Systems Flashcards
What is the purpose of a carburetor?
Mix the fuel and air in correct ratio and deliver that mixture to the cylinders
What happens when the butterfly valve opens?
Airflow through the Venturi accelerates, causing lower static pressure. The pressure differential between the float chamber and Venturi will increase and more fuel will flow into the carburettor
What are the three types of carburettor icing?
Fuel icing
Throttle icing
Impact icing
What are the conditions conducive to carburettor icing?
OAT below 30 degrees
Relative humidity above 80%
Low power settings for a long time
What do symptoms of carburettor icing include?
Partial or total loss of power
Degraded engine performance
Rough running
What can fuel icing also be referred to as?
Refrigeration icing
When does impact icing occur?
Super cooled water droplets hit the metal surfaces of the air intake to the fuel system
What conditions are for impact icing?
OAT close to or below zero
Aircraft is in visible moisture
What causes fuel icing?
Fuel vaporisation and cooling as it is mixed with the airflow in the carburettor
When can fuel icing occur?
OAT up to 20 degrees
Average to relatively high humidity
What causes throttle icing?
Cooling effects that result from air accelerating around the butterfly valve inside the carburettor
Is visible moisture required for throttle icing?
No
When should carby heat be used in icing conditions?
Full, intermittently
What is the most common fuel injection system?
Continuous flow injection system
Where is fuel injected by the fuel injection system?
Intake valve chamber for each cylinder
What is a supercharger used for?
Compensate for reduced density at altitude by maintaining power available at sea level
Boost the manifold pressure at sea level to a value above the normal sea level atmospheric pressure
What is turbo normalising?
Compressed air is pumped into the intake manifold to allow the engine to burn extra fuel and so produce extra power at altitudes where normally aspirated would struggle
What are the three types of wastegate?
Fixed
Manual
Automatic
What is full throttle height in a supercharged engine?
The altitude at which the rated boost is available at a certain RPM
What is the critical altitude?
The highest altitude at which maximum rated power can be obtained with full throttle
Advantages of fuel injection over carburetors?
Mixture strength can be controlled more precisely
Fuel is injected immediately adjacent to the intake valve
No icing problems
Fuel is distributed more evenly within the cylinders
What does the voltage regulator do?
Maintains correct voltage output from the alternator
Batteries in series give what?
Higher power
What is the alternator output voltage the same as?
The electrical system voltage
What kind of current does the alternator generate?
AC current
What is it that converts AC to DC power?
Rectifier
What converts DC to AC?
Inverter
How is it ensured the alternator powers the electrical system and not the battery?
Alternator output voltage is slightly higher
For a centre zero ammeter, what will you see directly after start and why?
A large plus as the alternator comes online and begins charging the drained battery
What would a large plus indicate on a centre zero ammeter in flight?
Could indicate an electrical system problem - however definitely indicates the battery is supplying power
What does a load type ammeter measure?
Alternator output
If you saw zero on a left zero ammeter, how would you determine alternator failure or no alternator load?
Turn equipment on to see if load goes up - if not suspect alternator failure
What does a voltmeter indicate?
How many volts are being supplied to the bus bar
In a 28V electrical system, what does a voltmeter indication of 24V indicate?
Battery is supplying the bus bar
Which way does propeller thrust reaction act?
Perpendicular to the plane of rotation
Which way does the propeller torque reaction act?
In the plane of rotation
Which way does the plane of rotation of a propeller work?
Perpendicular to the crankshaft
Propeller angle of attack?
Angle between the propellers chord and the relative airflow
What is the propeller blade angle?
The angle between the chord line and the plane of rotation
What is the helix angle?
Angle between the plane of rotation and the relative airflow
What is indicated horsepower?
Horsepower available at the cylinders
What does IHP indicate?
How much heat energy in the fuel is converted to mechanical energy
What is brake horsepower?
A measure of the useful work done by a piston engine
How is BHP determined?
IHP minus the power absorbed in the engine by friction and by driving the engine itself
What is friction horsepower?
The part of IHP that is absorbed by friction and driving the valves, ignition, lubrication systems etc
At a given RPM for a fixed pitch propeller, what happens between TAS and AoA?
Increase TAS = reduce the AoA
Lower TAS = higher AoA
At a given TAS for a fixed pitch propeller, what is the relationship between RPM and AoA?
Increase RPM = increase AoA
Lower RPM = smaller AoA
What do counterweights do? (Multi engine)
Coarsen pitch
Where does the MAP gauge read from?
Between the throttle valve and the cylinder inlet valve
What is the tendency of the centrifugal twisting moment?
To fine the propeller
What is the tendency of the aerodynamic twisting moment?
Coarsen the propeller
When increasing power… (CSU)
Increase RPM
Increase MAP
When reducing power (CSU)
Reduce MAP
Reduce RPM
How do you avoid detonation in a supercharged engine?
Use only approved power settings
Use correct leaning procedures
Which valve is usually smaller?
Inlet valve
What rate does the camshaft rotate?
Half crankshaft speed
What is valve lead?
Intake valve opening just before piston reaches TDC
What is valve lag?
Intake valve closes just after the piston reaches BDC
What is compression ratio?
Volume of cylinder with piston at BDC/volume of cylinder with piston at TDC
What are the consequences of an over rich mixture?
Reduced power
Rough running
High fuel consumption
Fouling of spark plugs
What are the consequences of an overlean mixture
High CHT
Detonation
What does octane rating refer to?
The resistance of the fuel to detonation
What are some possible causes of detonation?
Overlean mixture
Unnecessarily high power settings
Excessive MAP with low RPM
Incorrect or time expired fuel
What are some fuel tank types?
Wet wing
Rigid removable
Bladder
What does the ignition harness do?
