Powerplant

Question 1

How much power do they engines produce in MTOW and NTOP?

Answer 1

5071 SHP in MTOW

4580 SHP in NTOP

Question 2

Describe the engine. (Sections)

Answer 2

The engine has an axial low pressure compressor and a centrifugal high pressure compressor. These are connected to separate single stage turbine.

There is an independent two stage power turbine which is connected to the propeller reduction gearbox.

Question 3

How is the engine controlled?

Answer 3

Through a Full Authority Digital Engine Controller. (FADEC)

Question 4

What items are mounted on the Engine Accessory Gearbox?

Answer 4

• Fuel Metering Unit
• Starter/Generator
• Oil Pump
• Permanent Magnet Alternator (PMA)

Gearbox is on the top-center of the engine.

Question 5

What items are mounted on the Propeller Reduction Gearbox?

Answer 5

• Hydraulic Pump
• AC Generator
• Pitch Control Unit (PCU)
• Propeller Overspeed Governor (POG)

Question 6

Describe the operation of the power levers.

Answer 6

Throughout their travel the power levers command fuel demands via the FADEC and from a range starting slightly ahead of the Flight Idle gate through BETA range and MAX REV they also control propeller blade angle via the Propeller Electronic Control (PCU).

If advanced into the overtravel past the RATING detent an additional 25% power is commanded.

Question 7

Describe the operation of the condition levers.

Answer 7

The condition levers control propeller RPM and set engine power ratings.

Question 8

Describe the Fuel Metering Unit (FMU)

Answer 8

The FMU is mounted to the engine accessory gearbox. It takes in high-volume, low-pressure fuel from the primary ejector pump and tank aux pump. The FMU contains two pumps, a Low Pressure pump which sends the fuel through a fuel heater and filter to the High Pressure Pump. The High-pressure fuel is then sent to a metering valve and either on to the fuel manifold or returns to the wing tanks as motive flow.

Question 9

Describe the FADEC.

Answer 9

The FADEC for each engine is mounted on the left side of the engine and cooled by a NACA duct on the cowl. It is powered initially by the onside 28v DC Essential bus. After reaching 20% NH the Permanent Magnet Alternator provides power.

Question 10

What are the primary functions of the FADEC?

Answer 10

• Controls engine fuel flow via the FMU
• Controls engine bleed valves to prevent compressor surges or stalls.
• Prevents engine overspeed (108%)
• Controls the automatic engine start and shutdown sequences.
• Supplies voltage to the PEC
• Detects and indicates powerplant faults.

Question 11

What type of faults does the FADEC report?

Answer 11

• Critical (RED) - Either the power will reduce to IDLE or the engine will shutdown.
• Cautionary (YELLOW) - Caution is required when changing power setting to prevent surges and split power levers may be required.
• Advisory - Fault code is logged for MX with no indication.

Question 12

What is the Automatic Power Control System? (APCS)

Answer 12

During takeoff if a engine fails the system commands a 10% increase of torque on the operating engine. System will not increase power if it is an MTOP takeoff.

Question 13

When does the APCS arm?

Answer 13

System arms when both power levers are at high lever angles and the torque of both engines is more than 50%.

Question 14

When will the APCS trigger?

Answer 14

• Torque of failed engine drops below 25%.

- NPT falls below 80%

Question 15

What overspeed and over-torque protections are there?

Answer 15

The FADEC prevents torque exceeding 135% and NH overspeeds of more than 108%.

Question 16

What are the components of the propeller system?

Answer 16

• Propeller Electronic Control (PEC)
• Pitch Control Unit (PCU)
• Propeller Overspeed Governor (POG)
• Auxiliary Feathering Pump
• Automatic Propeller Syncophase system

Question 17

Describe the PEC.

Answer 17

The PEC is a dual channel controller which is soft mounted behind the propeller reduction gearbox. It provides safety functions such as Autofeather, Automatic Underspeed Propeller Control and initiates the UPTRIM signal to the FADEC in event of an engine failure.

Question 18

Describe the PCU.

Answer 18

The PCU is a hydro-mechanical unit which is commanded by the PEC and meters high pressure oil to control propeller pitch.

Question 19

Describe the POG.

Answer 19

The POG is a flyweight design, independent system which mechanically prevents a propeller overspeed. It incorporates a high-pressure oil pump which provides pressure to the PCU.

Question 20

Describe the Auxiliary Feather Pump.

Answer 20

The Aux Feathering Pump is a 28v DC pump which is mounted aft of the gearbox and provides a secondary source of high pressure oil for propeller feathering. It is automatically activated during an autofeather or can manually be activated.

Question 21

Describe the propeller syncophase system.

Answer 21

The PEC will automatically compare the master left prop to the slave right prop and change the phase angle to reduce propeller noise. It is not active on takeoff.

Question 22

In constant speed mode how is propeller speed controlled?

Answer 22

In constant speed mode the PEC commands the PCU to maintain the selected speed.

Question 23

In Beta mode how is propeller speed controlled?

Answer 23

In Beta mode the FADEC controls (through the PEC) blade angle and speed to maintain a minimum of 660rpm while one the ground.

Question 24

When will the Autofeather system arm?

Answer 24

• Switch in selected
• Engine torques above 50%
• Power levers beyond 60 degrees.

Question 25

When will the Autofeather system activate?

Answer 25

• engine torque falls below 25% for 3 seconds.

The system sill send an UPTRIM command to the other engine and three seconds later feather the failed engine.

The Aux Feathering pump activates for 30 seconds on an external relay.

Question 26

How are the Auxiliary Feathering Pumps powered?

Answer 26

They are powered by the offside 28v DC secondary buses.

Question 27

How does the POG prevent overspeeds?

Answer 27

The mechanical section of the POG reduces high pressure oil supply when prop speed exceeds 1071rpm.

The electrical section of the POG uses the FADEC NP overspeed circuit to reduce fuel when prop speed reaches 1122rpm.

Question 28

What faults does the PEC report?

Answer 28

Critical - propeller will move towards feather

Cautionary - No Beta control below flight idle.

Advisory - Fault code is logged for MX with no indication.

Question 29

Describe the ignition system.

Answer 29

Each engine has a dual channel exciter unit and two igniter plugs. FADEC automatically controls the igniters for start and in case of a flameout. During a flameout both igniters are triggered.

Question 30

Describe the engine start sequence.

Answer 30

With the start switch depressed and the condition lever in the start & feather position at 8% NH the FADEC activates an igniter and controls fuel scheduling. If the engine fails to light off in 8 seconds the second igniter is activated. At 50% NH the FADEC ends the start sequence and the start select switch centers. Apx 15 seconds later the start switch light extinguishes.

Question 31

What conditions will result in the FADEC auto aborting the start sequence?

Answer 31

• No light off within 16 seconds.
• ITT limit of 920 degrees is exceeded (20 seconds).
• NH does not reach 50% within 70 seconds.

Question 32

How does an airstart differ?

Answer 32

• Both igniters are activated
• The auto abort circuts are inhibited
• The ITT limiting feature is disabled

Question 33

How is engine oil temperature regulated?

Answer 33

There is an air cooled oil cooler for each engine. The cooler door on the bottom of the nacelle is automatically controlled to regulate oil temperature.

Door will open automatically when:

• On the ground
• Oil temps greater than 100 degrees
• Power levers less than 60 degrees

Question 34

What is torque limited to in reverse, forward power range and over travel?

Answer 34

Reverse - 35%
Forward Range - 106%
Over travel - 125%