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AT 103 > Lectures 2-11 > Flashcards

Lectures 2-11 Flashcards

1
Q

Failure of early aircraft was primarily due to

A

Lack of power source that could sustain flight

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2
Q

What were some causes of failed engines?

A

Poor efficiency
Lack of dependability
High cost
Excessive weight
Low power produced

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3
Q

What did we want to design engines with?

A

High power-to-weight ratio
Efficient
Reliable
Environmentally friendly

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4
Q

Who built the first flight simulator?

A

Edwin Link

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5
Q

In 1860 the first practical gas engine was built by _____ and were built to operate _____.

A

Jean Lenoir of France
Lathes and printing presses

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6
Q

The first four stroke concept was built in 1876 by _____ and _____.

A

August Otto
Eugen Langen

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7
Q

The first gasoline engine was built in 1885 by _____ and operated with the _____. A similar engine was built by _____ in the same year.

A

Gottlieb Daimler
four stroke principle
Karl Benz of Germany

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8
Q

The first successful aircraft engine was built in 1903 by _____ and was _____ cooled, had _____ cylinders, produced _____ hp, and weighed _____.

A

Charles Taylor
water
4
12
180 lbs

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9
Q

The first flight of jet engine power aircraft was in _____ in _____. It was the _____ engine in the _____ aircraft.

A

1939
Germany
Heinkel HeS 3B Turbojet
Heinkel He 178

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10
Q

The first turbojet engine in England and the US was built by _____ and was manufactured by _____. The engine is known as the _____.

A

Sir Frank Whittle
General Electric Company
Whittle W1 Engine

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11
Q

What are some challenges of gas-turbine engines?

A

Performance
Sound levels
Fuel efficiency
Ease of maintenance
Dependability
Reliability

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12
Q

What are the cons of rotary type radial engines?

A

Torque and gyro effect make aircraft difficult to control
Castor oil was used as the engine lubricant, was nauseating to pilots

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13
Q

What is one advantage and one disadvantage of in-line engines?

A

Small frontal area allows streamlining and low drag nacelles
Harder to cool as they increase in size

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14
Q

What are the pro(s) and con(s) of radial engines?

A

Pro: lowest weight to horsepower ratio of all reciprocating engines
Cons: large frontal area creating drag, cooling problems

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15
Q

Describe an opposed engine

A

Most popular and most efficient for light aircraft
Cylinders and crankshaft horizontal

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16
Q

What are some pros of opposed engines?

A

Low weight-to-horsepower ratio
Easily streamlined
Reasonably free from vibration

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17
Q

Name cylinder (engine) arrangements

A

In-line
V Type
Double V or Fan Type
X Type
Opposed or Flat Type
Radial Single Row
Radial Double Row
Radial Multiple Row

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18
Q

Engine Designations:
L
T
I
G
S
O
R
V
470

A

L = Left-Hand Rotation
T = Turbocharged
I = Fuel Injected
G = Geared
S = Supercharged
O = Opposed Cylinders
R = Radial Engine
V = V-type engine
470 = Displacement to the nearest 5 in^3

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19
Q

Lack of “i” in engine designation means the engine is _____.

A

Carbureted

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20
Q

V and O together in engine designation means the engine is _____.

A

V-type

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21
Q

Why is excessive heat undesirable for reciprocating engines?

A

Negatively affects behavior of combustion of the air fuel charge
Weakens and shortens the life of engine parts
Impairs lubrication

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22
Q

What is air cooling?

A

Excessive heat generated by the engine is removed from the engine by the convection process

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23
Q

What help direct air flow around cylinders?

A

Baffles

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24
Q

What are the pro(s) for air cooling?

A

Weighs less (no radiator, no connecting hoses/lines, no coolant liquid)
Less affected by cold weather
Less vulnerable to gunfire

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25
Q

What are the con(s) for air cooling?

A

Requires forward movement for ram air to sufficiently cool engine

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26
Q

How does liquid cooling work?

A

Cooling liquid is circulated through the engine areas that require heat removal
Heat is transferred to the liquid
Heated liquid then passes through a heat exchanger (radiator) and cools down
The cooled liquid is then cycled back into the engine to repeat the cooling process

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27
Q

What is the most common liquid used for liquid cooling?

