Engine Flashcards
The oil system is divided into
Oil pressure and scavenge system
Total loss lubrication system
Oil pressure and scavenge system provides lubrication for
Front bearing
Accessory gearbox
Reduction gearbox
The total loss lubrication system provides lubrication for
Center bearings and rear bearings, through the use of 2 metered pumps.
Oil is then discharged in the atmosphere
OIL PRESS light might appear in normal operations during
Zero or negative g flight
Oil system contains
11pints
Oil tank dimension
13.5pints
Oil qty contained in oil tank
9.5pints
Usable oil qty
6.5pints
Unusable oil qty
3pints
Max and min oil consumption
1.25pint/h and 0.9pint/h
The oil system is capable of ensuring correct engine lubrication for how long?
4h 50min
Oil qty must be checked within ____ from engine shutdown
20mins
The oil pump is connected to the engine via
The accessory gearbox
What does the oil pressure system do?
It lubriacates the front bearings, accessory gearbox and reduction gearbox
What does the oil scavenge system do?
It takes oil used from the pressure system to lubricate, and brings it back to the oil tank
OIL PRESS comes on when
Pressure drops below 0.4bar or above 2.4bar
What is the correct procedure to apply in case of OIL PRESS light?
85% RPM
If OIL PRSS is less than 0.4, then advance throttle 95%RPM for 10 sec, if it doesn’t reach at least 0.3bar, bring it back and maintain 85%RPM
Engine name
Rolls-Royce Viper MK632-43
Viper engine nominal thrust
17.8kN (at sea level under ISA)
BOV blows air when and from where
At low altitudes mainly, from 4th stage of the compressor
In what direction does the engine rotate?
Left (counterclockwise viewed from the back)
Max engine RPM
13760
The Viper is a pure turbojet based on what cycle?
Brayton Cycle
What is the peculiarity of Brayton Cycle?
It is an open cycle (since the engine is open)
What are the utilities attached to the accessory gearbox?
GEN1
GEN2
HYD PUMP
High pressure fuel pump
Oil pump
Tachometer generator
What is the function of the nose bullet at the early stage of the compressor?
To let the air smoothly flow into the engine, and not becoming turbulent (otherwise compressor stall)
Describe Viper structure
Air intakes
Nose bullet
Airflow stabilizers (3)
8 stages compressor
Annular combustion chamber
2 stages turbine
Exhaust cone
Jet pipe
How many trimmers are there in the jet pipe? What is their function?
6
Their function is to stabilize the air going out of the turbine and not become turbulent
Viper compression ratio
5,9:1
In the engine fuel system the RRV (Rate Reset Valve) function is to
Prevent fuel pressure variation coming out from high pressure fuel pump
Describe engine fuel system operation
Booster pump
LP filter
Engine Driven pump (RPM governor, RRV)
BFCU (EPC)
AFRC
Fuel flow transmitter
Pressure increase valve
6 atomizers
12 burners (24 nozzles)
What does the BFCU do?
- It controls the fuel pressure and qty to deliver to the AFRC according to:
- Engine Throttle position
- EPC - It regulates engine idling
- It incorporates the 2 fuel cocks connected to the throttle
The JPT LMTR system consists of
4 thermocouples (also used for JPT indicator)
JPTLA
EPC
JPT indicator in the cockpit receives signals from
The 4 thermocouples
The JPTLA senses temperatures thanks to
Through the 4 thermocouples by EMF (Electro Magnetic Field) changing according to the temperature
What does JPTLA do?
It compares EMG measurements (coming from thermocouples) to EMG preset values.
According to this it communicates with EPC for reducing fuel pressure in the BFCU
How does the EPC operate?
It is composed of a small pipe inside another pipe. When EPC receives signal from the JPTLA, it closes the small pipe, reducing the fuel qty and pressure going through the BFCU
JPT Limiting System can be affected by temporary overshoots during
Climbs at 100%RPM
Level flight at high altitude (above FL300), and moving the throttle to 100%RPM
EGT overshoots must never exceed _____ for more than _____
790ºC
10sec
Engine anti-ice system is provided by which bus?
Primary bus
ANTI-ICE/ENGINE switch when moved to on in flight operates
The anti-ice valve, that let hot bled air to reach the nose fairing (pin)
and
the resistors in the ducts and lips.
In case of electrical supply failure the anti-ice valve
Fails to the open position
To run the anti-ice test on the ground you must
Set power not less than 60%RPM
Move the ANTI-ICE/ENGINE switch to TEST
Why is it so important to heat the nose fairing (pin) with engine anti-ice system?
