ATA76 Engine Controls Jet Aircraft Maintenance Fundamentals

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Training Manual
Fundamentals
Jet
Aircraft
Maintenance
Fundamentals
ATA 76
Engine Controls
JAR-66

Book No:

JAMF ATA 76 ALL

Lufthansa
Technical Training GmbH
Lufthansa Base

Issue: July 2000
For Training Purposes Only
ã Lufthansa 1995


For training purpose and internal use only.
Copyright by Lufthansa Technical Training GmbH.

All rights reserved. No parts of this training
manual may be sold or reproduced in any form
without permission of:

Lufthansa Technical Training GmbH
Lufthansa Base Frankfurt
D-60546 Frankfurt/Main
Tel. +49 69 / 696 41 78
Fax +49 69 / 696 63 84
Lufthansa Base Hamburg
Weg beim Jäger 193
D-22335 Hamburg
Tel. +49 40 / 5070 24 13
Fax +49 40 / 5070 47 46


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ATA 76

ENGINE CONTROLS

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Page 1

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FUNDAMENTALS
ATA 76 Lesson 1

ENGINE START CONTROLS
INTRODUCTION TO ENGINE CONTROLS
The main engine controls are the engine start controls, the forward
thrust controls and the reverse thrust controls.
The start lever is used to switch fuel on and off and to switch ignition on during
engine start.
The forward thrust lever is used to control the thrust of an engine between idle
and take--off thrust. The lever informs the fuel control unit how much thrust is
requested by the pilot.
The third engine control is the reverse thrust lever.
When the reverse thrust lever is activated the deflector doors are deployed and
the airflow is deflected to give reverse thrust.
When the reverse thrust lever is pushed down the deflector doors move to the
stowed position and the engine delivers forward thrust.

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ENGINE CONTROLS
ENGINE START CONTROLS

HAM US sw

Sep 98

Page 2


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FUNDAMENTALS
ATA 76 Lesson 1
FORWARD THRUST
LEVER

REVERSE THRUST
LEVER

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Lufthansa Technical Training

ENGINE CONTROLS
ENGINE START CONTROLS

START
LEVER

THRUST CONTROL SIGNAL

Figure 1
HAM US sw

Sep 98

Mechanical Engine Controls
Page 3


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FUNDAMENTALS
ATA 76 Lesson 1

Introduction to Engine Controls
You can find similar engine controls on modern aircraft like this Airbus 320.
The master switches on the engine start panel are used to control the engine
start sequence, the control levers help to set the required thrust and the
reverse latching levers are used with the control levers to give reverse thrust.

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ENGINE CONTROLS
ENGINE START CONTROLS

HAM US sw

Sep 98

Page 4


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ENGINE CONTROLS
ENGINE START CONTROLS

REVERSE
LATCHING LEVER

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ATA 76 Lesson 1

CONTROL
LEVER

START CONTROL SIGNAL

TLA : thrust level angle

FUEL
ON

For Training Purposes Only

RESOLVER

ECU
THRUST CONTROL SIGNAL
REVERSE CONTROL SIGNAL

Figure 2
HAM US sw

Sep 98

IGNITION
ON

Edited by Foxit Reader
Copyright(C) by Foxit Software Company,2005-2008

For Evaluation Only.

FWD
THRUST

ENGINE
START
PANEL

Electrical Engine Control
Page 5


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FUNDAMENTALS
ATA 76 Lesson 1

START CONTROLS OVERVIEW
The last segment that the ignition and the fuel supply to the combustion
chamber are switched on by the engine start lever.
The fuel is supplied via a high pressure fuel shut--off valve and a low pressure
fuel shut--off valve.
The low pressure fuel shut--off valve is usually an electric motor driven valve.
The position of this valve is indicated by the fuel valve closed light. This light
illuminates when the valve is closed and goes out when the valve is open.

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ENGINE CONTROLS
ENGINE START CONTROLS

HAM US sw

Sep 98

Page 6


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ENGINE CONTROLS
ENGINE START CONTROLS

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FUNDAMENTALS
ATA 76 Lesson 1

For Training Purposes Only

LP FUEL
VALVE

Figure 3
HAM US sw

Sep 98

LP Fuel Valve Control
Page 7


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FUNDAMENTALS
ATA 76 Lesson 1

HP FUEL VALVE CONTROL
On this aircraft the high pressure fuel shut off valve is mechanically controlled.
The HP valve opens when the engine start lever is moved up and closes when
the lever is moved down.
The position of the HP fuel shut--off valve is indicated by the position of the
engine start lever.