A

Ethylene glycol

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28
Q

Name some characteristics of the crankcase

A

The foundation of the engine
Must support itself
Contains bearings in which the crankshaft revolves
Enclosure for lubricating oil
Provides mounting to the aircraft
Provides mounting for cylinders
Needs Strength and rigidity to prevent misalignment

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29
Q

Describe an opposed-engine crankcase

A

Consists of two matching, reinforced aluminum-alloy castings
Castings are divided vertically at the centerline
Fastened together with studs and nuts

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30
Q

What are the sections of a crankcase

A

Consists of multiple sections (3-7)
The Front Section (Nose)
Main Power Section
Fuel Induction and Distribution Section
Accessory Section

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31
Q

What is the purpose of aircraft bearings?

A

Produce minimum friction and maximum wear resistance

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32
Q

What are some characteristics of good bearings?

A

Made of material strong enough to withstand pressure imposed on it
Permit the other surface to move with minimum wear and friction
Be held in position with very tight tolerances
Provide quiet and efficient operation while not sacrificing freedom of motion

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33
Q

What are thrust bearings?

A

In addition to reducing friction of moving parts they also take thrust loads and radial loads

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34
Q

What are plain bearings?

A

Used in low-power engines
Can be used as a thrust bearing when flanges added
Made out of softer metal

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35
Q

What are roller bearings?

A

Used in high-power applications
Tapered rollers can withstand both radial and thrust loads
Straight rollers are used for radial loads

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36
Q

What is the bearing race?

A

Channel where rollers travel
Rollers are situated between the inner and outer race

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37
Q

What are ball bearings?

A

Provides less friction than any other bearing types
Races have grooves in them to fit the curvature of the balls
Balls within the bearings are held in place by a ball retainer to maintain proper spacing between the balls

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38
Q

What does the crankshaft do?

A

Transform reciprocating motion of the piston to rotary
motion to turn the propeller

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39
Q

What is the crankshaft?

A

“Backbone” of an internal combustion engine
Subject to all the forces within the engine
May be one or more pieces

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40
Q

What are the parts of the crankshaft?

A

Prop shaft
Main Journal
Crankpin
Crank Cheek
Counterweights and Dampers

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41
Q

What does the main journal do?

A

Keep the crankshaft in alignment
Centerline in the crankshaft

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42
Q

What do crankpins do?

A

Crankpins are off center from the main journals
When a force is applied to the crankpin in any direction other than parallel, it will rotate the crankshaft

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43
Q

Why are crankpins hollow?

A

Reduces weight
Passage for lubricants

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44
Q

What does the crank cheek do?

A

Connects the crankpin to the main journal
Extends beyond the main journal to support counterweights
Oil passages are drilled through

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45
Q

What is the purpose of counterweights?

A

Provide static balance for the crankshaft

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46
Q

What is the purpose of dynamic dampers?

A

Relieve whip and vibration
Overcome forces generated by the pistons

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47
Q

Connecting rods connect the _____ (large end) to the _____ (small end)

A

Crankshaft/crankpin
Piston/piston pin

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48
Q

At each stroke connecting rods go through

A

Stop
Change of direction
Start

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49
Q

Describe a plain connecting rod

A

Small end has bronze bushing serving as bearing
Large end has end cap with a two piece bearing installed
The cap is secured on the end of the rod by bolts

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50
Q

Describe a fork and blade connecting rod

A

Used for V-type engines
Fork rod is split on the large end
Blade rod fits between the split large end of fork rod

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51
Q

Describe a master rod

A

Subject to a lot of stresses
Design and construction is to the highest quality
Provides attachment points for articulated rods

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52
Q

Describe an articulating rod

A

Attached to the master rod by steel knuckle pins
A lock plate on each side of the knuckle pin prevents its movement laterally

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53
Q

Why are piston rings split?

A

So they can be slipped over the outside of the piston into ring grooves

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54
Q

What is the purpose of gap clearance?

A

Allow for heat expansion during operation

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55
Q

What is blowby?

A

Flow of gases from the combustion chamber into the crankcase

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56
Q

What is blowby caused by?

A

Worn out piston rings or no staggering of the piston rings

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57
Q

How can blowby be detected?

