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E-2C NATOPS > Stick Monkey Slang for Moles - The Prop System > Flashcards

Stick Monkey Slang for Moles - The Prop System Flashcards

To provide familiarization with NP200 prop components and interaction between the various prop systems and the A/C.

1
Q

Major subassemblies for the E-2C prop system?

A

Spinner, Pitch Change Actuator (PCA), Prop hub, counterweighted blade, Actuator Valve Module (AVM), Digital Electronic Propeller Control (EPC), and the Integrated Oil Control (IOC)

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2
Q

Integrated Oil Control (IOC) consists of what components?

A

Electronic Valve Housing (EVH) and a Pump housing Assembly.

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3
Q

Major functions of the Spinner?

A

Provides streamlined airflow for drag reduction and allows cooling air to enter the IOC.

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4
Q

What components of the Prop system are housed in the Spinner?

A

Pitch Change Actuator (PCA), Prop Hub, and AVM.

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5
Q

Major functions of the Pitch Change Actuator?

A

Establishes and maintains the pitch angle of the prop blades in order to achieve desired governing speed.

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6
Q

Course Pitch equates to?

A

Increased pitch hydraulic pressure.

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7
Q

Fine Pitch equates to?

A

Decreased pitch hydraulic pressure.

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8
Q

Pitch change hydraulic pressure is supplied from what prop component?

A

Electronic Valve Housing (EVH).

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9
Q

Major functions of the Propeller Hub Assembly?

A

Provides a means to attach and support the prop blades.

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10
Q

The oil in the Prop Hub Assembly is used for what?

A

To lubricate the ball bearings at the base of each prop blade.

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11
Q

Is the oil in the Prop Hub Assembly connected to the pressurized prop hydraulic fluid system?

A

No, separate from the hydraulic fluid system that controls blade angle.

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12
Q

Will loss of hub oil be indicated by an EPC fail, channel, or prop pump light?

A

No, loss of fluid may be visible and be indicated by increased prop vibrations.

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13
Q

What are the two CAUTIONs associated with the Prop Blades?

A

CAUTION: Extended prop operation in rain and other wet environments can be expected to cause minor erosion.
CAUTION: Severe damage can be expected in short time intervals at high power settings if operating over excessive amounts of standing water. Care should be taken when spotting aircraft for high power maintenance turns. Inspect the surrounding areas such as tiedown points (pad eyes) and concrete joints for standing water and other sources of FOD.

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14
Q

What is the function of the prop blade counterweight?

A

In the event of loss of hydraulic pressure the twisting moment imparted by the counterweight will drive the blade to an increased blade angle (i.e. towards feather)

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15
Q

What functions does the AVM provide?

A

Incorporates the Backup Governor (BUG) functions, the Secondary Low Pitch Stop (SLPS) function, the Pitch Rate Delay function, and a portion of the Reverse Enable function.

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16
Q

During normal operation what does the AVM do?

A

Passes course and fine pitch pressure from the EVH through to the PCA.

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17
Q

What functions does the Electronic Prop Control (EPC) provide?

A

The EPC performs speed governing, beta scheduling, synchrophasing, negative torque compensation and feathering control for the prop.

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18
Q

What indications will be displayed in the cockpit when essential prop functions have been transferred to the healthy channel in the EPC?

A

Illumination of the Respective CHAN light.

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19
Q

What is the NOTE concerning a primary channel failure?

A

In the event of a primary channel failure the respective NTS light will not intermittently illuminate during NTS activation. In addition during an NTS failure the light will not illuminate.

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20
Q

What occurs to prop governing if there is a loss of power or failure of the EPC?

A

Prop control will be transferred to the backup Governor.

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21
Q

If the EPC fail light illuminates will prop control always be transferred to the BUG?

A

NO, certain critical EPC faults not failures can also cause the EPC fail light to be illuminated. In these cases the normal (electronic) governing may be maintained.

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22
Q

What is the function of the Prop Battery?

A

To provide backup electrical power to the EPCs.

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23
Q

About how much time does the Prop Battery provide backup power to the EPCs?

A

With a full battery about 20 mins.

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24
Q

What is the function of the Integrated Oil Control Assembly (IOC)?

A

It provides metered hydraulic fluid pressure for prop control.

