Mod5_Aircraft systems_Instrumentations.pptx

HYDRAULLIC SYSTEMS
Definition
 A hydraulic system uses a fluid under pressure to drive machinery or
move mechanical components.
 Virtually all aircraft make use of some hydraulically powered
components.
 In light, general aviation aircraft, this use might be limited to
providing pressure to activate the wheel brakes.
 In larger and more complex aero planes, the use of hydraulically
powered components is much more common.
 Depending upon the aircraft concerned, a single hydraulic system, or
two or more hydraulic systems working together, might be used to
power any or all

PARTS CONTROLLED BY HYDRAULIC
SYSTEM
• Wheel brakes
• Nose wheel steering
• Landing gear
retraction/extension
• Flaps and slats
• Thrust reversers
• Spoilers/speed brakes
• Flight control surfaces
• Cargo doors/loading ramps
• Windshield wipers
• Propeller pitch control

BASIC
COMPONENTS
 A hydraulic system consists of the hydraulic fluid plus three major
mechanical components.
 Those components are
1. The “pressure generator” or hydraulic pump
2. The hydraulically powered “motor” which powers the
component concerned
3. The system “plumbing” which contains and channels the
fluid throughout the aircraft as required.

HYDRAULIC
FLUID
 Fluid is the medium via which a hydraulic system transmits its energy and,
theoretically, practically any fluid could be utilized.
 The operating pressure (3000 to 5000 psi) that most aircraft hydraulic
systems
generate.
 High Flash Point.
 In the event of a hydraulic leak, fluid ignition should not occur at
the normal operating temperatures of the surrounding components.
 Special hydraulic fluids with fire resistant properties have been developed for
aviation use. These fluids are phosphate esters and, unlike mineral oil based
hydraulic fluids,
 Adequate Viscosity
 Lubricant Properties.
 Thermal Capacity/Conductivity

HYDRAULIC
PUMPS
Gear Pumps.
 Gear pumps use meshing gears to pump fluid. Gear pumps are
fixed displacement type pumps as they move a specific amount of fluid per
rotation. Gear pumps may be used on low pressure systems (under 1500 psi)
but are generally not suitable for high pressure applications
Fixed Displacement Piston Pumps.
 Piston pumps utilize a piston moving in a cylinder to pressurize a fluid.
A
fixed displacement pump moves a specific amount of fluid with each stroke.
Variable Displacement Piston Pumps.
 This is the most common type of pump on large aircraft. The
variable displacement design allows the pump to compensate for changes in
the system demand by increasing or decreasing the fluid output. This allows
near constant system pressure to be maintained.

SYSTEM "PLUMBING"
COMPONENTS
Aviation hydraulic systems, in general, are of the "open loop" variety drawing fluid from a
reservoir, pressurizing it and making it available to the various user components before
returning the fluid to the reservoir
1. Reservoir.
 Hydraulic fluid reservoirs are required by most aircraft systems to
provide a ready source of fluid for the hydraulic pump(s) and to contain a varying
volume of fluid.
 This variance results from differential actuator volume and for fluid thermal
contraction or expansion.
 The reservoir size is optimized so that only the amount of fluid needed for proper
function is carried.
 In many installations, bleed air is used to pressurize or "bootstrap" the reservoir to
help prevent hydraulic pump cavitation.
2. Filters.
 Hydraulic fluid cleanliness is essential to proper system function. In-line filters are
incorporated into the hydraulic system to remove any contaminants from the fluid.

CONTD
..
3. Shut Off Valves.
 Hydraulic shut off valves are usually installed at the engine firewall. In
the event of an engine fire, the shutoff valve is closed to prevent possible
ignition of the hydraulic fluid.
4. Control Valves.
 Hydraulic motors and actuators have an associated control valve
which is positioned in response to a manual or automated system
selection such as moving the flap lever. The control valve responds to
that selection by positioning to allow pressurized hydraulic fluid to flow
into the motor or actuator in the appropriate direction.
5. Pressure Relief Valve.
 In some systems, especially those utilizing a fixed displacement pump,
pressure relief valves are incorporated to ensure that nominal system pressure
is not exceeded. If system pressure becomes too high, the relief valve opens
and fluid is returned to the reservoir.

