2 Flashcards
What are the tasks of an aircraft engine?
It supplies hydraulic power, electric power and bleed air for the pneumatic system. It also gives thrust.
What are the disadvantages of piston engines
over gas turbine engines?
High to power ratio and performance loss in
high altitudes.
How is propulsion force created?
By accelerating air pressure.
Jet propulsion is also called?
Reaction engine
What are the two ways of increasing the
pressure?
High pressure by compressor and volume of air when a fuel/air mixture is burned.
How is thrust generated by turbofan engine?
Large mass of air with low velocity.
How much thrust is generated by the secondary
airflow?
80%
What is the formula for thrust?
Mass of air X velocity of air
Which airflow produces the majority of the
thrust?
Secondary
What is bypass ratio?
Secondary over the primary airflow.
Exhaust Gas collide with ambient air?
Produce more noise.
Thrust?
Mass of air and velocity of air.
Turbo jet?
More velocity, less air. Low bypass engine.
Thrust generated by turbofan?
Secondary and primary.
Divergent?
Decrease in velocity, increase in static pressure
Gearbox in turbo prop?
Manage the torque being given by the turbine.
Modular?
modern aircraft engine. Is split into a set of separate major modules
Cobalt base alloys are used for?
Stator of the 1st stage of HPT.
Titanium base alloys are used for?
Mainly used in fan, the lpc and front stages the hpc.
Nickel based alloys are used for?
Hpc, hpt, lpt.
4 cycle of a gas turbine engine?
Induction, compression, combustion and expansion.
How do you increase the energy?
combustion
The static pressure in the combustion chamber is?
constant
It supplies a continuous flow of air to the combustion chamber?
compressor
Compressor
increase in pressure and
temperature
Kinetic energy to mechanical torque?
turbine
It drives the AGB and compressors
turbine
Pressure relationship between two different areas?
pressure ratio.
Compressor discharge pressure over compressor inlet pressure
40 : 1
means that the discharge is 40
times the inlet.
Turbine pressure discharge over inlet pressure.
To increase the service life of an engine?
flat rating
Engine indicators of thrust?
rpm or n1, EPR, TPR.
To monitor air flow in engine pressure and temperature
airflow station designations
Service life of an engine can be increased if the exhaust gas temperatures are always
kept as low as possible.
During cold day
more dense and more
thrust.
Test bench / test cell
on the ground, thrust
force of an engine can be measured on test
bench.
Why is the engine air intake a diffuser?
Divergent, to increase static pressure of the
air.
Engine is running but aircraft is not moving?
Negative pressure, no ram air effect
Why is there a need to decrease air entering the
compressor?
- Minimize energy losses caused by temperature increases.
- Disturbs or reduce the airflow and increase the temp. of compressor
What is the purpose of the divergent engine air
intake?
Decrease the velocity, increase static pressure.
What air is used for anti-icing the engine?
Hot air directly from the engine of that particular engine.
What air is used for anti-icing the wing?
Hot air from pneumatic system, apu or engine
Can you switch anti-ice in one engine only?
Yes, it has individual switch per engine.
Can you switch wing anti-ice individually?
No because it operates symmetrically.
How many switches are there for wing anti-ice valve?
Only one
How many switches are there for engine anti-ice valve?
One for each engine. Independent anti-ice switch.
In what position can you lock the wing anti-ice valve?
In closed position only.
In what position can you lock the engine anti-ice valve?
In both open or closed position.
When will the fault light appear in the switches?
During transit and when there is a
disagreement of switch.
Subsonic speed needed by the engine.
What are the 5 main sections of a gas turbine engine?
Fan, compressor, turbine, combustion and
exhaust
What is the purpose of the compressor?
Continuous supply of air to the engine combustor.
What are the characteristics of air as it comes out of the compressor?
Constant velocity. Temperature and
pressure increases. Volume decreases.
What are the two types of compressor?
Centrifugal and Axial
What is the main advantage of axial compressor
over centrifugal compressor?
It produces higher pressure.
How do you define an axial compressor stage?
Rotor followed by a stator
What is the purpose of rotor blade?
Imparts velocity
What is the purpose of stator vane?
