Propulsion Flashcards
What is the purpose of the engine cowling?
Protect engine components, decrease drag, and provide engine air intake
What kind of engine does the T-6 have?
PT-6A-68 free turbine, reverse flow design, turboprop
What does Free Turbine refer to?
The compressor and power turbines are not physically connected. Air movement from one turbine to the other provides power to the propeller
What does Reverse Flow Design refer to?
The flow of air through the engine. Air enters at the rear and moves forward during the combustion cycle
What three elements are necessary for engine operations?
Air, fuel, and heat
What are the major sections of the engine?
Accessory compartment, gas generation section, and power turbine section
What items are found in the accessory compartment?
Accessory gearbox, oil tank, starter/generator, and battery
What turns the compressor turbine and compressor initially?
The starter
What is contained in the gas generation section?
Compressor inlet, compressor, combustion chamber, compressor turbine
Where does inlet air flow into first?
Compressor inlet
What is inlet air compressed by?
Four-stage axial flow compressor and single stage centrifugal flow compressor
Where does air go after the compressor?
Combustion chamber
What happens in the combustion chamber?
Compressed air is mixed with fuel and ignited
What drives the compressor turbine?
Expanded gasses from the combustion chamber
What components are in the Power Turbine Section?
Power turbine, exhaust case, reduction gearbox, propeller shaft
What is the purpose of the Power Turbine Section?
Produce horsepower from the gasses generated by the gas generation section
What drives the reduction gearbox?
The power turbine
What drives the propeller shaft?
The reduction gearbox
What components are in the Engine Exhaust System?
Exhaust ports and exhaust stacks
What happens to the air after it comes off the power turbine?
It moves through the exhaust ports, followed by the exhaust stacks
What kind of ignition does the T-6 use?
A dual spark ignition system
What does the starter provide?
Initial air flow
What does the Fuel Management Unit (FMU) provide on startup?
Fuel (duh)
What does the ignition system provide on startup?
Initial heat source
What components make up the Ignition System?
An ignition exciter, two high voltage igniter cables, and two spark igniters
What does the ignition exciter receive to create a spark?
A low voltage input signal from the battery bus
What does the ignition exciter do with the input signal?
Transforms it into a high voltage output signal?
What do the ignition cables do?
Carry the high voltage signal to the spark igniters
What do the spark igniters do?
Provides a spark to the air/fuel mixture in the combustion chamber
What happens when the ignition switch is set to NORM and the starter switch is moved to AUTO/RESET?
The igniters will initiate
What does the Power Management Unit (PMU) do during startup?
Enerrgize and de-energize the igniters
Which annunciator lights up during the engine start sequence?
Green IGN SEL
What provides power for the ignition system?
The circuit breaker labeled IGN, located on the battery bus CB panel in the front cockpit
What does the PCL do?
Controls fuel flow to the engine
What is the PCL connected to mechanically and electrically?
The Fuel Management Unit
What three positions does the PCL have?
OFF, IDLE, and MAX
Where do you move the PCL to for start?
Between OFF and IDLE, when the green ST READY annunciator illuminates
What prevents inadvertent engine shutdown?
PCL cutoff gate
Where is the Power Management Unit located?
Under the engine in the accessory compartment
What does the Power Management Unit do?
Processes power requests from the PCL and keeps engine and propeller within operating limits
What does an amber PMU STATUS annunciator in flight mean?
Indicates a fault in either of, or a mismatch between the weight-on-wheels switches. The PMU will not revert to ground mode upon landing
What accompanies a PMU STATUS annunciator?
Yellow MASTER CAUTION light and an aural tone
What does a red PMU FAIL annunciator mean?
The PMU is nonfunctional
What accompanies a PMU FAIL annunciator?
MASTER WARN and MASTER CAUTION, and an aural tone
Where does power for the Power Management Unit come from?
A Permanent Magnet Alternator mounted on the reduction gearbox
What does the Permanent Magnet Alternator provide to the Power Management Unit?
32 VAC, which the PMU converts to DC
If the Permanent Magnet Alternator fails, where does the Power Management Unit get power?
