For Training Purpose Only
DETAILED TRAINING
VAR Part 7 - Aircraft Maintenance Basic Cat B1+B2
TRAINING MANUAL
M11.12
Issue: 01
Rev: 00
Date: 25/04/2014
© VAECO Training Center
Training Manual
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ICE AND RAIN PROTECTION
HAM US/F-4
SaR
01.12.2007
ATA_DOC
Page 1
FUNDAMENTALS
ATA 30
INTRODUCTION & ICE DETECTION
INTRODUCTION
This module will show you how modern aircraft are protected against the
negative effects of ice and rain.
When an aircraft operates in rain, for instance during takeoff or approach, the
visibility for the pilots is reduced.
To solve this problem we have 2 systems in the aircraft:
S A windshield wiper for each pilot and
S a rain repellent system.
When the aircraft flies in icing conditions, you can imagine that more problems
are possible.
An ice buildup on the aircraft mainly has the following effects:
S The aerodynamic quality of the aircraft is reduced and
S its weight increases.
The engines can also get problems and the ice can block the probes for the air
data system.
In addition ice on the windshields will decrease the visibility more than rain.
Before we show you the equipment which prevents these negative effects on
the aircraft, we will look at some general things about ice.
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INTRODUCTION & ICE DETECTION
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01.12.2007
01|Introduction|A,B1
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FUNDAMENTALS
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INTRODUCTION & ICE DETECTION
Figure 1
HAM US/F-4
SaR
01.12.2007
Negative Effects of Ice and Rain
01|Introduction|A,B1
Page 3
FUNDAMENTALS
ATA 30
WING ANTI-ICE
Usually, clouds have no ice but have supercooled water droplets.
When these droplets hit the aircraft they change from liquid water to solid ice.
If the temperature of the droplets is between zero and minus 10°C clear−ice is
produced on the surface.
The ice−build up begins on the leading edge of the surface. This is the hit point
where the droplets hit the surface.
Not all of the droplets freeze immediately and therefore some move aft on the
surface. This results in a clear ice layer which becomes larger and thicker the
longer you fly in these conditions.
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02|Wing Anti−Ice|A,B1
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Figure 2
HAM US/F-4
SaR
01.12.2007
Ice Build-up on Wing Leading Edge
02|Wing Anti−Ice|A,B1
Page 5
FUNDAMENTALS
ATA 30
wing anti-ice cont.
If the temperature of the droplets is below minus 10°C, mainly rime−ice is
produced on the surface.
Again, the ice−build−up begins on the leading edge of the surface where the
droplets hit the surface.
But these very cold droplets freeze immediately and build up a rime ice layer
on the leading edge only.
When you fly at high speed in this condition, the rime ice layer forms a typical
double horn shape.
Both types of ice can also occur together and therefore produce a combination
of all negative effects.
S Decrease of lift,
S increase of weight
S and increase of drag.
You have seen that the effect of ice on the aircraft is always negative and can
even become dangerous. It must therefore be prevented by either not flying in
icing conditions or by the use of an anti−ice system or de-icing system.
In jet aircraft, the anti ice system heats the wing leading edge where the
ice−build−up begins. It uses warm air from the engines and is therefore named
thermal wing anti-ice system.
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02|Wing Anti−Ice|A,B1
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Figure 3
HAM US/F-4
SaR
01.12.2007
Rime Ice Layer
02|Wing Anti−Ice|A,B1
Page 7
FUNDAMENTALS
ATA 30
ENGINE ANTI-ICE
In addition to the negative effect on aerodynamics and a higher weight, the
engines can also get problems when there is an ice build−up.
Ice has 2 important negative effects on the engine inlet. These are:
A disturbed air flow that reduces the performance of the engine and can lead to
a compressor stall and if the engine sucks in pieces of ice, these pieces can
damage fan blades or inlet vanes.
To prevent ice build−up on the engine inlet, all jet engines have a thermal antiice system.
If an aircraft has a center engine as shown here, you must make sure that ice
pieces from the fuselage do not hit the engine.
Usually the antennas get this ice build−up and therefore they are also heated
by warm air.
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03|Engine Anti−Ice|A,B1
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Figure 4
HAM US/F-4
SaR
01.12.2007
Effects of Ice on Engine Inlet
03|Engine Anti−Ice|A,B1
Page 9
FUNDAMENTALS
ATA 30
AIR FOIL DE-ICING
In propeller− driven aircraft not enough hot air for thermal anti-icing is available.
Therefore they use an airfoil de−icing system instead.
This system usually uses de−icing rubber boots at the leading edges of the
wing and the stabilizers, which normally have the shape of the leading edge
structure .
