u5 Flashcards
truss airframe:
- what holds the load
- what’s it made of
- what is added to it for improved aerodynamics
- steel tubes hold load
- longer ones and struts
- bulkheads and stringers for aerodynamics
semi-monocoque airframe
- what’s it made of
- what holds most of the load
- formers/bulkheads, stringers, stressed skin
- stringers hold load
monocoque airframe
- what’s it made of
- what holds the load
- formers/bulkheads wrapped in stressed skin
- stressed skin holds load
composite airframe
- what’s it made of
- advantage
- disadvantage
- fiber glass, carbon fibre, kevlar
- stronger and lighter than metal (less fatiguing )
- internal damage doesn’t show until it’s too late
compare the advantages between tricycle vs taildragger landing gear
tricycle - stable on ground, better visibility taxing
taildragger - higher propeller clearance, less parasite drag (smaller) = more thrust, better for shitty runways
which landing gear is susceptible to ground looping when there’s a strong cross wind
taildragger
t/f: retractable landing gear is better because it reduces induced drag which results in more thrust
false it reduces PARASITE drag
tires with high or low pressure are good for rough runways
low pressure
t/f: flaperons are heavier than having flaps and ailerons separate
false they’re lighter because less material
explain the 4 stroke piston engine cycle
- intake - intake valve opens, exhaust one closes and piston moves down to create a vacuum to suck in fuel/air
- compression - valves closed and piston moves up
- power - before top dead centre, spark plugs fire to burn fuel which creates gases that push piston downwards. before bottom dead centre, exhaust valve opens
- exhaust - exhaust valve open and piston moves up to remove burned gases
the linear motion of the piston is converted to rotational motion by the ________ , through the ______
crankshaft
connecting rod
compare air cooled vs liquid coooling for engines
air cooled is cheap and easy, but need direct airflow for it to be efficient - so if ur in slow flight for long period of time it can overheat easily
liquid cooling is more efficient but requires heavy equipment
when the mag is turned to the left, which mag is on and which one is grounded
left on
right grounded (p-lead grounded)
when doing mag check, there is no RPM drop. what does this mean.
there is a broken p-lead, so the magneto will continue to run when the plane is shut down
if you smell exhaust during your flight, what should you check first and do.
if cabin heat is on and you smell exhaust, that means your shroud ripped and exhaust (with carbon monoxide) is entering the cabin so turn off cabin heat
mixture control determines the fuel:air ratio by _______
weight
benefits of a lean mixture
save fuel
efficient engine
reduce spark plugs fouling
reduce pre ignition
benefit of rich mixture
keeps engine cool during high power setting
what happens if the mixture ratio is too rich
rough engine / engine failure
fuel wastage
spark plugs foul
pre ignition
what happens if the mixture ratio is too lean
rough engine
overheating
backfiring
idling for long period of time can cause what
spark plug fouling
what must you do when you turn on carb heat
lean mixture
bc hot air is less dense so we don’t want too rich ratio
in order for the engine to be turbocharged, is the waste gate open or closed
closed
when the waste gate is closed, the exhaust is sent to power the turbocharger
does a turbocharger compress air before or after it reaches the carburetor
before
does a supercharger compress air before or after it reaches the carburetor
after
a turbocharger vs supercharger. which one takes engine power to run? which one doesn’t require the engine but is prone to temperature stress
supercharger is efficient but requires engine power
turbocharger is powered by exhaust air (not engine) but prone to temperature stress because of the large temp differences between power turbine and compressor turbine
hot, high, humid = ______ density altitude = ____ density air
high density altitude = low density air
cold, low, dry = _____ density altitude = _____ density air
low density altitude = high density air
brake horsepower (BHP) vs thrust horsepower (THP)
BHP - available power from engine after accounting for engine friction
THP - available BHP after accounting for propeller friction
t/f: a turbocharged engine is a gas turbine engine
FALSE
- turbocharged engine = piston engine with a turbocharger to compress the air
- gas turbine engine = engine made from rotating parts with continuous airflow
how does a turbojet engine work
- air enters through air inlet
- spinning compressors will compress the air
- compressed air fed to combustion chamber where fuel gets injected
- after combustion , hot exhaust accelerated out the back and spins the turbine before exiting
- the turbine powers the rotation of the compressors and the cycle repeats
how does axial flow compressors work
rotors add kinetic energy to the air, and stators stop this swirling of air and increase the compression
what does a diffuser do in a turbojet engine
slows down air delivery from the compressor to combustion chamber so that there’s more combustion efficiency
turbine engines run very lean: ____ lbs of air to ____ lbs of fuel
100 lbs of air to 2lbs of fuel
military planes have ______ in the back of their turbine engine to increase power output
after burner
what is a turbofan engine
it is _____% more fuel efficient that turbojets and also quieter
turbojet core (fan at front sends air into compressor, combustion, exhaust powers the turbine to spin compressor and fan)
but it also sends air around the engine to generate additional thrust
30-40%
turbofan bypass ratio:
low vs high bypass
ratio of air that bypasses around the engine : air that gets sent into engine
low bypass (less 5:1) = high fuel consumption but high speeds
high bypass (more 5:1) = fan generates most of thrust so less fuel consumption and quieter
turboprop engine
- how does it work
- does it produce high or low jet thrust
- two ways that the propeller can get powered
- good for high or low speeds and altitudes
- turbine powers the compressor and gearbox that spins the propeller
- low jet thrust because most of exhaust powers the prop instead of being sent out the back for thrust
- direct drive (power turbine + compressor linked) or free turbine (both turbines not connected)
- good for low speeds at low altitudes
____ are good for high speeds
_____ are good for low speeds
____ is the best compromise between the two
turbojets
turboprops
turbofan
air from a low speed compressor can power what other aircraft system
cabin pressurization
low speed = low pressure = low temp = cold
air from a high speed compressor can power what other aircraft systems
de-icing
high pressure = hot
what is the purpose of the APU (auxiliary power unit)
mini turbine in the tail helps power up the electrical system and provide air pressure to spin the compressors during start up
is fuel safe to be injected into the burner before or after 20% N1 compressor speed. why?
