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Flight Class 22-13 > Engines- Electrical Systems > Flashcards

Engines- Electrical Systems Flashcards

1
Q

Describe AC/DC electrical systems

what are their relative advantages

A
  1. AC: alternates equally in a negative and positive direction
    1. requires less current loads = light wiring (less weight on aircraft)
  2. DC: Straight line voltage
    1. heavier components
    2. increased maintenance
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2
Q

Sources of AC Electrical Power

A

Sources

  1. AC:
    1. AC Generator (alternator)
      1. transforms mechangical energy into electrical energy
      2. main source of electrical energy
    2. Inverter
      1. transforms DC current into AC
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3
Q

Sources of DC electrical Power

A
  1. DC Generator
    1. Transforms mechangical energy into electrical energy
  2. Transformer Rectifier
    1. transforms AC Voltage into DC
    2. carries high current loads
    3. Stable DC output
    4. Reliable
  3. Battery
    1. Emergency power should generator fail
    2. Engine Starting
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4
Q

What are the electrical distribution networks

A

A Bus is the distribution network

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5
Q

What are the 3 different types of controls needed for electrical equipment? Where are they located?

A

Three types of controls:

  1. Switches- cockpit
    1. manual control allows the crew to control the particular system
  2. Circuit breakers:
    1. located throughout the aircraft including the cockpit
    2. manual or automatic
  3. Fuses:
    1. automatic circuit protection
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6
Q

What is the Master Caution Panel?

What does the CHIP warning light indicate

A

The master caution panel provides the pilot with a centralized warning center for systems pertinent to flight safety.

the CHIP warning light signals that there is excess metel on the engine

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7
Q

Volitility

A

ability of a fluid to evaporate

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8
Q

Flashpoint

A

The lowest temperature at which a sufficient amount of vapor is given off by a liquid to form an ignitable mixture with it

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9
Q

What is the relationship between temperature, volatility, and flashpoint?

A

A highly volatile fule will vaporize at a lower temperature than a fuel with low volatility

High volatility fuel has a low flash point, low volatility fuel has a high flash point

inverse relationship

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10
Q

What are the three types of thrust ratings?

A

Thrust ratings

  1. Normal:
    1. thrust produced at the maximum continuous ITT
    2. NO TIME LIMITATIONS
  2. Military
    1. MAX ITT
    2. 30 minute time limit
  3. Combat:
    1. thrust produced with the afterburner- not based on turbine temperature
    2. NO TIME LIMITATIONS
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11
Q

Fuel System: Afterburner fuel control unit

A

Afterburner fuel control unit

meters fuel to the afterburner fuel nozzles (Spraybars)

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12
Q

Explain the operation of an afterburner fuel control unit

A

During afterburner operations, the fuel transfer valve opens and allows fuel to flow to the afterburner fuel control unit. This unit meters fuel to the afterburner spray bars

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13
Q

JP-4 Fuel

volatility?

Flash point?

other notable characteristics

A

JP-4

Highly volatile

Flash point: -35F

other notable characteristics: Easier starting, slower acceleration, lower operating temps, shorter range

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14
Q

JP-5 Fuel

volatility?

Flash point?

other notable characteristics

A

JP-4 Fuel

volatility: thermally stable

Flash point :140F

other notable characteristics: Navy’s primary jet fuel, high heat content per gallon

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15
Q

JP-8 Fuel

volatility?

Flash point?

other notable characteristics

A

JP-8 Fuel

volatility: safe to store and thermally safe

Flash point: 100F

other notable characteristics: very expensive. Used by NATO and the air force

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16
Q

Civilian Aircraft Fuel

Flash point

two types

A

Avgas

  1. Flashpoint: -45F
  2. defined by their octane rating
    1. Avgas 100
      1. high lead
      2. dyed green
    2. Avgas 100LL
      1. lower lead
      2. dyed blue
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17
Q

Fuel System: Fuel Tank

A

Fuel Tank

Starting point for fuel

reservoir or holding cell for fuel

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18
Q

Fuel System: boost pump

A

Boost Pump

submerged in the fuel tank

prevents aeration of the fuel supply which may result from a rapid pressure change incurred during a climb

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19
Q

Fuel System: Pressure Monitor

A

Pressure Monitor

located at boos pump outlet with corresponding gauge in cockpit

20
Q

Fuel System: Low pressure fuel filter

A

downstream of the boost pump to strain impurities of the fuel

includes a bypass

21
Q

Fuel System: engine-driven fuel pump

A

Delivers fuel to the Fuel Control Unit (FCU)

HIGH PRESSURE PUMP provides fuel in excess for the engine and afterburner demands

like all pumps, it also has a filter

22
Q

Fuel System: Fuel Control Unit

A

“brain”

provides the fuel manifold with metered fuel to meet engine requirements

  1. Monitors:
    1. Starting
    2. Acceleration
    3. Deceleration
    4. Stabilizied (steady state) operation
  2. Senses the:
    1. Compressor Inlet Temperature
    2. RPM
    3. Turbine Temperature (ITT)
    4. PCL inputs from the aviator
23
Q

Fuel System: Fuel Flow Gauge

A

Functions:

  1. measures the rate of consumption (pounds per hour)
  2. indicates fuel useage to the crew
24
Q

Fuel System: fuel-oil cooler

A

fuel-oil cooler

  1. heat exchanger:
    1. cools oil, warms fuel
25
Q

Fuel System: Pressurizing and Dump Valve

A

Pressurizing and Dump Valve

  1. drains the combustion manifold upon engine shutdown
    1. helps prevent abnormal starts (hot/wet)
  2. Adjusts fuel flow during engine starts

