Fundamentals

M15
GAS TURBINE ENGINE
Rev.-ID: 1SEP2014
Author: DaC
For Training Purposes Only
ELTT Release: Sep. 19, 2014

M15.14
Engine Indication Systems

EASA Part-66
CAT B1

M15.14_B1 E
Training Manual

For training purposes and internal use only.

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Lufthansa Technical Training
GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS
M15.14 | M14.02

M15 GAS TURBINE ENGINE

M15.14 ENGINE INDICATION SYSTEMS
FOR TRAINING PURPOSES ONLY!

FRA US/O-5 DaC Jul 16, 2013 ATA DOC Page 1

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02

INDICATION SYSTEM LAY-OUT

Engine Indication System

Engine indications are used to monitor the parameters of the engine and its
systems.
The engine indications can be divided into 3 groups.
S First, there are the performance indications, that are also named primary
indications.
S Then there are the system indications, that are also called secondary
indications.
S The third group of indications is used for engine trend monitoring and
usually not shown in the cockpit.
The performance indications are used to monitor the performance and the
limits of the engine, and to set the thrust for the different flight phases.
The system indications are used to monitor the operation of engine systems
such as the oil or fuel system. They are also used to detect malfunctions
quickly.
Engine trend monitoring is done on the ground to detect engine problems at
an early stage. It uses engine parameters that are automatically recorded by
the aircraft condition monitoring system (ACMS).
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|Eng Ind Sys|L1|A/B1/B2 Page 2

Lufthansa Technical Training
GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02
FOR TRAINING PURPOSES ONLY!

Figure 1 Engine Indication System

HAM US/F SwD 01.04.2008 01|Eng Ind Sys|L1|A/B1/B2 Page 3
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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02

Engine Indication Systems cont.

You can find engine indications, such as the ones shown on this ECAM display
system, which have a combination of gauge type analog displays and digital
readouts.
There are also analog indications with moving vertical bars, such as the ones
shown on this EICAS display.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|Eng Ind Sys|L1|A/B1/B2 Page 4

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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02
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Figure 2 Engine Performance Indication

HAM US/F SwD 01.04.2008 02|Eng Ind Sys|L1|A/B1/B2 Page 5
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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02

Engine Performance Indications

The indication which is always located at the top is used to monitor and set the
engine thrust.
Because it is not possible to measure the thrust directly, there are 2 different
indications which give an equivalent value.
This is either
S the rotational speed of the fan, called N1, or
S the engine pressure ratio.
The other performance indications are the engine rotor speed indications for
each rotor system.
This means that in addition to N1 there is N2 and, if available, also N3.
There is also the exhaust gas temperature indication (EGT) and the fuel flow
indication.
Data for the indications is measured by specific sensors or probes. The data is
usually electrically transmitted to the indicators.
Sensors fitted to engines with a FADEC system will first transmit the data to
the FADEC system computer.
The computer then sends the data to the indicators or display system and also
uses it to control the engine.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|Eng. Perf Ind|L1|A/B1/B2 Page 6

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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02
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Figure 3 Engine Performance Indication 2

HAM US/F SwD 01.04.2008 03|Eng. Perf Ind|L1|A/B1/B2 Page 7
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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02

Engine System Indications

We use the secondary engine indications to monitor the correct operation of
engine systems. These are also called engine system indications.
The indications for the oil system monitor the oil quantity, the oil pressure and
the oil temperature.
The engine vibration indication shows you any imbalance that occurs in the
rotating parts of the engine. For example an imbalance can be generated by
damage to blades or bearings.
The nacelle temperature increases for example when there is a leakage of hot
air in the engine nacelle.
The indications on the EICAS generally give the same information as the
indications on the ECAM, although they are shown in a different way.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 04|Eng. Perf Ind|L1|A/B1/B2 Page 8

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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02
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Figure 4 Engine System Indication

HAM US/F SwD 01.04.2008 04|Eng. Perf Ind|L1|A/B1/B2 Page 9
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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02

Engine System Indications cont.