CONTD
..
6. Hydraulic Fuses.
 Hydraulic fuses are in-line safety devices designed to automatically seal
off a hydraulic line if pressure becomes too low.
7. Accumulators.
 A hydraulic accumulator is a pressure storage reservoir in
which hydraulic fluid is held under pressure by an external source of
energy.
 The external source can be a spring or a compressed gas.
 An accumulator enables a hydraulic system to cope with extremes of
demand using a less powerful pump and to respond more quickly to a
temporary demand.
 In the event of a hydraulic pump failure, the energy stored in an
accumulator can provide a limited number of brake applications after
landing.

PNEUMATIC
SYSTEM.
 Pneumatic systems use compressed air as a working fluid, and it
acts much like the hydraulic systems we already described
previously in our articles.
 In comparison with hydraulics there are advantages to be found by
using air instead of hydraulic fluid to transmit power.
 The principles (Pascal's law) in using air are the same as for
hydraulic
fluids but with a remarkable difference. .
 As the pilot in command of your aircraft you will need
some knowledge of where and how pressurized air is used and
how to inspect them during the preflight.
 This also includes the vacuum systems to power the gyro's in
the
instrument panel.

BLOCK DIAGRAM of PNEUMATIC SYSTEM

WORKING PARTS PNEUMATIC
SYSTEM
1. Backup systems
 Used when, for example, the landing gear hydraulic systems fails for
a reason.
 A backup pneumatic system uses a storage bottle with air
and an actuator as an emergency means to extend the gear.
2. Low pressure systems
 These are pressurized up to about 1000 psi and use an engine
driven vane type pump.
 They are mainly used to drive the air-conditioning, door seals, de-
icer
boots, mainly small low power applications.

3. HIGH PRESSURE SYSTEMS
 An engine driven compressor feeds air via an unloading valve to the
system keeping the pressure around 3000 psi, but this may vary
from aircraft manufacturer to another.
 There will usually also be a ground valve on the aircraft to enable the
system to be pressurized when the main engines are not running.
 You will also find a moisture separator, dryer (desiccant) and filter to
keep the air clean and free from water before it is stored in the high
pressure bottles.
 Pressurized air at 3000 psi is reduced before it is routed to valves and
actuators, this reduced pressure is monitored by gauges.
 Actuators can be a single acting device where air moves them one
way and a strong spring inside pushes the piston actuator back, or can
they be double acting. These are sometimes used with flap extension
systems.

 Pneumatic systems are often compared to hydraulic systems, but such
comparisons can only hold true in general terms.
 Pneumatic systems do not utilize reservoirs, hand pumps, accumulators,
regulators, or engine-driven or electrically driven power pumps for building
normal pressure.
4. Air Compressors
 On some aircraft, permanently installed air compressors have been added to
recharge air bottles whenever pressure is used for operating a unit.
 Several types of compressors are used for this purpose.
 Some have two stages of compression, while others have three, depending
on the maximum desired operating pressure.

PRO'S AND CONS of PNEUMATIC SYSTEM
Advantages of air
 No fire problem - Air will not burn by itself, however, bottles can
explode and cause damage
 Light weight - Air systems do not need a return line as is the case with
hydraulic fluids
 Simple - Pneumatic systems are by design very simple
 Supply - Air can be pumped in from around us and is
virtually unlimited in supply
Disadvantages
 It is not suitable for large and heavy mechanical devices.
 Air must be compressed to a large degree to have enough energy and
this would require large air tanks and actuators with very high
working pressures.

OXYGEN SYSTEM
 Oxygen — the life-sustaining gas we need in order to survive.
 At higher altitude we require supplemental oxygen due to the decreased density
of the air.
 At higher altitudes in non-pressurized aircraft, pilots require it to avoid hypoxia, a
physiological condition.
 Pressurized aircraft rely on oxygen systems as a supplement when pressurization
problems occur
 Aircraft emergency oxygen systems are emergency equipment fitted to
pressurized commercial aircraft, intended for use when the cabin pressurization
system has failed.
 It consists of a number of individual oxygen masks stored in compartments
near
passenger seats and near areas like lavatories and galleys, and an oxygen
source.