If an ice layer has built up the pilot must activate the de−Icing system which
inflates the rubber boots for a short time by pressurized air. This will crack the
ice layer and the ice pieces will be blown away by the airstream. To receive a
sufficient de−icing effect the pilots have to wait until a certain thickness of the
ice layer is reached before the system is switched on.
Usually the rubber boot inflation is rythmically repeated, to get a clean surface.
To prevent icing problems of the propulsion, propeller driven aircraft use an
engine inlet de-icing system, which usually uses hot air from the engine.
The propeller de−icing system is usually heated by electric current.
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04|Air Foil De−Icing|A,B1
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Figure 5
HAM US/F-4
SaR
01.12.2007
Air Foil De-Icing
04|Air Foil De−Icing|A,B1
Page 11
FUNDAMENTALS
ATA 30
GROUND OPERATION
The thermal anti-ice and the de−icing systems are very effective during flight
but what do you think happens when snow or ice falls on the aircraft when it is
on the ground, for instance over night?
Anti-ice systems prevent ice−build−up on critical aircraft areas during flight.
You cannot use them to de−ice an aircraft which has ice already on it and a
de-icing system is only approved for the operation during flight.
Therefore you must perform the de−icing shortly before takeoff with a de−icing
fluid. Always follow company procedures.
Allow an aircraft to fly only, when it is free of ice and snow.
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05|Ground Operation|A,B1
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Figure 6
HAM US/F-4
SaR
01.12.2007
Ground Operation
05|Ground Operation|A,B1
Page 13
FUNDAMENTALS
ATA 30
OPTICAL ICE DETECTOR
The thermal anti−ice systems can only do their task when they are switched on
before any ice builds up during flight.
On the other hand, it is not permitted to keep the systems on all of the time.
This is because taking hot air from the engines reduces their performance and
economy.
This means that the pilot must get accurate information when the aircraft flies
into icing conditions. This is the task of an ice detector.
Here you see an ice detector of an Airbus aircraft. You find it between the 2
windscreens where it is in sight of both pilots.
When the pilots see ice on this detector, then there is probably ice on other
parts of the aircraft. Therefore, the pilots must switch on the thermal anti-ice
systems.
This is performed manually by pressing the corresponding push buttons on the
overhead panel.
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06|Optical Ice Detector|A,B1
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Figure 7
HAM US/F-4
SaR
01.12.2007
Optical Ice Detector
06|Optical Ice Detector|A,B1
Page 15
FUNDAMENTALS
ATA 30
ELECTRONIC ICE DETECTOR
Now we look at a different type of ice detector.
It is installed near the air data probes and therefore is not visible to the
pilots.When this component detects ice, it generates a message in the cockpit
and can automatically activate the thermal anti−ice systems.
Some propeller driven aircraft also use this type of ice detector to help the pilot
to activate the de−icing system at the correct time.
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07|Electronic Ice Detector|A,B1
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Figure 8
HAM US/F-4
SaR
01.12.2007
Electronic Ice Detector
07|Electronic Ice Detector|A,B1
Page 17
FUNDAMENTALS
ATA 30
OPTICAL ICE DETECTOR FUNCTION
The part of the ice detector you can see outside the aircraft is a
magnetostrictive probe tip.
This tip vibrates with a certain frequency which is generated by an oscillator.
When ice builds up on the ice detector, the probe tip becomes heavier and this
reduces the frequency of the vibration.
When the frequency decreases below a certain value a feedback circuit
activates the heating. This melts the ice on the probe tip and the frequency
increases again.
When the frequency reaches the original value again the heating is switched off
and the cycle starts again.
A counter calculates the number of cycles and activates output signals when a
given number of cycles is reached.
The output signal of the ice−detector depends on the position of the thermal
anti−ice switches on the control panel.
When a switch on the panel is in the AUTO position, the ice detector
automatically activates the corresponding thermal anti−ice system.
When a switch on the panel is in the OFF position you get a message on the
EICAS display. When the pilot sees this ICING message he must switch on the
anti-ice systems.
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08|Optical Ice Detector Function|B1
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Figure 9
HAM US/F-4
SaR
01.12.2007
Electronic Ice Detector Operation
08|Optical Ice Detector Function|B1
Page 19
FUNDAMENTALS
ATA 30
ELECTRICAL ICE DETECTOR
In addition to the previously shown anti ice and de−icing systems, aircraft also
have very important electrical anti ice systems.
A probe heat system prevents blockage of air data probes, a window heat
system prevents ice on the windshield that would reduce visibility and a line
and drain mast heat system prevents frozen water−lines.
