PPL WRITTEN EXAM Flashcards
(153 cards)
1
Q
how is a truss airframe assembled?
A
struts, longerons for box portions, curved bits have bulkheads and stringers, covered for aerodynamics
2
Q
how is a semi-monocoque airframe assembled?
A
bulkheads and formers with stringers between, stressed skin overtop
3
Q
in a pure monocoque airframe which part is eliminated?
A
stringers
4
Q
what materials are used in composite airframes?
A
laminate layers of fiberglass, carbon fiber, or kevlar
5
Q
what are the pros and cons of composite airframes?
A
PRO: stronger and lighter than metal, easy to curve so more streamlined
CON: heat deterioration, hard to tell if its damaged inside, metal gives warning before breaking, expensive
6
Q
what are the advantages of tricycle landing gear?
A
doesnt nose over as easily, overall better handling and visibility on the ground as side to side movement tends to correct itself due to CG being ahead of mains.
7
Q
what are the advantages of conventional landing gear? Why are they harder to steer on the ground?
A
better prop clearance, gear gives less drag in air, less damage if a wheel gives out, overall better suited for rough/unimproved airstrips.
CG is behind mains so it can loop on the ground. More inertia behind wheels = wants to keep turning
8
Q
What kind of landing gear does a c152 use?
A
spring steel cantilever/leaf spring mains (steel flexes to absorb shock) and a single strut oleo up front (tricycle configuration)
9
Q
what does split axle landing gear look like?
A
two beams from each wheel, one attached to fuselage and one going inside, with either bungee cords or oleos inside providing the shock absorption
10
Q
do flaps make you go slower?
A
no, they ALLOW you to go slower but you don’t have to if you’re using them properly
11
Q
What kind of flap extends down from the middle of the wing rather than the end?
A
split flaps
12
Q
What kind of flap adds surface area to the wing>
A
fowler flaps
13
Q
what are flaperons?
A
what they sound like. Help you roll or can be put down same time as flaps (separate controls)
14
Q
when should you generally have cowl flaps open?
A
taxi, takeoff, climb, anytime you have high power and/or low airflow
15
Q
why do we close cowl flaps when they’re not needed?
A
cooling airflow over engine imposes parasite drag
16
Q
What’s a boxer engine? Whats the main advantage they have over radial engines?
A
horizontally opposed, reciprocating, air-cooled, even # of cylinders, 4 stroke
small frontal surface area = less drag
17
Q
whats a radial engine? why dont we make them anymore?
A
round, air cooled, odd # of cylinders firing in a star pattern, large frontal area w/ lots of drag, expensive to maintain and take a shitload of oil.
18
Q
how does the leading and lagging work in a 4 stroke engine? what does it do
A
Power:
exhaust valve leads (before BDC)
Exhaust:
intake valve leads (before TDC)
exhaust valve lags (after TDC)
improves performance
19
Q
what do baffles do?
A
channel air around (in cowling goes past all cylinders and through oil cooler)
20
Q
pros and cons of liquid cooled engines?
A
PRO: better temp control
CON: heavier and more complex, expensive (water jacket, radiator, pumps, coolant)
21
Q
why do piston helicopters need a cooling fan?
A
stay cool without airflow when hovering
22
Q
what is a magneto
A
engine-driven electrical generator, independent of bat and alt, uses rotating magnets to generate high voltage to power the spark plugs.
23
Q
what is a P Lead? how do you make sure they’re working?
A
grounding wire that stops a mag from working. Check w/ mag switch, no rpm drop can mean broken P lead, live mag check on shutdown makes sure theyre both working.
(another cause for little to no RMP drop could be bad mag timing)
24
Q
what does the exhaust system do?
A
gets pollution away from cabin, reduces noise, provides cabin and carb heat w/ muff shroud
25
what does the throttle set?
the amount of fuel- air mixture
26
what does the mixture knob set?
the amount of fuel (adjusts ratio fuel to air by weight)
27
what's a general good fuel-air ratio in most planes? What's normally the best power ratio?