Transforms velocity(constant across the compressor) in pressure(increase)
What is a centrifugal compressor?
Consist of impeller and diffuser. Used on small turbine engines like APU’s. Air is sucked horizontally.
A centrifugal compressor consists of?
Impeller and diffuser
What is the compressor ratio of an axial flow compressor?
1.3 : 1
What is the compressor ratio of a centrifugal flow compressor?
5 : 1
What is the most efficient centrifugal compressor?
2 stages only
Does double face impeller increase pressure?
No, it only gives higher airflow.
What is a compressor stall?
Separation of airflow
What is surge?
- Very severe form of compressor stall.
- Heavy vibrations and loud banging noises
What are the ways of preventing stall?
- Compressor bleed valves - bleed excess air in the engine. Open at low engine speeds.
- Dual or triple spool rotors -acceleration capability.
- Variable Vanes - optimum angle of attack
Where can you find the variable stator vanes?
In front/fwd of the HPC
Which kind of stall/surge is more serious?
Surge in the AFT stages of the compressor.
Where can you usually find variable inlet guide
vanes?
In front of the HPC
Is variable inlet guide vanes part of the compressor stage?
No
Streamline the airflow, mounted and bolted into the fan?
Spinner cone
What are the conditions that cause stall or surge in the engine ?
Dents or ice, damaged rotor blades, damaged or broken combustor, damaged
turbine components.
Compressor stall due to?
- Low speed - fed stages supply too much air
to the aft stages. - Fast dec. - rotor speed of hpc decreases faster than lpc.
- Fast acceleration - leads to much fuel into the combustion.
What component produce majority of the thrust?
Fan
. Outlet guide vanes? Location?
They improve the airflow into the fan nozzle. Stator vanes located in the fan duct.
Inlet guide vane? Location?
Improve the airflow into the first compressor stage. Fixed or movable. It is located in front
of HPC.
Data location on blades?
Blade root. You can find P/N, S/N, moment weight.
Where is fan blades mounted?
Rotor blades
Suck in air and push it to the outlet side of the rotor. Increases in energy flow.
Stator vane
Guide and slow the airflow to cause an increase in pressure
Rotor is always the first part of a compressor stage.
Angle of attack on the rotor blades and stator vanes is small?
Airflow is smooth
. Stall
high egt.
Soft tip spinner cone
Cause small imbalance which prevents large ice build up
Used to balance the opposite blade?
Balance screws
Used to scare birds away and to know if the engine is rotating.
Spirals or white markings
The most critical area of a blade?
Blade root.
Mid span shroud?
- Additional strength and rigidity
. - Use a special coating for sliding ops.
Do not have shrouds, they are more efficient than conventional blades, they can run at lower speed which reduces noise and they are very flexible. Can whistand FOD much better.
Wide chord fan blades
Shrouded fan blade
All the impact energy absorbed by the tip.
Help to stiffen the case and prevent deformation? Adds strength and rigidity. Used for
installing other components.
Flanges
Protection for the tip of the blade?
Abradable shrouds.
Reduce/absorb the noise created by the fan?
Acoustic panels.
Protect the engine/ fuselage when the fan blade
breaks?
Cowling
Note : Pylon - engine mount - fan frame
Struts
hollow
Blades are repairing is called
Fan blade blending
Moment weight = blade mass * distance
- Found in the root blade
- Old is crossed out if new moment weight is achieved after blade blending.
Process of welding the joint?
Inertia welding
VIGV
corrects the angle of attack to prevent
stall.
Compressor discharge pressure seal (CDP)?
Control the airflow/ minimize the leak.
Rotor attachment method
- Locking lug
- Retainer ring
What is used to inspect the engine ports?
Borescope Ports
Two zones of combustion chamber?
Dilution and primary zone.
Why do we have to slow down the air before
entering the combustion chamber?
To have a complete combustion inside the combustion chamber.
Used to reduce airflow?
Diffuser
Shape of diffuser?
Divergent
Coating used to protect excessive heat?
Ceramic coating
Flammable mixture requirements? Primary conditions for correct and safe combustion?
Correct ratio of fuel and air and air velocity must be slow enough inside the combustion
chamber.
types of combustion chamber?