All these electrical anti−ice systems are actived during the whole flight. They
are partially switched off on the ground to prevent overheat.
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09|Electrical Anti−Ice Systems|A,B1
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Figure 10
HAM US/F-4
SaR
01.12.2007
Electrical Ice Detection
09|Electrical Anti−Ice Systems|A,B1
Page 21
FUNDAMENTALS
ATA 30
THERMAL ANTI-ICE SYSTEM
INTRODUCTION
Two thermal anti−ice systems are installed in jet aircraft:
S The wing and
S the engine anti−ice systems.
The wing anti−ice system uses hot air from the pneumatic system.
One or two valves in each wing, named the wing anti−ice valves, connect the
wing anti−ice ducts to the pneumatic system.
The engine anti−ice system also uses hot air. The air comes from either the
pneumatic system or directly from the engine. An engine anti−ice valve
provides the connection.
When an anti−ice valve opens, the hot air enters the anti−ice duct.
The hot air sprays through small holes in the anti−ice duct into the wing leading
edge or engine cowling.
The hot air heats up the area of the leading edge and prevents ice build−up.
Later, the air leaves this area through openings in the lower part of the
structure.
Extreme caution is necessary during ground tests of thermal anti−ice systems
because the air is still hot.
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01|Introduction|A,B1
Page 22
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Figure 11
HAM US/F-4
SaR
01.12.2007
Wing and Engine Anti-Ice Systems
01|Introduction|A,B1
Page 23
FUNDAMENTALS
ATA 30
Introduction cont.
When the wing leading edge is equipped with slats then a telescoping duct is
necessary to supply the wing anti−ice duct.
The telescoping duct is short when the slats are retracted and long when the
slats are extended.
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Figure 12
HAM US/F-4
SaR
01.12.2007
Anti-Ice Telescopic Ducts
01|Introduction|A,B1
Page 25
FUNDAMENTALS
ATA 30
SYSTEM CONTROL
We will now see what it looks like with the two thermal anti−ice systems added.
The left and right wing anti−ice system use hot air which is already regulated by
the bleed valve.
The engine anti−ice system uses bleed air from the corresponding engine.
This air comes either from the engine bleed−air system, upstream of the bleed
valve, or from a separate port on the engine compressor.
You can control the thermal anti−ice systems with switches on the overhead
panel. Here you see the push buttons in an Airbus aircraft.
The wing anti−ice system always has only one switch. This switch controls the
two sides at the same time because the system must always operate
symmetrically.
On engine anti−ice systems you find a switch for each engine installed on the
aircraft.
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02|System Control|A,B1
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Figure 13
HAM US/F-4
SaR
01.12.2007
Anti-Ice System Schematic
02|System Control|A,B1
Page 27
FUNDAMENTALS
ATA 30
GROUND OPERATION
Wing anti−ice systems usually operate only in flight.
When you switch on the system on ground, the wing anti−ice valves open only
for a short time. This lets you check the correct operation before the flight.
When the aircraft lands, the wing anti−ice valves close automatically.
The engine anti−ice systems can always be activated when bleed air from the
engine is available.
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Figure 14
HAM US/F-4
SaR
01.12.2007
Anti-Ice System - Ground Operation
03|Ground Operation|B1
Page 29
FUNDAMENTALS
ATA 30
VALVE TYPES
In thermal anti−ice systems you find the same type of valves as in other parts
of the pneumatic system.
Electrical motor operated valves, like crossbleed valves, are also used in some
wing anti−ice systems.
You can find solenoid controlled pressure operated valves in engine and wing
anti−ice systems.
In the two systems they operate as shut−off valves, like the APU bleed valve,
or they can be pressure regulating valves like the engine bleed valve.
All thermal anti−ice valves have a manual override function like some other
valves in the pneumatic system. This manual function is used when there is a
valve or system failure.
You can lock the wing anti−ice valves in the closed position only. This is only
allowed when there is no risk of icing during the next flight. It is also very
important to remember that you must close the wing anti−ice valves always on
both wings.
The engine anti−ice valves you can lock in the open or closed position. The
position you use depends on several conditions and is stated in the
maintenance documentation.
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04|Valve Types|B1
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Figure 15
HAM US/F-4
SaR
01.12.2007
Valve Types
04|Valve Types|B1
Page 31
FUNDAMENTALS
ATA 30
SOLENOID CONTROLLED VALVE
We will now look at a solenoid controlled pressure operated valve.
This valve closes by spring force when there is no air pressure available.
