AIRSYS MOD 2 Flashcards
This is the science relating to the behavior of liquids under various conditions and in aircraft, these systems provides a
means of operating large and
remote components that it would
not be possible to operate
satisfactorily by other means.
Hydraulics
Aircraft systems provide a means of
power transmission through the
medium of hydraulics through an
incompressible fluid via ___________
Pipelines and Actuators
Who stated “If a force is applied to a liquid in
a confined space, then this force
will be felt equally in all
directions”.
Blaise Pascal
This principle where all hydraulic systems operate.
Pascal’s Law
The force employed when a hydraulic
system is operated is caused by
________.
Without some form of restriction there can be no _________.
Pressure
In hydraulic systems, this restriction
is provided by movable pistons
which travel backwards and
forwards in cylinders. These
assemblies being known as
_______________.
hydraulic jacks or actuators
Formula of Pressure
P=F/A
Who invented a hydraulic press and observed that:
a) The smaller the area under
load, the greater the pressure
generated.
b) The larger the area under
pressure, the greater will be
the load available.
Joseph Brahma
The ____________ is a Passive
Hydraulic System where a force is
applied to a piston (piston A) only
when it is desired to move the load
(piston B).
Brahma Press
Different Kinds of Hydraulic Fluid Properties
Incompressible
Good Lubricating Properties
Good Viscosity
High Boiling Point/Low Freezing Point
High Flash Point/Non-Flammable
Chemically Inert/Non-Corrosive
Resistant to Evaporation
Free from Sludging and Foaming
Reasonably Priced
Readily Available
Equivalent to H515 NATO,
OM15, and MIL-H-5606F
Clean mineral hydraulic fluid
Colored red
Used with synthetic neoprene
rubber seals
Recommended for all hydraulic
systems under high pressures
and low or very low
temperatures (-54 C° to 90 C°)
DEF STAN 91-48
Phosphate ester based
synthetic hydraulic fluid
Purple in color
Used with Synthetic Butyl
Rubber Seals
Prolonged exposure will
damage skin and eyes
Very high flashpoint (170 C°)
Less prone to cavitation
SKYDROL
It is of major importance that
only the specified hydraulic oil
or its approved alternative is
used in a hydraulic system If
the incorrect fluid is added to a
system breakdown of the seals
is likely causing fluid leakage,
both internally within
components and externally
from the actuators.
Hydraulic Fluids
The friction between the walls of the pipes and the fluid depends upon:
a) Velocity of the fluid in the pipes.
b) Length, bore, and the internal finish of the
pipes.
c) Number of bends.
d) Viscosity of the oil.
These perform a very important
function in a hydraulic system,
which is preventing leakage of
fluid.
Seals
__________ seals, fitted between
sliding surfaces, may be of
many different shapes,
depending on their use and on
the pressure involved.
Dynamic
___________ ring seals are
effective in one direction only,
but ___ rings and square
section seals are often used
where pressure is applied in
either direction.
“U“ and “V”
“O”
Where high pressures are used,
an O-ring is normally fitted
with ____________ which
retains the shape of the seal
and prevents it from being
squeezed between the two
moving surfaces.
stiff backing ring
Dynamic seals require
___________ to remain effective.
Wetting of the bearing surface
or a slight seepage from the
seals is normally acceptable.
lubrication
If a seal of an incorrect material is used in a
system, the sealing quality will
be seriously __________, and this
may lead to failure of the
component.
degraded
Seals are easily damaged by
grit, and a _________ is often
installed on actuators to
prevent any grit that may be
deposited on the piston rod
from contaminating the seals.
wiper ring
6 components of a hydraulic system
Reservoir of oil
pump
Selector or Control Valve
Actuators or Jack
Filter
Relief Valve
Two types of Hydraulic Systems
Passive and Active Hydraulic Systems
This type of System is where a pump supplies the pressure
Active Hydraulic System
Two types of Active Hydraulic System
Open Center and Closed
What is the disadvantage of an open center system
one service can be operated at a time
What is the main advantage of an open center system
It is simple
Fluid is passed directly to the
reservoir when no services are
being operated, this allows the
engine driven pump to run in
an “offloaded condition” as
little pressure is generated but
there is still a flow through the
pump to cool and lubricate it.
Open Center System
Advantage of Closed System Hydraulics
multiple services can be operated at the same time
In systems which employ a fixed
volume pump (constant delivery),
an automatic cut-out valve is
fitted, to divert pump output to the
reservoir when pressure has built
up to normal operating pressure.
Closed System
A _________ provides storage space for
the system fluid.
reservoir
They remove foreign particles from
the fluid.
FILTERS
Filters are fitted in both__________ lines that is at both sides
of the pump.
suction and pressure
Other filters are fitted with a
__________ valve which
allows unfiltered fluid to pass
to the system when the
element becomes clogged.
relief or bypass
It draws oil from the reservoir and deliver a supply of
fluid to the system.
Pumps
In most cases, ______________ are used to provide alternate supply as part of the
redundancy provision for the safe operation of the aircraft.
air pump, ram air turbine, and power transfer unit
_________ may be the only source of power
in a small, light aircraft hydraulic system, but
may also be used on larger aircraft:
To allow ground servicing to take place
without the need for engine running.
So that lines and joints can be pressure
tested.
So that cargo doors, etc., can be operated
without power.
Hand Pumps
Two types of powered or engine driven pumps
Constant Delivery, Constant Pressure Pumps
It supplies fluid at constant rate
irrespective of demand and
therefore needs an automatic cut
out or relief valve to return the
fluid to the reservoir.
Constant Delivery Pump
This pump supplies fluid at a
variable volume and controls
its own pressure.
This type of pump is typically
fitted in modern aircraft whose
systems operate at 3,000 –
4,000 psi
Constant Pressure Pump
It is fitted to a system
employing a constant delivery
(fixed volume) pump, to
control system pressure and to
return fluid to the reservoir.
Automatic Cut Out Valves
An _________ is fitted:
a) To store hydraulic fluid under pressure
b) To dampen pressure fluctuations
c) To allow for thermal expansion
d) To provide an emergency supply of fluid
to the system in then event of pump failure
e) To prolong the period between cut out
and cut in time of the ACOV and so reduce
the wear on the pump
f) Provides the initial fluid when a
selection is made, and the pump is cut out
accumulator
Used to convert fluid flow into
linear or rotary motion.
Hydraulic Jacks or Actuators
3 Types of Actuators
Single Acting, Double Acting Unbalanced, Double Acting Balanced
Hydraulically operated in one
direction only.
Is normally used as a locking
device, the lock being engaged
by spring pressure and
released by hydraulic pressure.
This has more fluid in the
cylinder when the rod is
extended.
Single Acting Actuator
An actuator that is used in most aircraft systems
Double-Acting Unbalanced Actuator
Equal force can be applied to
both sides of the piston.
It is often used in applications
such as nose wheel steering.
Either one or both sides of the
piston rod may be connected to
a mechanism.
Double Acting Balanced Actuator
When fluid is trapped between
the piston of the actuator and a
non-return valve or a selector
valve at its neutral position, a
“___________” is said to be
formed.
hydraulic lock
What are the flow control components
Non-Return Valves
Restrictor Valves (or choke)
Selectors
Electrically Operated Selectors
Shuttle Valves
Sequence Valves
Modulators
Flow Control Valves
Fuses
