Systems 1/Weaver/Lesson 2 Exam/Kent

Ohm’s Law is what?

-Defines the basic mathematical relationship of electricity

-(flow) through (wire) proportional to voltage (pressure) / V = I x R

What is current and what are some conductors?

-the electrical movement of electrons (flow or current flow, or just current) / movement of free electrons

-measured in amps (A)

-copper, silver, aluminum, and gold

Free electrons are what?

A condition in some atoms where the outer layer electrons are loosely bound to their parent atom and are easily motivated to move

One ampere (A) = ?

One coulomb (C) = ?

-(A) = 1 coulomb of charge passing through a conductor in 1 second

-(C) = 6.24 × 10^18 electrons

Direct current (DC) is what ?

-when current flows in one direction

-occurs when force is present to push electrons

-when voltage is applied across the conductor, an electromotive force creates an electric field within the conductor, and a current is established

-instantaneous

Conventional and electron theory are both what?

-both explain movement of electrons through a conductor but differ on which direction

-both are still utilized in industry

Conventional current theory is what?

-advanced by Ben Franklin

-flow from + to -

-common sense reasoning, but later discovered it is inaccurate

Electron theory is what?

-the later discovery

-proved flow of electrons occur from - to +

What is electromotive force (Voltage) ?

-electrical pressure force

-push or pressure from one end of a conductor to the other

-measures in (EMF) (V)/ also measures between two points, making that a value

-V1 - V2 = Vdrop

How do you know how much current will flow in an electrical circuit, when voltage gets applied to it?

-resistance - amount of current that flows under given voltage

-increased resistance = decreased current

-decreased resistance = increased current

Conductors are considered what ?

-materials that have a large number of free electrons

-silver, coppper, gold, aluminum / mostly metals/ carbon and water

Insulators are considered what?

-materials having few free electrons

-rubber, glass, ceramics, plastics

What are factors that affect resistance?

-conductor contains a maximum number of free electrons

-length (longer the more greater)

What things can be a generation of power for electrical energy?

-light - solar cell (photovoltaic cell)

-pressure - piezoelectric effect (mechanical pressure on a dielectric or non-conducting crystal)

-heat - thermo-electrical effect

-Chemical - remember batteries

-electromagnetic induction - moves magnetic felid in relationship to conductor to create voltage / most responsible power used by people

Electromagnetic generation of power consists of what?

-voltage can be produced by moving a magnetic field in relationship to a conductor (wire)

-current flow is then induced if it is a complete circuit and thus electrical power is produced

-one conductor moving between a magnet does not produce significant voltage/amp

Induced voltage/current relies on what three things?

-number of turns in conductor coil (more loops = greater induced voltage)

-strength of electromagnet (stronger the magnetic field, the greater induced voltage)

-speed of rotation (faster, the greater induced voltage)

Alternating current (AC) is what?

-found most on high performance turbine powered aircraft

-transported over greater distances with use of transformers

-saves space and weight compared to DC systems

-combination systems can use inverters to change AC to DC

Alternating current (AC) values consist of what?

-instantaneous - voltage at any instant in time along AC wave/ 0-360 degrees

-peak - largest instantaneous value (maximum)

-effective - always less than peak (maximum)/ also known as root mean square (RMS)

A cycle is considered what?

-completion of a pattern

-whenever a voltage or current passes through a series of changes, returns to starting point, and then repeats

Frequency is considered what?

-number of cycles of AC per second (CPS)

-measurement is Hz

A period (P) is conspired what ?

-time required for sine wave to complete one full cycle

-measured in seconds, milliseconds, or microseconds

What are types of aircraft batteries? And what is expected for batteries as well?

-dry charged lead acid battery

-valve-regulated lead acid batteries (VRLA)

-nickel cadmium batteries (NiCd)

-Maintenance & charging, inspection & installation, and troubleshooting

Aircraft batteries are used for ?

-ground power

-emergency power

-DC bus stability

-fault clearing

Batteries are categorized by what characteristics?

-weight

-cost

Volume

-service or shelf life

-discharge rate

-maintenance requirements

-charging rate

Dry charged cell lead batteries are what?

-flooded or wet batteries

-electrodes (plates) have been charged and dried

-electrolytes are added to begin service life

-typically 6-12 lead acid cells

Valve-regulated lead acid batteries (VRLA) are what?