A

Oil vapor, blue smoke, coming out of the exhaust

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58
Q

What is the function of a piston ring?

A

Provide seal against the cylinder wall to hold pressure in the combustion chamber
Prevent excessive oil from entering the combustion chamber
Conduct the heat from the piston to the cylinder walls

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59
Q

What happens when a piston ring is worn or defective?

A

Loss of compression
Excessive oil consumption
Excessively high oil discharge from the crankcase breather
Excessive blue smoke from exhaust during normal operation

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60
Q

What are the two types of piston rings?

A

Compression rings
Oil rings

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61
Q

What is the purpose of compression rings and where are they located?

A

Prevent gases from escaping past the piston during operation
Placed in the ring groove immediately below the piston head
Most engines have 2 or 3 per piston

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62
Q

What is the purpose of oil rings and where are they located?

A

Control the thickness of oil film on the cylinder walls
Prevent oil from passing into the combustion chamber
Placed in the ring groove immediately below the compression rings
Generally one per piston

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63
Q

What are the two types of oil rings?

A

Oil control rings
Oil wiper rings (Oil scraper rings)

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64
Q

What is the purpose of a piston pin?

A

To attach the piston to the connecting rod

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65
Q

What are the three types of piston pins?

A

Stationary
Semi-floating
Full-floating

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66
Q

How are stationary piston pins secured?

A

A set screw, not free to move in any direction

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67
Q

How are semi-floating piston pins secured?

A

A clamp screw

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68
Q

How are full-floating piston pins secured?

A

They aren’t secured, free to run or slide in the connecting rod and piston

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69
Q

What are piston pin retainers used for?

A

Inserted in the open ends of the piston pin
Soft material allows contact with cylinder walls without damage

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70
Q

Cylinder assembly requirements

A

Sufficient strength to withstand internal pressures
Light weight
Heat conducting properties for efficient cooling
Designed for inexpensive manufacturing, inspection, and maintenance

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71
Q

Why is surface roughness in the cylinder barrel controlled so much?

A

Too smooth – It will not hold sufficient oil for break-in period
Too rough – Excessive wear to piston rings and the cylinder wall

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72
Q

What is chokebored?

A

Bore nearest the head is made smaller to allow for heat expansion
At operating temperature, the bore will be straight

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73
Q

What does the cylinder head do?

A

Enclose the combustion chamber
Support rocker shafts

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74
Q

What does the cylinder head contain?

A

Intake valves
Exhaust valves
Valve guides
Valve seats

75
Q

What is the shrink-fit method for joining the cylinder head to the barrel?

A

Barrel is dunked in liquid nitrogen
Cylinder head is heated up
Pieces are put together
Welded through heat differential

76
Q

What is a valve?

A

Any device for regulating or determining the direction of flow of a liquid or gas by opening and closing a passage
Main purpose of valves is to open and close ports

77
Q

Why are exhaust valves hollow?

A

To dissipate heat by filling them with metallic sodium

78
Q

What is the purpose of a valve guide?

A

To support and guide the stems of the valves

79
Q

What is the purpose of valve seats?

A

Create a metal on metal seal with the valve face, they are ground to the same angle as the face of the valve

80
Q

What is the purpose of the valve spring?

A

Installed over the stem of each valve to close the valves

81
Q

What are valve spring retainers?

A

“Seats” for the valve springs

82
Q

What is the purpose of the valve operating mechanism?

A

To control the timing of the engine valves so that they open, stay open, and close at the correct time for the correct amount of time

83
Q

What are the components of the valve mechanism

A

Cam
Valve lifter
Pushrod
Rocker arm

84
Q

What does the cam do?

A

Actuates the valve lifting mechanism

85
Q

What does the valve lifter do?

A

Transmits the force of the cam to the pushrod

86
Q

What is the pushrod?

A

Rod between the valve lifter and the rocker arm that transmits the motion of the valve lifter

87
Q

What does the rocker arm do?

A

One end presses on the stem of valve while the other end receives motion from pushrod

88
Q

Heat engines utilize _____ to produce the power for _____.

A

heat energy
propulsion

89
Q

What is energy?

