Powerplant Flashcards
- Make and model of engines
- Propellers
- Normal SHP
- MTOP or auto uptrim SHP
• 2 Pratt & Whitney PW150A turboprop engines
• Engine drives a: Six bladed, constant speed, variable pitch, fully feathering Dowty propeller through the reduction gearbox
• Powerplant develops 4,580 SHP under normal take-off conditions
• Engines are capable of producing 5071 SHP during an automatic power uptrim or with a manual Max Takeoff Power rating selection after an engine failure
R
- Describe the compressors
- How are the engines controlled
- Engine has a low pressure (first stage) axial compressor and a high pressure (second stage) centrifugal compressor. Each compressor is attached to its respective single stage turbine by an independent shaft. A two-stage power turbine drives a third shaft to turn the propeller through a “Reduction Gearbox”
- Each engine is monitored by it’s own FADEC
Engine Accessory Gear Box
- Location and driven by
- Operates (4)
• Located at the top-center section of the engine, is driven by the high pressure (NH) compressor rotor and operates the following components: o Fuel Metering Unit (FMU) o Oil Pump o DC Starter-Generator o Permanent Magnet Alternator (PMA)
Propeller Reduction Gear Box
- Location
- Components mounted on the aft side (4)
- Propeller control system will automatically set propeller speed at ___ rpm whenever the power lever is advanced past the ___ detent
• Located at the FRONT section of the engine, is driven by the power turbine shaft
• Following components are mounted on the aft side of the reduction gearbox:
o Hydraulic Pump (main engine-driven pump)
o AC Generator
o Propeller Control Unit (PCU)
o Propeller Overspeed Governor (POG)
• Propeller control system will automatically set propeller speed at 1020 rpm whenever the power lever is advanced past the “RATING” detent
Engine FADEC
- How many channels
- Mounted where
- Controls fuel flow based inputs from (3)
- Also is used for (5)
• Dual Channel
• Mounted on the left side of each engine inlet
• Controls the engine fuel flow based on various inputs from the airplane, engine, and propeller control system
• FADEC also has the following additional functions:
o Controls various engine bleed valves to prevent compressor surges and stalls
o Prevents engine overspeed (@ 108% NH)
o Controls the automatic engine start sequence and engine shutdown
o Supplies voltage to the Propeller Electronic Control (PEC)
o Detects and indicates powerplant faults
Engine FADEC
• FADEC Primary source of electrical power is a ___, driven by the ___
• PMA provides electrical power to the FADEC when NH is above __%
• ___ initially provides electrical power to the FADEC during engine starts and in the event of a PMA malfunction
• Indication of a partial loss of function of the FADEC:
• Indication of a full failure of the FADEC:
• FADEC Primary source of electrical power is a “Permanent Magnet Alternator” (PMA), driven by the engine accessory gearbox
• PMA provides electrical power to the FADEC when NH is above 20%
• “Essential DC Bus” (28vDC) initially provides electrical power to the FADEC during engine starts and in the event of a PMA malfunction
• Indication of a partial loss of function of the FADEC:
o “#1 or #2 ENG FADEC” Caution light and possible surges or required staggering power levers
• Indication of a full failure of the FADEC:
o “#1 or #2 FADEC FAIL” Warning light and power on the respective engine failed or at idle
Automatic Take-off Power Control System (ATPCS)
- Define
- What causes the operating engine to respond
- How much will the power increase on the operating engine
- When will it arm
- Automatically augments the power of the operating engine in response to a loss of power of the opposite engine, without pilot intervention. Also referred as “Power Uptrim”
- In response to an engine failure during take-off, the working engines FADEC responds to an Uptrim signal from the failed engines Propeller Electronic Control (PEC) unit changing the engine power rating from NTOP to MTOP
- FADEC will increase the operating engines power by 10% (e.g. an NTOP of 92% will increase to an MTOP of 102%)
- ATPCS automatically arms when both power lever angles are “high” and when the torque on both engines is at least 50%
Automatic Take-off Power Control System (ATPCS)
• Uptrim condition is indicated in the cockpit by: (3)
• A power uptrim WILL occur when either of the following two conditions exist:
• Uptrim condition is indicated in the cockpit by:
o “UPTRIM” message appearing on the ED
o Change in the operating engine’s power rating from NTOP to MTOP on the ED
o Change in the operating engine’s torque bug position from NTOP to MTOP
• A power uptrim WILL occur when either of the following two conditions exist:
o Torque of the failed engine falls below 25% with the power levers in the RATING detent and MTOP not selected
o Power turbine speed (NPT) falls below 80% with the power levers in the RATING detent and MTOP not selected
Over-Torque Protection • Torque is limited to: % - reverse - forward - over travel range
• Torque is limited to:
o 35% in reverse
o 106% in the forward power range
o 125% in the over travel range
NH Overspeed Protection
• Overspeed (O/S) protection circuitry (dual channel) built into the FADEC cuts off the fuel flow to the engine through the ___
• Fuel shutoff command is issued when the measured frequency of the NH input signals exceed a preprogrammed threshold value of approximately ___% NH
- Overspeed (O/S) protection circuitry (dual channel) built into the FADEC cuts off the fuel flow to the engine through the Fuel Shutoff Solenoid (inside the FMU)
- Fuel shutoff command is issued when the measured frequency of the NH input signals exceed a preprogrammed threshold value of approximately 108% NH
Propeller
• The propeller system consists of the following components: (5)
• The propeller system consists of the following components:
o Propeller Electronic Control (PEC)
o Pitch Control Unit (PCU)
o Propeller Overspeed Governor Unit (POG)
o Auxiliary Feathering Pump
o Automatic Propeller Synchrophase System
Propeller Electronic Control (PEC)
- Describe the type of contrller
- Performs a number of safety functions including; (2)
- What does it command in the event of an engine failure
• Dual channel microprocessor-based controller
• Performs a number of safety functions including;
o Autofeather and Automatic Underspeed Propeller Control
• Initiates a power UPTRIM command to the FADEC of the operating engine in the event of an engine failure
Pitch Control Unit (PCU)
- Describe the unit
- How does it control prop pitch
- Hydromechanical device that interfaces with the propeller
- Controls propeller speed by directing the flow of high pressure oil into the fine pitch (i.e. DISC) or coarse pitch (i.e feather) chambers of the propeller pitch change cylinder as directed by the PEC
- Also controls the minimum blade pitch that can be obtained in flight
Propeller Overspeed Governor (POG)
- Describe the system
- Incorporates a ___ to provide the PCU with ___ from the engine gearbox
- Hydraulic Section of the POG reduces the high pressure oil supply when propeller speed exceeds approx ___ RPM
- Governor is a ___ design, driven directly from the ___ of the pump
- FADEC Overspeed Protection:
o FADEC commands the FMU to reduce the amount of fuel being supplied to the engine when a propeller overspeed of aprox.___ RPM is reached
• Independent mechanical system used to limit the propeller speed in case of a propeller overspeed malfunction
• Incorporates a high pressure pump to provide the PCU with high pressure oil from the engine gearbox
• Hydraulic Section of the POG reduces the high pressure oil supply when propeller speed exceeds approx 1071 RPM
• Governor is a flyweight design, driven directly from the drive gear of the pump
• FADEC Overspeed Protection:
o FADEC commands the FMU to reduce the amount of fuel being supplied to the engine when a propeller overspeed of aprox.1173 RPM is reached
Propeller RPM Underspeed
• At ___ RPMs the FADEC will provide propeller RPM underspeed governing (ground)
• At 660 RPMs the FADEC will provide propeller RPM underspeed governing (ground)