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Flashcards in Hydraulics Deck (26):

What should the main and standby hydraulic pressure indicate after start?

After pressing the "HYDRAULIC ISO VLV" switch, what should hydraulic #3 system pressure ?

Main: 2900psi - 3100psi

Stby: 2800psi - 3000psi

#3 Sys: 2400psi - 3000PSI


When is the #3 hydraulic system used?

What is the normal mode?

When does it come on?

Whenever either one of the PTUs in the elevator fails. Dual engine failure or either hydraulic system fails.

It is normally in "Active Standby Mode".

This means it will come on automatically when pressure is lost.


Where are PTU pressure indications displayed?

On the switch itself.


Where is the standby Hyd pump indicated?



How many parking brake applications are supplied by a fully charged accumulator?



How many hydraulic systems and what does each power?

3 Main and 1 Aux

#1 #2

Flaps Landing gear
Anti-skid Brakes Outboard Spoilers
Inboard Spoilers Nosewheel steering
Rudder (Lower PCU) Elevator (Centre PCU)
Elevator (Outboard PCU) Rudder (Upper PCU)
PTU Emergency Brake

#3: Inboard Elevator PCU

Aux: Alternate main landing gear extension


When is the min hydraulic pressure for the PTU?

2400 PSI in #1 hydraulic system.

Therefore the standby hydraulic pump is not efficient enough.


When does the priority valve modulate (closes)?

What services limit when the priority valve modulates?

2100 PSI

When the priority valve modulates, it cuts off flaps and PTU


What is the main requirement if you lose Hyd sys 2?

....Hyd Sys 1?

Alternate gear extension

Flapless landing


When is PTU and #1 sys standby pump on without any indication (not pushed)?

Engine failure

Loss of system pressure

Flaps greater than 0°

Reservoir not empty

AC power available


When does the #3 Hyd pump caution light come on?

When Hyd 3 pres is below 900 PSI or if DCMP has been operating for more than 60 seconds on the ground.


When would a hydraulic isolation valve close?

What services do you have if #1 hydraulic isolation valve closes?

...#2 hydraulic isolation valve?

If the hydraulic level is low for that particular system

#1 #2

Rudder Rudder
Elevator Elevator

***Hint: REFP


If green hash marks stay on after setting PTU switch to off in the air, what's the problem?

The PTU is supplying pressure because either:

-No2 sys lost pressure but still has fluid and No1 EDP is supplying at least 2400psi and.
-Flaps are selected more than 0°. You most likely didn't raise flaps completely. i.e flaps greater than 5 on takeoff and you raised them to 5 instead of 0.
-No 2 engine oil pres is low.


Why do we have to wait till the rudder check is complete before we turn on the PTU when doing a single engine taxi out?

To reduce stress on the STBY HYD Pump


Where are the hydraulic temperature sensors located?

In the reservoir.


When will the firewall shutoff valve close?

Associated pull fuel/Hyd off handle is pulled.

Fluid overheat.

Low fluid quantity.


Where is the hydraulic fluid to fuel heat exchanger located?

What controls the flow of hydraulic fluid?

Related fuel collector bay.

Bypass valve.


What kind of motor is the standby pump?

Hydraulic system 3 pump?

AC motor pump powered by the right 115 VAC bus.

DCMP powered by the standby battery.


If the standby hydraulic is automatically energized is there an indication on the switch?



What is essential for PTU operation?

Hydraulic pressure in both systems 1 and 2.


How is the DCMP controlled?

Two pressure switches. One commands the DCMP to automatically operate if system pressure drops below 2600 psi.


What is the purpose of the accumulator isolation valve in the No. 3 hydraulic system.

What is its normal mode?


Isolate elevators from No.3 hydraulic system pressure.

Normally in active standby mode.


What happens when you push the No 3 hydraulic ISO valve?

Energizes the DCMP.

Opens accumulator isolation valve.


What are the quantities of the hydraulic reservoirs.

#1. 8 quarts
#2. 12 quarts
#3. 2.6 quarts


Where is the alternate landing gear reservoir located?



Describe operation of hydraulic system system 3?

DCMP operates intermittently and is controlled by two pressure switches. One switch signals the DCMP to operate at 2600 psi to pressurize the accumulator and the other pressure switch signals it to shut off when pressure reaches 3250 psi.