Powerplant lesson 2 Flashcards
1
Q
In theory, when does combustion happen?
A
TDC power stroke
2
Q
When does combustion happen in practice?
A
Spark plug fires just before TDC
3
Q
What’s the name for the process where valves operate early/late?
A
valve lead
valve lag
valve overlap
4
Q
How does enough time get left for the valves to open and close?
A
value lead
valve lag
valve overlap
5
Q
What is ineffective crank angle?
A
The top 90 and bottom 90
6
Q
Power =
A
Power = Torque x RPM
7
Q
Torque =
A
Torque = Force x distance
Distance is the distance from centre of crank to the crank pin.
8
Q
Force =
A
force = pressure x area
9
Q
Area is equal to which engine component
A
Piston crown
10
Q
What is the only thing you can change in the power = torque x RPM
A
Throttle! This changes the air component which changes the air pressure.
This creates more power.
11
Q
What is the name of the cycle where charge is drawn into the cylinder.
A
Induction
12
Q
When the piston drops volume increases meaning that pressure _________?
A
Decreases
13
Q
What word means chemically balanced.
A
Stoichiometric
(chemically balanced)
14
Q
What is the ideal ratio of air to fuel (mass) AFR?
A
15:1
15 parts of air
1 part fuel
15
Q
Engine pressure is always lower than atmosphere!
True/flase
A
True
16
Q
What is the name of the engine cycle where the piston moves upwards (not exhaust)
A
compression
17
Q
What is the danger through the compression phase?
A
Detonation as the pressure and temperature increases.
18
Q
How would you describe the difference in pressure from atmosphere to the carburettor venturi.
A
Lower pressure in the venturi
19
Q
The U-Tube is in which component?
A
Carburettor
20
Q
U-Tube has fuel sitting in the bottom because of.
A
Gravity and equal atmospheric pressure on either side.
21
Q
As the throttle opens, more air comes in. Describe what happens with the fuel.
A
As more air comes in, the lower the pressure in the venturi and the more fuel gets sucked in.
22
Q
In a climb, without any change, what happens to the mixture
A
Becomes richer in the climb
23
Q
Describe a pressure balance duct.
A
U-tube connected back to the (pre-venturi) intake.
24
Q
What feature helps reduce the issue of a richer mixture in the climb?
A
pressure balance duct
25
The pressure balance duct helps correct for changes in which speed?
TAS
Altitude
26
Where does the 'main jet' sit and what does it do?
A narrowing of the tube to venturi to control flow.
27
Throttle sits upstream or downstream of the venturi?
downstream
28
What does an atomiser do and where does it sit
The atomiser sits in/just before the venturi and turns the fuel delivery into a vapour.
29
Liquid fuel doesn't burn. What does?
Vapour
30
What is the diffuser and where does it sit?
Physically, after or parallel the main jet.
It balances fuel flow to speed and O2 levels
31
What is another name for a diffuser?
Emulsification tube
32
The diffuser (emulsifier) takes a static pressure feed and it's job is?
Add air bubbles to the mixture
33
The straw in a glass drawing explains which component?
The diffuser (emulsifier)
More static pressure means the fuel sits lower, so fewer holes are submerged and there is less fuel added to the mixture
34
In which part is the mixture control applied?
The diffuser (emulsifier)
35
The mixture control over rides which component?
Diffuser. It intercepts the static intake and adjusts the pressure by bleeding to atmosphere.
36
Lycoming mixture graph which two lines are parallel?
EGT and CHT
37
CHT is measured from which cylinder?
Hottest cylinder
38
Lycoming mixture graph. What is the ratio at the top of the curve?
15 : 1
39
Fuel cooled / rich mixture. How does it cool the engine?
As the fuel is diffused it absorbs the heat of the engine.
40
What are the guide ratios for mixture?
9:1 starting
12:1 take off
14:1 climb
17:1 power cruise
19:1 economy cruise
41
The rich . lean graph.. what should you pay attention to?
Rich, lean scale. Which way around is it?
42
What is the name of the component that prevents lean cut?
Accelerator pump
43
The accelerator can also have a secondary function. What is it?
priming (3 pumps)
44
In a high performance aircraft you can have a component that will provide a rich mixture to cool the engine at high RPM / power settings.
Boost pump - manually triggered
45
What are the methods of priming
Accelerator pump
Priming hand pump - lock after use
electric pump (auto)
46
Where is the carb located physically on a lycoming engine?
