Propellers

Question 1

Define the propellers on the MC-12.

Answer 1

Four-bladed aluminum propeller. Full feathering, constant speed, counter-weighted, reversible type, controlled by engine oil pressure through single action, engine driven propeller governor.

Question 2

What does illumination of the (White) Prop PitchWarning indicate?

Answer 2

The L or R PROP PITCH annunciators are provided to inform the pilot of a blade angle more than 8° below the flight idle low pitch stop.

During normal ground operation, these annunciators will be illuminated. The system uses a magnetic proximity sensor to sense the position of the feedback ring and, thereby, the position of the propeller dome and blade angle.

Question 3

When is the ground idle stop solenoid inactive?

Answer 3

above 68-70% N1 because it is above the mircoswitch.

Question 4

What are the two essential functions of the Beta Valve?

Answer 4

Prevents the Prop from entering reverse un-commanded

Controls blade angle (& RPM) while in reverse

Question 5

What is the blade angle when the props are at Ground Idle Gate?

Answer 5

2 degrees

Question 6

As the blade angle _________, rotational drag increases, and the blade speed will ________?

Answer 6

increases, decrease.

As the blade angle increases, rotational drag
increases, and the blade speed will
decrease.

Question 7

State the component(s) that cause(s) the blades to seek a feathered position due to centrifugal force.

Answer 7

Counter Weights

Question 8

What controls the prop pitch when not in the governing range?

Answer 8

The Beta Valve in conjunction with the PLPS nuts & the prop pitch solenoids.

Question 9

What is the normal (on speed) range of the primary governor?

Answer 9

1450-1700 RPM

Question 10

If linkage should fail in the primary governor, where would the spring loaded propellers stabilize?

Answer 10

1700 RPM

Question 11

he Np shaft drives the governor pump to raise oil pressure from its normal range to a maximum of ___ psi.

Answer 11

375 psi

Question 12

Oil pressure is always trying to maintain a ___ pitch

Answer 12

Oil pressure is always trying to maintain a low pitch;

conversely the feathering springs and counterweights are trying to send the propeller to feather creating a balancing act of opposing forces.

Question 13

The overspeed governor maintains what RPM via a factory set screw?

Answer 13

1768 RPM

Question 14

What is the minimum propeller RPM?

Answer 14

1050RPM

Question 15

Are there any exceptions to be less than 1050RPM?

Answer 15

While in Feather

Question 16

How does the primary governor slow the propeller RPM down in an over-speed condition?

Answer 16

The pilot valve raises, allowing oil to drain to case, causing the blade angle to increase (drag) and slows down the propeller.

Question 17

When the overspeed governor test switch is placed in the test position, it provides ________ power to the N.C. solenoid and opens it allowing ________ to reset the speeder spring tension to ____ - ____ RPM?

Answer 17

Electrical / Oil pressure.

1500-1610

Question 18

What components feather the propeller?

Answer 18

Centrifugal counterweights and feathering springs

Question 19

What would be an indication of a primary governor failure during flight?

Answer 19

Propeller above 1700 RPM

Question 20

How does the fuel topping governor govern propeller speed?

Answer 20

The FTG limits propeller speed by limiting the amount of fuel flowing to the fuel nozzles through a reduction of P3 air pressure in the fuel control unit. This ultimately reduces the power applied to the propeller shaft and thus limits propeller rpm.

Question 21

What is the governing range of the Fuel Topping Governor?

Answer 21

106% of Selected RPM

95% of Selected RPM in reverse

Question 22

Which governor reduces fuel flow to the engine to limit propeller RPM?

Answer 22

The Fuel Topping Governor.

Question 23

What are the two functions of a Fuel Topping Governor?

Answer 23

Limits propeller RPM during stuck/sluggish prop situations & aids during reversing operations.

Question 24

What do the Fuel Topping Governor and the Primary Governor share with regard to components?

Answer 24

Speeder springs and fly weights.

Question 25

When is the autofeather armed?

Answer 25

Autofeather switch must be in the armed position

Both power levers must be advanced to approximately 88% N1.

Question 26

In the event of an engine failure at what percent torque will the opposite autofeather light extinguish?

Answer 26

17%

Question 27

At what percent torque does the autofeather dump valve open allowing the prop to feater?

Answer 27

10%

Question 28

What two functions does the synchrophaser perform?

Answer 28

The system automatically matches the RPM of both propellers and positions the propellers at a preset phase relationship in order to reduce cabin noise.

Question 29

Can the PROP SYNC be used for all operations?

Answer 29

Yes. PROP SYNC is certified for all operations including takeoff and landing.

Question 30

The Propellers have two forms of governing control.

What are they?

Answer 30

Primary (1450-1700) and Overspeed (1768) governor.

Question 31

Prop positions and angles

Feather
Idle Gate >68-70% N1
Ground Idle
Ground Fine
Reverse

Answer 31

79.3      Feather
12          Idle Gate >68-70% N1
2           Ground Idle
-3          Ground Fine
-14         Reverse