finals Flashcards
1
Q
The basic principles of engine operation is the relationship between:
A
Pressure
* Volume
* Temperature
2
Q
is a
device for converting heat energy into
mechanical energy.
A
internal combustion engine
3
Q
is the distance the
piston moves from one end of the cylinder
to the other, specifically from top dead
center (TDC) to bottom dead center
(BDC), or vice versa.
A
stroke
4
Q
Aircraft engines can be classified by several methods. They can be classed by:
A
- Operating cycles
- Cylinder arrangement
- The method of thrust production
5
Q
All are heat engines that convert fuel into 1._______that is converted to 2.______ to
produce thrust.
A
1.heat energy
2.mechanical energy
6
Q
Most of the current aircraft engines are of the internal combustion type because
A
the
combustion process takes place inside the engine.
7
Q
Reciprocating engines may be classified by:
A
- the cylinder arrangement (in line, V-type, radial, and opposed).
- method of cooling (liquid cooled or air cooled).
8
Q
y. Today, most of
the engines currently (2005) manufactured by1._________ are used by
major manufacturers of light aircraft Cirrus, Cessna and so on.
A
- Lycoming and Continental
9
Q
rely on the circulation of air
directly over heat dissipation fins or hot areas of
the engine to cool them in order to keep the engine
within operating temperatures.
A
Air-cooled engines
10
Q
In all combustion
engines, a great percentage of the heat generated
(1.____) escapes through the exhaust, not
through the metal fins of an air-cooled engine (2.___).
About 3.____ of the heat energy is transferred to the oil,
which although primarily meant for lubrication, also
plays a role in heat dissipation via a cooler.
A
1.around 44%
2.12%
3. 8%
11
Q
, the heat is transferred from the cylinders to the coolant, which is then sent through tubing
and cooled within a radiator placed in the airstream.
A
liquid-cooled engines
12
Q
The main problem with liquid cooling is
A
the added weight of coolant, heat exchanger (radiator), and
tubing to connect the components.
13
Q
If the engine is designed to
operate with the cylinders below the crankshaft, it
is called an
A
inverted engine
14
Q
generally has an even number
of cylinders, although some three-cylinder
engines have been constructed.
A
inline engine
15
Q
has two banks of
cylinders directly opposite each other with
a crankshaft in the center.
A
opposed-type engine
16
Q
, the cylinders are
arranged in two in-line banks generally set
60° apart.
A
V-type engines
17
Q
consists of a row, or rows, of
cylinders arranged radially about a central crankcase.
A
radial engine
18
Q
Some radial
engines have two rows of seven or nine cylinders
arranged radially about the crankcase, one in front of
the other. These are called
A
double- row radials
19
Q
There are several operating cycles in use:
A
- Four stroke
- Two stroke
- Rotary
- Diesel
20
Q
,
sometimes called the Otto cycle after its originator, a German physicist.
A
four-stroke cycle
21
Q
During the _______, the piston is pulled
downward in the cylinder by the rotation of the
crankshaft.
A
intake stroke
22
Q
After the intake valve is closed, the continued upward
travel of the piston compresses the fuel/air mixture to
obtain the desired burning and expansion characteristics.
A
Compression Stroke
23
Q
As the piston moves through the TDC position at the
end of the compression stroke and starts down on the
A
power stroke.
24
Q
As the piston travels through BDC at the
completion of the power stroke and starts upward
on the
A
exhaust stroke
25
The timing of the valve and ignition
events is always specified in degrees of
crankshaft travel.
Valve Timing and Valve Overlap
26
has re-emerged
being used in ultra-light, light sport, and many
experimental aircraft.
two-stroke-cycle engine
27
has a three-sided rotor
that turns inside an elliptical housing,
completing three of the four cycles for
each revolution.
rotary cycle
28
depends on high
compression pressures to provide for the
ignition of the fuel/air charge in the
cylinder.
diesel cycle
29
The basic major components of a reciprocating engine are
the crankcase, cylinders, pistons, connecting
rods, valves, valve-operating mechanism, and crankshaft.
30
The foundation of an engine is the
crankcase.
31
The shape of the nose or front of the crankcase
section varies considerably. In general, it is either
.
tapered or round
32
usually is of cast
construction and the material may be either
aluminum alloy, which is used most widely, or
magnesium, which has been used to some extent.
accessory (rear) section
33
, containing both spur- and beveltype gears, are used in the different types of
engines for driving engine components and
accessories.
Gear trains
34
are generally
used to drive the heavier loaded accessories or
those requiring the least play or backlash in
the gear train.
Spur-type gears
35
permit angular
location of short stub shafts leading to the
various accessory mounting pads.
Bevel gears
36
is carried in a position parallel to the longitudinal axis of the crankcase and is
generally supported by a main bearing between each throw.
crankshaft
37
Its main purpose is to transform the reciprocating motion of the piston and connecting rod
into rotary motion for rotation of the propeller
crankshaft
38
, each crankshaft has
three main parts—
a journal, crankpin, and crank cheek.