Because preventing ice formation on the pin, the airflow will be smooth and not turbulent, thus preventing compressor stall
What should you check during ANTI-ICE/ENGINE test?
RMP decreasing
TEMP increasing
LOADMETER increasing
The igniters power comes from
Essential bus
Igniters are fed with alternate current, but power comes from 28vDc essential bus. How is it possible?
AC Ignition Units convert power coming from essential bus into high-voltage alternating current to feed the igniters
The engine should light up within _____ from starter engagement or _____ from moving the throttle to idle. The system will automatically abort the start if the engine is not at self sustaining speed after ____
20sec
15sec
25sec
What is the action to take if the engine doesn’t light up within 20sec from starter?
Engine throttle STOP
ENG MSTR - OFF
In case of HOT START only Engine throttle STOP
The engine start sequence can be interrupted any time by
Moving the ENG/MSTR switch to OFF
ENG/MSTR switch controls
The starting system
The booster pump
That is why when you move the switch to ON prior to engine start, you check for BAT 1/2 and F. PRSS OFF
In what position the Engine Throttle operates the High Pressure Cock?
In the first range of travel (up to IDLE)
The High Pressure Cock moved by the engine throttle is incorporated in what unit?
BFCU
During engine start sequence, fuel coming through the AFRC and Fuel Flow Transmitter than goes into the
Starting Valve
How can the starting system automatically abort start sequence if self sustaining speed is not reached within 25sec?
By closing the Starting Valve, and de-energizing igniters and starter
Minimum windmilling is ____, but normally its value is ____
8-10%RPM
13%RPM
When is the starting valve open?
During engine start
During relight ops
The fire and overheat detection system is composed of
Fire detection system (front)
Fire and overheat detection system (rear)
Where do Zone1 and Zone2 in fire and overheat detection system start from?
From the stainless steel firewall installed just after the engine compressor
Higher temperature in Zone1 triggers _____ while in Zone2 triggers _____
FIRE
OHEAT
Fire in Zone1 can be more dangerous because of
Explosion hazards
Damage to structure and flight controls
(Fuel, Oil, Hydraulic etc are all in the front)
OHEAT light can also be triggered by
Hot gases escaping from the jet pipe
Minimum engine inflight temperature is
200ºC
Normal engine continuous inflight temperature is
300ºC - 670ºC
Igniters are located
In the combustion chamber at 4 and 8 o’clock position, in proximity of the atomizers to guarantee ignition
The fire and fire and overheat systems are capable of detecting both
Average temperature
Hot spot temperature
The HP Fuel Pump sends fuel at a pressure of
600-700psi
What does AFRC unit do?
According to the altitude and phase of fight, it manages the quantity of fuel to let in the combustion chamber according to the air quantity
When at low altitudes, BOV is open every time RPM are below_____.
It closes with increasing power at _____.
It opens again with decreasing power at _____.
78-80% RPM
80%RPM
78%RPM
Values referred to ISA
The exhaust cone has an inner case secured by
9 radial stay pins
What is the function of the Jet Pipe?
To direct gases in order to produce thrust
How many Nozzles, Burners and Atomizers in the combustion chamber?
12 burners (24 nozzles)
6 atomizers
Why the engine throttle is moved to idle only at 10%RPM?
Because at that rotation speed the HP fuel pump is providing enough pressure to the fuel going through the starting valve to be vaporized from atomizers during engine start.
If the system lets in fuel prior than 10%RPM the combustion chamber could be flooded, and therefore there’d be no ignition, or worse an explosion.
JPT limit
756ºC +5-12
JPT LMTR switch is located
In the front cockpit only
When are atomizers and igniters used?
During engine start and relight only.
NB. Secondary function of atomizers is to provide a bit of fuel during normal ops to prevent their obstruction.
HOT RELIGHT parameters
Below 20.000ft
Airspeed 120-200kias (150kias suggested)
COLD RELIGHT parameters
Below 20.000ft
Airspeed 120-150kias
Pressure increasing valve operation value
80psi
Primer check valve operation value
40psi
Why the engine is radioactive?
Because the compressor outer casing is made of Thorium (Th)
In what circumstances during takeoff you turn on engine anti-ice?
Temp<6ºC and humidity >50%
Or
Visibility<500mt
The fire and overheat detection system include 2 tests:
Failure Indication Test (by the pilot)
Failure Detection Test (by ground crew)
Illumination of FIRE SYS or OHT SYS cautions means that
The respective system is faulty
In case of FIRE/OHEAT illumination, what can be done by the pilot to confirm fire?
Run a test of the lights, if the FIRE/OHEAT doesn’t illuminate, then this is another indication of fire