When air pressure is present it fills the lower chamber of the valve cylinder,
this pushes the piston up and moves the air in the upper part of the cylinder to
ambient via the de−energized solenoid. This opens the valve.
To close this valve type you must energize the solenoid.
This brings high air pressure to the upper chamber.
With equal pressure on the two sides of the piston the spring closes the valve.
We have simplified this function to make the principle clear to you. In reality,
the internal build−up of the valve is more complicated.
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Figure 16
HAM US/F-4
SaR
01.12.2007
Solenoid Controlled Valve
05|Solenoid Controlled Valve|B1
Page 33
FUNDAMENTALS
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Solenoid Controlled Valve cont.
Now we can use this solenoid− controlled, pressure−operated, shut−off valve in
an engine anti−ice system. When the pushbutton switch on the overhead
panel is switched off, then the solenoid is energized and the valve closed.
Two limit switches monitor the valve position.
This type of valve is fail safe to open. This means that it automatically opens
when there is no electrical power.
You can also find other valve types which close when the solenoid is
de−energized, for example, in Boeing aircraft. In this case the engine anti−ice
system is off when there is no electrical power.
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Figure 17
HAM US/F-4
SaR
01.12.2007
Solenoid Controlled Engine Anti-Ice Valve
05|Solenoid Controlled Valve|B1
Page 35
FUNDAMENTALS
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PRESSURE REGULATING VALVE
Now we will look at a more complicated valve.
It is a shut−off valve which also has an additional pressure regulation function.
This pressure regulation is needed if pneumatic system air pressure is too high
for the anti−ice system.
This valve stays closed when you activate the pneumatic pressure. This is
because the pressure is not only in the lower valve chamber. It also goes, via
the pilot valve, to the upper chamber, when the solenoid valve is de−energized.
When you energize the solenoid the pressure in the upper valve chamber
decreases because it releases to ambient.
This permits the pressure in the lower chamber to push the piston up and open
the valve.
When the valve is open you get pneumatic pressure downstream of the valve
which goes to the wing anti−ice ducts.
This pressure is also connected to the pilot valve and moves its piston to the
right.
The result is that the pressure increases in the upper valve chamber. This
moves the valve in the closing direction.
The valve motion stops when the downstream pressure has the correct value
of about 20 psi, because the pilot valve then has a balanced situation.
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Figure 18
HAM US/F-4
SaR
01.12.2007
Pressure Regulating Valve
06|Pressure Regulating Valve|B1
Page 37
FUNDAMENTALS
ATA 30
Pressure Regulating Valve Cont.
This system is monitored by two pressure switches, which are found
downstream of the valve, and one valve limit switch.
The fault light illuminates when you switch on the wing anti−ice pushbutton but
the pressure does not reach 14psi.
It also comes on when the pushbutton is switched off but the valve is not fully
closed.
You get a special situation when the aircraft is on the ground.
As you already know, the wing anti−ice valves close automatically when the
aircraft lands. You do not need to switch the wing anti−ice pushbutton off at
this moment.
When the pressure decreases below 14 psi you will not get the fault light. This
is because the ground sensing switch opens the circuit.
The blue on−light stays on as long as the pushbutton is pressed.
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Figure 19
HAM US/F-4
SaR
01.12.2007
PRV Operation
06|Pressure Regulating Valve|B1
Page 39
FUNDAMENTALS
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MOTOR OPERATED VALVE
The last valve type we will look at is a motor−operated shut−off valve.
This type you find in the wing anti−ice systems of Boeing aircraft.
The electric motor of this wing anti−ice valve is an AC motor.
The motor opens the valve when you connect the right motor coil directly to AC
power and the left coil gets the power via the capacitor.
AC power reaches the motor via the contact of the valve open limit switch.
This happens when you switch the wing anti−ice switch on the control panel to
ON.
You also get AC power when you select the AUTO position, ice is detected and
the flaps are up.
You must remember that you can only activate the system in flight and for the
preflight test.
The electric motor closes the valve when the left motor coil gets the AC power
directly and the right coil is supplied via the capacitor.
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Figure 20
HAM US/F-4
SaR
01.12.2007
Motor operated Valve
07|Motor Operated Valve|B1
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ELECTRICAL ANTI-ICE SYSTEMS
INTRODUCTION
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Figure 21
HAM US/F-4
SaR
01.12.2007
Results of Ice on Aircraft
01|Introduction|A,B1
Page 43
FUNDAMENTALS
ATA 30
ELECTRICAL HEATING CIRCUIT
Before we look at the aircraft electrical anti ice systems we will have a quick
look at their main parts.
Each electrical heating circuit has a heating element, which usually is a metal
wire, a power supply and a temperature or power control circuit.