From the 28 VDC battery bus
Where is the starter/generator located at?
Attached to the accessory gearbox
What is the accessory gearbox attached to?
The compressor section via a shaft
During engine start, what does the starter/generator do?
The starter motor turns the compressor section. This generates air flow and compression until the engine starts and is able to run at idle speed
What does the starter/generator do after engine start?
Becomes a generator, which provides 28 VDC to many aircraft systems, and charges battery and aux battery to 24 VDC
What three positions does the starter switch have?
AUTO/RESET, NORM, and MANUAL
How is power provided for the starter?
A circuit breaker labeled START on the battery bus C/B panel
What is the purpose of the oil system?
Provides a steady flow of filtered oil to the engine bearings, reductions gears, accessory drives, and propeller
What components make up the oil system?
Pressure system, scavenge system, and cooling system
How is oil pressurized?
The pressure pump
What ensures oil can flow, even during inverted or negative G flight?
There is a normal pickup in the center of the oil pump, and an inverted pickup near the top of the tank
What does the scavenge system do?
Returns oil to the tank after being used in the bearings, reductions gears, accessory drives, and propeller
What does the oil system use to scavenge oil back to the tank?
Several pressure and scavenge pumps throughout the oil system
What does the oil cooler do?
Cools the oil before it’s returned to the oil tank
What filters the oil?
There is a main oil filter in the oil tank. There are also oil strainers in the power, compressor, and accessory drive areas
What happens if the mail oil filter gets clogged?
The oil travels through a filter bypass valve that allows unfiltered oil to continue lubricating the engine
Where is the chip detector located at?
In the reduction gearbox
What does the chip detector do?
Detects metallic particles in the oil and warns pilot of possible gear damage
What happens if the chip detector detects metal particles?
Red CHIP annunciator illuminates, MASTER WARNING illuminates, and an aural tone sounds
What is the purpose of the Signal Conditioning Unit (SCU)?
Illuminates the central warning system under certain oil pressure conditions
What pressure should oil be during steady state operations?
90 to 120 psi
What should oil pressure be during aerobatic flight?
40 to 130 psi
When at IDLE, when will the OIL PX amber annunciator illuminate?
Between 15 to 40 psi
When above IDLE, when will the OIL PX amber annunciator illuminate?
Between 40 to 90 psi for 10 seconds
When at IDLE, when will the OIL PX red annunciator illuminate?
Below 15 psi, or when between 15 to 40 psi for more than 5 seconds
Where is power for the oil system transducer provided from?
The OIL TRX circuit breaker on the battery bus circuit breaker panel in the front cockpit
What is the purpose of the propeller?
To provide thrust
What kind of propeller does the T-6 use?
Four blade, variable pitch, constant speed
What two components controller propeller speed (Np)?
The Power Management Unit and Propeller Interface Unit
What speed is the propeller held to?
2,000 rpm
How are varying levels of thrust provided?
By adjusting the propeller pitch
What altitude is 100% torque available for?
From sea level to between 12,000 and 16,000 MSL
What happens to torque above 16,000 MSL?
There will be a decrease in max torque
What is the propeller driven by?
The power turbine, through the reduction gearbox
What speed is the power turbine spun at?
30,000 rpm
What is propeller speed (Np) measured by?
The phase shift torque probe
What monitors the phase shift torque probe?
The Power Management Unit
What directs the Propeller Interface Unit to maintain propeller rpm?
The Power Management Unit
What does the Propeller Interface Unit use to restrict rpm?
An electronic governor
What happens if the electronic governor fails?
There is a backup mechanical governor
What does the backup mechanical governor hold the propeller to?
106% torque, or 2120 rpm
What changes propeller pitch?
Changes in oil pressure
What are the three basic blade pitch angles base upon?
The angle between the plane of rotation and the chord line of the propeller
What are the three basic pitch conditions?
Feathered, high pitch (coarse), and low pitch (flat or fine)
What is the default condition of the propeller?
The feathered position
What does the feathered position provide?
The least amount of drag and no thrust
What pitch will the propeller usually be in?
