighed, and the empty weight center of gravity is computed. these values are recorded new weight and balance records that are started for the aircraft .

what is meant by permanent ballast for an aircraft?

weight that is permanently installed in an aircraft to bring the empty weight center of gravity into allowable limits

which has the more critical center of gravity range, an airplane or helicopter?

a helicopter

what equipment must be installed in an aircraft when it is weighed to find its empty weight center of gravity?

all of the equipment that is listed in the aircraft equipment list as "required equipment" or as equipment that is permanently installed

what is the significance of the empty weight center of gravity range in an aircraft?

if the empty weight center of gravity falls within the EWCG range, the aircraft cannot legally loaded in such a way that is loaded center of gravity will fall outside of the allowable loaded CG range. not all aircraft have an EWCG range

Why is the empty weight center of gravity range not given in the Type Certificate Data Sheets for some aircraft?

the empty weight center of gravity range is given only for aircraft that cannot be legally loaded in such a way that their loaded center of gravity will fall outside allowable limits

of what materials are most low-pressure rigid fluid lines made?

1 100-1/2 hard or 3003-1/2 hard aluminum alloy tubing

Is the size of a rigid fluid line determined by its inside or its outside diameter?

by its outside diameter

When routing a fluid line parallel to an electrical wire bundle, which should be on top?

the electrical wire bundle should be on top

what is the function of the lay line (the identification stripe) that runs the length of a flexible hose?

this line shows the mechanic whether or not the line has been twisted when it was installed. the line should be straight not spiraled

How can you distinguish an AN fluid line fitting from an AC fitting?

the AN fitting has a shoulder between the end if the flair cone and the first thread. the threads of an AC fitting extend all the way to the flair cone

Where are quick-disconnect fluid line couplings normally used in an aircraft hydraulic system?

quick disconnect couplings are normally used where the engine-driven pump connects into the hydraulic system

Is the size of a flexible hose determined by its inside or its outside diameter?

by its inside diameter

what is the minimum amount of slack that must be left when a flexible hose is installed in an aircraft hydraulic system?

the hose should be at least 5% longer than the distance between the fittings. this extra length provides the needed slack

How tight should an MS flareless fitting be tightened?

tighten the fitting by hand until it is snug, and then turn it with a wrench for 1/6-turn to 1/3-turn. never turn more than 1/3-turn with a wrench

What damage can be caused by overtightening an MS flareless fitting?

overtightening drives the cutting edge of the sleeve deeply into the tube and weakens it

what kind of ridged tubing can be faired with a double flair?

5052-O and 6061-T aluminum alloy tubing in sizes from 1/8-inch to 3/8-inch OD

what is the principle advantage of Teflon hose for use in an aircraft hydraulic system?

Teflon hose retains its high strength under conditions of high temperature

what precautions should be taken when flaring a piece of aluminum alloy tubing?

the end of the tubing must be polished so it will not crack when its stretched with the flaring tube

How much pressure is used to proof-test a flexible hose assembly?

this varies with the hose, but it is generally about two times the recommended operating pressure for the hose

*** what is the proper type of nondestructive inspection to use for locating surface cracks in an aluminum alloy casting or forging?

zyglo or dye penetrant

*** Explain the procedure to use when making a dye penetrant inspection of a part.

clean the part thoroughly and apply the penetrant and allow it to soak for the recommended time. remove all the penetrant from the surface and apply the developer

*** explain the procedure to use when making a magnetic particle inspection of a part?

thoroughly clean the part, magnetize it as directed by the appropriate service manual, flow the indicating medium over the surface and inspect it under a blacklight. when the inspection is complete, thoroughly demagnetize the part

*** what inspection method would be most appropriate for checking a nonferrous metal part for intergranular corrosion?

Eddy current inspection

*** what inspection method would be most appropriate for checking the internal structure of an airplane wing for corrosion?

X-ray inspection

*** why is it important that all engine parts which have been inspected by the magnetic particle method be completely demagnetized?

if the parts are not completely demagnetized, they will attract steel particles that are produced by engine wear and will cause damage to bearing surfaces

*** why is it important that all parts be thoroughly cleaned before they are inspected by the dye penetrant method?

any grease or dirt in a fault will keep the penetrant from seeping into the fault

why is it important that a piece of aluminum alloy be quenched immediately after it is removed from the heat treating oven?

any delay in quenching aluminum alloy after it is removed from the oven will allow the grain structure to grow enough that intergranular corrosion is likely to form in the metal.

*** explain the way a steel structure is normalized after it has been welded?

heat the steel structure to a temperature above its critical temperature and allow it to cool in still air

*** why is a piece of steel tempered after it has been hardened?

when steel is hardened, it becomes brittle and tempering removes some of the brittleness

what is meant by an icebox rivet?

A rivet made of 2017 or 2024 aluminum alloy. These rivets are heat-treated and quenched, then stored in a sub-freezing ice box until they are ready to be used. The cold storage delays the hardening of the rivet.

What type of loading should be avoided when using a self-locking nut on an aircraft bolt?

a self-locking nut should not be used for any application where there are any rotational forces applied to the nut or to the bolt

what determines the correct grip length of a bolt used in an aircraft structure?

the grip length of the bolt should be the same as the combined thickness of the materials being held by the bolt

How tight should the nut be installed on a clevis bolt that is used to attach a cable fitting to a control surface horn?

the nut on a clevis bolt should not be tight enough to prevent the clevis bolt turning in the cable fitting and the horn

*** why is it very important that the surface of a piece of clad aluminum alloy not be scratched?

the pure aluminum used for the cladding is noncorrosive, but the aluminum alloy below the cladding is susceptible to corrosion. if the cladding is scratched through, corrosion could form

what determines the size of the tip that is to be used when gas welding steel?

the thickness of the material being welded. the size of the tip orifice determines the amount of flame produced, and thus the amount of heat that is put into the metal

How is the welding flux removed from a piece of aluminum that has been gas-welded?

it should be removed by scrubbing it with hot water and a bristle brush

what must be done to a welded joint if it must be rewelded?

all traces of the old weld must be removed so the new weld will penetrate the base metal