Underneath
47
Beneath the carb is the?
air intake
48
What kind of temperature drop would you expect in a carb?
25deg c
49
What conditions are you likely to find carb icing
visible moisure
50
What is the expected loss in power using carb heat?
15% loss in power
51
What are the potential issues with carb heat use?
Unfiltered air
15% power loss
Can create the icing conditions
Increase detonation risk
52
What is the name for the icing within a Carb
refrigeration icing
caused by lower temperature and fuel evaporation.
53
What is the name for icing at the air intake.
Impact icing
54
Fuel injection doesn't require a venturi so there isn't a risk of
carb icing
(there is still impact ice)
55
An injected engine is missing 'carb heat' what is it replaced with?
Alternate air
56
Injected engines are missing a few controls, what are they?
No mixture
no priming
no carb heat
57
Injected engines have a fuel pump which leads to which 4 things?
Manifold valve
metering valve
mixture valve
distribution valve
58
Injected engines have an extra switch. What is it
Fuel pump
Alternative air
59
The air in an injected or carburetted system is the same. Where is the fuel injected.
Either directly into the cylinder or after the butterfly.
60
The manifold valve is seen in which type of engine
Injected
61
When is the fuel pump on?
Startup and in critical phases of flight
62
What type of injectors do aircraft have?
Electronic solenoid injectors
63
Why the lead?
Temperature
Lubrication
valve strength
64
Difference between AVGAS and MOGAS
Water content.
AVGAS is regulated at max 20ppm
65
Can you use 80 fuel in an aircraft requiring 100
No
66
Can you use 100 fuel in an aircraft requiring 80
Yes, for short periods
67
What colour is found in 100ll fuel
blue
68
What colour is found in 100 fuel
green
69
What colour is found in 80 fuel
red
70
What colour is found in 82 unleaded fuel
purple
71
Purpose of lubrication (4)
Lubricate
Clean
Cool (control expansion)
Perform hydraulic functions (prop pitch)
72
Oil properties
Viscosity
Resistance to flow
thickness
73
Oil options (3)
Synthetic
semi-synthetic
Mineral
74
Synthetic oil allows Viscosity to get _______ as the engine gets hotter.
Thicker
Viscosity is closely controlled
75
Oil grades: what does W10 mean
At 15deg C, the oil will take 10 time as long as water to trickle down 45deg glass
76
What does 10W50
Viscosity increases as temperature increases.
Behaves like a 10 when cold and 50 when warm.
77
Do we mix oils?
Best not, but use the correct oil
78
What should you look for in an oil container?
Clean
labelled
sealed
79
Two types of oil system are?
Dry sump
Wet sump
80
Aerobatic and high altitude aircraft would favour what kind of oil system?
Dry sump
81
Standard aero system would be which oil system?
Wet sump
82
Describe the dry sump
Dedicated oil reservoir
has a scavenger pump
Sight glass
Dipstick
83
Describe the wet sump
No reservoir
Oil is stored in sump
84
What is inside a drysump reservoir?
Fins and baffles to stop liquid moving about
85
Downstream of a drysump reservoir is?
Non-return valve (check valves)
Main pressure pump
Non-return valve (NRV)
Pressure relief vale (PRV)
Oil filter
Engine
De-aeration / de-forming plate
86
Normal oil pressure is?
4.5 bar / 75psi
87
What happens if the oil filter gets blocked or the oil is cold?
There is a bypass that senses pressure difference.
88
What indications are there on the dry sump oil system?
Clog (on filter bypass)
Oil pressure
Oil quantity
89
Oil gets sent to specific location of the engine. What is this system called?
Pressure feeds
90
What ensured the dry sump stays dry?
Powerful scavenge pump driven by crank shaft.
91
Where does the oil go after the engine in a dry sump system?
Oil cooler.
(also has a bypass)
92
In a dry sump, oil gets returned to the reservoir. Where was it before the reservoir?
Oil cooler
93
There is a magnet in the oil system. What is it for?
Chip detectors to collect any ferrous metal debris.
(the location can vary)
Pistons are aluminium so won't get picked up.
94
When do you check the oil level on a dry sump oil system?
While the engine is running!!
95
Where is the oil stored in a wet sump system?
In the sump
96
Wet sump is missing an oil cooler so it compensates by doing what?
3 times as much oil
97
Oil pump sits above the oil level on which component?
Crankshaft
98
The oil pump collects from where?