1:15 normal 1:14 best power
28
is an air intake problem bad?
almost as bad as running out of fuel. Need lots of air coming in
29
why do we need to lean properly?
save fuel, better performance, keep combustion chamber and spark plugs clean, (no fouling, no pre-ignition)
30
what happens if the mixture is too lean?
rough engine, backfiring, overheating, sudden stoppage
31
what can you do with the mixture to help with cooling in high-power operation?
enrich slightly more than normal
32
can you use partial carb heat?
only if you have a carb temp guage, otherwise best to go full on or full off because in the middle can give you more ice
33
which is more expensive, a supercharger or a turbocharger?
turbos are more expensive due to needing more maintenance
34
what factors are influenced by density altitude?
engine output, lift generation, thrust generation
35
what engine guages do you need for vfr?
oil temp and pressure
36
what is considered too high a reading on the CHT?
what should you do if that happens?
4-500f, aluminum starts to weaken, must increase airflow and reduce power. (lower nose, cowl flaps open, throttle back)
37
what is a CHT gauge primarily used for?
leaning the mixture
38
how soon after starting should you get an oil temp reading?
within 30s of start, 60 if cold. shut down and investigate if you dont get a reading
39
what happens if oil pressure is too low? too high?
LOW: inadequate lube
HIGH: oil pushes past seals, can lose oil
40
what can a quickly rising oil temp along with low pressure indicate?
not enough oil in system -> leak somewhere. total pressure loss = imminent engine failure
41
what are good typical min and max values for oil temp in cruise? why? what do we want before doing our runup?
C: 180f to 235-245f (water boils at 212f. want to boil off any moisture in system)
R: 80-90f
42
in cold weather what is a common spot to find an oil blockage?
the cooler
43
how do you lean for best economy?
highest EGT value
44
where does the EGT measure from?
exhaust manifold
45
what is the most likely engine component to fail? why and what happens when it does?
the vacuum pump. powers heading and attitude indicators, and de-ice boots. thin carbon veins inside wear down and break
46
what kind of engine does the c152 use?
avco lycoming o235-n2c: 4 cylinder horizontally opposed, normally aspirated, carbureted, air cooled, 4 stroke piston engine. Generates 110 BHP
47
where is the voltage regulator?
small box mounted on the firewall, usually opposite the battery
48
what type of carburetor is used in most GA a/c engines?
updraft carburetor
49
what do you call the big gear behind the spinner?
ring gear
50
why shouldnt you idle for a long time?
need 10-1200RMP to activate lead-scavenging agents in fuel
51
where's the most likely spot for an oil leak?
oil cooler
52
what rotates the mags and the vacuum pump?
the camshaft
53
what does the float valve in the carb do?
keeps a constant amount of fuel in the chamber to satisfy engine demands
54
where is the mixture needle?
in the float chamber
55
where is the fuel discharge nozzle in the carb?
at the start of the venturi, before the throttle valve
56
what does the accelerator pump do?
provides additional fuel to prevent stumbling with a sudden power application
57
what does the economizer valve do?
small needle that lets more fuel in at higher power settings (above 60-70% or in a climb)
58
What does the idle jet do?
shoots fuel past throttle so engine can idle w/ throttle closed. (idle check on runup)
59
what happens to your mixture as you climb?
thinner air enriches it
60
with an EGT gauge, how do you lean for best power? where is rec. lean for cruise? "lean of peak?"
100f richer than max economy
rec: 50f richer
peak: 50f leaner, but need complicated engine analyzer to do properly
61
what kinds of a/c can induction icing affect?
all piston engine aircraft
62
what is impact ice, when does it happen?
Ice on air intake. Can happen 0c or below, with visible moisture in air. Worst -4c in snow, sleet, or fzrn. Main icing hazard for turbocharged engines
63
how much do the venturi drop the temperature of the air going through?
20-30c
64
how do you properly check for carb ice? what temperature is worst?
leave on full for 10 seconds, listen to engine. Icing is at its worst -5c to +15c w/ high relative humidity
65
why is mogas worse for induction icing than avgas?
more volatile (cools more on evaporation) and also more efficient at storing water molecules
66
when is throttle ice at its worst and why?
low power settings. (smaller gap has venturi effect, cooling air mroe)
67
why do you enrich the mixture for climbs?
cooling
68
what is fuel ice and when does it happen?
the part of carb ice that happens when the fuel is vaporized (water in fuel freezes). Can happen +4c to +27c, sometimes higher, or anytime relative humidity is above 5%
69
how does a fuel injected engine work?