The heating element is heated by an electrical current. The value of the current
depends on the voltage of the power supply and the resistance of the heating
element.
The amount of heat that is generated by a heating element is proportional to
the electrical power in the circuit.
The temperature of a heating element depends on the amount of electrical
power. A low power generates a low temperature and a higher power
generates a higher temperature.
This means that the temperature of a heating element is controlled by the
amount of electrical power that it receives.The temperature of the heating
element is also controlled by the cooling conditions.
For a given level of electrical power, a low or warm airstream gives a higher
temperature compared to a high or cool airstream. To have a sufficient
temperature always available, you need a control circuit.
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02|Electrical Heating Circuit|B1
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Figure 22
HAM US/F-4
SaR
01.12.2007
Electrical Heating Element
02|Electrical Heating Circuit|B1
Page 45
FUNDAMENTALS
ATA 30
HEATING POWER CONTROL
The aircraft’s electrical anti−ice systems use 2 different types of control circuits.
The temperature control circuit needs a temperature feedback signal. This
allows the exact control of the heating element temperature.
The power control circuit can only compensate for the effect of 2 different
cooling conditions. Usually, it increases the heating power at takeoff, because
in the air you have much more cooling.
You can increase the heating power at takeoff, when you switch the voltage of
the heating element from a single phase to a 2 phase operation. This means
that on the ground you use 115 volts and in the air 200 volts.
Another method to change heating power is to use a diode in the AC circuit.
When the aircraft is on the ground only the positive wave of the AC is used and
this reduces the power to 50%.
In the air you bypass the diode and full power is available.
The 2 power control circuits that we saw before, work only with AC power. This
example shows that you can also use this in DC circuits. The heating element
has 2 resistors.
On the ground the 2 resistors are switched in series and in flight they are
switched in parallel.
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03|Heating Power Control|B1
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Figure 23
HAM US/F-4
SaR
01.12.2007
Heating Power Control
03|Heating Power Control|B1
Page 47
FUNDAMENTALS
ATA 30
TEMPERATURE CONTROL
2 different types of temperature control are used in aircraft electrical heating
circuits:
Either a bimetal switch controls the heating circuit directly, or a thermistor
senses the temperature and controls an electronic switch.
A bimetal switch is always located near the heating element.
The bimetal switch has 2 switching points. The contact of the bimetal always
closes when the temperature is below the low switching point, this switches the
heating on.
The contact opens when the temperature reaches the high switching point, this
switches the heating power off.
This gives an average temperature of the heating element which is in the
middle between the high and the low switching points.
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04|Temperature Control|B1
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Figure 24
HAM US/F-4
SaR
01.12.2007
Temperature Control
04|Temperature Control|B1
Page 49
FUNDAMENTALS
ATA 30
TEMPERATURE CONTROL
The second type of temperature control circuit uses electronic components.
With this circuit you can control the temperature more precisely and you can
use larger currents.
A closer look shows you that this circuit also switches the heating power on
and off. But this happens more often compared to the bimetal.
The main advantage of this circuit is that the electronic switch has no
mechanical parts which can wear.
Electronic switches are usually semiconductor controlled rectifier or SCR in
short.
On the other hand the electronic temperature control circuits need an additional
sensor to measure the temperature. The temperature sensor is named
thermistor.
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04|Temperature Control|B1
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Figure 25
HAM US/F-4
SaR
01.12.2007
Electronic Temperature Control
04|Temperature Control|B1
Page 51
FUNDAMENTALS
ATA 30
TEMPERATURE MONITORING
A failure in the temperature control circuit has 2 different results.
One result is a permanently open contact. In this case the heating is switched
off.
The second result is a permanently closed contact.
You can see that the heating element will overheat when the heating is
permanently switched on.
To prevent this, many electrical anti−ice systems have an overheat protection
circuit. This is usually a bimetal switch located in series to the control switch.
This bimetal switch has a higher temperature setting, so it is usually closed and
will only open in case of an overheat.
Also, in electronic circuits, you can often find an electronic overheat circuit
instead of a bimetal switch, but with basically the same function.
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05|Temperature Monitoring|B1
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Figure 26
HAM US/F-4
SaR
01.12.2007
Temperature Monitoring
05|Temperature Monitoring|B1
Page 53
FUNDAMENTALS
ATA 30
DRAIN MAST HEAT SYSTEM
The drain mast heat system prevents freezing of the waste water outlets on the
lower part of the fuselage.
The system is switched on automatically, when electrical power is on.
In drain mast heat systems you find nearly all types of power and temperature
control circuits.
