Hydraulics (S1)

Question 1

What are the 2 types of fluid system

Answer 1

Fluid Transport
Fluid power

Question 2

What is fluid transport

Answer 2

Delivery of liquid or gas from one location to another

Question 3

What is fluid power

Answer 3

Using pressurised liquid or gas to do work using a cylinder or motor

Question 4

What are the 4 advantages of fluid power

Answer 4

Ease of control
Multiplication of force
Constant force
Simple, safe, cheap

Question 5

What are the advantages of using hydraulic oils

Answer 5

Very high forces
Rapid response to input
Power to weight ratio
Reliable
Not affected by electromagnetics

Question 6

What is the flash point of a liquid

Answer 6

The temperature at which a liquid gives off vapour that can be ignited. Higher flash point is more desirable

Question 7

What are the 3 methods of transmitting power

Answer 7

Electrical
Mechanical
Hydraulic

Question 8

What methods can be used to identify oils

Answer 8

JSD (Joint service designation)
Colour dyes

Question 9

What are the 6 favourable properties of a hydraulic oil

Answer 9

Good lubricity and viscosity
Chemical and environmental stability
Comparability with system materials
Fire resistance
Low density
Inexpensive

Question 10

What are the 7 parts of a reservoir

Answer 10

Pressure gauge
Replenishment point
PRV
Sighting glass
Inlet
Outlet
Baffles

Question 11

Where are unpressurised reservoir’s mounted

Answer 11

The highest possible point in the hydraulic system

Question 12

What are the basic parts of a hydraulic system

Answer 12

Reservoir
Pump
PRV
Filter with bypass and blockage indicator
NRV
Accumulator
Gauge warnings
Selector valve
Jack

Question 13

What does an accumulator do

Answer 13

Stores nitrogen to be used for a short while in case of hydraulic failure so aid the pilot using his controls

Question 14

What tubing is used on low pressure systems (below 1000psi)

Answer 14

Aluminium alloy

Question 15

Where are flexible hoses used

Answer 15

In areas of high vibration

Question 16

What types of hose inner liner are there

Answer 16

Butyl
Teflon

Question 17

What are the 4 categories of seals

Answer 17

Positive - do not allow any leakage

Non-positive - permit a small amount of a leakage

Static - used between 2 non-moving parts

Dynamic - used between 2 parts moving relative to each other

Question 18

What are the 6 types of seals

Answer 18

O-Rings
Back up rings
V rings
Piston rings
Wiper rings
Bonded seals

Question 19

What 4 parts are standard in a pipe to pipe coupling

Answer 19

Sleeve
Union nut
Collar
Adaptor nipple

Question 20

What identification is used for hydraulic pipelines

Answer 20

Blue and yellow sticker, black circle labelled HYDRAULIC

Question 21

What are the 2 types of PFCU

Answer 21

Power assisted
Power operated

Question 22

Why is it integral to have a feedback system

Answer 22

So the pilot can accurately feel the response back from his input

Question 23

What is the accuracy of a response

Answer 23

The effectiveness of the feedback system as well as the precision of parts installed

Question 24

What is the stability of a response

Answer 24

The ability to hold the control position without unwanted movement. Affected by system tolerances and competent maintenance

Question 25

What is manual reversion

Answer 25

Manually controlling the flying control system following a loss of hydraulic power, only acceptable for light aircraft

Question 26

What is multiplication

Answer 26

Using 2 separate hydraulic systems to ensure the security of the flying controls in the event of one system becoming damaged or unusable. Uses a tandem jack arrangement

Question 27

What type of artificial feel is fitted to helictopters

Answer 27

Fitted to cyclic pitch controls - spring feel

Question 28

What types of autopilot are there

Answer 28

Single axis Double axis Triple axis

Question 29

How does an autopilot operate

Answer 29

Detect disturbances to the aircraft by 3 gyros (one for each axis) which send signals to a processor which corrects and changes the control surfaces to right the axis

Question 30

What are the 3 abnormal flight characteristics

Answer 30

Uncommanded Flying Control Movements (UFCM) Control Restrictions (CR) Unusual Occurrences (UO)

Question 31

What is a system redundancy

Answer 31

Atleast 2 hydraulic systems present so that if one becomes damaged or malfunctions, there is a backup from which all systems can be run

Question 32

What are some system safety features

Answer 32

Alternative power sources System redundancy Manual reversion Manual deployment of systems

Question 33

What does hygroscopic mean

Answer 33

Hydraulic fluids can absorb moisture from the air at a small level, causing issues within the system

Question 34

What 2 devices can be used to replenish hydraulic reservoirs

Answer 34

Juniper rig Risbridger pump

Question 35

What are the 4 possible causes of a pipe bursting or cracking

Answer 35

Excessive vibration Improper installation Metal fatigue Damaged by collision

Question 36

What is meant by chemical stability

Answer 36

Resistance to oxidisation

Question 37

What do baffles in a reservoir prevent

Answer 37

Fluid surge

Question 38

What are the 2 types of pumps

Answer 38

Constant displacement Self regulating

Question 39

What does a sequence valve do

Answer 39

Allows flow in one direction but can be opened to allow both directions

Question 40

What are the 3 areas where filters can be found

Answer 40

Suction lines Pressure lines Return lines

Question 41

What is used to help prevent O-Rings from wearing

Answer 41

Back up rings

Question 42

What type of seal is used in rams, jacks and pistons

Answer 42

V-Ring

Question 43

What is a bonded seal

Answer 43

Used to seal unions or plugs. A metal washer prevents deformation and over compression of the seal

Question 44

Where are bonded seals likely to be found

Answer 44

Banjo unions

Question 45

What is power assisted flight

Answer 45

Pilot inputs aided by hydraulic power, but can be flown manually

Question 46

What is jack stall

Answer 46

Servo jack cannot overcome the aerodynamic forces acting against it

Question 47

What is a common source of emergency power, to continue the operation of hydraulic systems

Answer 47

Ram air turbine