-sometimes referred as sealed batteries

-used in general aviation and turbine powered aircraft

-no water loss during charging

NiCd batteries are what?

-nickel cadmium

-metallic box (usually stainless or plastic covered steel) containing multiple cells to obtain 12 or 24 volts in series

-usually monitored closely for faults to avoid thermal runaway

Battery capacity is what?

-measured quantitatively in amp-hours delivered at specified discharge rate to a specified cut-off voltage (1.0 amps) at room temp

Amp/hour rating (Ah) (or one-hour rate) is what in a battery?

-the rate of discharge (how many amps) a battery can endure for 1 hour with the battery voltage at or above 1.67 volts per cell, or 20 volts for a 24-volt lead-acid battery

Emergency rate of a battery is what?

-the total essential load, measure in amps, required to support essential bus for 30 min. This is the rate of discharge a battery cab endure for 30 min with voltage battery at or above 1.67 volts per cell

Lead acid batteries need to be fully charged when operating at what temperatures?

-below freezing

Specific gravity in batteries is what?

Ratio of weight of a solution to the weight of an equal volume of water at a specified temp

Battery maintenance and charging consists of what?

-batteries need to be charged according to manufacturers instructions/ if not it can cause damage

-inspection and maintence vary chemicals in battery

-install date is how you determine battery life

-when the specific difference from a hydrometer measures 0.050 or more, it is getting close to the end of its life

-adding distilled water can adjust electrolyte level

A hydrometer is used for what in a battery?

-used to determine specific gravity of lead-acid battery electrolyte

Battery inspections consist of what?

-level and overall condition

-battery sump jar (if installed)

-battery terminals/ unplug plugs and pins to see if there is any corrosion, pitting, arcing, and burns

-drain and vent lines for restriction, deterioration, and security

-routine preflight and post flight / should look for physical damage like loose connections and electrolyte loss

Aircraft battery installation consists of what?

-fully charge battery, check installation level, specific gravity

-installation date on new battery

-prevent inadvertent shorting of the battery terminals

-connect ground lead of battery to minimize risk of shortening hot terminal of battery during instal

Aircraft battery removal consists of what?

-remove ground lead , remove positive head first

-ensure battery is held down securely with clamps/bolts, but not to tight because it could cause battery to buckle causing internal shortening

Generators are classified in what categories?

-DC generators and controls

-generator controls

-DC alternators and controls

-power systems

-AC alternators

DC generators and controls are classified how, and do what?

-transform mechanical energy into electrical energy

-DC generators produce DC power

-typically older, light aircraft

-mostly replaced by DC alternators

-require control circuit

Electromagnetic induction creates a voltage in the ___ throughout the 360 degree rotation.

-armature - the rotating portion of a DC generator (coil and commutator)

__ and brushes allow for transfer of electrical energy from rotating loop to the stationary aircraft circuits in aircraft generators.

-Slip rings

(AC) to (DC) electricity in a generator ?

-replace slip rings with segmented commutator

The variation of DC voltage is called a __ and can be reduced by using more loops or coils.

-ripple

-voltage generated by basic DC generator with only a two piece slip rings varies from zero to maximum value twice for each revolution of the loop

-each additional loop in rotor, another two commutator segments are required

Field frame in a generator is what?

-holds the windings needed to produce magnetic field and is support for the other components of the generator

-contains the electromagnetic conductor called the field coil that is wrapped around pieces of laminated metal called field poles

-a DC current is fed to field coils to produce an electromagnetic field

Rotating armature is what in a generator ?

-contains the wire coils (windings) wound around an iron core and commutator assembly

Commutator assembly is what?

Located at the end of an armature and consists of copper segments by a thin insulator

___ rotates inside the magnetic field produced by the field coils and produces electrical current which is sent through the commutator and brushes to the aircraft electrical system.

-Armature assembly

Brush assembly is what in a generator ?

-rides on the commutator and made of high grade carbon

-carbon must be soft enough to prevent undue wear of commutator and hard enough to provide reasonable brush life

-contact resistance is fairly high, so the brush must be large to provide a current path for armature windings

Basic generator maintenance and inspection consists of what?

-security of generator mounting

-condition of electrical connections

-dirt and oil in generator - if oil is present, check engine oil seals / blow dirt out with compressed air

-brush conditions

-voltage regulator operation

Generator controls and the two basic types of controls?