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25
Q

What is the functions of the Electronic Valve Housing (EVH)?

A

Modulate hydraulic pressure supplied to the pitch change actuator.

Senses the positions of the input lever and the gearbox NTS push rod and provide the information to the EPC.

In conjunction with the EPC plays a primary role in implementing the electronic governing, electronic beta scheduling, negative torque sensing, air start, synchrophasing, and feathering functions.

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26
Q

What Prop system provides the electrical control signal to control the coarse and fine pitch pressure?

A

EPC

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27
Q

What system provides the hydraulic flow to the EVH?

A

Hydraulic flow is provided by the pump housing assembly.

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28
Q

What are the primary components of the EVH?

A

Electrohydraulic servo valve (EHSV), EVH input lever, feather solenoid valve, and manual feather valve.

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29
Q

What are the functions of the Electronic Servo Valve EHSV?

A

Meters the hydraulic flow to the coarse and fine pitch sides of the PCA.

Controls the rate of blade angle change based on signals from the EPC.

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30
Q

What does the EPC use to determine PLA and when the condition lever has been moved to feather?

A

The Input lever

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31
Q

What is the function of the Feather Solenoid Valve?

A

The Feather Solenoid diverts hydraulic supply pressure from the EHSV to the increase pitch side of the PCA. Thus driving the prop towards feather.

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32
Q

What actions cause the Feather Solenoid Valve to divert the hydraulic supply pressure?

A

T-Handle, Auto Feather Relay, or the Condition Lever.

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33
Q

What is the function of the Manual Feather Valve?

A

Allows feather to be commanded by positioning the EVH Input Lever to feather, directing all fluid pressure from the EHSV to be supplied to the increase pitch side of the PCA. That is to drive the blades to feather.

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34
Q

What will cause the Manual Feather Valve to be activated?

A

Placing Condition Lever to FEATH.

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35
Q

What are the functions of the Pump Housing and Reservoir?

A

Provides pressurized prop hydraulic fluid for prop control.

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36
Q

The Pump Housing Reservoir is divided into how many sections and what are they?

A

Two. An atmospheric and a pressurized sump.

37
Q

How many Prop Pumps does each Pump system have and what are they?

A

Three. A Main, Standby, and an Aux pump.

38
Q

What is the purpose of the Prop Aux Pump?

A

Provides prop hydraulic pressure flow during times that prop RPM is insufficient to drive the main and standby pumps.

39
Q

What does illumination of the MAIN PUMP warning lights mean?

A

Output flow from the prop Main Pump is insufficient to control pitch rate changes or the Aux Prop Pump is in operation.

40
Q

What does the illumination of the STBY PUMP warning light mean?

A

Output flow from the prop Standby Pump is insufficient to control pitch rate changes .

41
Q

How are the three prop pumps orientated within the prop Pump Housing and Reservoir?

A

Main Pump is located higher than the Standby Pump and the Aux Pump is the lowest pump in the system.

42
Q

Explain Electronic Governing.

A

Normal mode of prop control when the PLA is at or above FLT IDLE.

EPC determines actual prop rotation speed via magnetic sensors.

EPC will command blade angle changes based on the error sensed by the magnetic sensors in order to maintain 100% RPM.

The EPC’s error signal is supplied to EHSV in the EVH. The EHSV converts the electical signal into a hydraulic fluid flow which in turn drives the PCA at the desired rate, thus changing the blade angle.

43
Q

What is the normal blade angle range for normal governing to occur?

A

FLIGHT IDLE (13 degree) to approx 45 degree. PLA below FLIGHT IDLE resets governing set point to allow for Beta operations.

44
Q

What is Prop Synchrophasing?

A

Creates a master-slave relationship between props to allow for minute changes to blade angle and the governing schedule to reduce aircraft vibration and noise. The Master is the left Prop.

45
Q

When will Synchrophasing be automatically disabled?

A

When the difference between the Master and Slave prop exceeds 10.0 RPM.

46
Q

Explain Backup Governing “BUG”.

A

A strictly hydromechanical means to control prop speed.

Prop speed is determined by displacement of flyweights. Once activated the BUG will govern at a set speed of 102-104 percent RPM to avoid the electronic governing schedule.