A

The capacity for doing work

90
Q

Energy cannot be _____ or _____

A

created
destroyed

91
Q

Energy can be _____ from _____ to _____

A

transformed
one kind
another

92
Q

What is kinetic energy?

A

Energy of motion

93
Q

What is potential energy?

A

Energy of position or stored energy

94
Q

What is Boyle’s Law?

A

Increasing the pressure on a volume of confined gas reduces its volume correspondingly (3 times more pressure decreases volume to 1/3)

95
Q

What is Charles’ Law?

A

As the temperature of a gas increases, the volume remains the same

96
Q

What is a cycle?

A

A complete sequence of events that return to the original state (the seasons)

97
Q

What are the four strokes?

A

Suck, squeeze, bang, blow
Intake, compression, power, exhaust

98
Q

What are the five events?

A

Intake, compression, ignition, combustion, exhaust

99
Q

What is a stroke?

A

The distance the piston travels, TDC to BDC

100
Q

What is TDC?

A

Top dead center
The top limit of the stroke

101
Q

What is BDC?

A

Bottom dead center
The bottom limit of the stroke

102
Q

Why is BDC and TDC important?

A

For setting timing and valve overlap of the engine

103
Q

What is compression ratio?

A

The ratio of the volume of the space in the cylinder when the piston is at BDC to the volume when the piston is at TDC

104
Q

When does ignition happen?

A

A few degrees before TDC

105
Q

What keeps the engine running?

A

One cylinder is always in the power stroke, moving the crankshaft

106
Q

What is valve overlap?

A

Intake valve opens before TDC
Exhaust valve closes after TDC

107
Q

Why is there valve overlap?

A

Taking advantage of the inertia of outflowing exhaust gas to provide more complete scavenging and allow air fuel mixture to enter at the earliest possible moment

108
Q

What determines valve overlap?

A

Position of cam lobes on the camshaft

109
Q

Cons of two stroke engine

A

Less efficient
More difficult to lubricate
Harder to cool

110
Q

Describe the process of a two stroke engine

A

Piston up: draws air fuel mixture into crankcase
Piston down: compresses mixture in crankcase, transfer port opens and compressed mixture enters the cylinder
Piston up: compresses mixture in combustion chamber, ignition of the mixture pushes the piston down, exhaust opens with transfer port

111
Q

Who invented the rotary cycle engine and when?

A

Felix Wankel
1957

112
Q

What is a disadvantage of rotary cycle engine?

A

Problems with internal seals

113
Q

How many spark plugs are in a rotary cycle engine and how do they work?

A

Two individually firing spark plugs are used
One spark plug fires sooner (Leading and trailing spark plug)

114
Q

How do “strokes” happen in a rotary cycle engine?

A

Intake, compression, power, and exhaust are completed three times per revolution
The rotor has three sides forming three combustion chambers
Each chamber is completing a different cycle simultaneously

115
Q

What are some differences between two stroke and 4 stroke engines?

A

Half as many strokes
No valves, only ports
Moves down to compress
More robust
Oil is in the air fuel mixture

116
Q

What are the pros of a diesel engine?

A

High compression ratio
No electric ignition
Fuel and oils are heavier and cheaper than gasoline
No need for spark

117
Q

How is the intake of fuel air different in a diesel engine?

A

Fuel is injected under high pressure and atomized then injected into the cylinder while air comes in from the intake valve

118
Q

What happens on the compression stroke of a diesel engine?

A

Air is compressed to an extent that the temperature is high enough to ignite the fuel without electric spark

119
Q

What is the compression ratio for diesel engines?

A

As high as 14:1

120
Q

What is the max compression ratio and most common ratio for gasoline engines?

A

11:1
7:1

121
Q

Where can firing order of an engine be found?

A

Engine operators manual
Stamped into the crankcase

122
Q

What is power and what does it depend on?

A

The rate of doing work
Force extended, distance the force moves, and time required to do the work

123
Q

Who is James Watt?

A

Invented the term horsepower after finding that an English workhorse could work at the rate of 550 foot-pounds per second

124
Q

What is piston displacement?

A

Multiplying the cylinder bore by the total distance that the piston moves during one stroke stated in cubic inches of volume

125
Q

What is bore?

A

The diameter of the cylinder

126
Q

What is total piston displacement?

