PPL-AGK Flashcards
What is the crankshaft responsible for?
Turning the linear motion of the piston into rotational motion of the propeller
What does the camshaft do?
Provides the timing sequence for the intake and exhaust valves
What is the intake manifold
The ‘tube’ that the gas flows through into the cylinder
What is the outlet manifold
The ‘tube’ that exhaust gases flow out from the cylinder
What are the four stages of the otto cycle?
Induction
Compression
Combustion
Exhaust
How many revolutions of the crankshaft are involved in one cycle
2
power output depends on what?
The amount of gas induced into the cylinders
The temperature reached during combustion
When is engine overspeed most likely to occur given no power changes
descent
Complete combustion only occurs at…
The stoichiometric ration (15:1)
Air and fuel mixture will burn between
8:1 (rich) and 20:1 (lean)
what is the advantage to a richer mixture
Aids in engine cooling (result of excess fuel)
What is density affected by
Pressure
Altitude
Temperature
When does detonation occur
With spontaneous explosive combustion
What are some common causes of detonation
High CHT
bad/wrong fuel
over-leaned mixtures
What is an octane rating
resistance to detination
What are some symptoms of detonation
high CHT
significant power loss
Engine vibration
pinging sound
If detonation is occurring, what actions should be undertaken
reduce power
increase IAS
richen mixture
What is pre-ignition
when the mixture ignites before the spark plugs fire
What are some causes of pre-ignition
Cylinders too hot
high power with lean mixture
overheated spark plugs
What are some symptoms of pre-ignition
rough running
backfire
high CHT
What pressure is used for fuel delivery in a carby
low pressure
What pressure is used for fuel delivery with a fuel injected system
high pressure
avgas 100/130 colour
green
avgas 100ll colour
blue
avtur colour
yellow
mogas colour
red
why is the fuel tank vent important
it prevents excessive pressure buildup and thus prevents implosions or tank damage
what part of the carby sucks fuel to get mixed with air
the venturi
What are the three types of carby icing
Impact ice (ice occurs on walls) Evaporation ice (fuel vaporises) Throttle ice (pressure drop results in temperature drop)
What is a symptom of carby icing
Drop in rpm without movement of the throttle
What conditions is carby ice most likely to occur
< 20 degrees C
>80% humidity
What does carby heat do
Use heat from the engine rather than the intake
Why is carby heat use on the ground undesirable
unfiltered air=bad for the engine
Why do we want the carby heat OFF during take-off
warmer air=less dense air=less power output
What doe the accelerator pump do?
Adds additional fuel to the air/fuel mixture to compensate for the lag that otherwise would occur (because the air travels faster than the fuel=leaner mixture=less power)
What are two core disadvantages to a carby system
Carby icing
Can’t be operated inverted
Why is the correct amount of fuel sent to the fuel injector nozzle in a fuel injection system?
Because the Fuel Control Unit monitors the position of the throttle and adjusts accordingly
What two sources of power are available for a fuel pump
electrical system
Engine
In the event of a fuel pump malfunction, what will occur
bypass opens allowing fuel to flow around the pump
Is higher or lower temperature fuel more likely to vaporise?
high temperature
Vapour locks can occur in what type of fuel system
Fuel injection system
What is one way to alleviate a vapour lock
fuel pump/boost pump
What is a likely indication of fuel vaporisation/vapour locks
fluctuating fuel pressure gauge
define the chordline
straight line joining the leading edge and the trailing edge
define the angle of attack
angle between chordline and relative airflow
The single force that lift acts through is known as the
centre of pressure
When will rpm be constant in terms of torque
Engine torque=Propeller torque
If engine torque > propellor torque, what happens to rpm
increase
If engine torque < propellor torque, what happens to rpm
decrease
Coarse pitch propellors are most suitable for what airspeeds
High
Fine pitch propellors are most suitable for what airspeeds
low
What does a constant speed unit do?
Varies the pitch of the propellor to maintain an optimum angle of attack
What is the aerodynamic twisting moment
A force which attempts to twist the blade towards coarse pitch ( a result of the total reaction force)
What is the centrifugal twisting moment
The natural tendency for any rotating body to align itself with the plane of rotation (attempts to achieve fine pitch)
Which is stronger, CTM or ATM
CTM
Why are propellors twisted
Because if they weren’t, the outside travels further (therefore faster), and thus produces more thrust than the inside, resulting in uneven thrust being produced and the propellor bending.
What does the term ‘feather’ refer to when talking about propellors
When the blade chord line is parallel with the aircraft’s relative airflow, minimising drag, and stopping the propellor from spinning.
When reducing power on aircraft with pitch control, what rule can we follow
power down prop down
When increasing power on aircraft with pitch control, what rule can we follow
mix up, prop up, power up
CTM moved blades towards what pitch
Fine
Hartzell is associated with …. pitch
fine
McCauley is associated with …. pitch
coarse
When is spark plug fouling most likely to occur
Low power settings when engine isn’t warm enough to burn excess oil
What is a gyroscope
An object that has mass and is rotating
What is rigidity
The tendency for an object to get all of its mass in the same plane of rotation
What 3 factors affect rigidity
Mass
Radius of mass from the object
Angular velocity
What is precession
The tendency to resist a force in one spot and displace it by 90 degrees in the direction of motion
Why would electric gyros be necessary at high altitudes
Because it is likely that not enough vacuum can be generated
What is the advantage of a vacuum driven gyroscope
Independent of electrical system
What are the advantages of electrically driven gyroscopes
Operate more efficiently (more predictable)
The AH operates off which gyroscopic principle
rigidity
The DG operates off which gyroscopic principle
rigidity
The turn coordinator operates off which gyroscopic principle
Precession
what is PUDSUC (for the ASI)
Pitot blockage under-read descent
Static blockage under-read climb
If the static vent becomes blocked, what does the altimeter do
over-reads on descent and under-reads in a climb (remains constant)
If the static vent becomes blocked, what does the VSI do
reads zero
