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Bell 407 > Hydraulics > Flashcards

Hydraulics Flashcards

1
Q

Purpose of the hydraulic system

A

Provides pressurized fluid to operate all flight control servo actuators to reduce pilot workload

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2
Q

Describe the operation of the hydraulic switch

A

The switch electrically controls the system
Fail Safe - ON: in case of total electrical failure

ON - solenoid valve de-energized open = pressurized hydraulic fluid flows to the 4 servos
OFF - solenoid valve energized closed = pressurized hydraulic fluid flows to the reservoir and bypasses the 4 servos

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3
Q

Describe the relationship between the switch and the circuit breaker

A

Circuit breaker protects the electrical circuit that the switch is on.
Switch - OFF
Circuit Breaker - OUT
Hydraulic fluid flows to the servos

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4
Q

What are the components of the hydraulic system?

A 
Reservoir
Pump
Filters
Solenoid valve
Relief valve
Cyclic and collective servo actuators and supports
Tail rotor servo actuator
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5
Q

Describe the hydraulic cooling system

A

No specific cooling system

- Heat dissipates from the hoses and lines as air circulates beneath forward cowling

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6
Q

Describe the hydraulic reservoir

A

Reservoir and cover are magnesium alloy

  • mounted on brace and support
  • site glass must not have any bubbles

Capacity: 1.3 US Pints
Total system capacity: 1.68 US Quarts

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7
Q

Capacity of the Hydraulic Reservoir

A

1.3 US Pints

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8
Q

Capacity of the Hydraulic System

A

1.68 US Quarts

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9
Q

What type pump does the hydraulic system use?

A

Pump is a constant pressure, variable delivery, self-lubricating type

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10
Q

Describe the pump system

A

Pump is a constant pressure, variable delivery, self-lubricating type

  • designed to operate continuously and provide rated discharge pressure of 1000 +/- 25 PSI
  • mounted on transmission
  • driven by transmission accessory drive
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11
Q

How many filters does the system have?

A

2

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12
Q

When do the Hydraulic Filter LRBs pop?

A

70 +/- 10 PSID

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13
Q

At what temp do the hydraulic filter LRBs not work?

A

Indicators wont work with fluid temp < 2C

- to prevent inaccurate indications

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14
Q

Which hydraulic filter has bypass capability?

A

Only the return line filter has bypass capability (interior filter)
- to prevent over pressurization of return system

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15
Q

Describe the filters

A

2 filters, one on pressure line and one on return line, both with impending bypass indicators

  • LRB pops at 70 +/- 10 PSID
  • Indicators wont work with fluid temp < 2C to precent inaccurate indications
  • Only the return line has bypass capability (interior filter) to prevent over pressurization of return system
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16
Q

What is the purpose of the solenoid valve?

A

Opens or closes the flow of hydraulic fluid to the servos based on the position of the hydraulic switch, or the state of the electrical system
Fail Safe - ON: in case of total electrical failure

ON - solenoid valve de-energized open = pressurized hydraulic fluid flows to the 4 servos
OFF - solenoid valve energized closed = pressurized hydraulic fluid flows to the reservoir and bypasses the 4 servos

17
Q

Where is the solenoid located and what does it look like?

A

Mounted on cabin roof, left side of servos

- dark gray tube closest to deck floor

18
Q

What is the purpose of the relief valve?

A

Relief valve opens to protect the system from damage.

19
Q

Where is the relief valve and what does it look like?

A

Mounted on cabin roof, left of servos

- light grey tube, long and slender

20
Q

What is the state of the relief valve during normal operations?

A

During normal operations: relief valve is closed

21
Q

At what pressures does the relief valve open?

A

1075 - 1375 PSID

22
Q

Describe the operation of the relief valve?

A

When the system pressure rises to within a range of 1075 - 1375 PSID the relief valve opens to protect the system from damage

  • returns excess fluid to reservoir
  • closes when pressure returns to normal
23
Q

Which are the cyclic servos

A

The 2 outboard servos

24
Q

Which is the collective servo

A

The single center servo

25
Q

How are the cyclic and collective servos supported?

A

Springs installed parallel to push/pull tubes

- assist pilot with increased control feedback forces if hydraulic pressure is lost

26
Q

Where is the tail rotor servo located?

A

Intermediate section

- above the baggage compartment

Bell 407 (19 decks)

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