Exam 1 Flashcards
Needs necessary for engines for modern military applications such as multi role aircraft
Drag of the engine
High specific thrust
Short takeoff and vertical landing
What are the advantages of turbine engines over rockets, ramjets, and pulse jets?
- can operate without forward momentum
* do not need to carry an oxidizer
How can missile firing and operating the aircraft at high angles of attack effect the engine
Can stall the compressor blades
Surge
What percent of the fuel burned in the combustion section of a turbine engine is used to drive the compressor?
66%
Disadvantage of interstage bleeds vs the advantage of variable stators during turbine engine part speed operation
When using the bleeds energy is wasted through the work done to compressor air, air that is not used for combustion
Advantages of using a multiple chamber combustor system
- reduces time to maintain combustor
- can accommodate larger combustors for better emissions
- testing during development is simpler using only one chamber
Regarding military engines and being able to cope with missile plume ingestion, what are some conditions that might cause extinction of hue flame in the combustor?
- momentary increase in inlet mass flow and temp
* secondary effect of depletion of oxygen
What is the main purpose of the rotating turbine blades?
Drive the compressor
Accessory gearbox
Power the prop/rotor blades/fan
What are the consequences with new technology that allows for turbine blades to withstand more heat
High temps in turbines Less cooling air Smaller compressor High % of fuel used for thrust Lower TSFC
What is the purpose of using bleed air on the turbine case?
Cooling turbine blades
What tool is used in access ports in turbine engine casings that support health monitoring
Borescopes
What engine indicating probes are typically found in exhaust ducts
Thermocouples (EGT)
Pressure ratio probes (EPR)
Why are thrust reverses not typically used below 50 knots
Foreign object damage
What are the circumstances for which a pilot could accidentally over temp an engine during reverse thrust
On a non computer controlled engine
How does burning fuel in the afterburner increase thrust
Increase thrust by adding fuel to the exhaust gasses and igniting it
What greatly affects operational noise levels of an aircraft
Engine design and airframe
Emissions produced from a gas turbine engine are a direct result of what
The combustion process
Why is the starter typically the basis design with regards to the accessory drive system
Starter often provides the highest torque that the drive system encounters
What type of forces can ball bearings withstand
Radial and axial forces
How does a labyrinth seal work?
Seal creates a resistance to airflow by forcing the air to transverse through a series of fins
What is the correlation between the FMU and VIGVs
The FMU is a servo pressure source for a remote actuator to operate the VIGVs of the HP compressor
How does fuel within the wing tanks rarely go below -35 degrees Celsius
Heating of he wing structure caused by the aircraft speed
What is the function of a FOHE
Extract heat from the engine oil providing oil cooling and fuel heating
Why is it that turboprops have spa separate oil reservoir that cannot be depleted by leakage from the basic oil system
So that the propellor pitch can be feathered if the engine has to be shut down inflight after loss of oil
What is he correlation between FADEC and EEC
At the center of the FADEC is he EEC
What does the FMU do with unwanted fuel and what are the consequences
Cycles it back through causing he fuel to heat up