Carries the current from the magneto to the spark plugs
What are some functions of the oil system?
Lubrication
Cooling
Cleaning
Lengthening engine life
Providing a seal between cylinder walls, pistons and rings
Providing oil for variable pitch propeller system
What are oil types?
Ashless dispersant oil
Mineral oil
Synthetic oil
What are the benefits of a dry sump?
Prevention of oil starvation with high g
Increased oil capacity
Better oil temperature control
More power as the crankshaft doesn’t have resistance from oil splashing
Where is the oil pressure sensor?
Just after the oil pump
What are the benefits of even cylinder distribution of fuel?
Each cylinder produces the same amount of power
Smoother running
Easier starting
Less chance of detonation
Better power output
Disadvantages of fuel injection systems
More complex and expensive than float carburettors
More susceptible to fuel contamination due to fine fuel lines
More prone to fuel vaporisation
Vapour locks can make hot starts difficult
What are the main components of a supercharger?
Impeller
Diffuser
Compressor
What happens when a wastegate is fully open?
All exhaust gas is directed away from the turbine and the engine functions as if it were normally aspirated
What happens when a wastegate is fully closed?
All exhaust gas is directed over the turbine, creating a maximum amount of compression of the incoming air
What is full throttle height in a supercharged engine?
The altitude at which the rated boost is available at a certain RPM
What is a supercharged engine critical altitude?
The highest altitude at which maximum rated power can be obtained with full throttle
What happens above the critical altitude of a supercharged engine?
Reduction in MAP and power output
What is the name of the spring in a CSU?
Speeder spring
What happens in a failure of the speeder spring?
No resistance for the flyweights and will cause the governor to sense an overspeed condition which will drive the blades to the coarse pitch stops
Advantages of hydraulic systems
Large amounts of power can be transmitted using relatively small components
Power can be multiplied even without the use of a hydraulic pump
Hydraulic lines can be easily routed through inaccessible parts of the aircraft
Disadvantages of hydraulic systems?
System integrity is required for it to work
Loss of fluid can have serious implications such as fire, loss of control, loss of system
Weight, components and fluid can be heavy
What are the two types of hydraulic system?
Active
Passive
What should the properties of a hydraulic fluid be?
Non compressible
Thermally stable
Fire resistant
Non corrosive to its systems
Purpose of a hydraulic reservoir
Provides a reserve of fluid
Allows for variation in fluid volume
Allows for expansion of fluid due to temperature
Provides a head of pressure to prevent cavitation at the engine driven pump
Two types of hydraulic lines?
Pressure line - carries fluid under pressure
Return line - returns fluid to the reservoir
What are the functions of the hydraulic accumulator?
Help the pump maintain pressure when the system demand is high
Provide a limited emergency pressure supply if the pump fails
Smooth out pressure fluctuation and surges and so reduce vibration and noise
What are some possible hydraulic system faults?
Air in the system
Fluid leakage
Low accumulator pressure
What can air in the hydraulic system cause?
Pump may overheat due to inadequate cooling and lubrication
Air may also allow for compression reducing the power the fluid can generate
What can hydraulic fluid leakage cause?
An actuating piston which has just moved forward may move back again as the oil that drove it forward escapes
What are the effects of low hydraulic accumulator pressure?
The pump does more of the work resulting in slower operation of the system
Reduction in the emergency supply of fluid if the pump fails
May cause noisy operation and vibration
What are the two main types of gear shock absorbers?
Spring steel struts
Oleo pneumatic struts
What does the nose gear consist of?
Oleo pneumatic strut
Shimmy damper
Torque link
What does the torque link do?
Fitted to an oleo to prevent it turning left or right of its own accord
What are the two types of retractable undercarriage?
Hydraulic
Mechanical
What are the three common types of fire detectors?
Overheat - thermal switch
Rate of temperature rise - thermocouple
Flame detector - optical
What are the four types of fire extinguishers?
Water
Dry chemical
Carbon dioxide
BCF
What barometer is in an altimeter?
Aneroid barometer
How does the air enter a VSI?
Capsule is directly from the static vent
Instrument case via a choke
How does an ASI measure indicated airspeed?
Taking the total pressure entering the pitot tube and subtracting the static pressure
What happens to the altimeter with a blocked static vent
Indicates the altitude at which the blockage occurred
What happens to the VSI with a blocked static vent?
It will read zero
What effect does a blocked static vent have on the ASI?
Under read in a climb
Over read in a descent
What instruments will a blocked pitot tube affect?
ASI
What is the effect of a blocked pitot tube on the ASI?
Over read in a climb
Under read in a descent
What is PUD SUC?
Pitot blocked - ASI
Underread
Descent
Static blocked - ASI
Underread
Climb
What causes VSI lag?
The restricting diffuser in the pressure case slows the equalisation process of air pressure between the outside atmosphere and that of the instrument pressure case
What instruments are effected by alternate static source?
ASI and altimeter tend to overread
What are the two main properties of gyroscopes?
Rigidity
Precession
What is a space gyro?
Mounted in gimbals
Can be isolated from movement in roll, pitch and yaw
Main advantage of electrically driven gyros?
Faster speed providing greater rigidity and a more stable reference platform
The AH uses which gyroscopic property?
Rigidity
What property does the turn and balance rely on?
Precession
What errors does the AH show when the aircraft is accelerated?
Roll effect - false right wing low
Pendulous vanes precess into false climb
What is real wander?
DG drifting out of alignment due to friction and small imbalances. Also called mechanical drift
What are the compass acceleration errors?
South
Accelerating
North
Decelerating
What is the main purpose of fuel vents?
To avoid fuel starvation
An aircraft fitted with a constant speed propeller, what effect will reducing airspeed have on propeller pitch and RPM?
Propeller pitch becomes fine
RPM remains constant