*At engine start, the FCU sends a pressure signal to close the dump valve and the pressure valve. Fuel is directed into the primary fuel manifold (smaller in size allowing for faster pressurization)

26
Q

Fuel System: Manifold assembly

A

Manifold Assembly

  1. Primary
    1. smaller
    2. high degree of pressure leading to higher atomization during starting and altitude idling conditions
  2. Secondary
    1. supplies fuel when engine RPM raises fuell pressure to a set level
27
Q

Fuel System: Fuel Nozzles

A

Fuel Nozzles:

inject fuel into the combustion area in a highly atomized, precise spray pattern

28
Q

Functions of lubricants

A

to reduce the friction caused by metal to metal contact

29
Q

What are the characteristics of synthetic lubricants

A

Synthetic lubricants:

lower volatility

less coking deposits

improved chemical stability at high temps

but: corrosive and have a limited shelf life

30
Q

Define: Viscosity

A

Viscosity is the property of a fluid that resists the force tending to cause the fluid to flow (resistance to flow)

Inversely related to temp (higher temps = less viscose)

31
Q

Lubrication Systems:

function

A

function of a lubrication system is to reduce the friction caused by metal to metal contact

essential to avoid mechanical deterioration

32
Q

What is the most common contaminat of lubricating systems?

A

metal particals are the most common contamination of lubricating systems

33
Q

Lubrication Systems: Wet Sump System

A

the kind of system you have in your car. Oil collects in a pan under the engine

34
Q

Lubrication Systems: Dry Sump System

subsystems

A

3 subsystems:

  1. pressure
    1. pressurized oil is provided to the engine and accessory gear box
  2. scavenge
    1. removes oil from the main bearing components and accessory drives. Circulates oil through the coolers, and sends it back to the tank
  3. Breather Pressurizing
    1. uses pressure bleed air to pressurize the oil tank and engine bearing compartments
    2. minimizes oil leakage and ensures proper spray patterns
35
Q

Lubrication Systems: Weighted Swivel Outlet Assembly

A

Weighted Swivel Outlet Assembly

ensures the pick up end is constantly submerged in oil (pump won’t suck in air)

36
Q

Lubrication Systems: chip detector

A

magnetized metal plug in the scaenge oil path

if it collects enough metal particals it illuminates a warning light in the cockpit

37
Q

Lubrication Systems: Oil Cooler

2 types

A

Oil Cooler

  1. Air-oil Cooler
    1. radiator type device
    2. outside air that passes through its fins to cool oil
  2. Fuel-Oil Heat Exchanger
    1. cools oil from bearings and preheats fuel for combustion
    2. allows for a bypass if no cooling is necessary
      1. bypass regulated by the oil temperature regulating valve and the fuel temperature sensing switch (if fuel is getting too hot in the exchanger it actuates the air-oil cooler to cool oil before it gets to the Fuel-oil exchanger)
38
Q

Lubrication Systems: Breather Pressurizing subsystem

function

components

A

Breather Pressurizing Subsystem:

  1. Function: minimize oil leakage and ensure proper spray patterns
    1. uses compressor bleed air to pressurize the tank and encases the oil sumps with pressurized air
  2. Components:
    1. aneroid operated valve
      1. closes with increase in altitude
      2. goal is to maintain 29.92 inches of pressure
    2. blow off valve
      1. pressure relief
39
Q

Accessory Systems: types

A

examples of accessory systems:

environmental systems

cabin pressurization

Engine Anti-ice

tachometer

hydraulic pumps

alternator/Generator

40
Q

How are accessories driven?

A

2 ways:

  1. Bleed Air
    1. axial-flow compressor engines
      1. Environmental systems
      2. Cabin Pressure
      3. Anti-icing
  2. Mechanically- driven
    1. Attached to the Accessory Gear Box
    2. Tachometer, hydraulic pumps, alternator/generator
41
Q

What is the starting sequence for a gas turbine?

A

Starting sequence

  1. starter engages until engine attains self-accelerating speed
  2. Fuel Flow occurs after engine RPM >30%
  3. Ignition occurs when sufficient airflow supports combustion of the fuel/air mixture

*The purpose of any Starter System is to accelerate the engine until the turbine is producing enough power for self-accelerating speed

42
Q

4 types of abnormal starts

A
  1. Hot
    1. turbine tempeature exceeding the max temp allowed
  2. Hung
    1. low compressor RPM with high turbine temps
  3. False
    1. low compressor RPM with normal turbine temp
  4. Wet
    1. no initial ignition of fuel/air mix
    2. MOST DANGEROUS
43
Q

DC Electric Motor Starter

what type of engine is it used in?

description

A

DC Electric Motor Starter

Use: Smaller engines

mechanically connected to the compressor

a battery or aux power unit is used to supply voltage to the starter motor

44
Q

Bleed Air accessories

examples

type of engine?

A

Bleed Air systems are found on axial-flow compressor engines

can be low pressure or high pressure

examples: cockpit/cabin pressurizing and heating units, engine de-icing (high pressure),

45
Q

Air Turbine Starter (ATS)

use:

description:

A

ATS

Use: larger gas turbine engines

small geared air turbine attached to the engine delivers air to the turbine to accelerate the compressor

46
Q

what type of starter is used by today’s military aircraft?

A

Today’s military aircraft use a high heat-intensity capacitor ignition system

47
Q

What are the two types of spark igniters?

A

Spark Igniters:

Annular- gap: protrudes into the chamber to provide an effective spark. MOST COMMON

Constrained-gap: Extends the spark beyone the face of the chamber liner. Operates at cooler temperatures than annular-gap

Flight Class 22-13 (11 decks)

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