A

The number of cylinders multiplied by the displacement of one piston

127
Q

The _____ piston displacement, the ______ max _____ the engine can develop

A

Greater
Greater
Horsepower

128
Q

What is a square engine?

A

Bore and stroke are the same distance (6in and 6in)

129
Q

What is indicated horsepower?

A

Horsepower developed by the engine

130
Q

What is brake horsepower?

A

Actual horsepower delivered to the propeller by the engine
85%-90% of indicated hp

131
Q

What is friction horsepower?

A

The part of the total horsepower needed to overcome friction in the engine

132
Q

How do you calculate brake horsepower?

A

bhp = ihp - fhp

133
Q

How is takeoff power rating determined?

A

Max rpm and manifold pressure the engine can be operated at during takeoff, usually has a time limit

134
Q

What is overspeed condition or Maximum Except Takeoff (METO) power?

A

About 10% over maximum allowance, the level above takeoff power, normally in twin engines

135
Q

What is rated power or standard engine rating?

A

Max horsepower output for continuous operation

136
Q

What is maximum power?

A

Greatest power output the engine can develop

137
Q

What is critical altitude?

A

The highest altitude at which an engine will maintain a given horsepower output

138
Q

What increases the critical altitude of engines?

A

Turbochargers or superchargers

139
Q

What is Manifold Absolute Pressure (MAP)?

A

Absolute pressure of the air fuel mixture immediately before it enter the intake port

140
Q

What are the risks of Manifold Absolute Pressure (MAP)?

A

Primary concern of high performance engines because they operate at close to max
Excessive or incorrect MAP leads to excessive cylinder pressure and temp
When operating under excessive cylinder pressure, components are overstressed
Excessive temp will cause detonation, pre-ignition, and loss of power

141
Q

What is detonation?

A

When temperature and pressure of the compressed mixture reach levels to cause explosion instead of even burn

142
Q

What is detonation caused by?

A

High inlet temperature
Insufficient octane rating
more octane=slow burn (prevent detonation)
less octane=fast burn (detonation)
Excessive engine load
Over advanced ignition timing
Excessive leaning of fuel-air mixture
Excessive compression ratio

143
Q

What is preignition?

A

Hot spot in the engine ignites the air fuel mixture before the spark plug fires

144
Q

What can cause preignition?

A

Hot spark plug electrodes
Carbon particles in the cylinder that reach burning temp

145
Q

If compression ratio is higher than 10:1 then:

A

Pre-ignition or detonation may occur
Overheating
Loss of power
Cylinder pressure increases

146
Q

What is maximum compression ratio limited by?

A

The type of fuel used

147
Q

What factors affect performance?

A

Manifold Absolute Pressure
Detonation
Pre-ignition
Compression Ratio
Fuel-Air Ratio

148
Q

What are the two base types of crude petroleum?

A

Naphthenic (found in Texas and California, 60mil years old)
Paraffinic (found in Pennsylvania region, 100mil years old)

149
Q

What is lubricant?

A

Natural or artificial substance that have a greasy or oily property
Used to reduce friction between moving parts

150
Q

List the pro(s) and con(s) of animal lubricants

A

Pro: highly stable at normal temperatures
Con: unsuitable for engines because fatty acids are produced at high temperatures

151
Q

List the pro(s) and con(s) of vegetable lubricants

A

Pro: lower coefficient of friction than mineral oils
Cons: oxidizes when exposed to air, wears away steel rapidly

152
Q

What did castor oil do to pilots?

A

Sprayed out of engine, causing use of goggles
Fumes caused nausea and diarrhea, causing use of scarf

153
Q

List the pro(s) and con(s) of SOLID mineral lubricants

A

Pro: provide a slippery film that reduces friction
Con: does not dissipate heat enough for high-speed machines

154
Q

List the pro(s) and con(s) of SEMI-SOLID mineral lubricants

A

Cons: extremely heavy, not suitable for circulating or continuous operating lubrication systems

155
Q

List the pro(s) and con(s) of FLUID mineral lubricants

A

Pros: sprays easily, pumps easily, absorbs and dissipates heat quickly

156
Q

What is the most common oil used in aviation?