after 20% N1 speed, there’s enough air to force the hot exhaust out the rear
if the compressor is still too slow to push the exhaust out the back, the hot exhaust just sits in the engine an can melt it
hot start vs hung start
hot start - fuel gets injected when the compressor is still too slow to push hot exhaust out rear
hung start - not enough engine cooling but not because of compressor speeds (b/c high density altitude or fuel control malfunction)
how do you know your compressor stalled? recovery? how do Variable Inlet Guide Blades (VIGB) limit compressor stalls
strong vibration and load roar
reduce power, decrease AoA, increase airspeed
VIGB are little airfoils on the compressor rotor that can change their AoA to limit stalls
explain diesel engines
what are the 4 strokes
advantages and disadvantages
cylinder takes in air, compresses, air gets hot, disel gets injected and diesel ignites on its own
suction, compression, power, expulsion
fuel efficient, no spark plugs needed, durable
not good for cold temperature because during compression the cold air might not get hot enough for diesel to self ignite
how many inches of propeller clearance do you need
7 in
why is the propeller twisted
what sections of the propeller have high vs low blade angles
so ensure equal thrust along entire blade (won’t stress blade)
centre = small distance so travel slower = high angle
tips = far distance so travels faster = low angle
geometric pitch
effective pitch
propeller slip
geometric pitch = theoretical distance a propeller should move in one rotation
effective pitch = actual distance the propellor moves in one rotation
propeller slip = difference between geometric to effective pitch
explain propeller TORQUE
propeller forcing the plane to rotate in the opposite direction to propeller rotation (tendency plane roll left)
explain propeller SLIPSTREAM
when is this effect strongest
prop creates drag, and this air loops around fuselage and hits vertical fin on left = nose yaw left
strongest at high power + slow speed (takeoff, slow flight)
explain propeller GYROSCOPIC PRECESSION
force on a spinning wheel causes a reaction 90º along the direction of rotation
pitch up -> yaw right
explain propeller ASYMMETRIC THRUST / P FACTOR
in level flight, the propeller is vertical so both blades have same AoA = equal thrust
nose up = propeller is angled up so blades have different AoA = more thrust on descending (right) blade = left yaw
propellers designed for max climb efficiency has a small or large blade angle
small but fast bites of air
a coarse pitch blade = ____ blade angle = _____ RPM = good for _____ phase of flight
high blade angle = low RPM = cruise
a fine pitch propeller = ____ blade angle = _____ RPM = good for _____ phase of flight
low blade = high RPM = takeoff
how often must a propeller be inspected
every 100h or yearly (whichever is sooner)
i have a high speed plane with a strong engine, should i get a propeller with a short or long diameter?