-designed to operate within a specialized voltage range (27.5-28.5 volts etc.)

Electro mechanical and solid state (transistorized)

What are the functions of the generator control unit (GCU)?

-voltage regulation - monitors and regulates output to generator and aircraft

-over voltage protection - on more complex systems, prohibits gen. damage

Parallel generator operations - used on multiple generator to compensate for bad generator

-differential voltage - designed to ensure all generators are within close tolerance

-reverse current sensing - does not allow drawing current form system if malfunctioning

Starter generators are what ?

-combines two units into one housing, saving space and weight

-has a more complex control system and two sets of field windings: one to control starting and one for generating

Alternators and controls?

-two major components
-lighter and more efficient than DC generators

-normally mounted in engine compartment driven by belt or gear

-will have a control system that automatically regulates alternator output and holds correct system voltage

-changes from AC to DC with rectifiers

Field winding is what?

Produces a magnetic field, rotates inside armature

-receives a current from aircraft battery to excite the field (electromagnet)

-will have brushes and two slip rings mounted on rotor to send power to rotating field /brushes can be smaller than what is found on generators because they carry low current

Armature is what ?

-produces the voltage by electromagnetic induction

-contains three coils of wire (phases)

-each coil receives current as the (magnetic) field rotates

-known as three-phase armature/alternator

Alternator control unit (ACU) consists of what?

-voltage regulators

-adjusting field current that controls the output of the alternator

-vibrating relay type

Solid-state (most common) (ACU’s)

AC power systems in a generator consist of what?

-AC alternator - normally only on aircraft that use large amount of electrical power

-regulating system

-AC power distribution buses

-related fuses and wiring

Small single engine aircraft electrical systems consists of what ?

-usually one electrical system powered by alternator or generator

-battery used for start-up and emergency power

-distributed through one or more common points, electrical bus or bus bar

Small single engine aircraft electrical systems faults include?

-Open: when a circuit becomes disconnected

-Short : when a positive wire creates an unwanted connection (especially ground) ; often causes more damage than open faults

Small single cell engine aircraft electrical systems, circuit protection mechanically and electrically function how?

-mechanically - wires and components are protected from abrasion through proper install and protective covers and shields

-electrically - wires can be protected using circuit breakers and fuses/ fuses are typically older aircraft

Small single cell aircraft engines, battery circuits function how?

-provide power for engine start in case of alternator/generator failure

-battery master switch is on flight deck, used to control master solenoid

-solenoid/relay/contactor -

Small single cell engine aircraft, in the battery circuit, what is ammeter?

-it monitors current flow to or from the battery

-rubber boots protect wire connections

Small single cell engine aircraft electrical systems, the generator circuit does what?

-used to control electrical power between the aircraft generator and the distribution bus

-typically found on older aircraft that have not upgraded to an alternator

-controlled by GCU or voltage regulator

Small single cell engine aircraft, electrical systems, the alternator circuit is what?

-similar to generator circuit, controls both power to and from alternator

-alternator master switch sends current to the field

-if the field is excited as soon as the engine begins running the alternator will produce electrical power

-ammeter and voltmeter are useful for monitoring alternator output

Small single cell engine aircraft, electrical systems, external power circuit is what?

-used to provide aircraft with electrical power from a ground source

-primarily used for starting or maintenance activities without discharging the battery

Small single cell engine aircraft, electrical systems, starter circuit is what ?

-an electric motor to start aircraft engine

-draws 100 or more amps, so controlled through a solenoid

-must be connected as close as practical to battery since wire powers the starter motor (weight savings)

Small single cell engine aircraft, electrical systems, avionics power circuit is what ?

-a separation power distribution bus for electronics equipment /called Avionics Bus

-allows to disconnect sensitive electronic circuits entirely during start and shut off

-reset them in flight if necessary without disrupting electric functions

Small aircraft landing gear circuit is what?

-operates the retractable landing gear system on high-performance light aircraft

-gear up/ down lever (switch), a series limit switches are needed to monitor the position of each gear during the operation system

-a (reversable) electric motor then powers a hydraulic pump

Light multi-engine aircraft electrical systems is what?

-designed for safety and redundancy

-multiple systems, backups, and auxiliaries

-paralleling alternators / generators: regulators and control circuits designed to help with limiting and matching power

Large Multi-engine aircraft electrical systems consist of what?

