11.11 Flashcards
1
Q
How much psi in large transports
A
5000psi
2
Q
Civil aircraft pressure figure
A
207 bar or 3000 psi
3
Q
How do we create a higher force
A
Increase diameter of actuator or pressure
4
Q
What are the 2 types of hydraulic pressure
A
Hydrostatic pressure
Hydrodynamic pressure
5
Q
How do you make sure there is enough redundancy for safe flight
A
Several hydraulic systems
6
Q
Aircraft with two or more hydraulic systems are required to have what
A
Independent mechanical system
7
Q
Airbus pressure distribution section
A
Manifold
8
Q
Boeing pressure distribution section
A
Module
9
Q
An open centre system has fluid flow but what does it not have
A
No pressure in system when actuating mechanisms are idle
10
Q
When is the fluid under pressure in a closed centre system
A
Whenever the pump is operating
11
Q
Advantage of open centre vs closed centre
A
Continuous pressurisation of system is eliminated
12
Q
Why are small power packs good
A
Reduces weight by eliminating hydraulic lines and large quantities of hydraulic fluid
13
Q
What pressurises quicker and transmits force more efficiently , fluid or gas?
A
Fluid
14
Q
What is chemical stability
A
Ability to resist oxidation and deterioration for prolonged periods
15
Q
What flash point do we want
A
High for good resistance to combustion and Low degree of evaporation at normal temperatures
16
Q
What fire point do we want
A
High
17
Q
Diffrenve between flash point and fire
A
Fire point is when it will continuously burn
18
Q
When would mineral oil be used and is it interchangeable?
A
When fire hazard is low & it is interchangeable and dyed red
19
Q
What is a problem with polyalphaolefin based oil
A
High viscosity at low temperatures
20
Q
Most common aircraft hydraulic fluid
A
Skydrol
21
Q
What the advantage to type IV type 1 have
A
Weight saving
22
Q
What fluids don’t mix
A
Petroleum and phosphate ester
23
Q
Where does pressurised filling happen
A
Service panel
24
Q
Where is the sampling valve
A
Hp manifold
25
What’s the sampling valve end cap
Products valve from dirt and also tool to open needle valve (sampling valve)
26
How often is a routine sample for hydraulic sampling
Once a year
every 3000 flight hours
when airframe manufacturer suggests
27
What should you do if u suspect contamination
Fluids drained and replaced and samples taken
28
Where is leak measurement manifold linked to
Hp manifold
29
What aircraft uses non pressurised resouvoris
Aircraft that is non designed for violent manouvers
Fly at high altitudes
Or where resouvoir is in a pressurised area
30
What’s the purpose of the reservoir pressurisation module
Supplies bleed air to the reservoirs
31
How many filters and check valves does a pressurisation module have
2
32
What does an accumulator do
Accumulate energy and smoothen out pulsations
33
What is a spherical accumulator and what does it contain
Steel sphere divided into 2 chambers
Top is fluid at system pressure
Bottom is charged with nitrogen or air
34
What is a cylindrical accumulator
Piston separates fluid from air
35
How is a piston sealed in a cylindrical accumulator
Double seal rings to prevent internal leakage
36
Where are cylindrical accumulators used
High pressure systems
37
What is an accumulator preload
Nitrogen chamber charged to pre determined pressure lower then system operating temperature
38
What’s the primary source of pressure generation
Mechanical driven pumps
39
What’s a non positive displacement pump
Produces continuous flow but output varies with pressure
40
What’s a constant displacement pump
Forces a fixed amount of fluid with each revolution
41
What kind of pump is a gerotor
Positive displacement
42
What type of pump is a piston pump
Constant displacement or variable
Most common main system (positive displacement)
43
What is a drive coupling
Short shaft with set of male splines on both ends
44
What kind of device is a pump drive coupling
Saftey device
45
What type of pump is axis piston
Constant displacement axial pump
46
What type of pump is a vane pump & many blades in a vane pump
Constant displacement pump with 4 blades
47
What does a variable displacement pump convert
Mechanical energy to hydraulic and vice versa
48
What pump is more energy efficient
Variable displacement is more efficient then fixed
49
What term is used to describe primary hydraulic power
Main pressurisation
50
When are electrically driven pumps used
Emergencies and during ground operation when engines aren’t running
51
Why are hand pumps installed
Testing and emergencies
52
Why is single action hand pump not used
Inefficient
53
What type of pump is the RAT
Vdp
54
How is the electric motor of the pump cooled
With air or hydraulic fluid
55
What percentage of system failure is down to contamination
85%
56
How many microns in an inch
25400 microns
57
What filter is used for surface cleaning
Wire mesh
58
Which filter has the best filtration quality
Micro glass as it stops anything bigger then 10 microns
59
What does a bypass relief valve do
Opens if the filter clogs as dirty oil is preferred over no flow
60
What is the purpose of a filter bypass system?