fuel atomized by nozzles, discharged into airstream entering intake manifold. (or if diesel direct to cylinder) throttle is connected to a fuel metering valve, which sets the mixture automatically (METERED AMOUNT OF FUEL GOING INTO A KNOWN AMOUNT OF AIR)
70
why are carbureted engines worse?
mixture in each cylinder slightly different, ones closer to carb run richer, further run leaner. = different temp, worse fuel efficiency, fuel can pool up at corners,
70
advantages of fuel injected?
uniform fuel distribution, more power since carb doesnt need to be heated, more uniform cooling, less risk of icing (just impact and throttle ice), more fuel efficient, faster/more accurate throttle response, easier cold start (no primer)
71
what is vapour lock? how do you test for it? what do you do if it happens? what can you do in general to prevent it?
gas bubbles forming in fuel injection lines. happens when plane is shut off on ground on a hot day (heat from engine radiates up). testing: set high power, mixture full rich, and turn on electric fuel boost pump. Want as much cold fuel running through lines as possible. Look in POH for cold vs hot start procedures.
prevention: park into-wind, open oil hatch, cowl flaps if equipped
72
whats an alternate air intake?
inside cowling in case you get impact ice. some open automatically
73
how many fuel pumps does a fuel injected engine normally have?
one engine driven, one electric backup
74
whats the voltage of the battery in the 152? what about the alternator? What kind of battery is it?
24v, around 28v
Lead acid battery
75
whats the difference between an alternator and a generator?
alt can produce pwr at a wide range of rpm. gen needs a specific, small, high range of rpm to produce power (typically used in turbine engines)
76
how is the master switch set up?
alt on left, bat on right.
bat can be on on its own
alt can be on or off with bat
bat off turns off both
77
what do the numbers on the circuit breakers mean?
the amount of amps that system uses
78
what does a loadmeter show?
total amps being used
79
how do you read an ammeter?
shows rate of charge in system. zero means no charge. + means alt providing power, - means bat providing power (load past alt capacity)
full + deflection means voltage regulator is broken
80
what does the voltage regulator do?
stabilizes output from alt/gen to control rate of charge to battery.
81
What's the difference between circuit breakers and fuses?
Circuit breakers are more modern. You can push them back in the complete the circuit again. Fuses, you have to carry extras
82
What should you do if a circuit breaker pops?
Generally would push it back in. If it pops again, don't reset it
83
what does a bus bar do?
takes current from alt and branches it out to each component (c152 has a main bus and an avionics bus)
84
why should you make sure all electrics are off before starting the engine?
sudden surge of current can damage hardware (radios, gps etc)
85
how do you figure out how long a battery will last with a failed alternator?
amp hours divided by component load. (c152 w/ nonessentials off youll get about a half hour)
86
what are the four functions of oil in an engine?
lubricating, cooling, sealing, cleaning
87
what kind of oil system does the c152 use? what are the disadvantages of it?
wet sump (splash type)
-innefficient at cooling
88
how do we prevent combustion from moving out of the cylinders into the crankcase?
oil seals between piston rings
89
is 20w50 a single or multiple grade oil?
what's good about multi grade oils?
multiple (two numbers) single grade would be something like 100w
dont have to change to a different viscosity for summer/winter
90
synthetic oil vs natural?
s: simpler molecoles, more slippery
n: better at cleaning and sealing
91
what is viscosity?
resistance to flow
92
what should you do to keep the engine warm in the winter?
hangar, plug in, engine cover, partially cover cowl openings
93
what happens as oil is overheated?
gets cooked into sludge
94
what is detergent oil?
contains additives to keep sludge from forming, keep engine clean. Another name for them is "ashless dispersant oil)
95
what is mineral oil?
used to break in new engines for first 50hrs. Aka non-detergent oil.
Brand-new engines have some extra friction. Mineral oil allows it to smooth itself out for a better seal, whereas detergent oil would varnish it, making the engine a high oil consumer forever.
96
whats the difference between a splash and a force-fed oil system?
splash: old-fashioned, no longer used in new a/c. oil splashed around by crankshaft. Unpredictable, inefficient, but lightweight.
Force-feed: oil forced under pressure to various engine parts.