- Can type
- Can annular
- Annular combustor
2 airflows in the combustion chamber?
- Primary airflow 20% to 30%
- Secondary airflow 70% to 80%
Primary is for what and how many percent? (In combustion)
20% to 30% for combustion.
Secondary is for what and how many percent?
(In combustion)
70% to 80% for cooling.
Dilution holes is for what?
Large
Film cooling holes?
o create a film preventing direct contact of the inner liner and the heat from the combustion chamber.
To produce a hot stream of gas for the turbines and for jet nozzle?
Combustion chamber
Ideal air to fuel ratio?
15 : 1
It accommodates the fuel nozzles and igniter plug?
Combustion case
Turbine stage
- HPT Stator/Nozzle guide vane - unang tatamaan ng hot air.
- HPT Rotor 2nd.
Igniter plug
- Lower part, because more parts of air is in the lowest part of the chamber.
- Can be used also as borescope hole.
To create turbulence for proper mixing of air:fuel?
Swirl vanes
Why do we need fixed and movable liner?
To have a thermal expansion allowance.
Turbine section is consist of?
Stator and rotor
Purpose of nozzle guide vane?
Direct the air to the rotor blades.
Purpose of the rotor vane in the rotor stage?
Kinetic into mechanical torque
Rotor blades in axial?
Fir tree
. Advantages of fir tree shape?
- Many contact surfaces advantage and the loads are transmitted gradually.
Why are turbine blades are susceptible to damage compared to compressor blades?
Because of high temperature.
Two main function of turbine?
It drives the compressor and accessory gearbox
What part of the high pressure turbine (hpt) has the highest heat to metal contact? First component that will be hit by hot gases from the combustion.
HPT nozzle guide vane (stator)
Two types of turbine blades?
Impulse and impulse-reaction/reaction
What is impulse?
- Impulse turbine relies more in the impact of the air in the blade
What is impulse reaction?
Accelerate by impulse and reaction
What is Creep?
Permanent deformation
3 factors of creep?
High temp., centrifugal force and time.
Purpose of the shroud in the turbine?
Reduce vibration
Why maximum egt should not exceed?
Can cause damage
N1?
Fan speed, LPC, LPT
N2?
Core speed, HPC, HPT
Turbine cooling
- Convection - easiest method hollow turbine nozzle vanes and rotor vanes
- Impingement - inserts with many holes.
- Film cooling - drilled cooling air holes.
Large tip clearance cause what?
More fuel consumption
Engine speed tip clearance
- Low STC - no much cf, only temp.
- High STC - due to high centrifugal force.
Clearance control system
- Active - regulated by vanes
- Passive - unregulated
Best speed tip clearance?
Optimum STC.
. Cooling tubes
- LPT cooling tubes - circular shaped, holes pointing directly to the turbine case
- HPT cooling tubes - rectangular shapes, bleed holes are at the edges, blows air to
the thickest layers/parts.
Solenoid valve
- Close or open only.
- Also called two position valves
FADEC
Full Authority Digital Engine Control
Interstage seal
minimize the leakage
It is designed to absorb the loads of the blade?
Stage disc
Turbine frame function
- First absorb the aft bearing loads
- 2nd is to provide attachment points for turbine frame/ rear engine mount.
Frame struts
- Radial - minimize expansion of struts and keeps stress on the frame hub low. But it
tends to crack. - Tangential - minimize stress caused by thermal expansion. If they expand, they will cause the hub to rotate slightly.
Purpose of exhaust nozzle?
Accelerate the exhaust gases into the hub of the turbine rear stage.
Purpose of exhaust system in turbo prop?
To discharge safely the airflow overboard
Purpose of exhaust system in turbo fan?
To discharge safely the airflow overboard. And create 20 % of thrust from the primary
airflow.
Purpose of exhaust system in turbo jet?
Accelerate airflow and make thrust.
Interlock position? Thrust reverser interlock sys.
- It makes sure that the engine power can only be increased after the reverser is fully
deployed.
. If only one thrust reverser is not fully deploy, it
goes to reverse idle.
The reverser control system is always protected
by the air ground logic.
