EMB-120 Propeller Flashcards Preview

Embraer Brasilia EMB-120 > EMB-120 Propeller > Flashcards

Flashcards in EMB-120 Propeller Deck (38):
1

What safety function provides protection against Overspeed when supply oil pressure is lost?

Pitch Lock- gap closes to protect against the loss of supply oil.

2

How is the Prop Blade angle changed on the ground?

Power levers

• WOW switch allows power levers to go into beta mode.

• Beta Mode- power levers below flight idle (17.6˚ blade angle).

• Primary pitch stop (17.6˚) and secondary pitch stop (12.6˚) prevent power levers from going into beta mode in flight.

3

How is the Prop Blade angle changed in the air?

Condition levers

• Supply oil drives the blades toward a high pitch / feathered condition.

• Supply oil opposes metered oil and aerodynamic and centrifugal forces that drive the prop blade to a low angle / overspeed condition.

• The blade angle is changed by varying the metered oil.

4

List the ways of feathering the propeller?

• Manually- condition levers to feather

• Automatically- Autofeather
o arms when torque > 62%, power levers > 62˚
o activates when torque drops below 22%

• Electric feather switch

• Fire Handle

5

What is the purpose of the Beta mode?

• Assist in stopping- control prop between 17.6 and -11.9˚

• Reverse thrust

6

Describe pitch lock gap:

The pitch lock gap is a small (.030–inch) space between the acme screw portion of the selector valve assembly and the propeller hub assembly. Oil from either side of the actuator pis- ton passes through this gap to drain. Should the sup- ply of oil to the PCU fail, the aerodynamic forces on the propeller (which tend to drive it toward flat pitch) close the pitch lock gap. This shuts off the drain to both sides of the actuator piston, creating a hydraulic lock.

7

FEATHER ____˚ BLADE ANGLE.

FEATHER 79.2˚ BLADE ANGLE (80˚).

8

REVERSE ____˚ BLADE ANGLE.

REVERSE -11.9˚ BLADE ANGLE (12˚).

9

Aerodynamic and centrifugal forces on the prop
continually try to drive the blades to what blade angle?

Aerodynamic and centrifugal forces on the prop
continually try to drive the blades to at low blade angle.
In flight, this will produce a PROP OVERSPEED.

10

Full Feather =
Full Reverse =

Lowest blade angle possible with Power Levers at or above Flight Idle is ____˚.

Beta Range =

Full Feather = 79.2˚

Full Reverse = -11.9˚

Lowest blade angle possible with Power Levers at or above Flight Idle is 17.6˚.

Beta Range = below 17.6˚

Beta Mode – operating on the ground with the Power Levers below Flight Idle.

11

Supply oil drives the prop:

Metered oil does what?

Supply oil drives the prop away from overspeed, toward feather (higher blade angle). Metered oil prevents the prop from going all the way to feather by providing a balance pressure to keep the prop at the speed you are demanding.

12

Supply oil drives the prop toward:

Feather

13

________ ____ provides a balance against ________ ____ to maintain the prop at a constant Np.

Metered oil provides a balance against supply
oil to maintain the prop at a constant Np.

14

We can manually fx the prop via the CL’s. When the CL’s are moved to the fx position, this opens the _________. Then the _______ from the ___ oil pump drives the prop to fx.

We can manually fx the prop via the CL’s. When the CL’s are moved to the fx position, this opens the Manual Fx Valve. Then the supply oil from the PCU oil pump drives the prop to fx.

15

When the prop is electrically feathered the __________ is opened and metered oil is drained out. At the same time the elec. feather pump is turned on. This pump has ______ authority than the _____ oil pump. This allows ______ oil to win the battle at the servo piston and drives the prop to the feathered position.

When the prop is electrically feathered the Elec Feather Solenoid Valve is opened and metered oil is drained out. At the same time the elec. feather pump is turned on. This pump has greater authority than the pcu oil pump. This allows supply oil to win the battle at the servo piston and drives the prop to the feathered position.

16

Electric Feathering Pump Is ____________ powered.

Electric Feathering Pump Is Emergency DC powered.

17

Reverse is part of the ____ Mode. With the EEC’s on and the CL’s in max, the EEC’s will increase fuel flow to create __% Np for reverse.

Reverse is part of the Beta Mode. With the PL’s in the full reverse position, the beta valve fully closes. This allows pressure on the metered side of the servo piston to drive the prop to a -11.9˚. With the EEC’s on and the CL’s in max, the EEC’s will increase fuel flow to create 80% Np. This created the reverse thrust. Without the EEC’s you not get the 80% Np spool up, but you will still get the -11.9˚ prop pitch.