97
what is a dry-sump oil system?
oil stored in a separate tank. Pumped in and out of crankcase as needed. Was typically used in radial engines. Usually GALLONS instead of quarts.
98
why does the oil system have a vent?
allows gases to exit crankcase withouot damaging seals/gaskets, or if there's too much oil it can get out through there. (thats the tube under the plane ofir likes to check)
99
why is the oil pump upstream of the oil filter?
so it keeps working if the filter gets blocked. (oil goes past it via bypass valve)
100
what can very dark oil mean?
could be exhaust getting past piston rings, or it's just due for a change.
101
what can happen with the oil cooler in the winter?
Can cool the oil too much, and get clogged. Good to partially cover it when its cold out to prevent this.
102
what can happen with oil that is too low viscosity? What about high viscosity?
How does viscosity relate to pressure in terms of OAT?
L: engine wear due to a too thin film between moving parts. However, less likely to overheat.
H: causes overheating. Flow to cooler is slowed, and in extreme cases with high pressure, a relief valve can open, bypassing the cooler altogether.
Too high visc. for existing temp causes high pressure. Too low visc. for OAT causes low pressure.
103
what does it usually mean if you have low oil pressure but a steady temperature? What about a rising temp?
steady usually means a bad gauge. Rapid fluctuations or sudden high readings also mean there's usually a problem with the guage. Low P and rising T means there's a leak somewhere. (look outside to check for a leak)
104
what do the two numbers mean in a fuel grade?
first is octane rating with a lean mixture, second is octane rating with a rich mixture.
105
how can a fuel be "130% octane"?
lead in fuel makes it perform as if it's 130%
106
whats the difference between octane and heptane? Which is it worse to have too much of? Which gives more power? Why?
octane produces a slow, controlled burn. Heptane is fast, violent combustion.
If correct fuel is unavailable, use next highest octane available. Too much heptane can cause detonation. Top of piston head will be damaged.
Too much octane can foul up spark plugs due to high lead content and low temperature.
High octane fuel provides more power due to slower, more controlled burn. The more a fuel mixture resists combustion, the higher compression possible in cylinder. Higher compression = more heat, longer stroke, more power.
107
How much does avgas weigh on average at 15c? what about jet fuel?
6lb/gal. Jet fuel is around 7lb/gal
108
what is the effective "octane rating" of jet fuel? What happens if you put it in a piston plane by accident? How can you tell it apart from avgas?
close to zero. Will be okay at low RPM but engine will blow up when higher power is applied. Jet fuel is clear, smells different (kerosene) and feels oily.
109
what is ethylene dibromide?
what is lead tetra-ethylene?
what do anti-icing additives do?
1. cleans, prevents spark plug oxidation
2. slows combustion, boosting octane rating
3. delays formation of ice crystals
110
how long roughly does it take for fuel to go stale?
around 6 months of storage should be tested.
111
what is the main cause for water getting into fuel? What should you do if you suspect water in tanks? what's the most likely spot to find water or sediment in the fuel?
temperature changes causing condensation. Don't leave them sitting half-empty overnight, that makes it worse.
Check for water by shaking tail of plane to get water to settle down into tank.
most likely spot is gascolator/carb bowl. It has a screen to catch dirt, and is the lowest point in the system.
112
what happens if you have a loose fuel cap?
low pressure above wing acts like a vaccuum, sucking fuel out. Drain speed depends on type and speed of plane. Indicated by smell, blue vapour trailing behind.
113
why shouldn't you fill fuel all the way to the top?
whats the fuel vent
fuel expands w/ warming OAT.
not a huge deal, it'll just spill out the fuel vent. Fuel vent's main purpose is to let air in as fuel level drops, preventing a vacuum. (most planes have a small hole on at least one gas cap that does same thing if vent blocked, only one = cross-fed tanks)
114
what do the baffles in the fuel tanks do?
keep fuel from sloshing around, making gauges more accurate, keeping plane balkanced, and minimizing wear on tank.
115
why are low-wing fuel systems more complex?
can't be gravity-fed. Must have pumps.
116
What is detonation?
fuel burns too fast (explosively), resulting in power loss, overheating, eventual engine failure (all cylinders). Caused by too lean mixture or too low octane rating. Sudden CHT rise means its coming soon
117
What is pre-ignition?