There are also warnings and cautions displayed on the ECAM / EICAS page
S when an indication exceeds a limit, or
S when, as shown here, the system detects a low oil pressure, or
S when a filter gets clogged as indicated here, or
S when an unlocked thrust reverser is detected.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 05|Engine Sys Ind|L1|A/B1/B2 Page 10

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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02
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Figure 5 Engine System Indications

HAM US/F SwD 01.04.2008 05|Engine Sys Ind|L1|A/B1/B2 Page 11
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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02

Engine Trend Monitoring

Modern engines are very reliable and economic, but the performance of the
engine modules decrease during their lifetime.
To prevent larger performance reductions or even engine problems during
flight, you need a monitoring tool that alerts us to a problem at an early stage.
This tool is called engine trend monitoring.
The engine trend monitoring is done in the workshop by analyzing engine data
that is periodically recorded during flight by the aircraft condition monitoring
system.
The ACMS provides this data on a print-out from the cockpit printer, and it can
also usually transmit the data via the ACARS data link to the ground.
The transmitted engine data is analyzed by a computer system in order to find
any parameters that indicate a trend towards a limit.
3 different analyses are usually done:
S the thermodynamic analysis,
S the mechanic−dynamic analysis, and
S the oil consumption analysis.
The thermodynamic analysis checks the pressures and temperatures along the
gas flow path. It also monitors the feedback signals from the VSV and VBV, the
active clearance control, and the fuel flow.
The data gives exact information about the condition of the engine components
involved in the thermodynamic process.
The mechanic-dynamic analysis mainly checks for failures in the rotor system,
for example imbalances and bearing failures. To do this it checks engine
vibration and rotor speed signals.
FOR TRAINING PURPOSES ONLY!

The oil consumption analysis generates an alert when the oil consumption
exceeds a certain level.

HAM US/F SwD 01.04.2008 06|Eng Trend Mon|L1|A/B1/B2 Page 12

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ENGINE INDICATION SYSTEMS Indication System
M15.14 | M14.02
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Figure 6 Engine Trend Monitoring

HAM US/F SwD 01.04.2008 06|Eng Trend Mon|L1|A/B1/B2 Page 13
Lufthansa Technical Training
GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

ROTOR SPEED INDICATION

Introduction
In all engines there is a rotor speed indication for each individual rotor system.
There is a N1 indication for the low pressure rotor and a N2 for the high
pressure rotor. There is also a N3 indication if the engine has 3 rotors.
The engine rotor speed indications are always expressed as a percentage of a
100% design speed.
Now read the N1 value for engine number 2 in the example.
Each rotor speed indication has 3 main parts:
S the sensor
S the data transmission
S and the indication.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 14

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02
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Figure 7 Introduction
HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 15
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Tachometer Generator
There are 2 different types of sensor, which can measure rotor speed on
engines.
One is the variable reluctance type sensor.
The other is the tachometer generator type, which is usually located on the
gearbox.
The tachometer generator has a permanent magnet that is driven by the
gearbox with a speed that is proportional to the N2 rotor speed. The rotating
magnetic field generates a 3−phase AC voltage with a frequency that is
proportional to the input speed.
The frequency is converted back to the speed signal in either a computer or
indicator.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|Tach Gen|L2|B1/B2 Page 16

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02
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Figure 8 Tachometer Generator

HAM US/F SwD 01.04.2008 02|Tach Gen|L2|B1/B2 Page 17
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Tachometer Generator cont.

In older generation aircraft there are rotor speed indicators, which are driven
directly by the voltage from the tachometer generator.
The indicator has a synchronous AC motor that generates a speed proportional
to the input frequency, which is the same as the speed of the drive shaft on the
tachometer generator.
An eddy current clutch transfers the speed into a proportional torque, which
moves the gauge pointer to the correct indication.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|Tach Gen|L2|B1/B2 Page 18

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02
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Figure 9 Direct Indication

HAM US/F SwD 01.04.2008 03|Tach Gen|L2|B1/B2 Page 19
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Tachometer Generator cont.

In modern aircraft systems the tachometer generator sends the 3−phase AC
voltage to the FADEC computer, where it is used to calculate the speed signal.
The tachometer generator also supplies electrical power to the computer and is
therefore also called dedicated generator or control alternator.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 04|Tach Gen|L2|B1/B2 Page 20

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02
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Figure 10 FADEC Generator

HAM US/F SwD 01.04.2008 04|Tach Gen|L2|B1/B2 Page 21
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Variable Reluctance Speed Sensor

Now let us have a look at the variable reluctance speed sensor, which is
normally used to measure the N1 rotor speed.
The variable reluctance sensor is positioned directly in line with the phonic
wheel on the compressor shaft.
As you can see phonic wheels have different shapes, but this is not important.
The important thing is that the rotating phonic wheel alternates metal and air at
the tip of the sensor to change the sensor’s magnetic field.
Because the sensor must be located near the compressor shaft, it often needs
a long support tube to make replacement of the sensor possible.
You must be very careful during replacement not to bend or damage the probe.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 05|Var Rel Sensor|L2|B1/B2 Page 22

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02
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Figure 11 Sensor and Phonic Wheel

HAM US/F SwD 01.04.2008 05|Var Rel Sensor|L2|B1/B2 Page 23
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Variable Reluctance Speed Sensor cont.

