Hydraulics

Question 1

What’s the purpose of Power Transfer
Unit?

Answer 1

Provides operational redundancy to left
system (especially to get gear up with
failure of left engine on takeoff)

Question 2

What’s the purpose of Aux pump?

Answer 2

Primarily designed for ground and
maintenance operations

Question 3

Where are hydraulic reservoirs
located?

Answer 3

There are two (2) hydraulic reservoirs
located in forward section of tail
compartment: left hydraulic system
reservoir on left and right hydraulic
system reservoir on right.

Question 4

A visual sight gage is installed on
high pressure end of each hydraulic
reservoir and clearly indicates proper
FULL and REFILL levels of
reservoir. What is required for
accurate reading?

Answer 4

Electrical power is not required to read
sight gage; however, system must be
pressurized to obtain correct reading.

Question 5

Describe engine-driven pump.

Answer 5

It’s constant pressure, variable volume
pump, which means it produces 3000 psi
anytime engine is running (except for
pump unloading feature during engine
start in-flight).

Question 6

What’s the purpose of hydraulic heat
exchangers and where are they
located?

Answer 6

There are two hydraulic heat exchangers:
one for each system located in each
hopper close to floor. Functioning as a
radiator, heat exchanger allows
surrounding, cooler fuel to cool the hotter
hydraulic fluid.

Question 7

How many hydraulic accumulators are
there and what’s the pre-flight
requirement?

Answer 7

There are two accumulators: one for each
system. Check for 1200 psi at 70°F
nitrogen pre-charge on preflight.

Question 8

What are requirements for PTU
operation when ARMED?

Answer 8

1) left system pressure < 2400 psi
2) fluid in left system
3) right system not hot

Question 9

How would gear and flaps operate
differently with aux pump?

Answer 9

They’d operate much slower due to low
flow rate

Question 10

How does Aux pump operate
differently in air when selected to
ON?

Answer 10

It operates regardless of hydraulic quantity
or temperature; however, it automatically
shuts off after two (2) minutes to prevent
inadvertent depletion of the batteries.

Question 11

There are two replenishing systems in
tail compartment. What are they for?

Answer 11

One is for hydraulics and one is for oil
replenishing

Question 12

What are the requirements for Aux
pump operation when ARMED?

Answer 12

In-flight:
1) left system pressure < 1500 psi
2) fluid in left system
3) left system not hot
4) flap handle position doesn’t match flap
position OR landing gear handle position
doesn’t match gear position

Aux pump activates on ground with left
system and inboard accumulator pressure
< 1200 psi and brake pedals depressed.

It deactivates when inboard brake
accumulator is replenished.