OXYGEN SYSTEMS AND COMPONENTS
 Storage Cylinders
1. Low-pressure Cylinders
2. High-pressure Cylinders
 Regulators
1. Manual Continuous Flow Regulator
2. Automatic Continuous Flow Regulator
3. Demand Regulators
4. Diluter Demand Regulators
5. Pressure Demand Regulators
 Masks
1. Continuous Flow Masks
2. Demand-type Masks

Low-pressure Cylinders
 Most military aircraft at one time used a low-pressure oxygen system.
 In which the gaseous oxygen was stored under a pressure of approximately 450
psi in large steel cylinders painted yellow.
High-pressure Cylinders
 Oxygen cylinders may be mounted permanently in the aircraft and connected
to an installed oxygen plumbing system.
 The cylinders should be painted green and identified with the words AVIATORS
BREATHING OXYGEN written in white letters on the cylinder, under a
pressure of between 1,800 and 2,400 psi.
Manual Continuous Flow Regulator
 This type of regulator the user is able to adjust the flow to correspond with the
altitude being flown, and the regulator will meter the correct amount of
oxygen.
Automatic Continuous Flow Regulator
 An automatic regulator has a barometric control valve that automatically
adjusts
the oxygen flow to correspond with the altitude being flown.

Demand Regulators
 This type of regulator is far more economical of the oxygen than the continuous
flow
type, but there are regulators that are even more efficient.
Diluter Demand Regulators
 The oxygen regulator used by the flight crews for most commercial jet aircraft are
of the diluter demand type.
Pressure Demand Regulators
 Pressure demand regulators operate in much the same way as diluter demand
regulators except at the extremely high altitudes, where the oxygen is forced into
the mask under a positive pressure.
Continuous Flow Masks
 Almost all of the masks used with a continuous flow oxygen system are of
the rebreather type and vary from the simple bag-type.
Demand-type Masks
 All demand-type masks must fit tightly to the face so no outside air can enter
to disturb the metering of the regulator.

FLIGHT INSTRUMENTS
 Flight instruments are the instruments in the cockpit of an aircraft that provide
the pilot with information about the flight situation of that aircraft, such as
altitude, airspeed and direction.
 They improve safety by allowing the pilot to fly the aircraft in level flight, and
make turns, without a reference outside the aircraft such as the horizon.
 The flight instruments are of particular use in conditions of poor visibility, such
as in clouds, when such information is not available from visual reference outside
the aircraft.

Altimeter
 The altimeter shows the aircraft's altitude above sea-level by measuring the
difference
between the pressure.
 It is adjustable for local barometric pressure which must be set correctly to
obtain accurate altitude readings.
 As the aircraft ascends, the capsules expand and the static pressure drops, causing
the altimeter to indicate a higher altitude.
 The opposite effect occurs when descending.

Airspeed indicator
 The airspeed indicator shows the aircraft's speed relative to the surrounding air.
 It works by measuring the ram-air pressure in the aircraft's Pitot tube relative to
the ambient static pressure.
 The Indicated airspeed (IAS) must be corrected for nonstandard pressure and
temperature in order to obtain the True airspeed (TAS).

Vertical speed indicator
 The VSI (also called as rate of climb indicator) senses changing air pressure, and
displays that information to the pilot as a rate of climb or descent in feet per
minute, meters per second or knots.
 The image on the below shows we are in level flight (VSI = 0). Keep in mind that all
aircraft tend to vary their altitude, even when trimmed for straight and level flight.

Attitude Indicator (artificial horizon)
 The attitude indicator shows the aircraft's relation to the horizon.
 From this the pilot can tell whether the wings are level (roll) and if the aircraft nose
is pointing above or below the horizon (pitch).
 This is a primary instrument for instrument flight and is also useful in conditions
of poor visibility.

Turn and slip indicator
 In aviation, the turn and slip indicator (turn and bank indicator) and the turn
coordinator variant are essentially two aircraft flight instruments in one device.
 One indicates the rate of turn, or the rate of change in the aircraft's heading, the
other part indicates whether the aircraft is in coordinated flight, showing the slip or
skid of the turn.

Heading Indicator
 This instrument is a directional gyro and shows you the direction you are heading.
 In many advanced aircraft the heading indicator is replaced by a horizontal
situation indicator (HSI) which provides the same heading information, but also
assists with navigation.