- Deploys only on ground
- Some a/c 10ft below can deploy.
- Must be manually selected on the cockpit
It prevents reverse flow of the exhaust gases into the hub of the turban rear stage? It guides the
discharge flow and prevents excessive turbulence
of gases.
Exhaust Cone
Exhaust nozzle
- Separate - primary and secondary airflow.
- Common - mixes hot and cold gas flow. Reduce high exhaust gas velocities and gives higher propulsion efficiency
It improves the mixing of the hot and cold gas
flow to get higher propulsion efficiency?
Exhaust gas mixer
It aerodynamically stop the aircraft during landing?
Thrust reverser and brakes
Type if thrust reversers:
- Bucket door
- Clamshell
- Cascade vanes
- Pivoting door
Stall is accompanied by high egt.
Ball / Fixed
axial and radial
Roller / floating
radial load and it supports thermal
expansion.
Direct lubrication
- oil is directly sprayed onto the bearings.
- bearings with low loads.
- more intense lubrication
Indirect / underace lubrication
- sprayed on the inner wall
- oil stays on wall due to centrifugal force
Carbon seal
- used in AGB and sumps in bearing compartments.
- prevent leakage of oil
Do we use brush seals?
No
Pressure balancing
reduces axial load
Mas malakas na axial load sa compressor?
forward direction.
Mas malakas na axial load sa turbine?
aft direction
Accessory drive system is used to power the electric and hydraulic system.
High pressure rotor
the rotor which is used to
turn the AGB
The diameter of the radial bevel gear is usually
smaller than the diameter of the horizontal.
Horizontal bevel gear
more teeth, rotates
slower than radial bevel gear.
Radial bevel gear
- less teeth, rotates faster
than horizontal bevel gear.
At a certain speed bibitaw yung starter using the
CLUTCH
During starting
HPC starts first, then followed
by ignition then fuel. Painitin muna using ignition then fuel.
In the AGB all the accessory units rotates and
interconnected to each using the
Gear Train /
Spar gear
Wind milling
can damage the bearings of your engine due to not enough oil is lubricating the
bearings.
1:1
1 revolution sa manual hand crank device
equals 1 revolution sa HP rotor.
Hand crank device
for maint.
Oil damped bearing
reduce dynamic loads. Oil
muna mag absorb ng load then the bearing.
Air seals / outer seals
minimizing air escaping
from the cavities
Oil seals / inner seals
prevent oil from
escaping from the bearing compartment.
Viscosity
Resistance to flow
Flash point
the lowest temperature at which it begins
to vaporize.
Flash point of oil?
high flashpoint
Flush point of fuel?
low flash point
Synthetic
recommended engine oil for gte.
3 purpose of oil in the engine?
Cleaning, cooling, lubrication.
It houses the bearing compartments?
Sump
What is dry sump?
Scavenge system and external tank
What are the basic lubrication subsystems?
- Vent
- Monitoring
- Scavenge
- Oil reservoir and supply
Under oil cooler:
What is used to cool in oil cooler?
Fuel
Also known as a heat exchanger?
Oil cooler
Which has the higher pressure ?
Fuel
Which is better: oil to contaminate the fuel? Or
fuel contaminate the oil?
Fuel to contaminate the oil
How will you know if your oil is contaminated with
fuel?
- If you smell fuel in the oil tank (fuel contamination)
- abnormal quantity of oil (laging uno or pabago-bago yung oil tank)
It can damage the heat exchanger or leak?
Mixed fuel and oil
What type of sump is the scavenge system?
Dry sump
Meaning of SOAP? And what particles it can
detect?
- Spectrometric Oil Analysis Program
- Small particles that cannot be caught by oil
filters. (0.001 to 0.02 mm)
Consist of 2 magnet?
Electronically Monitored Magnetic chip
detector
What will happen if the gap between two magnet is filled with metal?
- The resistance between the 2 magnets gets below its limit and sends a maint. message
for the PFR. (MAGNETIC CHIP
DETECTED) - This completes the circuit. There is a chip
detection
Why low pressure pump is needed?
To prevent cavitation going to the high pressure pump
Oil temperature sensor
Thermocouple - hot areas. Return and scavenge lines.
