Hydraulics

Question 1

Hydraulic System Description

• number of systems
• names
• minimum dispatch quantity for systems 1, 2, and 3

Answer 1

• (4) hydraulic systems:
o #1 and #2 Main systems
o #3 Backup system
o Auxiliary system

NOTE: The minimum dispatch quantity for the #1, 2, and 3 systems is 40% of their normal volume

Question 2

1 Hydraulic System

• number of reservoirs and quarts
• number of pumps
• when will the AC standby pump activate
• describe the PTU and when it activates
• min parking brake pressure prior to starting the left engne

Answer 2

• 1 reservoir (8 quarts)
• 1 Engine Driven Pump (EDP)
• 1 AC Standby Motor Pump (ACMP) used as a back-up for the EDP
• AC Standby pump will automatically activate when the No. 1 engine fails, or whenever the flaps are selected to any position greater than 0° (the parking brake must be released)
• PTU (Power Transfer Unit) uses hydraulic POWER from system 1 to provide hydraulic PRESSURE to system 2
• PTU will automatically turn ON when the #2 engine fails or whenever the flaps selected to any position greater than 0° (the parking brake released)

NOTE: Minimum indicated parking brake pressure prior to starting the LEFT Engine first is 1000 psi

Question 3

1 Hydraulic Abnormal Operation

• A “Hydraulic System Isolation Valve” remains open for all normal operations
• If inadequate fluid quantity or loss is detected in the system, #1 Hydraulic system HYD ISO valve CLOSES, hydraulic power is only AVAILABLE to the following #1 services: (4)

Answer 3

• PTU
• Rudder (lower pcu)
• Elevators (outboard pcu)
• Flaps

Question 4

#1 Hydraulic Abnormal Operation
- "priority valve" remains open for normal ops: at what pressure will it close and shuts of power to what (2)

Answer 4

• A “Priority Valve” remains open for all normal operations
• If the hydraulic pressure in #1 system decreases below 2100 psi, the “Priority Valve” automatically closes
• Closing of the “Priority Valve” shuts off hydraulic power to the Flaps and PTU

Question 5

1 Hydraulic Abnormal Operation

• when must the standby hydraulic pump be manually activated
• when will the standby hydraulic pump automatically be activated

Answer 5

• Standby hydraulic pump must be manually activated in the event of a #1 EDP failure to maintain pressure to the system
• Standby hydraulic pump will automatically activate in response to a #1 engine failure

Question 6

1 Hydraulic Abnormal Operation

• If the #1 and/or #2 Main hydraulic systems fail, #3 hydraulic system will automatically activate to supply pressure to the
• If automatic activation does not take place, #3 system can be activated manually by pressing the

Answer 6

• If the #1 and/or #2 Main hydraulic systems fail, #3 hydraulic system will automatically activate to supply pressure to the left and right elevator (inboard PCUs) to maintain pitch control
• If automatic activation does not take place, #3 system can be activated manually by pressing the “HYD #3 ISOL VLV” switchlight on the HYDRAULIC CONTROL panel

Question 7

2 Main Hydraulic System

• number of reservoirs and quantity
• number of pumps
• what valves does it/does not have
• min parking brake pressure prior to starting the right engine

Answer 7

• 1 Reservoir (12 quarts)
• 1 Engine Driven Pump (EDP)
• Has no PTU
• A “Hydraulic System Isolation Valve” remains open for all normal operations
• “Priority Valve” does not exist on the #2 Hydraulic System because it is assisted from the #1 Hydraulic System PTU

NOTE: Minimum indicated parking brake pressure prior to starting the RIGHT engine first is 500 psi

Question 8

2 Hydraulic Abnormal Operation

• A “Hydraulic System Isolation Valve” remains open for all normal operations
• If inadequate fluid quantity or loss is detected in the system, #2 Hydraulic system HYD ISO valve CLOSES, hydraulic power is only AVAILABLE to the following #2 services:

Answer 8

• Rudder (upper pcu)

- Elevators (center pcu)

Question 9

2 Hydraulic Abnormal Operation

• when must the PTU be manually activate
• when will the PTU automatically activate

Answer 9

• PTU must be manually activated in the event of a #2 EDP failure to maintain pressure to the system
• PTU will automatically activate in response to a #2 engine failure

Question 10

2 Hydraulic Abnormal Operation

• If the #1 and/or #2 Main hydraulic systems fail, #3 hydraulic system will automatically activate to supply pressure to the
• If automatic activation does not take place, #3 system can be activated manually by pressing the

Answer 10

• If the #1 and/or #2 Main hydraulic systems fail, #3 hydraulic system will automatically activate to supply pressure to the left and right elevator (inboard PCUs) to maintain pitch control
  • If automatic activation does not take place, #3 system can be activated manually by pressing the “HYD #3 ISOL VLV” switchlight on the HYDRAULIC CONTROL panel

Question 11

3 Backup Hydraulic System

• number of reservoirs and quarts
• powered by
• accumulator pressure maintained by and kept between what psi
• If Both EDPs, Standby Hydraulic Pump, and the PTU FAIL, the DCMP in the #3 hydraulic system will provide hydraulic power to the

Answer 11

• 1 Reservoir (2.6 quarts)
• Powered by a gas charged accumulator
• Accumulator pressure is maintained by a DC Motor-Driven-Pump (DCMP)
• DCMP operation is to maintain the accumulator pressure within 2600 to 3250 psi
• If Both EDPs, Standby Hydraulic Pump, and the PTU FAIL, the DCMP in the #3 hydraulic system will provide hydraulic power to the left and right elevator for pitch control

Question 12

#3 Hydraulic Abnormal Operations
- If the #3 Hydraulic system accumulator pressure falls to \_\_ psi, or if the DCMP has been running for longer than \_\_ seconds while on the ground, it results in the illumination of the #3 \_\_ caution light

Answer 12

• 900, 60, STBY HYD PUMP

Question 13

#3 Hydraulic Abnormal Operations
- If the #3 Hydraulic system isolation valve fails OPEN during normal operations, it results in

Answer 13

• all three hydraulic systems supplying pressure to the elevator actuators and the illumination of a “ELEVATOR PRESS” caution light

Question 14

4 Auxiliary Hydraulic System

• reservoir and quantity
• quantity indication
• purpose of the system

Answer 14

• 1 reservoir (1.2 quarts) located in the right forward lower compartment, aft of the crew O2 bottle
• There is NO quantity indication in the cockpit
• Manually operated system and serves as an alternate means of extending the main landing gear
• This manual system is used to ensure the main landing gear is completely extended