Engine - Propeller Control Flashcards
What is the normal take off power rating?
2475 SHP
What is the SHP in case of an engine failure during take off?
2750 SHP
Why is the duct S-shaped?
- To remove FOD that may have been ingested by inertia
- To divide the airflow into a primary flow for the engine and a secondary flow for the oil cooler
What is the accessory gearbox used for?
- driven by the high pressure compressor shaft
- operates the engine driven fuel pump, an oil pump and the DC starter/generator
- mounted at the top of the engine
Why is the high pressure spool used for engine starting?
It is smaller and lighter weight so easier to spin up
What does the propeller reduction gearbox drive?
- propeller over speed governor (POG)
- 115 V ACW generator
- propeller valve module (PVM)
- high pressure pump
- fuel cooled oil cooler (FCOC)
How is the propeller driven?
Driven by the free power turbine through a reduction gearbox
Spin by exhaust gases
How is propeller pitch controlled?
Hydro mechanically controlled by a Propeller Valve Module (PVM) installed on the reduction gearbox
How is propeller pitch changed?
Oil pressure supplied by a feathering pump which is supplied by the engines lubricating system
What does the Propeller Electronic Control (PEC) unit do?
- Control their associated PVM as well as the synchronisation of the phases of the propellers
- Controls the Pitch Change Mechanism through two channels (if one channel fails back up will take over
- Calculates correct prop speed using altitude and airspeed data and info from the Np sensors
What is the Propeller Interface Unit (PIU)?
Provides an interface between the engine controls in the flight deck and the PEC
Two PIUs installed in the electronic rack
What does the Propeller Valve Module (PVM) do?
- provides for governed constant speed operation
- power lever controlled beta range from idle to full reverse
- propeller feathering
- synchrophasing
- low prop pitch angle protection
- prop overspend protection
What are the components of the PVM?
- electro hydraulic valve
- protection valve
- feather solenoid
- rotary variable differential transducer
What does the electro hydraulic valve (EHV) do?
Meters oil to the pitch change actuator and allows a normal feathering of the prop
What does the feather solenoid do?
Acts as a back up to the electro-hydraulic valve
What does the Rotary Variable Differential Transducer do?
Adjusts and confirms the power lever angle
Where is the prop brake installed?
On a counter shaft of the right engine gearbox
When can the prop brake be engaged?
- aircraft is on the ground
- prop brake switch in the ON position
- gust lock must be engaged
- right CL must be in feather or fuel shut off position
What does the EEC do?
Controls the flow of fuel through the HMU (hydro-mechanical Unit) by means of a stepper motor
What are the EEC information inputs?
- power lever angle information
- mode selected on pwr mgt panel
- position status of the bleed air valves
- engine parameters
- air data information
What does the EEC fault light mean?
Fuel control is ON and there is an EEC failure
Fuel scheduling is fixed at the point at which the failure occurred
If fault occurred with the power lever above 52 degrees, EEC fault light will flash and movement of the affected power lever will not result in a change of power
Deselection of the affected EEC is prohibited while the FAULT light is flashing
How can you turn off a fault EEC?
Power lever should be moved below 52 degrees and the EEC light will illuminate steady
Once below 52 degrees the power lever is able to control the engine and affected EEC can be selected OFF
What FAULT light illuminates, the ENG light illuminates, master caution and a single chime
What happens to the HMU if EEC is selected OFF?
The HMU will control the fuel flow and control of the Nh will be based on the associated power lever angle
What happens to under speed control when the EEC is selected OFF?
It is lost at low power
How is manual fuel scheduling controlled?
By power lever angle setting
Settings provide fuel demands and control the prop blade angle in the beta range (below 62 degrees)
What is Base Law?
Used when the associated EEC is inoperative
Fuel control is relative to power lever angle
Changes in ambient conditions will result in changes of Nh so need to adjust the power lever angle in order to maintain the max engine torque
Loss of prop under speed control at low power
What is Top Law?
Operates when the EEC is on
Will provide Nh over speed protection
Will command a specific engine power based on the rating selected on the pwr mgt panel, the power lever angle, flight conditions and the position of the bleed air valves
When is Nh back up law activated?
Low power settings, engine torque control failure or in hotel mode
What does top law provide?
- minimum prop speed control on the ground and at low power settings
- automatic uptrimmed take off power in the event of an engine failure on take off
- controls the modulation of the Handling Bleed valve to optimise low pressure compressor operation
What are the modes of propeller speed governing?
- blade angle governing
- fuel governing
- the transition mode
What is blade angle governing?
The normal mode of governing in flight
The PVM adjusts prop pitch to maintain a constant prop speed
Available regardless of EEC status
What is blade governing mode?
The pwr mgt selector commands the prop speed through the PEC and the power levers command power
What is fuel governing mode?
Used at low speed and low power
EEC automatically increases fuel flow to maintain a minimum prop speed
Available when the associated condition lever is in the AUTO
Not available when associated EEC is OFF or prop is feathered
What is transition mode?
Active when aircraft is on the ground or in flight at low power settings and low speed
Prop speed will be between 70.8% and 100%
What is the flight beta range?
Power lever movement above FLT IDLE
What is ground beta?
Range between FLT IDLE and MAX REV
When is the FLT IDLE gate unlocked?
As soon as one landing gear shock absorber is compressed
What do the condition levers provide input to?
The PVM and the HMU of the associated engine
What sets propeller RPM in the forward thrust constant speed range?
The condition levers through input to the governor in the PVM
What is prop RPM at 100% override?
1200 RPM
Where are the lift gates on the condition levers?
AUTO to prevent movement from auto to feather
FEATHER to prevent movement from feather to fuel shut off
What does the Automatic Takeoff Power Control System (ATPCS) provide?
Auto prop feathering on the failed engine and power uptrim on the non affected engine
When is the ATPCS system armed?
- pwr mgt set to take off
- ATPCS pb pushed in
- both power levers above 49 degrees
- both torques above 46 degrees
- aircraft on the ground
Also armed in flight given the conditions but no uptrim logic once pwr mgt selector out of take off position
When does power uptrim occur?
2.15 secs prior to prop auto feather
What does the fuel governing cancel signal do?
Permits the feathering prop to decrease RPM through an underspeed condition
How is the ATPCS disabled in flight following an engine failure?
- selecting any position other than TO on pwr mgt
- selecting ATPCS pb to OFF
- retarding both power levers
UPTRIM light extinguishes
How can the prop be unfeathered after a restart?
Only by selecting MCT position on the pwr mgt panel after engine has been started