A

Fluid mineral lubricants

157
Q

List the pro(s) and con(s) of synthetic lubricants

A

Pro: tolerates high temps and does not evaporate or break down
Con: Fumes can cause harmful side effects such as Parkinson’s disease

158
Q

List some important oil properties

A

Flash Point
Viscosity
Pour Point
Chemical Stability
Gravity
Color
Cloud Point
Carbon Residue
Ash Residue
Oxidation
Precipitation
Corrosion
Neutralization
Oiliness

159
Q

What is gravity in relation to weight?

A

The weight of a measured volume of a product

160
Q

What is viscosity?

A

Fluid friction of an oil
Resistance an oil offers to flowing

161
Q

Oil must have chemical stability against

A

Oxidation
Thermal cracking
Coking (prevention against carbon deposits)

162
Q

Oil must have physical stability against

A

Pressure
Temperature

163
Q

What is sliding friction?

A

When one surface slides over another
No matter how smooth the surface is there is always sliding friction

164
Q

What is rolling friction?

A

When a cylinder or sphere rolls over the surface of a plane object
Total friction by rolling contact is less than sliding contact

165
Q

What is wiping friction?

A

Occurs between gear teeth
Continuously changes load and direction
Usually in extreme pressure

166
Q

List some characteristics of aircraft oil

A

Viscosity
High antifriction characteristics
Maximum fluidity at low temperatures
Minimum changes in viscosity with changes in temperature
High anti-wear properties
Maximum cooling ability
Maximum resistance to oxidation
Noncorrosive

167
Q

Name at least 3 functions of engine oil

A

Reduce friction between moving parts
Cools various parts of the engine
Seal combustion chamber by filling spaces between the cylinder walls and piston rings
Cleans the engine by carrying sludge and residue away from moving engine parts to oil filter
Prevent corrosion by protecting metal from corrosive agents
Serves as cushion between parts that sees impact loads

168
Q

The purpose of a lubrication system is to supply oil at

A

Correct pressure
Correct volume
Correct location
(Correct time)

169
Q

Why is oil capacity important?

A

The capacity must be sufficient to supply the engine
Fuel-Oil ratio should be around 30:1 by volume

170
Q

Plumbing for oil systems must be _____. Protective _____ aids in protection in high temp areas.

A

fire-resistant
fire sleeve

171
Q

What is the purpose of temperature regulation of oil?

A

Maintains a good temperature of the oil
Commonly includes oil coolers

172
Q

How does a thermostat valve affect oil flow?

A

Oil flow through the oil cooler is controlled by a thermostat valve
Thermostat will open or close depending on oil temperature

173
Q

What does the oil pressure relief valve do?

A

Control and limit the lubricating oil pressure
Prevent damage to the lubrication system
Ensure lubrication in case of a system failure

174
Q

What are full-flow type engine oil filters?

A

Filters all circulated oil of contaminants before passing through bearing surfaces
If filter is clogged, a relief valve will open, allowing oil bypass

175
Q

What are bypass type engine oil filters?

A

Filters about 10% of the oil through filtering element and returns oil to sump (where oil is contained, oil pan)
Oil passing through bearings are not filtered oil

176
Q

What are strainer type engine oil filters?

A

A simple tubular screen
Designed to collapse when clogged or designed with relief valves that also open when clogged

177
Q

What are spin-on type engine oil filters?

A

Newest style
Canister and filter element are one unit
Full-flow type

178
Q

What are cuno type engine oil filters?

A

Series of laminated plates or disks
Contaminants are trapped on the outer diameter of the plates
The spacing of the plates determine the particle size that may pass through

179
Q

What is oil inspection? Why is it important?

A

Excellent method for discovering internal engine damage
Filter screen and filter housing are examined for metal particles
If unusual metal particles or residues are found, engine should be taken out of service and inspected

180
Q

What is oil analysis?

A

Determine the origin of the foreign particles discovered
Predict potential future failures
Oil samples are sent for analysis periodically or when metal particles are found in the filter elements

181
Q

What does the oil pressure gage do?

A

Measures from no pressure up to above the maximum pressure

182
Q

Where are oil temperature gages found?

A

The oil inlet line or on the oil filter housing

183
Q

What are the two types of oil pressure pumps?

A

Gear Type
Vane Type

AT 103 (12 decks)

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