Wet sump
99
The oil pump pushes out the engine to which components before re-entering the engine?
Pressure relief valve
Filter (and bypass)
optional cooler
100
If fitted, where would the cooler be fitted on a wet sump system.
Feed line - just before re-entering the engine
101
Where would you measure oil pressure?
After the pressure release valve
102
Where would you measure oil temperature?
After the cooler (if fitted).
103
Pumps produce?
Flow
104
Pressure is produced when you ______ flow
resist
105
What are the two methods to keep an engine cool?
Air
Liquid (water/antifreeze)
106
What component regulates the temperature in a water-cooled system?
Thermostat
107
What physical process means that cool water is brought into the bottom of the system?
The heater water rises
(Thremo syphon)
But a water pump helps it too.
108
Temperature range is:
88 - 92
109
The pressurised system 15psi means that the boiling point changes in which direction?
Boiling point is now higher (about 140degc)
110
Expansion tank (containing coolant) needs checking it's between the high and low. How hot should it be.
40deg C
cool enough to the touch
111
Air cooling relies on what in the engine to direct incoming air around the cylinders?
Baffles / air scoops
112
What do cowl flaps do?
Regulate the airflow around the engine.
They are adjusted inflight and on the ground.
113
Examples of power augmentation
Turbo
supercharger
114
Turbo and super are there to do what?
Delay the onset of power loss by forcing pressurised air into the engine
115
MAP is short for
Manifold Absolute Pressure
116
Manifold cylinder pressure =
cylinder pressure
117
More air + more fuel =
more power
118
MAP guage lives where and measures what?
After the carburettor, before the cylinders
It measures ALL the contents going into the engine.
119
Manifold cylinder pressure gauge is what type of guage
Vacuum
120
1013Hpa =
29.92inHG
121
What's the maximum pressure we can get into an engine with the throttle wide open?
Atmospheric pressure
122
Idle speed is ___est manifold air pressure
lowest
123
Throttle opened is ____est mainfold air pressure
highest
124
Maniford air pressure guage will show what when the engine is off (masters on)
QFE - atmospheric
125
Why would Manifold pressure never be QFE?
The engine wouldn't work as no air would be pulled into the cylinder
126
Aircraft service ceiling is define by
127
Aircraft performance ceiling is defined by what (using MAP)
When atmospheric pressure = manifold air pressure
128
In a constant MAP climb, what happens to power
Increases until performance ceiling
129
What instrument is common with a super or turbo charger?
Boost gauge
130
On a boost gauge what are the two sides?
Augmented boost
MAP side
131
As you climb, a boost gauge will do what?
Decrease until the critical altitude when the turbo/super isn't working any more.
132
Two types of supercharger are?
Ground boosted
Altitude boosted
133
Describe a ground boosted supercharger
Boost from sea level
decrease with increasing altitude
134
Describe a altitude boosted supercharger
boosts above a given altitude
MAP at sea level
calibrated to a specific pressure
135
How is a turbocharger driven?
exhaust gas
136
How is a supercharger driven
crankshaft
it's a parasitic load taking some power from the engine
137
What part of a turbo helps prevent detonation
Charge air cooler (outputs at about 25 deg)
138
In a turbo there are two components on a single shaft. What are they?
Compressor and turbine
139
In a turbo, the exhaust leaves the engine and hits a controller called the _____ ____ that sits after the engine
waste gate
140
After the waste gate, the exhaust proceeds to the
Turbine
141
The shaft in a turbine spins very quickly so the brass bearings need a fresh feed of
Oil, direct from the oil pump.
142
The waste gate in a turbo can direct flow in two directions in any proportion. What are the two directions?
Turbine
Atmosphere
143
What controls the wastegate?
oil pressure controlled by a capsule
144
If the engine is off, what position is the wastegate in?
Open (to atmosphere)
145
If the engine is idling, what position is the wastegate in?
Almost closed
146
If we are taking off, what position is the wastegate in?
Partially open
147
If climb to out ceiling, what position is the wastegate in?
Closing (Turbine)
148
If we are at our performance ceiling what position is the wastegate in?
Fully closed
149
In a decent, what position is the wastegate in?
opening
150
What is an overboost safety valve?
Sits between engine and waste gate as a fail safe.
151
Smooth throttle operation is required when using what?
Turbo and super chargers
152
How long should you idle a turbocharged engine before shutting down?
3 - 5 mins
153