- Thermistor - supply lines. Warm areas.
Lube analysis
If there’s an engine deterioration
When you identify the material…
You can identify the engine part with wear.
Scavenge oil filter
- 0.015 mm particles
Magnetic chip detectors
- Manual - removed manually to check for chips.
- Electronic - electronically monitored. Only
one, called main/master.
Wait for 5-20 min.
Anti-Siphon which stop the flow of oil during
shutdown.
A wrong detector installation can lead to a leak
in the oil system and in-flight shutdown of the
engine.
Fuel is used for?
- Combustion
- Servo fuel/muscle pressure
Where is the main fuel flow?
Combustion
What is fuel heater? And what it is used to heat
the fuel?
- Heat the fuel
- Oil is used to heat the fuel
Can FCU can control the engine it self?
Yes it can.
Two major sections of FCU?
- Fuel metering section - make sure that necessary fuel gets to the fuel nozzles and
all the fuel, which is not needed for combustion returns to the fuel pump - Computing section - governing and limiting
section. Limiting is for protection, governing
is for N2.
It meters the fuel that is needed for combustion.
It is also responsible for supply and shut off of fuel
to the fuel nozzles at the combustion chamber
Fuel control unit
It measures the actual fuel flow and transmit
signals to the cockpit for fuel flow and fuel used
indicator.
Fuel flow transmitter
To have a better spray saturation of the nozzle?
- High pressure compressor
- 900psi
Over- pressure relief valve?
- To prevent damage
- 1250psi
It only opens when the fuel is too hot?
- Fuel recirculation valve
- Fuel goes back to the tank or cooling of idg
or engine oil.
It can control engine speed and fuel servo
system?
FCU
FCU signals uses
- Hydraulic signals
- Mechanical signals
- Pneumatic signals
A digital computer as a full authority over the
engine control functions?
FADEC
t talks about cooling, clearance control and
compressor control?
AIR SYSTEM
Compressor control?
IN HP AND LP (the
variable bleed valves).
During engine shutdown the VIGV and VSV
is medyo close, it allows the smallest
possible angle of attack because your
engine needs less air going shutdown.
During shutdown, HPC slows down
because less air is needed at the same time
the VBV is open.
At designed speed, VBV is close. VBV is
open to prevent stall and pag shutdown and
starting.
HPC bleed valves
in mid-point or bandang
last stage. To bleed excess air.
Clearance control?
UN HPT AND LPT,
SOMETIMES COMPRESSOR
What kind of air is used in the HPC rotor? -
HOT AIR or WARM AIR.
What kind of air is used in the turbine case?
cold air
It improves the efficiency of the engine?
CLEARANCE CONTROL
The purpose of external cooling system
aside form cooling?
FOR VENTILATION
OF THE CORE, TO PREVENT
ACCUMULATION OF FUMES AND
GASES. IT ALSO VENTILATE LEAKS
What is used to cool the fan compartment?
ram air
What is used to cool the core
compartments?
fan air
What is more pressurized? The fan or core
compartment?
the fan air, to prevent the
propagation of fire coming from the core.
The air called after the low pressure
compressor
the lpc discharge or the hpc
inlet air
Components of ignition?
lead, exciter,
starter.
Starter/starting system consist of
starter
duct, starter motor and starter shut-off
valve.
There are two INDEPENDENT ignition
system.
One independent is always powered by
EMERGENCY BUS
- it’s a NO-GO item.
The other one is normal powered.
Starter supply duct
connects the
pneumatic system and the starter motor.
Sources of air for starting?
APU, the other
engine, or GPU.
Time at starter can be used continuously?
Time at starter can be used continuously? -
Duty Time (2mins)
Indicates a successful start?
EGT indicates.
Two types of starter?
pneumatic and
electric.
Pneumatic starter
for engine, (may turbine)
Electric starter
for APU (walang turbine)
Starter has HI TORQUE, LOW SPEED.
Common to both electric and pneumatic
starter?
starter clutch
Starter shut-off valve?
spring loaded
closed so the solenoid is used to energize
the valve to open
Cooling for starters?
oil is used
Starter check for oil level and for chip
detection. Check for contamination and
deterioration.