There are similar sensor types located near the fan blades on some engines.
The fan blades are used instead of a phonic wheel to change the magnetic field
of the sensor.
You can find also a variable reluctance type sensor on the gearbox which
measures the N2 rotor speed.
In this installation a gear in the gear box has the function of the phonic wheel.
In all applications a computer is used to calculate the rotational speed from the
sensor pulses.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 06|Var Rel Sensor|L2|B1/B2 Page 24

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
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Figure 12 Variable Reluctance Speed Sensor

HAM US/F SwD 01.04.2008 06|Var Rel Sensor|L2|B1/B2 Page 25
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Speed Indications
There are 3 different types of rotor speed indication:
S a display with a clock type scale,
S a display with a moving vertical bar, and
S the classical electromechanical indicator.
All 3 indications show the actual N1 value with an analog and a digital
indication.
There is always a speed limit indication, which is usually a red line. This is the
maximum permitted rotor speed.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 07|Speed Ind|L1|A/B1/B2 Page 26

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
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Figure 13 Speed Indications

HAM US/F SwD 01.04.2008 07|Speed Ind|L1|A/B1/B2 Page 27
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
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Speed indications cont.

When actual N1 exceeds the red limit it can damage the engine.
To make this dangerous situation clear to the pilot, the indications on the
displays change to red accompanied by warnings from the central warning
system.
The maximum exceedance value is recorded and in modern aircraft it also
initiates an exceedance report from the engine trend monitoring.
This is used for planning the necessary maintenance actions.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 08|Speed Ind|L1|A/B1/B2 Page 28

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
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Figure 14 Exceedance Recording

HAM US/F SwD 01.04.2008 08|Speed Ind|L1|A/B1/B2 Page 29
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Limit Indications
When N1 decreases below the red limit, a red exceedance pointer shows the
recorded maximum exceedance value or you just get a red box around the
digital readout to show that an exceedance occurred.
You can read the value with the onboard maintenance system.
You can reset the exceedance value when you finish the necessary
maintenance actions.
You can reset the exceedance indication by pressing the corresponding push
button in the cockpit. In modern aircraft this is done automatically with the next
engine start.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 09|Limit Ind|L2|A/B1/B2 Page 30

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ENGINE INDICATION SYSTEMS Rotor Speed Indication
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Figure 15 Exceedance Pointer

HAM US/F SwD 01.04.2008 09|Limit Ind|L2|A/B1/B2 Page 31
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ENGINE INDICATION SYSTEMS Rotor Speed Indication
M15.14 | M14.02

Limit Indications cont.

When the N1 indication is used to set engine power, then an additional
indication is needed to show the pilot the N1 value for the required thrust.
This value is called
S N1 limit, or
S N1 command, or
S reference N1.
The N1 limit or N1 command shows the N1 that is required for a specific flight
phase, such as take-off or climb. The value is calculated by the flight
management or autothrottle system.
There is always an analog indication on the scale and an additional digital
readout.
You can also set this value manually with the knob on the lower indicator. For
the displays you set the value via the flight management system.
On some displays you also can find an amber line that shows the N1 for the
maximum available thrust, and a blue circle or white line that shows the N1 for
the actual throttle position.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 10|Limit Ind|L2|A/B1/B2 Page 32

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Figure 16 N1 Command
HAM US/F SwD 01.04.2008 10|Limit Ind|L2|A/B1/B2 Page 33
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ENGINE INDICATION SYSTEMS EPR Indication
M15.14 | M14.02

ENGINE PRESSURE RATIO INDICATION

Introduction
You only find an EPR indication for some engine types. It is always located at
the top of the engine indications, because it is used to set the engine power.
The EPR corresponds to the engine thrust, because it is the ratio of the total
pressure at the turbine outlet to the total pressure at the fan inlet.
Other engine types do not need an EPR indication, because the power is set
with the N1 indication.
Each EPR indication system has 3 main parts:
S 2 pressure pickups that are connected by tubes with a computer,
S a computer, which is either a separate EPR transmitter or part of the
FADEC computer, and
S the indicator, which is located in the cockpit.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 34

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ENGINE INDICATION SYSTEMS EPR Indication
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Figure 17 EPR Indication System Components

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 35
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ENGINE INDICATION SYSTEMS EPR Indication
M15.14 | M14.02