39
is supported by, and rotates in, a main bearing. It
serves as the center of rotation of the crankshaft.
journal
40
is the section to which the connecting rod is
attached.
crankpin
41
and a crankpin make a throw. When a
force is applied to the crankpin in any direction other than
parallel or perpendicular to and through the center line of
the crankshaft, it causes the crankshaft to rotate.
Two crank cheeks
42
Excessive vibration in an engine not only results in fatigue failure of the metal structures, but also causes
the moving parts to wear rapidly.
Crankshaft Balance
43
is merely a pendulum that is fastened to the
crankshaft so that it is free to move in a small arc.
dynamic damper
44
is the link that transmits forces between the piston and the crankshaft.
connecting rod
45
There are four types of connecting-rod assemblies:
1. Plain
2. Fork and blade
3. Master and articulated
4. Split-type
46
are used in inline and opposed engines.
Plain-type connecting rods
47
is
commonly used in radial engines.
master-and-articulated rod assembly
48
serves as the connecting link between the
piston pin and the crankpin.
master rod
49
are attached to the
master rod by knuckle pins, which are pressed into holes
in the master rod flanges during assembly.
articulated rods
50
is used
primarily in V-type engines.
fork-and-blade rod assembly
51
___ of a reciprocating engine is a
cylindrical member which moves back and forth
within a steel cylinder.
piston
52
top of the piston, or head, may be
flat, convex, or concave.
53
prevent leakage of gas pressure from the combustion chamber and reduce to a
minimum the seepage of oil into the combustion chamber.
piston rings
54
is most often used in making piston rings.
Gray cast iron
55
is to prevent the escape of combustion gases past the piston during
engine operation.
compression rings
56
are placed in the grooves immediately below the compression rings and above the
piston pin bores.
Oil control rings
57
usually has a beveled face and is installed in the groove at the bottom of the
piston skirt.
oil scraper ring
58
The portion of the engine in which the power is developed
is called the
cylinder.
59
Each cylinder is an
assembly of two major parts:
cylinder head and
cylinder barrel.
60
is to provide a place for combustion of the fuel/air mixture and to give
the cylinder more heat conductivity for adequate cooling
cylinder head
61
Aluminum alloy is used in the construction for a number of reasons:
* It is well adapted for casting or for the machining of deep;
* closely spaced fins;
* it is more resistant than most metals to the corrosive attack of tetraethyl lead in gasoline.
62
is made of a
steel alloy forging with the inner surface hardened to resist wear of the piston and the piston rings which
bear against it.
cylinder barrel
63
The steel soaks up nitrogen from the gas, which forms iron nitrides on the exposed
surface. As a result of this process, the metal is said to be
nitrided.
64
This is a process that plates chromium on the
surface of the cylinder barrel and brings it back to new standard dimensions.
chroming.
65
The fuel/air mixture enters the cylinders
through the intake __ ports, and
burned gases are expelled through the
exhaust ___ ports.
valve
66
The valves used in aircraft engines
are the
conventional poppet type
67
acts as a pilot
for the valve head and rides in
the valve guide installed in
the cylinder head for this
purpose.
valve stem
68
consists of a cam ring or camshaft equipped with lobes that work against
a cam roller or a cam follower
the valve operating mechanism
69
The valve mechanism of a radial engine is operated by one or two
___, depending upon the number of rows of cylinders
cam rings
70
The valve mechanism of an
opposed engine is operated by a
camshaft
71
The function of the tappet assembly
is to convert the rotational
movement of the cam lobe into reciprocating motion and to
transmit this motion to the push rod, rocker arm, and then to
the valve tip, opening the valve at the proper time.
72
The tappet assembly consists of:
A cylindrical tappet,
A tappet roller
A tappet ball socket or push rod socket;
and
4. A tappet spring
73
, which slides in and
out in a tappet guide installed in one of
the crankcase sections around the cam
ring;
A cylindrical tappet
74
, which follows the contour
of the cam ring and lobes;
tappet roller
75
require the valve clearance to be adjusted manually by
adjusting a screw and lock nut.
Solid lifters or cam followers generally
76
Some aircraft engines incorporate hydraulic tappets that automatically keep the valve clearance at zero,
eliminating the necessity for any valve clearance adjustment mechanism.
Hydraulic Valve Tappets/Lifters
77
, tubular in form, transmits the lifting force from the valve tappet to the rocker arm. A
hardened-steel ball is pressed over or into each end of the tube.
push rod
78
transmit the lifting force from the cams to the valves. Rocker arm assemblies are
supported by a plain, roller, or ball bearing, or a combination of these, which serves as a pivot.
rocker arms
79
are to close the valve and to hold the valve securely on the valve seat.
valve springs
80
is any surface which supports, or is supported by, another surface.
bearing
81
are generally used for the crankshaft, cam
ring, camshaft, connecting rods, and the accessory drive
shaft bearings.
Plain bearings
82
consists of grooved
inner and outer races, one or more sets of balls, in
bearings designed for disassembly, and a bearing
retainer
A ball bearing assembly
83
are made in many types and
shapes, but the two types generally used in the
aircraft engine are the straight roller and the
tapered roller bearings
Roller bearings
84
The increased brake horsepower delivered by a high horsepower engine results partly from increased
crankshaft rpm.