Happens if the engine has hot spots in the cylinders. (areas of glowing carbon buildup due to improper mixture settings). Ignites mixture before spark plug fires (may only happen in 1 or 2 cylinders). Damages engine.
118
what is a fuel heater?
prevents congealing at extreme cold temp/high alt. Jet fuel is more likely to congeal in the cold.
119
How does the primer work? What do you do if you flood it?
similar to a fuel injector. Atomizes fuel and sprays onto a cylinder entrance. Minimizes starter wear and battery drain when used properly. ]
Overpriming floods the cylinder. (indicated by weak, intermittent explosions and black smoke puffs. typically will want full throttle and full lean mixture to get a bunch of air in, then once it starts go back to rich and idle)
One trick if it's very cold is to give it a prime while cranking the starter. See POH for info.
120
how do you safely fuel a plane
Ground, contact, fuel, stop fuelling, break contact, remove ground wire
touching nozzle to side of tank grounds it to the airframe. Plane builds up lots of static in flight. Ground wire neutralizes static charge between pump and a/c.
also NO SMOKING
121
what is the bonding property of an a/c?
ability of components to pass static charge between them, and eventually onto ground wire. May have little metal strips between parts to help this.
122
What are some good things to remember if you have an L/R fuel switch? (4)
-Can mess with it to try to restart fuel flow if you have an engine failure
-engine is hard to restart if you run a tank dry (vapour lock)
-some planes have a max fuel imbalance, may have to switch back and forth every half hour ish.
-when switching tanks, turn on boost pump and watch fuel pressure.
123
what do you need to remember when fuelling from drums?
Important to use a proper filter/water separator. Fuel line should also sit about an inch off the bottom, don't pump from the very bottom of the drum.
124
What can you use as an emergency water separator?
a chamois (pronounced 'shammy'), lining a funnel. Reduction of flow through it indicates water contamination. Wringing it out will nullify water-separating properties. Thoroughly check fuel system for contamination after flying a plane that was fueled this way.
125
describe the following supplemental oxygen systems:
1. constant flow rebreather bag
2. constant flow nasal cannula
3. on-demand mask
1. standard on commercial planes, breath combo of fresh oxygen and rebreathed air. innefficient and typically approved below FL200.
2. oxygen bottle behind seat or back of plane. Looks like the hospital thing. Similar to previous
3. Fighter pilot. No recycled air, flows only when inhaled, mask sealed to face, high altitude.
126
how are piston engine planes pressurized? How are turbine engine planes pressurized?
piston: comes from turbocharger
turbine: bleed air from compressor section, used to power another compressor which pressurizes the cabin
127
what's a typical cabin altitude setting? Whats a comfortable cabin 'rate of climb'?
8000ft. typical climb of 500fpm up or 300fpm down. Engineer's job is easier with high cabin alt (low pressure differential between cabin and outside air) For pressurized a/c, usually the max cert alt is based on the PSID, not the climb performance.
128
what does the vacuum system do? what are the 3 main types?
provides suction to spin the gyros. (4-6in hg required)
engine driven pump: common, okay
venturi outside plane: old school, cheap and shitty
electric motor: reliable and expensive
129
how often do vacuum pumps fail?
every 500hrs. Carbon veins inside wear down and break. Most unreliable thing on the c152.
130
whats the difference between de-icing and anti-icing systems?
de = get rid of it once its there. Boots inflate along leading edge of wing.
anti = plane coated with a fluid that prevents ice formation. Can be applied on ground, or secreted by plane in flight.
Can have heated components that can be used as either (windshield, prop, pitot, etc)
131
which is heavier, anti-icing fluid, or fuel? What are the 3 main types of anti-icing fluid?
anti icing fluid is much heavier than fuel
3 types are TKS fluid, glycol, and antifreeze
132
What are the 3 types of control rigging? What type does the 152 have?
cable, pushrod, fly-by-wire (electronic)
-152 uses cables
133
What does a manifold pressure gauge measure? How does the throttle affect it? Where does it measure from?
The amount of air available to the engine. If you have one of these, it means you have a variable pitch propellor. Represents engine power in these systems as opposed to RPM of a fixed pitch prop. Tachometer is no longer an accurate measure of engine power.
Tach measures RPM set by the pitch of the prop. Like what "gear" you're in
MP measures the pressure of the mixture entering the intake manifold, in inches of mercury.