short diameter so blades don’t reach speed of sound
how does a constant speed propeller work? pitch is changed hydraulically via _______**, which uses oil to change the pitch of the propeller blades
when the pilot decreases power in flight, RPM usually decreases, but *** will _______ the blade angle so that it increases of the original RPM
when the pilot increases power in flight, RPM usually increases, but *** will _______ the blade angle so that it decreases the original RPM
governor **
decrease power = increase RPM by decreasing the blade angle (finer)
increased power = decrease RPM by increasing the blade angle (coarse)
in a non-feathering system (single engine), when the governor decreases oil pressure, the blades become more ________ (fine/coarse)
fine
** easier for engine to restart when the propeller is windmilling -> the crankshaft is still being rotated by the propeller so it helps the starter to “catch” onto it
in a feathering system (multi engine), when the governor decreases oil pressure, the blades become more ________ (fine/coarse)
coarse until fully feathered 90º
**we’d rather cut our losses with one failed engine and focus on minimizing that drag since we still have another working engine. plus it’s hard to try to restart a windmilling propeller, whereas single-engine you don’t have another option but to try to restart that engine
in a non-feathering propeller, the governor has ______ to oppose the oil cavity
in a feathering propeller, the governor uses __________
spring
counterweight and large springs
what is an un-feathering accumulator
if we want to restart the engine after the propeller blade is feathered, we can use this accumulator - sends high pressure oil from storage to the propeller hub so that the blades can quickly become full fine so that you can restart
what gauge will give you the best indication that your engine has failed
exhaust gas temperature (EGT)
when the engine fails the MP gauge is not a useful instrument to show that it quit because it’ll still show some pressure. How?
what about the propeller RPM gauge?
even when windmilling, the pistons still try to draw air in (which the MP gauge reads)
when windmilling, still getting an RPM value
only gauge is EGT because a dead engine drops to 0ºC
while cruising at 4000 ft with 20in MP and 2000 RPM, you reduce the RPM to 1200 RPM. what would the MP gauge show.
what would it show if you increased RPM to 2700 RPM?
(nothing else changes but RPM)
slower RPM = slower pistons = sucks in less air = less of a vacuum = higher MP
faster RPM = more of vacuum = lower MP
the carburetor regulates the amount of fuel/air that enters the engine by _______
weight
what does an accelerator pump do
provide additional fuel for sudden engine acceleration
what does the economizer valve do?
small needle that allows more fuel to flow through at high power settings (to keep engine extra cool during high power)
what does the idle jet do
allows engine to keep running by adding a small splash of fuel periodically when throttle is closed
induction ice vs impact ice
induction ice = ice on intake port at front of cowling (below 0º)
impact ice = inside pipes (oat -4 to 25ºC because in venturi it gets colder)
severe carb ice when _____ humidity and oat between _________ OCCURS
high
-5 to 15º
fuel ice occurs between _____ºC
4 to 27ºC
what’s the first sign of carb ice in a fixed pitch propeller? constant speed plane?
fixed = RPM drop
constant speed = MP gauge
if there’s an increase in RPM or manifold pressure after turning on carb heat, what does that tell you about your mixture
it was set too lean
how does a fuel injected system work?
the fuel control unit senses how much air is passing by the throttle
the FCU sends metered fuel to the fuel distributor
the fuel distributor calculates ratio corrections and sends a specific amount of fuel into the intake manifold of each cylinder
fuel sprayed into pipe
a fuel injected plane is hard to start at high temperatures. why?
vapour lock
fuel sitting in pipes evaporates = air bubbles in pipes
explain the electrical system
battery alternator ammeter
load meter
voltage regulator
battery supplies power to the starter, which starts the propeller spinning
spinning propeller = spins the alternator, so that it can generate it’s own electricity and recharge the battery
ammeter shows the rate of electrical flow
load meter shows total load that the entire electrical system is using
voltage regulator controls the amount of electricity that the alternator pumps out
why must avionics be off before you start your plane?
if they’re open when you turn on the starter, the flood of electricity could fry the avionics. just want initial power surge to start up alternator, once that’s going you can turn on other systems
piston planes have what material of battery
lead
what gauges that are currently malfunctioning could suggest an electrical failure
failed flaps
fuel indicators zero
oil temperature zero
TC not working
for what purposes do we use synthetic oil
lubrication (linear = slippery = less friction when gliding against each other)
cooling (small = weak IMF = easy to break apart when splashed)
for what purposes do we use non-synthetic oil
cleaning (branches catch dust)
sealing (easily tangled with each other)
when do we use non-detergent oil (mineral oil)
first 50 h of new engine
when do we use detergent oil (ashless)
after 50h, it has additives to keep engine clean going forward
splash lubrication vs force feed (dry vs wet) system of oil lubrication
splash: oil at bottom of crankcase splashed upwards via crankshaft
dry sump: separate tank holds oil, which is sent to engine for lube
wet sump: oil at bottom of engine, which is sent to the engine for lube
what is the purpose of having an oil vent
in summer when oil heats up and expands, excess oil can escape out the vent so that the seals don’t get damaged
even if exit vent freezes, there’s a small backup hole close to the warm engine (oil exits into cowling so not good long term but better than short term engine failure)
is the oil filter located before or after the oil pump? why?