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ENGINE CONTROLS
ENGINE START CONTROLS

HAM US sw

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ENGINE CONTROLS
ENGINE START CONTROLS

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ATA 76 Lesson 1

For Training Purposes Only

HP
FUEL
VALVE

Figure 4
HAM US sw

Sep 98

HP Fuel Valve Control
Page 9


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FUNDAMENTALS
ATA 76 Lesson 1

ELECTRICAL START CONTROLS
On some aircraft, for example the Airbus A320, the LP fuel valve position is
indicated on the ECAM display.
It is controlled by the engine master switch.
The HP fuel valve is not indicated directly but you know when it is open by the
fuel flow indication, the increase in the exhaust gas temperature or, by the fuel
used indication.

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ENGINE CONTROLS
ENGINE START CONTROLS

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ENGINE CONTROLS
ENGINE START CONTROLS

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ATA 76 Lesson 1

START CONTROL SIGNAL

CLOSE
For Training Purposes Only

HP
FUEL
VALVE

OPEN

LP
FUEL
VALVE

ECU

Figure 5
HAM US sw

Sep 98

Electrical Start Controls Indication
Page 11


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FUNDAMENTALS
ATA 76 Lesson 1

LP FUEL VALVE CONTROL
The low pressure fuel shut--off valve on modern Airbus aircraft is controlled by
the engine master switch.
You may remember from the Fire Protection lessons that this valve is also
called the fire shut--off valve and therefore it is also controlled by the engine fire
switch.
When you operate the fire switch the fire relay opens and the low pressure fuel
shut--off valve closes.
The amber colour of the valve symbol on the ECAM display indicates an
emergency closure of the valve.
The engine fire switch always has priority over the engine master switch.
This applies on all aircraft with electrically controlled low pressure fuel shut--off
valves.
Mechanically controlled low pressure fuel shut--off valves are only found on
very old aircraft. They are not described in this lesson.

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ENGINE CONTROLS
ENGINE START CONTROLS

HAM US sw

Sep 98

Page 12


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ENGINE CONTROLS
ENGINE START CONTROLS

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ATA 76 Lesson 1

START CONTROL SIGNAL

For Training Purposes Only

CLOSE
OPEN

ECU

Figure 6
HAM US sw

Sep 98

LP FUEL
VALVE

Edited by Foxit Reader
Copyright(C) by Foxit Software Company,2005-2008
For Evaluation Only.

khi keo can cuu hoa thi` lap
tuc dong cac valve chua dau lai
va tat dong co.

LP Fuel Valve Control
Page 13


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FUNDAMENTALS
ATA 76 Lesson 1

MECHANICAL HP FUEL VALVE CONTROL
The controls for mechanical high pressure fuel shut off valves are routed from
the cockpit below the cabin floor to the center section and then via the wing
leading edges and the pylons to the fuel control units.

The engine start lever has detents to secure it in the idle and cut--off positions.
Inputs from the lever are transmitted via rods, pulleys and cables to the start
drum in the pylon.
The start drum is connected to the fuel control unit via a long push pull cable.
Mechanically controlled high pressure fuel shut--off valves are usually found on
older aircraft types. Mechanical controls are more reliable than electrical
controls but they are heavier and they usually require more adjustments.

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ENGINE CONTROLS
ENGINE START CONTROLS

HAM US sw

Sep 98

Page 14


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ENGINE CONTROLS
ENGINE START CONTROLS

ADVANTAGE

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DISADVANTAGE

ATA 76 Lesson 1

START
DRUM
START
DRUM

FCU
START
CABLE

START
DRUM

TO ENGINE

For Training Purposes Only

HP
FUEL
VALVE

Figure 7
HAM US sw

Sep 98

PUSH-PULL
CABLE

Mechanical Hp Fuel Valve Control
Page 15


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FUNDAMENTALS
ATA 76 Lesson 1

ELECTRICAL HP FUEL VALVE CONTROL
Electrical high pressure fuel shut--off valves are normally found on modern
aircraft engines. They are located behind the fuel metering valve in the fuel
control unit. They can be motor controlled or solenoid controlled, but they have
similar construction.
Here you can see a more detailed view of the high pressure fuel shut--off valve
in the fuel control unit.
The valve assembly has two main parts -- the electrical component which

controls the servo valve and a spring loaded shut--off valve which is connected
to the servo valve. The spring loaded valve is usually called the pressurizing
valve.
The high pressure fuel flows across the partially open fuel metering valve and
then through the servo valve to the aft side of the pressurizing valve. The high
pressure fuel and the spring force keeps the pressurizing valve in the closed
position if the start lever is at cut--off.
This example shows a HP valve with a standard single coil solenoid. Note that
the solenoid is energized when the HP shut--off valve is closed.