Throttle open -> more mixture sucked towards cylinders, higher pressure
Throttle closed -> engine trying to suck air thats not there, like a vacuum, lower pressure
Line is downstream of carb, just before combustion chamber
134
What is Static Manifold Pressure?
MP reading before starting engine. Will be whatever the air pressure is outside.
In a perfect system, it would read the same as static w/ full throttle open, but friction and obstacles/turns through the pipe (filter, venturi, throttle valve etc) cause a pressure drop when the air starts moving. Minimizing bends in ducts gives better performance.
135
How does climbing affect your manifold pressure?
the higher you get, the less air there is, meaning less pwr available. MP gauge shows this very clearly.
136
How do you check the MP gauge, pre-flight?
-set altimeter
-subtract an inch per 1000'ASL
-MP gauge should be close to that number. Check before every flight to make sure the engine can generate full power.
137
What will be your MP reading at idle? What about at full throttle? Are high or low power settings more stressful on the intake manifold?
For most planes its around 12"Hg. Due to the near vacuum conditions, low power settings are more stressful on the intake pipe than high settings. At high settings it gets closer and closer to outside ambient pressure, meaning less stress on system. Engine can now draw in as much air as it is capable of mixing w/ fuel.
138
How do you identify an engine failure with a variable pitch prop?
Must use EGT. MP and Tach can and will both still have a reading.
With prop windmilling, you'll still see an RPM reading. Engine will also be still turning meaning it's still sucking air in, so you'll see a MP reading as well.
139
In what conditions might you see a higher MP reading than static?
In a dive with high airspeed, high throttle setting. "Ram effect".
Turbocharged planes also experience this, due to the compressed air entering the system.
140
With a constant MP setting, what happens if you reduce RPM? What happens if you increase RPM?
Reduce: MP rises because pistons are creating less of a vacuum
Increase: MP drops due to increased suction.
141
With a variable-pitch prop system, what happens if you have an induction system leak? What are some of the warning signs?
More air getting into system, causing too lean a mixture, unless at full throttle.
Warning signs: Engine roughness during ground idle. Sometimes a whistling can be heard at idle
- abnormally high MP reading for the throttle position.
142
describe the airflow over and under an aerofoil. What is camber and how does it affect this?
Above: fast, low pressure
Below: slower, higher pressure
both deflected down.
Camber is how curved the top of the wing is. More camber means faster air, lower pressure, more downwash, to a point. Once you have too much, the air won't be able to make it around the corner anymore, won't generate lift.
143
How does AoA work? (greek α)
AoA is the angle at which the chord line meets the relative airflow. Increasing AoA has a similar effect to increasing camber. You generate more lift to the point of stalling
144
What determines the Coefficient of Lift CL?
Airfoil shape and AoA
145
What is the lift formula? What does each variable represent?
L = 1/2 CL p V^2 S
CL: coefficient of lift
p: air density
V: velocity
S: surface area
146
What is the induced drag formula? What does each variable represent?
D = 1/2 CD p V^2 S
CD: coefficient of drag
p: air density
V: velocity
S: surface area
147
what are the 3 types of parasite drag?
form drag: due to shape of object
skin friction: skin has friction
interference: caused by differences in airflow (mainly speed) over different parts, happens where the parts are connected.
148
How are wingtip vortices generated? When are they strongest? what direction do they flow?
Airflow over top of wing speeds up and moves inward, towards fuselage. Airflow under wing slows down and moves out. Due to this and the pressure differential (wants to equalize), air at tip of wing forms a vortex.
They are strongest with a heavy aircraft, moving slow, in clean configuration. (high aoa, high induced drag)
From the back of the plane, they flow clockwise on the left wing and counterclockwise on the right wing
149
Where is the best glide speed on the drag graph?
aka best L/D, best range
It's where induced drag and parasite drag intersect on the graph. (lowest total drag)
150
When in equilibrium, how do the forces acting on the plane look?
lift = weight, thrust = drag
no acceleration
can be in a climb/descent in equlibrium but not in a turn
151
what is the center of gravity? Where do we normally want it when properly balanced?
the point through which the total weight appears to act through in every attitude. Plane would be balanced if held from a string through there. Normally want it around the center of the wing, near the spar.
152