Fwd. thrust lever
informs the FCU on how
much thrust is requested.
Starter lever
switch the fuel on and off.
It is used to transform mechanical input to
electrical signals
resolver
Control lever has two seperate switch
signals.
Thrust reverser / reverse lever lock system
prevents simultaneously movement
between reverse thrust and fwd. thrust
Continuous ignition
pag nag flame-out or
icy conditions.
Start ignition
one time only pag
combustion, tapos off na.
ECU
ignition system. Spark and ignite the
fuel: air mixture in the combustion system.
Ignition system
ignition exciter, igniter
plug, ignition leads and electrical power
supply and switches
DC high voltage ang labas.
Ignition lead sa
core area may cooling, sa
fan area wala masyado kasi medyo
malamig na dun.
Immersion test
pag nagalaw mo lang yung
bushing pero pag remove and replace lng
ng plug no need test.
Ceramic igniter plug
must not drop
Ignition exciter
may low voltage (1
spark/sec.) and high voltage (2 spark/sec.)
ignition lead cooling
fan air or booster air.
Pag nasa self-sustaining speed na di pa rin
bibitaw ang clutch until maabot nya yung
starter cut-out speed. (N2)
EPR
has an inlet pressure switch and
turbine discharge pressure switch.
If one thermocouple probes is damage or
loss
may indication pa rin pero it’s less accurate.
EPR
indicates or measure thrust using
pressure.
Thermocouple is made up of chromel and
alumel.
Fuel flow transmitter
fuel flow and fuel
used. 2nd law of motion.
Tachometers
units in RPM, used to
measure thrust by rotation
Engine trend monitoring
To prevent larger
performance reductions or even engine
problems during flight. Monitoring tool that
alerts us to a problem at an early stage
EPR corresponds to engine thrust?
yes
Vibration increases
deterioration in engine.
Vibration sensors
sense radial
measurement direction.
Vibration sensor in HPR
distance of
vibration
Vibration sensor in LPR
bilis ng vibration.
Oil pressure indication and low pressure
indication
senses the press. diff. between
the total oil pressure in OIL SUPPLY LINE
and the VENT pressure in the oil tank.
SOAP
can find small particles that the
magnetic chip detector or oil filter can’t
detect.
Methods of power augmentation?
water or
water-methanol injection and after burners.
Water methanol injection
increase the
density of air, and higher thrust. Applied in
combustion inlet, compressor inlet, engine
inlet.
Water injection
decreases the temperature
in the combustion chamber so that you can
add fuel. It results in increase of volume
gases
Ordinary water is not used because of its
high mineral content that could cause
deposits sa turbine.
Methanol
to prevent icing, less freezing
point than water.
After burner fuel is introduced in the LPT.
50% of thrust
Exhaust of afterburner is variable.
Catalytic ignition, spark ignition, hot shot
ignition
methods of ignition.
Afterburning
also called Augmenting
Variable exhaust nozzle
must be larger
when used.
Turbo-shaft
a gas turbine energy, has
energy to shaft energy
Turbo-prop
is a turbo-shaft
APU
turbo-shaft
Turbo-shaft
not a turbo-prop.
Turbo-shaft
almost all of the power is in
the shaft.
APU
is a turbo-shaft. Turbine power to
pneumatic and electric.
Turbo-shaft is efficient than turbo-jet.
1st action when propeller speed increases
always move the blades into a more coarse
position.
2nd option is to reduce the fuel flow.
90%
turbo-prop generated thrust
Turbo-prop exhaust
static pressure and
temperature decrease.
Twin levers found in the turbo-prop?
condition lever and engine lever
Alpha mode
engine power controlled by
engine lever and propeller is controlled by
condition lever
Beta mode
engine power controlled by
condition lever and propeller is controlled by
power lever.
Propeller speed
condition lever
Fast rotation speed and small angle results
in
slow aircraft speed.
Shaft power engines
turboprop and
turboshaft
TPE
almost always an axial reaction type
turbine
TPE
free turbine connected to the
reduction gearbox.
Propeller
is connected to the reduction
gearbox.
Reverse flow combustion
reduce the
length
It reduces the shaft speed
reduction
gearbox.