AIRCRAFT COMMUNICATION SYSTEMS
• Communication systems involves the voice transmission and
reception between aircraft or aircraft and ground
• Some special systems are required for transmitting the data
as
well as good quality transmission should be achieved
• Radios are used for this purpose.
WORKING PRINCIPLE:
 Energy required for illuminating the light is transferred by
alternating the EMF in the core of the transformer.
 Basic radio communication also works on the same principle by
transmission and reception of EMF through space.

• Alternating current passing through conductor creates a EMF around the
conductor
.
• Energy is stored in these fields and returns to the conductor for typical
transforming operation.
• As frequency of current alternation increases, lesser energy stored in the field
returns to the conductor and then emitted into space in form of EM waves

AIRCRAFT FUEL SYSTEMS
• The fuel system is designed to provide an
uninterrupted flow of clean fuel from the fuel tanks to
the engine.
• The fuel must be available to the engine under all
conditions of engine power, altitude, attitude,
and during all approved flight maneuvers

Two common classifications apply
to fuel systems in small aircraft:
1. Gravity-feed
2. Fuel-pump systems.

GRAVITY FEED
SYSTEMS.
 The gravity-feed system utilizes the force of gravity to
transfer the fuel from the tanks to the engine.
 For example, on high-wing airplanes, the fuel tanks are
installed in the wings.
 This places the fuel tanks above the carburetor, and
the fuel is gravity fed through the system and into the
carburetor.
 If the design of the aircraft is such that gravity cannot
be used to transfer fuel, fuel pumps are installed.

Mod5_Aircraft systems_Instrumentations.pptx

WORKING OF GRAVITY FEED
SYSTEMS.
 The system normally comprises of two fuel tanks
 The outlets from the tanks are connected to the
selector valve which helps to draw the fuel from
the separate tanks or both the tanks together.
 Then the fuel passes through the strainer and
to the carburetor unit.
 Fuel for the primer is drawn from the strainer.

FUEL
PRIMER
 Both gravity-feed and fuel-pump systems may incorporate a
fuel primer into the system.
 The fuel primer is used to draw fuel from the tanks to
vaporize fuel directly into the cylinders prior to starting the
engine
 During cold weather, when engines are difficult to start, the
fuel primer helps because there is not enough heat available
to vaporize the fuel in the carburetor.
 It is important to lock the primer in place when it is not in
use.If the knob is free to move, it may vibrate out during
flight and can cause an excessively rich mixture.

PRESSURE FEED SYSTEM.
 If the design of the aircraft is such that gravity cannot
be used to transfer fuel, fuel pumps are installed.
 For example, on low-wing airplanes, the fuel tanks in
the wings are located below the carburetor.
 Aircraft with fuel-pump systems have two fuel
pumps.
 The main pump system is engine driven with an
electrically driven auxiliary pump provided for use in
engine starting and in the event the engine pump fails.

GENERALIZED FUEL SYSTEMS.
• The fuel tanks are installed on the wings and fuselage to
store fuel for the use by engines.
• Main tanks – on the wings ; Center tanks – on the
fuselage
• Pressure fueling system enables to add fuel into each
tank.
• Both main and center tank has two booster pumps.
• Center tank supplies fuel at high pressure, so it is used
first
than the main tanks.
• The Engine Fuel Feed system supplies the fuel from the fuel tank
to the engines.
• Cross Feed Valves permits a single fuel tank to supply fuel for
both the engines.

• Water scavenge jet pumps are installed in the fuel
tanks to remove water from low points of each tank to
avoid corrosion.
• Surge tanks collect fuel over flow only.
• The fuel over flow in left and right surge tanks drains
to right and left main tanks.
• Fuel vent systems keeps the pressure of the ffuel tanks
near the ambient pressure.
• Pressure relief valves prevents damage to the wing
structure when there is huge pressure difference.

AIRCRAFT NAVIGATION SYSTEM.
 The aerospace planform needs to navigate the aircraft
with sufficient accuracy to a target
 Fuel efficiency is also a major concern.
 Some other features are (i) Avoiding the air traffic (ii)
Tight airline schedule. (iii) Rules for military and Civil
A/C.