High pitch
What does a low pitch propeller provide?
Some thrust and the most drag
What controls the oil flow to the propeller?
The Propeller Interface Unit
What happens as oil pressure is increased in the propeller?
The blades move from the feathered position to high pitch, then to low pitch
What PCL position causes the prop to feather?
OFF
What happens if there is any residual oil pressure in the system if the engine fails?
The prop might not feather
When the engine fails and the PCL is placed in off to feather, what happens in the system?
Two valves are activated in the Propeller Interface Unit, the feather dump solenoid valve, and an oil pressure release valve. This allows the prop to feather
What circuit breaker controls the feather dump solenoid valve?
The PROP SYS circuit breaker on the battery bus circuit breaker panel
Where is the Engine Data Manager located?
In the left avionics bay
What engine related tasks does the Engine Data Manager do?
Drives primary, alternate, and engine/system displays, and illuminates advisory, caution, or warning annunciators when appropriate
What non-engine related tasks does the Engine Data Manager do?
Fuel balancing, fuel quantity indications, activation of nose wheel steering annunciator, display of DC volts, amps, hydraulic pressure, cockpit pressure altitude, and cockpit pressure differential
What provides power to the Engine Data Manager?
Two EDM circuit breakers. One on the battery bus circuit breaker panel, and one on the generator bus circuit breaker panel in the front cockpit
What is the Primary Engine Data Display (PEDD)?
An electronic instrument display that presents engine information from the Engine Data Manager
What processes the information from various sensors around the engine?
The Power Management Unit
What monitors engine parameters and passes the information to the Primary Engine Data Display?
The Engine Data Manager
What does the Primary Engine Data Display do during abnormal engine operations?
Changes the color of the scales
What is the normal operating range color?
White or green
What is the cautionary operating range color?
Amber
What is the exceeding operating limits color?
Red
What information is provided on the Primary Engine Data Display?
Torque, Inter-Turbine Temp, Propeller RPM (Np), and Indicated Outside Air Temp (IOAT)
What are the in-limits for torque?
0 to 100%
What are out-of-limits for torque?
Anything more than 100%
What does ITT indicate on the Primary Engine Data Display?
The temp between the compressor turbine and power turbine
What are ITT operating limits during start sequence?
400° to 1000°C
After start sequence, what are the ITT operating limits?
400° to 820°C
What are out-of-limits for ITT?
Above 820°C
What does the N1 indication on the Primary Engine Data Display indicate?
Gas generator speed
What are normal operating limits for N1?
60 to 104%
What are out-of-limits readings for N1?
Above 104%
What are the ground operation limits for Np?
0 to 61% and 81 to 100%
What percentage of Np is prohibited on the ground?
62 to 80%
What is out-of-limits for Np in flight?
Above 102%
What circuit breaker controls the PEDD?
PRI ENG DIS on the generator bus circuit breaker panel
What does the Alternate Engine Data Display do?
Provides each cockpit with a backup visual indication of engine operations
Except for torque, what displays information for the Alternate Engine Data Display?
The Engine Data Manager
What does the Alternate Engine Data Display show?
Raw ITT, Torque, Gas Generator Speed (N1), Cockpit pressure altitude, Cockpit differential pressure, fuel flow, and fuel quantity
What happens if your cockpit altitude exceeds 19,000 feet?
The Cockpit Alt information on the AEDD is boxed in yellow, and an amber CKPT ALT annunciator illuminates, along with an aural tone
What happens if the differential pressure exceeds 3.9 to 4.0?
The differential pressure readout is outline in a red box, and a red CKPT PX annunciator is illuminated, along with an aural tone
How is the AEDD powered?
ALT ENG DIS circuit breaker on the battery bus circuit breaker panel
What does the engine/system display show?
Oil, hydraulic, and electrical system data
What are the normal operating limits for oil temp?
10° to 105°C
What are the cautionary operating limits for oil temp?
105° to 110°C
What is the out-of-limits readings for oil temp?
Above 110°C
What powers the engine/systems display?