Optimal rpm of the propeller is 850 to 2500
Adjustment areas of propeller blades
high
pitch, low pitch, feather position and
reverse.
High pitch
high airspeed
Low pitch
low airspeed
Feather position - for emergency and
for emergency and
Flight idle is higher than ground idle.
Free turbine connected to the reduction gearbox and from the RGB to the propeller.
How is one engine prevented from driving
the other engine in helicopter?
Free wheel
To allow the engine to drive the
transmission and prevent the rotor from
driving the engine.
free wheel
Transmission
direction of movement,
torque, force and speeds can be changed
using gears.
It provides elec. and pneumatic?
APU
APU can be used in flight?
YES, when
IDG fair or engine tapos need mo more
pneumatic and electricity, mag susupport
sya.
what is the speed of the APU after starting?
CONSTANT
It controls the constant speed of the APU
APU control unit
Opening of APU inlet door?
manually and
electrically
Can you automatic start the APU ?
No,
only manually by switches sa overhead
panel sa cockpit
Purpose of load compressor ?
Provide
bleed air pneumatic to the user
Compressor of the APU do what?
provide
air for cooling and combustion
It opens the apu fuel pump and apu shut off
valve near the APU ?
APU fuel line vent
push button. It is also used for maintenance
para di kana pumunta cockpit.
2 main diff. Of engine oil system and apu oil
system?
APU has a de-oiler valve and yung oil ng apu ginagamit mismo ng generator
nya compared sa engine oil system yung oil
ng generator nya (idg) is separated.
Apu oil is cooled?
through an air/oil heat
exchanger. (Air is used to cool the oil)
3 main sections of APU?
AGB, bleed
suction and power section.
A separate compressor called load
compressor. May variable inlet guide vanes
siya. Meaning can be closed, in between,
and open.
Iikot parin ba yung load compressor kahit
nakasara yung VIGV ?
Yes because
connected sya sa turbine shaft.
Load compressor
very fuel efficient, low
egt
APU PRESSURE
30 to 45 psi
Apu does not have a constant speed drive
ang nag cocontrol ng constant speed nya is
APU FUEL CONTROL UNIT
Pre-start test
makes sure that cpu control
unit itself operates properly and sensor
signals are available
If restart test is ok
normal, automatic, apu
fire switch
Manual
using master switch, safe
shutdown. Cool down of 120s
Automatic
due to defective components.
Oil pressure, high egt, high temp. No cool
down
Apu fire switch
sa cockpit. Meron din sa
nose landing gear, main wheel well ay
refueling station
Apu fuel pump is on if not enough yung
pressure na galing sa boost pumps ng fuel
tank. To prevent also cavitation
Primary fuel system of the apu
low
pressure fuel system. Fuel tank to apu fuel
control unit.
Secondary fuel system of the apu
high
pressure fuel system. FCU apu papunta sa
nozzles.
Apu air system
bleed air and cooling air
system
Anti-surge valve
normally open during
flight. Not very efficient
Surge control valve
sa may load
compressor. More efficient
De-oiling valve? -
Apu master switch
supplies electrical
power to the apu control unit which starts its
pre-test.
Apu does not have starter shut off valve.
Common sa engine at apu ?
Starter clutch
Starter duty time
time when apu can be
used
Starter cool down time
time to be cooled
Starter duty cycle
on/off, on/off, on/off
cycle
Ignition lead ng apu
walang cooling
Class 1?
most critical parts like the air inlet cowl. Only small dents are allowed.
Class 2?
fan cowling
Opening of cowling should be in sequence because diff. Cowling overlap each other.
For example : fan cowl must be open first before you can open the core cowling.
Air inlet cowling is cannot be split.
Two index pins
this makes sure that the air
inlet cowl can only be installed in the correct
position.
2 hold positions
fully open ( access to all
components) and half closed/open
(gearbox)
fan cowl open when engine is in ground idle
is allowed. Fan reverse cowl
release the
latch then use hydraulic to open.
Cowl load sharing
uses v - shaped grooves
and blades.
