Powerplant

Question 1

• Make and model of engines
• Propellers
• Normal SHP
• MTOP or auto uptrim SHP

Answer 1

• 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
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Question 2

• Describe the compressors

- How are the engines controlled

Answer 2

• 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

Question 3

Engine Accessory Gear Box

• Location and driven by
• Operates (4)

Answer 3

• 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)

Question 4

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

Answer 4

• 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

Question 5

Engine FADEC

• How many channels
• Mounted where
• Controls fuel flow based inputs from (3)
• Also is used for (5)

Answer 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

Question 6

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:

Answer 6

• 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

Question 7

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

Answer 7

• 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%

Question 8

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:

Answer 8

• 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

Question 9

Over-Torque Protection
• Torque is limited to: %
- reverse
- forward 
- over travel range

Answer 9

• Torque is limited to:
o 35% in reverse
o 106% in the forward power range
o 125% in the over travel range

Question 10

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

Answer 10

• 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

Question 11

Propeller

• The propeller system consists of the following components: (5)

Answer 11

• 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

Question 12

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

Answer 12

• 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

Question 13

Pitch Control Unit (PCU)

• Describe the unit
• How does it control prop pitch

Answer 13

• 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

Question 14

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

Answer 14

• 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

Question 15

Propeller RPM Underspeed

• At ___ RPMs the FADEC will provide propeller RPM underspeed governing (ground)

Answer 15

• At 660 RPMs the FADEC will provide propeller RPM underspeed governing (ground)

Question 16

Autofeathering System

• Describe
• When will the system arm
• How is arming indicaed
• How long is the delay
• How long will it stay armed
• Note: Failure of the autofeather “A/F ARM” advisory message to appear on the ED during the takeoff roll prior to 80 knots is a mandatory abort

Answer 16

• Automatic propeller feathering following an engine failure during take-off
• System will “arm” when the torque of both engines exceeds 50% and both power levers are advanced beyond a 60° angle
• Successful arming is indicated by an A/F ARM message appearing on the ED (this message replaces the A/F SELECT message)
• “Auto Feather Delay” A 3 second delayed is placed in between engine failure and activation of the auto feather
• Autofeather system will ARM for a total of 30 seconds and conversely Disarm after 30 seconds

• Note: Failure of the autofeather “A/F ARM” advisory message to appear on the ED during the takeoff roll prior to 80 knots is a mandatory abort

Question 17

Auxiliary Feathering Pump

• Describe the pump
• Where is it mounted
• What is it’s purpose
• When is it automatically/manually activated

Answer 17

• 28vDC electrical motor driving an external gear pump
• Mounted on the aft side of the propeller reduction gearbox
• Provides a secondary source of oil pressure for feathering the propeller
• Pump is automatically activated when autofeather occurs and is manually activated when “alternate feather” is selected

Question 18

Alternate Feathering

• Purpose
• Accomplished how
• # 1 and #2 ALT FTHR switchlights are only functional when

Answer 18

• Provides an additional means of feathering the propeller in the event that the Autofeather system should fail
• Alternate feathering is accomplished by pressing the #1 or #2 ALT FTHR switchlight (guarded)
• # 1 and #2 ALT FTHR switchlights are only functional when their associated power lever is at FLIGHT IDLE and their associated condition lever is at or aft of the START & FEATHER gate

Question 19

Engine Ignition System
• Each engine incorporates an ignition system consisting of (2)
• Activated and Deactivated automatically by
• As soon as a flameout on has been detected, FADEC automatically

Answer 19

• Each engine incorporates an ignition system consisting of one dual channel Exciter unit and two igniter plugs in the combustion chamber
• Activated and Deactivated automatically by FADEC during the start sequence
• As soon as a flameout on has been detected, FADEC automatically activates the ignition circuitry for both igniters