ENG SYS DIS on the generator bus circuit breaker panel
What does the Firewall Shutoff Handle do?
Shuts of hydraulic fluid and fuel flow to the engine, as well as bleed air flow from the engine
What provides power for the Fire #1 warning system?
FIRE 1 circuit breaker panel on the battery bus circuit breaker panel
What provides power for the Fire #e warning system?
FIRE 2 circuit breaker panel on the generator bus circuit breaker panel
What are possible indications of a Hot Start?
- High/rapidly rising ITT
- Lower N1
- Lower Np
What are possible causes of a Hot Start?
- PMU failure
- FMU failure
- Incorrect air/fuel mixture
- Low battery
What are possible indications of a Hung Start?
- Slow rising ITT
- Lower N1
- Lower Np
What are possible causes of a Hung Start?
- PMU failure
- FMU failure
- Incorrect air/fuel mixture
- Ignition system failure
- Starter failure
- Low battery
What are possible indications of a No Start?
- No ITT indication
- Lower N1
- No Np indication
- No torque indication
What are possible causes of a No Start?
- PMU failure
- FMU failure
- Starter failure
- Ignition system failure
- Incorrect air/fuel mixture
What are initial indications of Engine Failure In-Flight?
- Loss of power and airspeed
- Rapid decay of N1, torque and ITT
- MASTER WARN light and tone
- Propeller moves toward feather
What are accompanying indications of Engine Failure In-Flight?
- Rapidly decreasing ITT, Np
- Lower than normal oil pressure
- Engine noise
- GEN, FUEL PX, OIL PX, OBOGS FAIL annunciators
- Possibly PMU FAIL and CKPT ALT annunciators
What are possible causes of Engine Failure In-Flight?
- Fuel starvation
- Mechanical failure
- Compressor stall
What should you do if you experience an engine failure in-flight?
Proceed with appropriate emergency procedure
What are possible indications of a PMU Failure?
- Power step change
- PMU Fail and PMU STATUS annunciators
- MASTER WARN light
- Aural tone
What are possible causes of a PMU Failure?
- System failure
- System malfunction
What is the appropriate procedure for a PMU Failure?
Proceed with PMU failure procedure
What are possible indications of Uncommanded Power Changes/Loss of Power?
- Reduction in power/thrust
- Lower than expected fuel flow
- Uncommanded decrease in N1
- High raw ITT on AEDD
- With oil/engine/fuel system contamination, additionally:
- Power surges
- Uncontrollable high power
What are possible causes of Uncommanded Power Changes/Loss of Power?
- Engine rollback due to PMU scheduling
- Oil/engine/fuel system contamination
What are possible indications of Uncommanded Feather?
- Rapid loss of power
- High torque
- Lower Np
- Possible PMU FAIL/PMU STATUS annunciators
- Engine vibration
- Engine noise
What are possible causes of Uncommanded Feather?
- Feather dump solenoid malfunction
- Loss of oil pressure to propeller pitch control mechanism
What are possible indications of Prop Sleeve Touchdown?
- Np fluctuations
- Increasing torque
- Decreasing thrust
- Engine vibrations
- Possible CHIP detector warning light
What are possible causes of Prop Sleeve Touchdown?
Loss of oil pressure to propeller pitch control mechanism from momentary contact between oil transfer sleeve and propeller shaft
What is the appropriate procedure for Pro Sleeve Touchdown?
- Proceed with uncommanded propeller feather procedures
What are possible indications of Engine Fire In-Flight?
- FIRE annunciator
- MASTER WARN light
- Aural tone
What is the FEVER check for Engine Fire?
- Fluctuating oil pressure, oil temp, or hydraulic pressure
- Excessive turbine temp
- Visual indications (smoke or flames)
- Erratic engine operation
- Roughness or vibration
What are possible cause of Engine Fire In-Flight?
- Fuel or oil leaks
- Fire getting outside of engine
What procedure should you take for Engine Fire In-Flight?
Proceed with fire warning in-flight procedure
What does an amber PMU STATUS annunciator after landing mean?
The PMU has accommodated a fault that needs to be cleared by maintenance