Propeller Reduction Gearing
85
s. Many
types of reduction gearing systems are in use. The three types most commonly used are
spur
planetary, bevel planetary, and spur and pinion.
86
Propeller shafts may be of three major types:
tapered, splined, or flanged.
87
common unit of mechanical power is the
horsepower
88
is a comparison of the volume of space in a cylinder when the piston is at
the bottom of the stroke to the volume of space when the piston is at the top of the stroke.
compression ratio
89
is the horsepower calculated from the indicated mean
effective pressure and the other factors which affect the power output of an engine.
indicated horsepower
90
The power delivered to the propeller
for useful work is known as
brake horsepower (bhp).
91
is a measure of load
Torque
92
There are numerous devices for measuring torque, such as a
dynamometer or a torque meter
93
is the indicated horsepower minus brake horsepower.
Friction horsepower
94
is the average pressure produced in the
combustion chamber during the operating cycle and is an expression of the theoretical, frictionless power
known as indicated horsepower.
indicated mean effective pressure (IMEP),
95
The first power overcomes internal friction, and the
horsepower thus consumed is known as
friction
horsepower.
96
The second power, known as ____
produces useful work at the propeller.
brake horsepower,
97
That portion of IMEP that produces brake
horsepower is called
brake mean effective
pressure (BMEP).
98
The remaining pressure used to overcome internal
friction is called
friction mean effective pressure
(FMEP).
99
The ratio of useful work done by an engine to the heat energy of the fuel it uses, expressed in work or heat
units, is called the
thermal efficiency
100
Reciprocating engines are only about ___ percent thermally efficient
34
101
is the ratio that shows how much of the power developed by the expanding gases in
the cylinder is actually delivered to the output shaft.
Mechanical efficiency
102
. It is a comparison of the volume of fuel/air
charge (corrected for temperature and pressure) inducted into the cylinders to the total piston displacement of
the engine.
Volumetric efficiency
103
most common fuels are
AVGAS for reciprocating engines and Jet A for turbine engines.
AVGAS is generally either 80 (red) or 100LL (blue) octane.
104
is a measure of a liquid's tendency to vaporize under given conditions.
Volatility
105
is a
com-plex blend of volatile hydrocarbon compounds that have a wide range of boiling points and
vapor pres-sures.
Gasoline
106
three general causes of vapor lock are:
* lowering of the pressure on the fuel;
* high fuel temperatures;
* and excessive fuel turbulence.
107
When fuel
changes from liquid to vapor, it extracts heat from its
surroundings.
CARBURETOR ICING
108
is the explosive, uncontrolled burning of the fuel-air charge.
Detonation
109
is precisely timed in a properly func-tioning ignition system.
Combustion
110
is caused by hot spots in the cylinder
Preignition
111
The basic parts of a fuel system include .
tanks, boost pumps, lines, selector valves, strainers, engine-driven
pumps, and pressure gauges
112
is a
passageway or tube in which there is a narrow portion called the throat.
Simple venturi
113
To provide for engine operation under various loads and at different engine speeds, each
carburetor has six systems:
1. Main metering
2. Idling
3. Accelerating
4. Mixture control
5. Idle cutoff
6. Power enrichment or economizer
114
supplies fuel to the engine at all speeds above idling. The fuel discharged
by this system is determined by the drop in pressure in the venturi throat.
main metering system
115
- separate system is necessary for idling because the main metering system can be erratic
at very low engine speeds.
Idling system
116
supplies extra fuel during sudden increases in engine power.
accelerating system
117
determines the ratio of fuel to air in the mixture
mixture control system
118
The carburetor has an ______so that the fuel can be shut off to stop the engine.
idle cutoff system
119
automatically increases the richness of the mixture during high power
operation.
power enrichment system
120
, the most common of all carburetor types, has several distinct disadvantages.
float-type carburetor
121
essential subsystems of a float-type carburetor are:
1. Float chamber mechanism system
2. Main metering system
3. Idling system
4. Mixture control system
5. Accelerating system
6. Economizer system
122
is provided between the fuel
supply and the main metering system of the
carburetor.
float chamber
123
main metering system supplies fuel to
the engine at all speeds above idling and
consists of:
1. Venturi
2. Main metering jet
3. Main discharge nozzle
4. Passage leading to the idling system
5. Throttle valve
124
On float-type carburetors, two types of purely manual or cockpit controllable devices are in general use
for controlling fuel/air mixtures,
the needle type and the back-suction type.
125
In this system, a certain amount of
venturi low pressure acts upon the fuel in the float chamber so that it opposes the low pressure existing at
the main discharge nozzle.
e back-suction-type
126
is provided by a needle valve in the base of the float
chamber.
needle-type system
127
When the throttle valve is opened quickly, a large volume of air rushes through the air passage of the
carburetor
Accelerating System
128
For an engine to develop maximum power at full throttle, the fuel mixture must be richer than for
cruise.
Economizer System
129