Once flyweights do not sense a displacement normal governing can be resumed by a functioning EPC.

The “BUG” blocks hydraulic fluid flow from the EHSV and changes to the blade pitch is controlled from a valve within the “BUG”

47
Q

When will the prop be on “the BUG”?

A

Loss of electrical power or failure of the EPC which results in the inability to perform electronic scheduling.

48
Q

Where are the components located that perform BUG functions?

A

Located in the AVM.

49
Q

What components consist of the “BUG”?

A

Backup Governor, flyweight assembly,and a shutoff valve.

50
Q

Is the “BUG” responsive to PLA changes?

A

No, The “BUG” is a purely hydromechanical component and therefore is not responsive to rapid changes in flight conditions such as approaches and flight idle conditions.

51
Q

What is the purpose of the Electronic Beta Scheduling?

A

The Primary purpose of the electronic beta schedule is to control blade angle during prop operation in the ground range.

52
Q

What is the blade angle range for a prop blade operating in the beta range?

A

13 degree - - 12 degrees at max reverse.

53
Q

How is the beta operation controlled?

A

Control signals sent by the EPC

54
Q

How is the electronic BETA schedule different when the PLA is above flight idle?

A

With the PLA above flight idle to 70 degree PLA the electronic BETA schedule establishes a min blade angle of 13 degree; between 70 - 90 degree PLA the blade angle is lineraly increased to 24 degree.

55
Q

Name the ways to feather the prop.

A

Mechanically opening the feather valve with the condition lever; electrically opening the feather solenoid valve with the condition lever, the T-handle or the auto feather relay; and electrically by the EPC through the EHSV.

56
Q

Discribe the purpose of the Prop aux pump during prop feathering.

A

The aux pump provides additional output to complete the feathering process when pressure from the main and standby pump output is insufficient to complete feathering.

57
Q

What will satisfy the EPC’s pressure cutout logic, which in turn once satisfied will sutoff the prop Aux pump?

A

1) Blade angle > 60 degree; 2) prop fluid pressure builds up to 600-800 psi, 3) 4 seconds has elapsed following feather command input.

58
Q

If 1 of the 3 EPC pressure cutout logic criteria is not met, when will the prop aux pump shutoff?

A

The EPC will deenergize the aux prop pump after 12 secs.

59
Q

Describe the purpose of the NP2000 auto feather?

A

The auto feather system will feather a prop when it is producing less than 500 lbs of prop thrust, thereby avoiding situations during takeoff and landing with a prop stuck in a low blade angle and thus creating significant drag on one side of the aircraft.

60
Q

What conditions need to be met in order for the prop to be feathered by the auto feather system?

A

Engine producing less than 500 lbs of prop thrust, and the respective autofeather switch armed, and the PLA above 75 degree.

61
Q

Will the auto feather system return the prop to normal governing once the engine is determined to be producing >500 lbs of thrust?

A

Yes, however, only if the prop has not fully feathered.

62
Q

List the NP2000’s prop safety features.

A

Negative torque sensing (NTS), safety coupling, blade counterweights, pitch rate delay (PRD), secondary low pitch stop (SLPS), and reverse blade angle logic.

63
Q

Describe Negative Torque Sensing (NTS) operation.

A

Normally the engine produces sufficient power to drive the prop resulting in a positive torque condtion. If the engine does not produce enough power there is a chance the prop will begin to drive the engine. This condition will produce negative torque which, if high enough, can damage the engine-prop coupling. The NTS safety feature of the prop prevents this from occuring.

64
Q

What is the negative torque power range which will cause the NTS to activate?

A

-200 to - 350 shaft horsepower.

65
Q

What Prop components accomplish Negative Torque Sensing Operation?

A

The EVH senses the NTS condition and sends signal to the EPC which commands an increase in blade angle.

66
Q

Does the Negative Torque Sensing logic of inceasing blade angle override the electronic beta or electronic governor schedules decreasing blade angle signals?

A

Yes, however NTS is disabled when PLA is below FLight Idle or the EPC detects the Reverse Enable Solenoid is powered. This enables the prop to operate in reverse.

67
Q

What is the significance of a steady NTS light during prop rotation?

A

Indicates NTS system fault.