You can also find identical circuits for the heating of water pipes in the non
heated fuselage areas.
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06|Drain Mast Heat Syst|A,B1
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Figure 27
HAM US/F-4
SaR
01.12.2007
Drain Mast Heat System
06|Drain Mast Heat Syst|A,B1
Page 55
FUNDAMENTALS
ATA 30
PROBE HEAT SYSTEM
A very important anti−ice system for flight safety is the air data probe heating.
You can find 4 different types of probes on the aircraft:
S the temperature probe, also named rosemount probe, measures air
temperature for various calculations
S the pitot tubes measure the dynamic air pressure to calculate for example,
the airspeed
S the static ports measure the static air−pressure to calculate, for example,
the altitude
S and the angle of attack or alpha sensors which are mainly needed for the
stall warning and flight control systems.
The probe heat system is switched on automatically, when you start one of the
engines.
You can also switch on the system manually from the control panel if there is a
failure in the automatic circuit or for ground tests.
The probe heat system has no temperature control circuits.
The heating power is controlled only in some circuits by the air−ground
switching.
If there is a failure in the probe heating during flight, you can get unreliable
information from the probes. This can be very dangerous.
Therefore, you get a message on the display of the central warning system,
when the heating current is too low.
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07|Probe Heat System|A,B1
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Figure 28
HAM US/F-4
SaR
01.12.2007
Probe Heat System
07|Probe Heat System|A,B1
Page 57
FUNDAMENTALS
ATA 30
WINDOW HEAT SYSTEM
You can find window heat systems on all aircraft.
Each cockpit window has its own temperature control circuit.
The main components of a window heat system are:
S the window itself,
S the temperature control
S and monitoring circuits.
These usually use a window heat control computer which is located in the
electric compartment and a system control circuit with an automatic and
manual operation.
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08|Window Heat|A,B1
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Figure 29
HAM US/F-4
SaR
01.12.2007
Window Heat System
08|Window Heat|A,B1
Page 59
FUNDAMENTALS
ATA 30
WINDOW HEAT COMPONENTS
Windows number 1, which are also called windshields, are mainly heated to
prevent icing.
Therefore, you find the heating element behind the outer glass panel.
The heating element is a transparent, electrically conductive film.
Near the heating film you also find the temperature sensor, which is a
thermistor.
In most windows you find a second sensor. You use this spare sensor when the
first sensor has a failure. This prevents replacement of the complete window.
All other windows, such as windows number 2 and 3, are mainly heated to
prevent misting.
Therefore the transparent heating film is located near the inner glass panel.
The warm inner window surface also improves the crew comfort.
One or two temperature sensors are also installed near the heating film
On the side windows of some aircraft, you find one or two bimetal switches.
They are pressed against the inner window pane by spring force.
These bimetal switches detect the temperature of the heating film, because
they are close together.
This simple type of window heat control system works exactly like the general
system you learned about in the first segments. The circuit is permanently
powered.
The temperature control switch controls the temperature by an on − off cycling.
The overheat switch is usually closed. It opens only for an overheat condition
because of a failure of the control switch.
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HAM US/F-4
SaR
01.12.2007
Window Heat Components
09|Window Heat Components|B1
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FUNDAMENTALS
ATA 30
WINDOW HEAT OPERATION
Window heat systems are switched on manually with the corresponding switch
on the overhead panel, or are automatically activated when an engine is
started.
This is the same function that you saw earlier for the probe heating system.
When you switch on the window heat system, usually the window is cold. This
means that there is a maximum demand of heating power, which is about 2
kilowatts for the windshield.
With this maximum power, the window heats up very fast. This rapid heating
produces stress on the glass layers and can damage the window.
To prevent this problem, the window heat systems have a ramp function. The
ramp increases the heating power slowly to the necessary level in approximatly
4 minutes.
The temperature control circuit takes over the control of the heating power,
when the target temperature of about 40°C is reached near the heating film.
The window heat systems usually use PTC thermistors as temperature
sensors.
When the resistance increases, the controller decreases the power for the
window and vice versa.
Two different sensor failures are possible:
S When there is an open sensor the controller reduces the power to zero.
S With a shorted sensor, the resistance is near zero. This usually means a
very low temperature and therefore requires maximum heat. Because this
would damage the window, a monitoring circuit interrupts the heating power
when it detects a shorted sensor. This means that a sensor failure always
shuts−down the window heat system.
An automatic shutdown of the window heat system not only happens when
there is a sensor failure, but also when there is a failure in the window heat
controller.
The failure of the system is shown to the flight crew by a message on the
ECAM display.
To identify the faulty component, you do a test with the CMC.