Different types of Navigation systems.
1. Radio navigation systems
2. Classic dead reckoning systems.
1. Inertial navigation system.
3. Satellite based navigation
system
1. Integrated navigational systems

RADIO NAVIGATION
SYSTEMS.
• There are 3 types under Radio Navigation system
 DISTANCE MEASURING EQUIPMENT
 VERY HIGH FREQUENCY OMNIDIRECTIONAL RADIO RANGE
 NON DIRECTIONAL BEACON

Distance Measuring Equipment DME
• It provides the information about the transverse distance between
the aircraft and the radio ground station.
 Its physical principle is based on runtime measurement, where
the relative slope distance between the DME ground station and
the aircraft is calculated.
R=c*t/2
 where c = 299.792.458 m/s is the speed of light and t is the
runtime between sending out the signal from the aircraft and
receiving the response from the DME ground station.
 In practice there is a system specific time shift of 50 μs introduced
to the runtime signals calculated

• The accuracy of the DME is therefore limited by the combination
of flight level and relative distance
• Due to the interrogation and respond principle of the system the
maximum capacity of a single DME station is limited to 360
aircraft theoretically.
• In practice a lower amount of about 250 aircraft can use the
station.
• DME stations are very often combined with VOR stations, which
provide the corresponding relative bearing or directional
information.
• Providing both type of information the precise aircraft position
can be determined.

N ON DIRECTION A L BEA CON
 In combination with the onboard device called “Automatic
Direction Finder” (ADF) this system also provides directional
information.
 The operational range of the ground station is between 25–150 nm.
NDBs are often used in the vicinity of airports,
 They are widely used by airliners for cross-check or as “locators” for
pre-visual clearance to an airport.
 Since NDB provides only horizontal directional information it is
used
as a Non-Precision-Approach device.
 Because it is not providing the direction, which the aircraft is
approaching to and it is sensitive to interferences.
 The NDB cannot be used as a primary navigation device. Only in
conjunction with the ADF installed on aircraft accurate directional
information can be determined.

VO
R
• The Very High Frequency Omnidirectional Radio Range (VOR)
provides a relative bearing information to the aircraft.
• Typically VOR stations are positioned along major traffic
routes,
and offer a measurement range of about 130 nm.
• Like DME stations also VOR stations are identified by an
individual code, which is associated to the radio frequency of the
station.
• The pilot has to set this code or frequency in the cockpit, when
he
wants to use the VOR station.
• VOR stations are also placed within the vicinity or directly on the
site of airports,
• Their range is limited to approximately 25 nm.

SATELLITE BASED SYSTEM.
• In the 1970s, the American military services developed a satellite-
based navigation system called Global Navigation Satellite System
(GNSS) of Global Positioning System (GPS).
• Four satellites each are operating on at least six nearly circular
trajectories at about 20200 km altitude. The resulting 24 satellites
are required to ensure a worldwide coverage over 24 h,
• Also four different satellites are required to provide the
necessary runtime information to calculate the position
parameters latitude, longitude, altitude and time.
• In conjunction with high precision short-term navigation devices
like Inertial Navigation Systems (INS) more dynamic and flexible
approaches and departures will become possible.

INERTIAL NAVIGATION SYSTEM.
 Onboard navigation subsystems are to provide two main
functions.
 First, they have to deliver the critical control parameter like
air data, attitudes, angular rates and acceleration.
 Second, the aircraft positioning information like position, time
reference and speed is needed to allow more accurate and safer
aircraft guidance.
 Gyroscopes and accelerometers are known as inertial sensors
because they are representing the property to resist a change in
momentum.
 This principle is used to sense angular and linear motion.

INTEGRATED NAVIGATION
SYSTEM
 Based on the principle navigation systems described
previously today integrated navigation systems are used to
provide high performance navigation in terms of
accuracy, reliability, weight and energy consumption.
 Integrated navigation merges the positive characteristics
of single navigation devices and tries to compensate their
disadvantages.
 Because radio navigation systems as described before are
ground-based systems they are typically limited in their
range and show increasing inaccuracies in position
determination with increasing distance.

Mod5_Aircraft systems_Instrumentations.pptx

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