The filter bypass system is activated when the filter element becomes clogged and unable to filter, allowing unfiltered fluid to bypass the filter element.
## Footnote
Example sentence: A spring-loaded valve opens to allow the unfiltered fluid to bypass the filter element.
61
What is a differential pressure indicator used for?
A differential pressure indicator is used to provide a visual sign that the filter is clogged and the filter bypass has been activated.
## Footnote
Example sentence: A red button installed on the filter pops into view when the filter is clogged, and it stays in view even if the bypass valve opens.
62
What are the configurations of differential pressure indicating devices?
electrical switches, continuous reading visual indicators, and visual indicators with memory.
## Footnote
Example sentence: Visual indicators with memory usually take the form of magnetic or mechanically latched buttons or pins that extend when the differential pressure exceeds that allowed for a serviceable element.
63
Why are visual indicators with memory useful?
Visual indicators with memory provide a permanent warning of a loaded element, particularly in remote locations where continuous monitoring is impossible.
## Footnote
Example sentence: The button or pin, once extended, remains in that position until manually reset, providing a permanent warning of a loaded element.
64
What does a pressure relief valve consist of
Spring loaded valve which is operated by hydraulic pressure and spring tension
65
3 most common pressure relief valves
Ball
Sleeve
Poppet
66
What does a thermal relief valve do
Relieve pressure due to thermal expansion
67
Purpose of pressure regulator
Manage output to pump to maintain system operating pressure within a predetermined range
Pump to turn without resistance
68
What seals are used on moving parts
Packing’s
69
What seals are used on non moving parts
Gaskets
70
What are v rings
One way seal and it faces the pressure
71
What are u ring seals used for
Brake assemblies and pressure under 1000psi
72
What direction does a u ring seal
One direction
73
What direction is an o ring
Both
74
What’s a red oring for
Fuel
75
What colour is a hydraulic fluid o ring
Blue
76
Backup ring material
Teflon
77
What to check in a back up ring
Coils don’t separate more then 1/4 inch when unrestrained
78
When are static seals used
Steady or pulsating force
79
When is a dynamic deal used
Stroking or rotational movement
80
What do we sue a asbestos gasket
Heat resistance
81
When do we use a copper gasket
Non compressive semi soft gasket , spark plug
82
When do we use cork gaskets
Oil seal between engine crankcase and accessories
83
When do we use a rubber gasket
When a compressible gasket is needed
84
Before you install an oring what should you do
Immerse it in clean hydraulic fluid
85
What are the 3 common valves
Ball , sleeve , poppet
86
What do flow control valves do
Control speed and direction of fluid in hydraulic system
87
What are the two selector valves and what do they do
Open - continuous flow even when selector can’t actuate a unit
Closed - blocks flow where valve is in neutral or off position ( 4 port valves most used)
88
What the purpose of a quick disconnect valve
Prevent loss of fluid when unit is removed
89
What does a shuttle valve do
Isolate normal system from an alternate or emergency system
90
What a heat exchanger used for
Cool hydraulic fluid
91
How do we ensure there is a leak proof joint on a disconnecting pipe fitting
Locate the sleeve on the pipe in the right position
92
What’s a non disconnecting pipe fitting used for
Repair broken pipes by swaging
93
Hose classification
Low
Medium
High
( always disconnecting type)
94
What’s case drain fluid used for
Cool and lubricate pump before entering reservoir
95
How is a subsystem indicated
Particular number and colour
96
What does a pressure transducer do
Convert one form of energy to another
97
What’s a bourdon tube
Elastic type pressure transducer
Used for liquid and pneumatic pressure measurements
Range of 100,000 psi
98
How do you overcome the short comings of fly by wire
Use power by wire
99
How do you overcome the short comings of fly by wire
Use power by wire
100
When is a hydraulic motor driven generator used
When electrical failure occurs as it’s an alternative source of power
It’s an AC generator