HAM US/F-4
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01.12.2007
10|Window Heat Ops|B1
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Figure 31
HAM US/F-4
SaR
01.12.2007
Window Heat Operation
10|Window Heat Ops|B1
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RAIN REMOVAL SYSTEMS
FUNDAMENTALS
ATA 30
RAIN REMOVAL SYSTEMS
RAIN REPELLENT
In this lesson we will show you the systems that are used to improve the
visibility for the pilots, when the aircraft operates in rain.
You can find 2 different types of rain removal system in the aircraft. One type
removes the water from the windshield mechanically, this is the windshield
wiper.
The other system repels the water from the windshields by use of a rain
repellent fluid or a special windshield coating.
To repel water from glass the contact angle between the water droplets and the
glass is important.
On normal glass the contact angle is about 20°. This results in the water
droplets remaining on the windshield and gives poor visibility.
When you increase the angle to more than 60°, it is not easy for water droplets
to remain on the windshield. This means that they are blown away by the
airstream or easily removed by the windshield wiper.
By using rain repellent fluid, you get a high contact angle between water
droplets and glass of more than 80°.
This fluid is stored under pressure in a container in the cockpit.
You spray the fluid onto the windshield when you press the corresponding
control push−button on the overhead panel. This opens a valve for a short
time.
You also can find a hydrophobic coating of the windshield instead of a rain
repellent system. With this coating you can increase the contact angle between
water and glass up to about 100°.
This system needs no pilot action to operate. Also no maintenance action is
necessary as long as the repellent effect of the coating is sufficient.
Re−application of the coating onto the windshield is possible. You do it, if for
instance, the pilot complains about poor visibility.
To get a long lifetime from this coating, you must do proper windshield cleaning
procedures. You must also make correct adjustments of the windshield wipers.
HAM US/F-4
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01.12.2007
01|Rain Repellant/A/B1
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Figure 32
HAM US/F-4
SaR
01.12.2007
Rain Removal Systems
01|Rain Repellant/A/B1
Page 65
FUNDAMENTALS
ATA 30
WINDSHIELD WIPER
A second rain removal system which is on all aircraft is the windshield wiper
system.
Each pilot controls his or her own windshield wiper with the corresponding
switch on the overhead panel.
The windshield wiper has 2 different speeds.
Slow speed is used during normal rain or during taxi on the ground.
When you switch the wiper to off, the wiper arm moves to the park position.
This park position is outside the normal wiper area. In some aircraft the wiper
blade is also lifted from the windshield to prevent dirt collecting on the wiper
blade.
You must never switch on the windshield wiper when the windshield is dry. This
will make scratches on the glass layer and will also damage the windshield
coating.
Also, the wiper must not be switched on at airspeeds higher than about 250kts.
Here the dynamic pressure of the air is too high and can damage the wiper.
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Figure 33
HAM US/F-4
SaR
01.12.2007
Windshield Wiper
02|Windshield Wiper/A/B1
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FUNDAMENTALS
ATA 30
WINDSHIELD WIPER COMPONENTS
Each windshield wiper has the following components:
S the adjustable wiper assembly with the wiper blade
S the wiper motor assembly
S and the control switch in the cockpit.
The pressure of the wiper blade on the windshield must be sufficient to have a
good wiper performance under all operational conditions.
It must be sufficient to keep contact on the windshield even at high airspeeds.
On the other hand it must not be too high to cause damage to the windshield
and wiper components.Therefore you adjust the pressure with a screw to be
within limits.
The windshield wiper motor assembly has:
S a DC motor,
S a power control circuit,
S a motor speed control circuit, which changes the motor current
S and a bimetal switch. The bimetal opens when there is an motor overheat,
for example when the wiper is blocked.
A converter is usually directly connected to the motor. It changes the rotating
output of the motor to the cycling movement of the wiper.
The converter also drives the wiper into the park position if the control switch is
off.
As you know already, the park position of the wiper is outside the normal wiping
area. To reach this position the converter changes the transfer ratio.
This is usually done by inversing the rotation of the motor.
When the wiper reaches the park position, the converter activates a park
switch in the motor assembly.
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Components/B1
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Figure 34
HAM US/F-4
SaR
01.12.2007
Windshield Wiper Components
03|Windshield Wiper
Components/B1
Page 69
FUNDAMENTALS
ATA 30
WINDSHIELD WIPER OPERATION
When you select the slow speed position of the wiper switch, you first activate
the power control relay.
The activated current moves the wiper out of the park position and when the
normal wiper area is reached, the wiper cycles with a slow speed.
When you select the fast speed position of the wiper switch you activate the
power relay and the speed control relay.