68
Q

What is the importance of having a working NTS system?

A

1) Prevents damage to the engine-prop coupling during negative torque conditons, 2) Allows the prop to come out of feather (i.e during airstarts) in a controlled manner and not rapidly go from high blade angle (fully featherd) to a low blade angle (flat blade angle) which would produce significant negative torque.

69
Q

Explain the purpose of the NP2000’s safety coupling feature.

A

Disengages the reduction gear assembly from the power section in order to prevent significant damage to the engine in very high negative torque situations.

70
Q

When will the safety coupling be activated?

A

During conditions that produce -950 to -1600 shaft horsepower.

71
Q

What should activate first, NTS or the Prop safety coupling?

A

NTS should be activated first and the safey coupling is a backup system in case the NTS can not reduce the negative torque situation.

72
Q

What is the purpose of the props counterweight system?

A

To allow the blade angle to increase in situations where there is a loss of prop hydraulic pressure/fluid and therefore prevent excessive drag situations by a prop with a low blade angle.

73
Q

Describe the purpose of the prop’s pitch rate delay(PRD) operation.

A

Designed to allow for momentary loss of hydraulic pressure by either 0 g or gegative g manuevers without changing the blade anlge of the prop.

74
Q

How does the Pitch Rate Delay feature work?

A

PRD significantly limits the rate at which the counterweights will drive the blades to an increased pitch when a loss of hydrualic pressure is sensed.

75
Q

What prop components implement the prop’s Pitch Rate Delay Function?

A

The EPC and the AVM. The EPC senses a change in blade angle > 1 degree and the output pressure of the main and standby prop pumps to determine if PRD will be activated. The AVM redirects the prop fluid thereby slowing the rate at which the blade angle will increase.

76
Q

Although designed as a safety feature, what is the negative impact that Pitch Rate Delay Operations could have?

A

The system can not determine the difference between a loss of pressure due to negative G flight and a complete loss of prop hydraulic oil due to a leak in the system. Therefore the system will slow down the rate at which the prop will go to feather and give the impression to the aircrew the prop has failed to feather when in reality the prop may feather if given enough time for PRD to complete or PRD is disengaged.

77
Q

What is the purpose of the Secondary Low Pitch Stop (SLPS) function?

A

SLPS is a backup to the electronic Beta Schedule in the event the EPC losses power or fails.

78
Q

What does the Secondary Low Pitch Stop function do and how does it work?

A

It enforces a min in-flight blade angle by assuming control of blade angle changes. It assumes control by blocking the fluid from the EHSV, which is controlled by the EPC and instead modulates the fluid to PCA.

79
Q

Where is the Secondary Low Pitch Stow assembly located?

A

Within the AVM.

80
Q

What is the min in-flight blade angle the Secondary Low Pitch Stop function enforces?

A

11 degrees.

81
Q

What blade angle does the electronic Beta schedule establish when the Power Lever is set to Flight Idle?

A

13 degrees.

82
Q

What disables the Secondary Low Pitch Stop to enable reverse operations or operations in the Beta range?

A

Movement of the Power Level to the top of the Flight Idle Gate will energize a Reverse Enable Solenoid which disables the SLPS function.

83
Q

A loss of power to the EPC will have what affect on reverse operations?

A

It will disable the reverse enable solenoid preventing blade angle from going below the Flight Idle position. Thus preventing reverse operations.

84
Q

What is the purpose of the BETA LH and BEAT RH lights on the cockpit glare shield?

A

It provides a visual indication to the pilots that the SLPS have been disabled and therefore the prop can operate in the Beta range.

85
Q

What conditions must be met in order for the BEAT LH and BETA RH lights to be illuminated?

A

1) PLA below 40 degree, 2) the Reverse Enable Solenoid is powered (ie SLPS have been disabled) and the blade angle <23 degrees.

86
Q

What prop component controls the illumination of the BETA LH and BETA RH lights?

A

The EPC.

87
Q

What does the FEA OVERRIDE switch do?

A

Allows for activation of the aux pump by overriding the EPC aux pump cutout logic thereby restarting the feathering process.

88
Q

What systems does the Prop IBIT test?

A

The BUG, fuel control overspeed governor and the SLPS.

E-2C NATOPS (6 decks)

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