2 passive fire protection of fan thrust reverse cowling - fire protective coating (for
inner side of the cowl) and fire seal (on the connection to the fan frame)
fire protective coating (for
inner side of the cowl) and fire seal (on the connection to the fan frame)
parking and mooring
close all holes on the
engine
Forward mount
bolted to the fan frame
Aft mount
bolted to the turbine frame
Aft mount
Y,Z load or the vertical(weight)
and side loads.
Aft load has no axial mount load
to allow
thermal expansion.
Bootstrap (most common), crane method
(30% faster than bootstrap), uplift method
(40% faster)
drain mast is made of frangible material
para sya lang yung masisira incase na
tumama.
Fuel overboard drain
found on pylon
Collector
can’t be emptied, if it is full the
fluid goes to the holding tank
Holding tank
can be emptied
Before you open the cowls
slats must be
retracted
In a fire protection system what happens
when you operate fire handle
generator
switched off, bleed air valve closes, shut-off
valve closes, hydraulic valve closes and
FIRE CIRCUIT engages.
Squib light is found in the AGENT push
button.
What will illuminate when the FIRE
CIRCUIT engage or activates ?
- SQUIB LIGHT.
If the bottle is empty
DISCHARGE light
illuminates.
If fire warning is still on after 30 s, must
discharge the second bottle.
What do you mean by 2 shots
can apply
two bottles in 1 engine.
Halon
used in engine fire
What will trigger the fire bottle ? Or the switch to trigger the fire bottle ?
AGENT
FIRE PUSHBUTTON
Local warning
RED LIGHT inside the
switch. The red light near the engine master
switch SHOWS the pilot what engine must
be shut down.
Central warning
aural, visual and warning
message on exam or eicas.
Dual cont. loop
engine fire detection
system
Hot start ?
high egt
Most common error when handling
magnetic chip detectors?
O-ring installation (they forgot to put O-ring)
What is blending?
repairing of blade
Borescope ports?
To view the internal parts
of the engine. INSTALLED IN BETWEEN
STATOR VANES
High egt
can be also compressor damage
Pag maagang nag disengage yung start
valve, fuel metering is wrong, duct pressure
is too low
HUNG START
When rotor cranking N1-by hand through
fan, n2 by hand cranking device through the
accessory gearbox.
Auto start steps :
Auto start
FADEC system computer
controls the whole start system. This
computer is the ECU
Auto start
step 1: engine mode selector
switch to IGN / START. Check pressure, oil,
engine start page.
Auto start
check for minimum duct
pressure of 25psi
Auto start
step 2: engine master switch on
(low pressure valve open and flows to the
HMU, starter valve will open)
Auto start
check n2 at 16% ecu activates
ignition
Auto start
check n2 at 22% ecu send
signal to hmu to open the metering valve
Fuel pressure opens the fuel shut off valve
and fuel flows to the spray nozzle.
Increasing EGT
successful start
Engine will accelerate on the thrust lever
position. Kaya dapat naka ground idle lang.
When n2 passes the starter cut out speed,
ecu send signal to color the starter valve
and deactivates the ignition
Engine master switched off
close signal is
sent to fuel shut off valve and fuel low
pressure valve
Engine spools down
Manual :
Manual step 1
ign/start mode
2:
engine manual start push button
3:
master switch on
In the manual start both ignition is on, in
auto only 1 ignition.
Engine Motoring
for engine leaks and sys.
checks. Starter motor is used
Wet motoring is always followed by dry
motoring.
Wet start
normal operation, fuel is sprayed
into the combustion chamber but engine
does not light up. (Due to ignition
malfunction). Dry motoring is need to
remove fuel
Engine stall
fuel metering is wrong, bleed
valve stuck close, degraded compressor
performance. ( also egt indication
fluctuates) ——patukan to ni sir.
First indication of a hot start?
egt is higher
than max allowable start value.
Hot start causes
maybe fuel metering is
wrong or remaining fuel from wet start isn’t
blown out.
Nick is more serious than dent
Ways to inspect an engine
borescope,
trend monitoring, lube analysis and vibration
analysis.
Preservation of engine
to protect against
elements like dirt, corrosion, FOD and etc.
Desiccants
If more than 30 days
more comprehensive
preservation is needed.
Operable
can be started