AFTER (downstream) of the oil pump
if the oil filter gets blocked the oil pump can still pump oil through the bypass valve into the engine
in winter, a non-congealing oil cooler (one without a bypass) can get plugged up with cold oil. what do the oil temperature and pressure gauges look like
oil temp: oil stuck in one place = heat from engine will heat up oil = increase oil temperature gauge
oil pressure = increased
if you use oil that’s too low viscosity how does that affect your engine? too high viscosity ?
too low viscosity = too thin = pre-mature engine wear
too high viscosity = too thick = engine overheating
100/130 fuel
what is the octane rating at a lean vs rich setting?
at lean setting (1st) - fuel is 100% octane
at rich setting (2nd) - fuel is 130% octane
octane vs heptane
octane = slow burn
heptane = rapid explosion of combustion (can result in detonation - rapid combustion forces piston down when the upward stroke isn’t finished and damages connecting rods)
why do guys add lead in fuel
lead increases the amount of octane in the fuel
but too much can cause spark plug fouling
weight of avgas vs jet fuel
avgas = 6lbs/gal
jet fuel = 7lbs/gal
why is ethylene dibromide added to fuel
cleaning agent that scavenges lead so that the spark plugs don’t get blocked
what the heck is a gascolator
it’s like a filter
fuel pushes against the screen at high pressure, so all the dirt gets pushed against the screen but can’t get through. as you’re flying the screen gets dirtier. but when you shut down, there’s no more fuel flowing so the dirt drops to bottom of gascolator. we test the fuel sumps in wings and gascolator to see how dirty our fuel is
why do we have to immediately refill the fuel tank after flying
if we leave a tank half empty, the air at the top of the tank will eventually cool, condense as water and water goes into the fuel
- but don’t overfill tank because on a hot day the fuel will expand so we don’t want it to burst
uh oh, someone forgot to put the fuel caps back on the top of the wing. why is that a problem
the airflow over the top of the wing is such low pressure (vacuum) that the fuel will get sucked out the wing
why do we have fuel vents
where are they located
what happens if the vents get blocked
allows air to enter fuel tank and force fuel towards the engine
and if it’s a hot day and fuel expands, excess fuel can drain out so that it doesn’t burst
under wing and fuel caps
fuel starvation
what are fuel baffles for
prevent fuel from sloshing around
- less wear on tank
- keeps bob more stable = accurate readings
detonation vs pre-ignition
do this issues occur in each cylinder or only one specific one?
detonation: fuel has too much heptane so it combusts explosively and sends piston downward early (occurs in all cylinders because it’s a fuel mixture issue)
pre-ignition: sticky lead puddle on ONE cylinder head overheats and causes combustion with the gases before the spark plugs fire and sends piston downward early
what do you do when you have vapour lock
get cool fuel circulating through lines before starting plane
what is primer used for? what happens when you over prime
sprays atmoized fuel into cylinder so that the first combustion is easy
over priming = flooded engine that can lead to fire
why must the plane be grounded when filling up the tanks? how can you ground different parts of the plane?
to discharge the built up static that accumulated on the plane during flight
bond different components to each other, and connect it to the ground wire
high wing vs low wing fuel system
high wing system: fuel to engine via gravity, and can drain from both tanks at same time
low wing system: need a pump to drive fuel upwards, either right or left tank at once
is jet A or jet B fuel good for extra cold temperatures? does it require Prist?
jet B for cold weather
doesn’t require prist because prist is an anti-ice agent, but since jet B fuel is good in cold conditions we don’t need an additional ice additive
any jet without fuel heaters is required to have
FSII
fuel system icing inhibitor (prevents ice from forming)
air transport planes without fuel heaters are required to have
Prist
- anti-ice
- kills bacteria/fungi
- prevents fuel from congealing
what is waste paste (kolor kut)
(fueling from a drum)
put this water paste on your dipstick before inserting into drum. if it changes colour, there’s water in your drum
in a piston plane, pressurization is done by a __________
in a big jet, pressurization is done by the __________
turbocharger
compressor
how does an engine-driven vacuum pump work
how long until a vacuum pump expires
engine connects to gear, gear spins the cylinder inside. as the inner cylinder spins, loose pieces of carbon pop out. as the vacuum pump spins, it sucks air into system and past gyros, which spins the gyros
500h because the carbon pieces get worn out
types of anti-icing systems for wing and propellers
- glycol (anti-freeze) fluids
- heated propellers/windshielf
- hot bleed air directed to wing (in flight only because when taxiing you won’t have enough cold air so the wing will melt)
the maximum allowable speed that a plane can accelerate to during takeoff, is determined by what
tires
- don’t want to accelerate faster than tire limit
peak power is reached by during climb by: doing full rich during or peak EGT?
full rich
peak EGT is best economy for cruise
during flight in a piston-powered, TWIN plane, there’s a drop in airspeed and carb icing. after carb heat is turned on, what gauge is affected and what will it show?
MP will drop and then increase as carb ice is melted off
twin plane = multi engine = constant speed prop = RPM always stays same via governor, the only thing that changes is the MP