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ENGINE CONTROLS
ENGINE START CONTROLS

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Sep 98

Page 16


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FUNDAMENTALS
ATA 76 Lesson 1

For Training Purposes Only

ENGINE CONTROLS
ENGINE START CONTROLS

Figure 8
HAM US sw

Sep 98

Electrical HP Fuel Valve OFF Postition
Page 17


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ATA 76 Lesson 1

Electrical hp fuel valve control cont.
When the start lever is moved to idle the solenoid is de--energized and the

servo valve moves down.
The pressure on the aft side of the pressurizing valve escapes into the case of
the fuel control unit.
The pressure from the high pressure fuel pump pushes the pressurizing valve
open and the fuel can flow to the fuel nozzles.
When the start lever is moved to the cut--off position the solenoid is energized
and the servo valve moves up.
This allows the fuel pressure to enter the aft side of the pressurizing valve
piston. The piston closes and the supply to the fuel nozzles is cut--off.
The critical disadvantage of this single coil solenoid control system is that if the
electrical signal is lost the high pressure fuel shut--off valve cannot be closed.

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ENGINE CONTROLS
ENGINE START CONTROLS

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Page 18


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FUNDAMENTALS
ATA 76 Lesson 1

For Training Purposes Only

ENGINE CONTROLS
ENGINE START CONTROLS

Figure 9
HAM US sw

Sep 98

Electrical HP Fuel Valve Open Position
Page 19


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FUNDAMENTALS
ATA 76 Lesson 1

Electrical hp fuel valve control cont.
Other aircraft have dual coil solenoids at the HP valve as you can see here.
These solenoids need electrical power to close the valve and to open the valve.
The danger is that the valve can move to the closed position if there’s a short
circuit because of a damaged wire -- even if the start lever is in idle.
Aircraft manufacturers have added protection circuits to prevent this dangerous
situation.
These protection circuits differ from aircraft to aircraft. Here you see a
simplified example where the pressurizing valve is equipped with a limit switch.
The limit switch is activated by the plunger of the pressurizing valve.
When the start lever is moved to idle the open coil of the dual solenoid is
energized and the servo valve moves down.
This moves the pressurizing valve up and the plunger activates the limit switch.
The limit switch de--energizes the protection relay and this disconnects the
electrical power from the solenoid.
This makes sure that the valve cannot move by mistake.
Remember that this is a simplified example. On many aircraft the power supply
and the ground are disconnected from the electrical control element.

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ENGINE CONTROLS
ENGINE START CONTROLS

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Page 20


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FUNDAMENTALS
ATA 76 Lesson 1

For Training Purposes Only

ENGINE CONTROLS
ENGINE START CONTROLS

Figure 10
HAM US sw

Sep 98

Protection Circuit HP Fuel Valve
Page 21


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FUNDAMENTALS
ATA 76 Lesson 2

MECHANICAL THRUST CONTROLS
INTRODUCTION
The mechanical thrust control system transmits the thrust lever input signals to
the fuel control unit on the engine. The forward thrust levers are also called the
throttles. They are located on the center pedestal. There is one thrust lever for
each engine.
The main positions of the forward thrust levers are idle and take--off thrust.
The reverse thrust levers are located at the top of the forward thrust levers.
The main positions of the reverse thrust levers are reverse idle and full reverse
thrust.
Forward thrust and reverse thrust use the same components.
At the drum below the trust levers the forward thrust lever rotates the drum
counter clockwise and the reverse thrust lever rotates the drum clockwise.

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ENGINE CONTROLS
MECHANICAL THRUST CONTROLS

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Sept.98

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ENGINE CONTROLS
MECHANICAL THRUST CONTROLS

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THRUST
LEVER

HAM us sw

Sept.98

ATA 76 Lesson 2

FUEL
CONTROL
UNIT

CENTER PEDESTRAL

Figure 11

FUNDAMENTALS

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For Evaluation Only.

REVERSE
THRUST
LEVER

FORWARD
THRUST
LEVER

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Mechanical Thrust Control
Page 23