-typically have two or more AC generators driven by the aircraft turbine engines / to share electrical load and provide redundancy

-more than one backup generator

-DC power is common with battery supplying emergency power in case of failures

-AC power has a variety of flight controls / lighting, audio visual systems, galley power, flight controls systems, electronic engine controls, communication and navigation systems

Wiring diagrams in electrical systems consists of what?

-Block diagrams - used for troubleshooting complex electrical and electronic systems

-Pictorial diagrams - pictures of components instead of electrical symbols /helps with maintenance

-schematic diagrams - illustrate principle of operation / doesn’t show parts, show location of components with respect to each other, best utilized for troubleshooting

What are the two types of wires?

-solid conductor

-stranded conductor

What is a cable ?

-two or more separately insulated conductors in same jacket

-two or more separately insulated conductors twisted together

-one or more insulated conductors with a metallic braided sleeve

-a single insulated center conductor with a metallic birdied outer conductor

A wire harness is what?

-an array of insulated conductors bound together by a lacing cord, metal bands or other binding equipment

When it comes to wires, what are the conductors?

-copper - higher conductivity, more ductile, higher tensile strength, easily soldered / downsides is that it is more expensive and heavier

Aluminum - more lighter / downsides is that it is 60% conductivity of copper

Plating / coating a wire to prevent oxidation consists of what?

-Tin, silver, nickel

-each has own beneficial properties

Insulation resistance and dielectric strength in a wire is what ?

Insulation resistance - resistance to the current leakage through and over the insulating material

-dielectric strength - ability of an insulator to withstand potential difference

Wire shielding is what ?

-applying a metallic covering to wiring

-used to eliminate electromagnetic interference (EMI)

Wire sizes (AWG - American Wire Guage) ?

-wire diameters become smaller as gauge numbers become larger

-typical wire sizes range from 40 to 0000

-factors into wire selection include mechanical strength, load/current carrying capability, and current loss/heat generated

All wire must be properly identified by :

-imprinted along its length

-15” maximum interval

-3” or less - no identification required

-3” to 7” - identified approximately at center

Wire identification methods are :

-direct marketing - printing on the cable’s outer covering

-indirect marketing - printing on a heat shrinkable sleeve

Dealing with wire installation and routing, what is open wiring ?

-point to point open harnesses

-installed in aircraft without special enclosing means

-offers ease of maintenance and reduced weight

Dealing with wire installation and routing, wire groups , bundles , amend routing are what ?

-organized in bundles to create organized installation

-often called wire harness

-slack and bend radii are considerations for wire bindles

Slack in wire groups , bundles , and routing needs to be ?

-no more than 1/2inch between support points

Bend radii in wire groups , bundles , and routing need to be and are what ?

-not less than 10 times the outside diameter of the largest wire

-protection : chaffing, high temp, solvents and fluids

-can be performed on a jig to fit perfectly in aircraft

Wire installation and routing, clamp installation needs to be ?

-intervals not exceeding 24 inches

-snug fit without pinching wires

Wiring installation, bonding is what ?

-the electrical connecting of two or more conducting objects not otherwise adequately connected

Wiring installation, what is grounding ?

-the process of electrically connecting conductive objects to either a conductive structure or some other conductive return path for the purpose of safely completing either … not done

Wiring inspection should be inspected (at least annually) for :

-abrasions

-defective insulation

-condition of terminations

-potential corrosion

-grounding connections for power

-shielding and electrical bonding resistance

-loosening of connections

In electrical system components, switches are what :

-devices that open and close circuits

-current in circuit flows when contacts are closed

-momentary contacts actuate circuit temporarily, then return to normal with internal spring when switch is released

-switches with continuous contacts reman in position when activated

In electrical systems, what are the types of switches ?

-toggle and rocker switches - control most of aircrafts electrical components

-rotary switches - activated by twisting knob or shaft radio control panels / rotary switches are utilized for controlling more than two circuits

-precision (micro) switches - require little pressure to activate / spring loaded once pressure is removed / contacts return to normal position

In electrical system components, circuit limiting devices are :

-circuit breakers or fuses , to protect possible electrical power source bus

Aircraft lighting systems in electrical systems are :

Exterior lighting - position lights, anticollision, landing, taxi lights

Interior lighting - cockpit and cabin