18

The propeller is feathered by dumping:

Metered Oil.

19

The Auxiliary Propeller Feathering pump is powered by:

Emergency bus electric power.

20

Auto FX arms when autofeather Switch is on and:

Above 62˚ PLA and 62% torque.

21

Name the three propeller overspeed protections:

103%- The Overspeed Governor bleeds metered oil pressure.

109%- The Overspeed Governor bleeds P3 bleed air to reduce fuel to the engine to slow it down.

PITCHLOCK GAP- Closes to protect loss of Supply Oil.

22

103% propeller overspeed protection:

103%- The Overspeed Governor bleeds metered oil pressure.

23

109% propeller overspeed protection:

109%- The Overspeed Governor bleeds P3 bleed air to reduce fuel to the engine to slow it down.

24

PITCHLOCK GAP- Closes to protect loss of _______. When this occurs, the prop losses __ degree of pitch and gains ___ Np.

The cause of oil pressure loss to the prop could be a result of many things. Some causes could be:

PITCHLOCK GAP- Closes to protect loss of Supply Oil. When this occurs, the prop losses 1˚ of pitch and gains 2% Np.

The cause of oil pressure loss to the prop could be a result of many things. Some causes could be: oil leak, TMM oil pump failure, or engine failure.

25

Does the Electric Feathering pump have more authority than the Mechanical pump to feather the propellers?

The Electric Feathering pump has more authority (820psi) than the Mechanical pump (780)psi).

26

Why is it good that can we operate the electric feathering pump ___________?

20 seconds / 6 consecutive cycles. Sometimes there are air bubbles in the system and it may take more than one cycle of the Fx. Switch.
The PCU pump will almost never have the authority to feather an overspeeding prop. You will almost always have to complete entire procedure for an overspeeding prop.

27

Autofeather activates when one torque drops below______.

22%

28

The Overspeed Governor drains metered oil at ___%?

103%

29

FAILURE OF THE MAIN ENGINE OIL PUMP OR LOSS OF ENGINE OIL DURING CRUISE FLIGHT WILL RESULT IN:

Pitch Lock

30

WHAT ARE THE THREE LOW BLADE ANGLE PROTECTIONS:

1) FLIGHT IDLE GATE (PRIMARY LOW PITCH STOP) @ 17.6˚ blade angle. (This is reached when the Power Levers are brought back to the Flight Idle Gate)

2) SOLENOID LOCK-OUT @ airborne 17.6˚ (SECONDARY FLIGHT IDLE STOP). This is a backup to the Flight Idle Gate and is wired thru the Squat Switches as a further protection from bringing the Power Levers below Flight Idle while airborne.

3) SECONDARY LOW PITCH BACK STOP @12.6˚ Blade angle.

31

UNCOMMANDED BETA: Secondary low pitch backstop activates when: (3)

1) Circuit breaker closed
2) Power Levers above flight idle
3) Blade angle = less than 12.6˚

When the blade angle drops below 12.6˚ uncommanded, the Low Blade angle switch sends a signal to energize the Electric Feather Solenoid which opens to drain Metered Pressure. This allows Supply Pressure to raise the blade angle above 12.6˚ and the Low Blade Angle switch senses this and the Electric Feather Solenoid close to stop the draining of Metered oil. The Beta Light illuminates whenever the blade angle goes below 12.6˚ and extinguishes whenever the blade angle goes above 12.6˚.

32

What is the difference between BETA MODE & BETA RANGE?

BETA MODE= Operating on the ground with the Power Levers below Flight Idle.

BETA RANGE= Propeller blade angle below 17.6˚

33

Lower oil temperature equals _____ oil pressure.

Higher oil temperature equals ____ the oil pressure.

Lower oil temperature equals higher oil pressure.

Higher oil temperature equals lower the oil pressure.

34

Why is it important to abide by the 10˚C limitation to feather the prop?

During an aircraft's first flight on a cold day, a crew experienced a propeller overspeed. When the PCU was inspected on the ground, maintenance could find nothing wrong. It then became known that
the crew performed the Prop Aux Feather Test with oil temperature below the limitations. Because of this, cold oil remained in the propeller hub and PCU. The oil was too thick to run the system, and
therefore, the prop over sped.

35

In order for Prop Sync to function you must
have the switch on and:

Props within 2.5% Np of each other and Np above 80%.

36

What warning lights would you ‘typically’ see with an inadvertent feather?

Probably only ‘ELEC’ on the MAP and ‘AUX GEN’ on the overhead panel.

37

RGB rotation speed is a function of:

Nh%

38

The only Propeller system that can be deferred is:

Synchrophaser.