Airframes and Systems Flashcards
(34 cards)
Sections of a Turbine Engine
- Intake
- Compressor
- Combustor
- Turbine
- Nozzle
Centrifugal Compressor
- One or two stages
- Air enters near centre is pushed to the outside
- Diffuser slows air from compressor and further compresses it
- More durable than axial, easier to make
Axial Compressor
- Utilizes rotor blades and stator vanes
- Many stages, different spools (low pressure and high pressure)
Turbojet
- Thrust is produced solely by exhaust gases
- Poor efficiency at low speeds
- High efficiency at high speeds
Turbofan
- Twin compressor stages
- Exhaust velocity reduced
- High bypass ratio
Turboprop
- Have higher thrust efficiency at lower speeds and altitudes than other turbine engines
- Core referred to as gas generator
- Direct drive and Free Turbine
Direct Drive Turboprop
- Reduction gear directly connected to gas generator
- Faster power response, increased efficiency
Free Turbine Turboprop
- Reduction Gear has independent power turbines
- Uses fluidic coupling to drive power turbine
- Gas generator can operate at optimal RPM without fixed relationship to prop RPM
- Usually reverse flow
Compressor Bleed Valves
- Used to off-load the compressor
- Prevents surges or compressor stalls
Turbojet/Turbofan Instrumentation
N1 - Low pressure spool
N2 - High pressure/intermediate pressure
N3 - High pressure spool
EGT
ITT - Interstage Turbine Temperature
FF - Fuel Flow
Turboprop Instrumentation
RPM - Prop RPM or NP
Torque - Load acting on prop shaft
NG - Single-stage free turbine gas generator
N1
N2
EGT
ITT
TIT - Turbine Inlet Temperature
FF
Tur bojet/Turbofan Controls
- Fuel Cutoff
- Thrust levers
- Thrust Reversers
Turboprop Controls
- Condition Levers
- Prop Controls
- Power Levers
Hot Start
- Combustion begins, but airflow is insufficiency for cooling
- Temp climbs rapidly
Hung Start
- Combustion begins, but engine does not accelerate normally
- Idle RPM will be lower than normal
- Temp may be high
Hydraulics
- Based on principle that fluids are flexible
- Pressure is very high
- Systems consist of pumps, hydraulic motors, cylinders, accumulators, reservoirs, and valves
Power Transfer Unit (PTU)
- Supply’s hydraulic fluid to system B from system A in event of hydraulic pressure dropping below limits
- Used to assist movement of flaps and slats
Bleed Air
- Higher number pressure station, further back air comes from, higher temp and pressure
- Used for engine starting, anti icing, pressurization, air conditioning
Pressurization - positive pressure relief valve
Releases excess pressure to prevent overpressurization
Pressurization - Negative Pressure relief valve
Ensures cabin pressure never fails below outside atmospheric pressure
Pressurization - Dump Valve
Can be opened by pilots to rapidly depressurize airplane
Pressurization - Outflow Valves
Regulate pressurization by controlling escape of air from cabin
Oxygen Systems - Continuous-flow Diluter
- Found on some turboprops and most light GA aircraft with built in oxygen systems
- Oxygen flow controlled by simple on/off switch
- Compressed oxygen stored in tank and flows through regulator to masks
- Crew can monitor remaining O2 level
- Oxygen can be supplied at 100% or diluted with ambient cabin air
Oxygen Systems - Diluter Demand
- Common on turboprops and jets with lower operating altitudes
- NORM Operation: Regulators dilute O2 with cockpit air based on cabin altitude
- 100% Operation: Pure oxygen supplied regardless of altitude when you breathe
- EMER Operation: 100% O2 with positive pressure forced into the mask for smoke removal