Question 20

Propeller Synchrophase System

• Controlled by
• Reduces propeller noise by
• System does not operate during

Answer 20

• Controlled by the PEC (propeller electronic control)
• Reduces propeller noise by:
o Calculating the phase angle by timing the differences between the master propeller (left prop) and slave propeller (right prop) Magnetic Pickup Unit (MPU) signals over a complete propeller revolution
• System does not operate during take-off

Question 21

MTOP Limits
•	Max Torque = 
•	Max ITT = 
•	Max NL% RPM =  
•	Max NH% RPM = 
•	Max NP RPM = 
•	Oil Pressure PSID = 
•	Oil Temp °C =

Answer 21

• Max Torque = 106%
• Max ITT = 880°C
• Max NL% RPM = 100
• Max NH% RPM = 100
• Max NP RPM = 1020
• Oil Pressure PSID = 61-72
• Oil Temp °C = 0-107

Question 22

Engine Ignition System
• Each engine incorporates an ignition system consisting of (2)
• Activated and Deactivated automatically by
• As soon as a flameout on has been detected, FADEC automatically activates the ignition circuitry for

Answer 22

• Each engine incorporates an ignition system consisting of one dual channel Exciter unit and two igniter plugs in the combustion chamber
• Activated and Deactivated automatically by FADEC during the start sequence
• As soon as a flameout on has been detected, FADEC automatically activates the ignition circuitry for both igniters

Question 23

1 and #2 Engine Ignition Switches (overhead panel)

• OFF
• NORM

Answer 23

• OFF - FADEC disables ignition regardless of ground or flight status
• NORM - FADEC automatically activates and deactivates ignition during engine starts (ground starts or air starts)

Question 24

Engine Start Select Switch (overhead panel)
• Selecting this switch to position 1 or 2
• Switch is magnetically held in position during the engine start sequence and is released (automatically resets to center position) when engine NH reaches approximately __%

Answer 24

• Selecting this switch to position 1 or 2 arms the engine start control circuits for the respective engine and results in the illumination of the SELECT segment on the upper half of the engine “START” switchlight
• Switch is magnetically held in position during the engine start sequence and is released (automatically resets to center position) when engine NH reaches approximately 57%

Question 25

Engine Start Sequence | - Describe

Answer 25

1. Engine start is initiated by pressing the START select switch and moving the condition lever from the FUEL OFF position to the START & FEATHER position upon first indication of NH 2. When NH reaches approximately 8%, FADEC commands ignition on (activating only one igniter) and controls fuel scheduling. Engine light-off is defined as an increase in ITT of 20°C. If the engine fails to light within 8 seconds, FADEC activates both igniters 3. When NH reaches approximately 50%, FADEC terminates the automatic start sequence. This is indicated on the start control panel by the release of the SELECT switch back to its center position. “START” segment of the Start switchlight will extinguish approximately 15 seconds after the SELECT switch resets

Question 26

Engine Start Malfunctions • FADEC will automatically terminate the start sequence and shutdown the engine (auto abort) if any one of the following conditions should develop: (3)

Answer 26

• FADEC will automatically terminate the start sequence and shutdown the engine (auto abort) if any one of the following conditions should develop: o Engine does not light within 16 seconds after introduction of fuel flow o ITT limit of 920°C is exceeded (20 second max limitation) o NH does not reach 50% within 70 seconds (e.g., hung or slow start)

Question 27

Air Starts | • Air starts are similar to ground starts with the exception of the following: (3)

Answer 27

• Air starts are similar to ground starts with the exception of the following: o BOTH igniters are activated during the start sequence o FADEC’s Auto Abort circuits are disabled o FADEC’s automatic ITT limiting feature is disabled

Question 28

Engine Oil System - Provides/supplies oil for - How is the temp controlled - If engine oil pressure drops below __ psi, a “(1) or (2) ENG OIL PRESS” Warning light will illuminate

Answer 28

* Provides lubrication of the engine bearings and gearboxes, and also supplies oil for propeller operation * Oil temperature is controlled by the automatic routing of oil through an air cooled oil cooler * If engine oil pressure drops below 44 psi, a “(1) or (2) ENG OIL PRESS” Warning light will illuminate