Revision Flashcards
3 advantages of modular engine design to the operator?
Considered a minor repair
Easy transportation
Reduced need for spare parts
Modules replaceable on the wing
No re-balancing
Easy removal of modules
When a fan thrust reverser system is designed what must be ensured about the airstream?
The cascades direct the air away from other engines and the undercarriage
What effect will increasing the airflow velocity have on the angle of attack of a blade?
Decreasing angle of attack
At what angle is the air deflected forward on a cold stream thrust reverser?
Between 45 and 60 degrees
what is the optimal fuel/air mix?
1:15
What is the purpose of the turbine?
To provide the torque to drive the compressor also driving the accessory gearbox.
What effect will ram air have on engine thrust?
Engine thrust will increase
What shape does an inlet form?
A divergent duct
What percentage of air from the compressor is used for cooling?
70-80%
What is meant by the term “sub critical”?
The demand from the engine has dropped and the shock wave has been expelled to create a bow wave causing a reduction in pressure
Where are abradable shrouds found on a fan module?
On the inner wall of the fan case
What is used in airflow linings to reduce noise and how is itachieved?
Honeycomb acoustic liners that convert noise energy (sound waves) into heat energy.
What is the maximum number of stages used on a centrifugal compressor engine?
Two
Why is the flame tube only secured at one end?
To allow for thermal expansion
What will hotspots on the flame tube indicate?
The cooling airflow us not correct or the ceramic lining is damaged
What is the most common method of attaching turbine rotor blades?
Fir tree root
What components comprise the combustion section?
The casing and the flame tube
What percentage of air from the compressor is used for combustion?
20-30%
What are the three different methods of securing rotor blades?
Axial dovetail slots, circumferential dovetail slots and bolts/spins
On engine shut down what is the contraction sequence of the turbine and the casing?
Turbine shrinks faster first then casing shrinks faster after
What is the highest heat to metal contact in the engine?
1st stage hp turbine ngv
How is vibration reduced in LP turbine blade?
By the use of shrouds
What is the purpose of the exhaust cone?
The cone guides the discharge flow and prevents turbulence, it also prevents gas re-ingestion at the turbine frame.
What section of the FCU is responsible for engine speed control?
The governing section (part of the computing section)
What is the purpose of the reverse interlock?
To prevent power being increased until the thrust reverser is fully deployed
Where on a FADEC engine would you normally find the FCU?
There is no FCU fitted to a FADEC engine
Why must the engine be run at idle rpm prior to shutdown?
It allows the engine to cool down
Which of the following pumps has the greater pumping capacity? Pressure or scavenge?
Scavenge
The engine fuel system is split into which two sub systems?
Control and distribution
What two methods are available for latching hydraulically operated thrust reverser do in position?
A latch mechanism or locks with an actuator
What is the purpose of the de-oiler in a vent system?
To separate the oil from the air before the air is vented overboard
What type of anti-freeze will damage titanium blades?
Methanol
At what pressure will the frangible disc in a fire bottle burst?
1700psi
Where do fire extinguisher firing circuits get their power?
Hot bus
Which compressor is protected by the variable bleed valve?
LP compressor
What is used for active clearance control on a compressor and why?
Warm air is used as there is no source of air cold enough for cooling
If bypass fuel is used to cool the IDG, what else is usually fitted and why?
A recirculation valve is fitted
What systems are affected when the fire button is pressed?
Fuel, hydraulic, air & electric
What is the definition of a turbo shaft?
A gas turbine engine that delivers power to anything other then a prop
What is a bowed rotor condition?
Where the engine bends due to different contracting and expanding rates due to temperature
How does a centrifugal particle separator remove debris?
A swirl is intruded into the air flow by vanes, this cause any debris to be flung outwards
Why do we have apu on aircraft?
Standby source of bleed air and electrical power in the event of engine failure.
How is the flame tube protected from extreme temperatures of combustion?
By using the secondary airflow
What is a compressor stall?
Airflow separation from the compressor aerofoils causing turbulent flow across the stage, the engine rpm drops and the engine can run roughly
What effect will pneumatic engine anti-icing have on the operation of an engine?
EGT will rise as air is bled away from the engine