This cycles the wiper with a high speed.
When you select the off position of the wiper switch you deactivate the power
and the speed control relay.
This reverses the direction of the motor current and the converter drives the
wiper to the park position.
When the park position is reached the contact of the park switch moves up.
This switches off the motor power and provides a short circuit which stops the
motor and wiper immediately.
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Figure 35
HAM US/F-4
SaR
01.12.2007
Windshield Wiper Operation
04|Windshield Wiper Ops/B1
Page 71
EJ M11.12 B1 E
TABLE OF CONTENTS
ICE AND RAIN PROTECTION . . . . . . . . . . . . . . . .
1
INTRODUCTION & ICE DETECTION . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
WING ANTI-ICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE ANTI-ICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AIR FOIL DE-ICING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GROUND OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OPTICAL ICE DETECTOR . . . . . . . . . . . . . . . . . . . . . . . . .
ELECTRONIC ICE DETECTOR . . . . . . . . . . . . . . . . . . . .
OPTICAL ICE DETECTOR FUNCTION . . . . . . . . . . . . . .
ELECTRICAL ICE DETECTOR . . . . . . . . . . . . . . . . . . . . .
2
2
4
8
10
12
14
16
18
20
THERMAL ANTI-ICE SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SYSTEM CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GROUND OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VALVE TYPES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SOLENOID CONTROLLED VALVE . . . . . . . . . . . . . . . . .
PRESSURE REGULATING VALVE . . . . . . . . . . . . . . . . . .
MOTOR OPERATED VALVE . . . . . . . . . . . . . . . . . . . . . . .
22
22
26
28
30
32
36
40
ELECTRICAL ANTI-ICE SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ELECTRICAL HEATING CIRCUIT . . . . . . . . . . . . . . . . . .
HEATING POWER CONTROL . . . . . . . . . . . . . . . . . . . . . .
TEMPERATURE CONTROL . . . . . . . . . . . . . . . . . . . . . . .
TEMPERATURE MONITORING . . . . . . . . . . . . . . . . . . . .
DRAIN MAST HEAT SYSTEM . . . . . . . . . . . . . . . . . . . . . .
PROBE HEAT SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . .
WINDOW HEAT SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . .
WINDOW HEAT COMPONENTS . . . . . . . . . . . . . . . . . . .
WINDOW HEAT OPERATION . . . . . . . . . . . . . . . . . . . . . .
42
42
44
46
48
52
54
56
58
60
62
RAIN REMOVAL SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RAIN REPELLENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
WINDSHIELD WIPER . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
64
66
WINDSHIELD WIPER COMPONENTS . . . . . . . . . . . . . .
WINDSHIELD WIPER OPERATION . . . . . . . . . . . . . . . . .
68
70
Page i
EJ M11.12 B1 E
TABLE OF CONTENTS
Page ii
EJ M11.12 B1 E
TABLE OF FIGURES
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16
Figure 17
Figure 18
Figure 19
Figure 20
Figure 21
Figure 22
Figure 23
Figure 24
Figure 25
Figure 26
Figure 27
Figure 28
Figure 29
Figure 30
Figure 31
Figure 32
Figure 33
Figure 34
Figure 35
Negative Effects of Ice and Rain . . . . . . . . . . . . . . . . . . . . . . . . .
Ice Build-up on Wing Leading Edge . . . . . . . . . . . . . . . . . . . . . .
Rime Ice Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Effects of Ice on Engine Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Foil De-Icing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ground Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Optical Ice Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electronic Ice Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electronic Ice Detector Operation . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Ice Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wing and Engine Anti-Ice Systems . . . . . . . . . . . . . . . . . . . . . .
Anti-Ice Telescopic Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anti-Ice System Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anti-Ice System - Ground Operation . . . . . . . . . . . . . . . . . . . .
Valve Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Solenoid Controlled Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Solenoid Controlled Engine Anti-Ice Valve . . . . . . . . . . . . . . . .
Pressure Regulating Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PRV Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Motor operated Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Results of Ice on Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Heating Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heating Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electronic Temperature Control . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Drain Mast Heat System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Probe Heat System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Window Heat System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Window Heat Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Window Heat Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rain Removal Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Windshield Wiper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Windshield Wiper Components . . . . . . . . . . . . . . . . . . . . . . . . .
Windshield Wiper Operation . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
53
55
57
59
61
63
65
67
69
71
Page i
EJ M11.12 B1 E
TABLE OF FIGURES
Page ii
EJ M11.12 B1 E
TABLE OF FIGURES
Page iii
EJ M11.12 B1 E
TABLE OF FIGURES
Page iv