Pressure Sensors
To calculate and indicate the EPR you must measure 2 pressures.
The pressure is given the name of the station that detects it, for example the
P2 and the P5 pressure.
P2 is the total air pressure at the fan inlet. It is measured by a pressure probe,
which is located in the fan airstream. Like other air data probes it is electrically
heated to prevent icing.
P5 is the total gas pressure at the turbine exit. This pressure is also sensed by
probes or, like in this example, with small holes in 3 of the turbine nozzle guide
vanes.
The individual pressures are collected by pickups in the turbine case and
guided by tubes to a common pressure manifold. This gives an average P5
pressure value.
The 2 pressure values are passed to the computer for it to calculate the
pressure ratio. Shown here is an EPR transmitter, which is an earlier type of
computer. Before the calculation can occur, the computer must change the
pressure into a proportional electrical signal.
The EPR transmitter uses electromechanical pressure transducers with, for
example, bourdon tubes.
The photo shows an example of bourdon tubes.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|Pressure Sensors|L2|B1/B2 Page 36

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ENGINE INDICATION SYSTEMS EPR Indication
M15.14 | M14.02
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Figure 18 Sensors and Transmitter

HAM US/F SwD 01.04.2008 02|Pressure Sensors|L2|B1/B2 Page 37
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ENGINE INDICATION SYSTEMS EPR Indication
M15.14 | M14.02

Pressure Sensors cont.

On modern engines the EPR calculation is done in the FADEC computer. It
uses electronic pressure transducers like in the air data system.
These transducers are much smaller, more reliable and more exact than the
electromechanical transducers.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|Pressure Sensors|L1/B1/B2 Page 38

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ENGINE INDICATION SYSTEMS EPR Indication
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Figure 19 Sensors and FADEC

HAM US/F SwD 01.04.2008 03|Pressure Sensors|L1/B1/B2 Page 39
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ENGINE INDICATION SYSTEMS EPR Indication
M15.14 | M14.02

EPR Indication
In this segment we will show you 2 different types of EPR indication.
Firstly, the indication on a display unit which you find on modern aircraft, and
secondly, the classical electromechanical indicator on older generation aircraft.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 04|EPR Indications|L1|A/B1/B2 Page 40

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Figure 20 EPR Indications

HAM US/F SwD 01.04.2008 04|EPR Indications|L1|A/B1/B2 Page 41
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ENGINE INDICATION SYSTEMS EPR Indication
M15.14 | M14.02

Additional Indications
You may have noticed that the actual EPR indication is shown by an analog
and a digital value.
The EPR command has the same function as the N1 command. This example
shows the EPR required for a flexible take-off.
On the classical indicator this value is called the EPR limit, which is also shown
in both analog and digital format.
You can also set the value manually by pulling the knob.
On the display you can find 2 more indications. These are:
S the amber line that shows the EPR for the maximum available thrust and
S a blue circle that shows the EPR that corresponds to the actual throttle
position.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 05|Add Indications|L2|B1/B2 Page 42

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ENGINE INDICATION SYSTEMS EPR Indication
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Figure 21 Additional Indications

HAM US/F SwD 01.04.2008 05|Add Indications|L2|B1/B2 Page 43
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ENGINE INDICATION SYSTEMS EGT Indication
M15.14 | M14.02

EXHAUST GAS TEMPERATURE INDICATION

Introduction
There must be an exhaust gas temperature indication for each engine. The
indication is necessary to monitor the high temperatures in the engine exhaust
in order to see when a limit is exceeded.
The highest temperature is directly behind the combustion chamber where the
hot gas hits the high pressure turbine. This temperature is called the turbine
inlet temperature or TIT.
Because this temperature can be higher than 1,400_ C, it is not easy to
measure the TIT.
The exhaust gas temperature (EGT) is therefore measured at a colder location
in the engine either between the high and low pressure turbine or directly
behind the low pressure turbine. This is possible because the EGT has a direct
relationship to the TIT.
Because of the different measuring points you can find maximum EGT
indications between 600_C and 900_C.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 44

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ENGINE INDICATION SYSTEMS EGT Indication
M15.14 | M14.02
FOR TRAINING PURPOSES ONLY!

Figure 22 EGT Indication System

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 45
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ENGINE INDICATION SYSTEMS EGT Indication
M15.14 | M14.02

EGT Probes
To measure and indicate the EGT you need:
S temperature sensors,
S a means of transmitting data, and
S a method of indication.
To measure high temperatures you need sensors of the thermocouple type.
There are several thermocouples on the engine. In the example shown here
there are 9. They are installed in the turbine case of the engine.
All thermocouples are connected to each other in order to generate a common
temperature value. The thermocouples for the EGT are always connected in
parallel in order to measure the average exhaust gas temperature.
The paralleling is done in junction boxes. To make probe replacement easier,
on some engines the thermocouples are paralleled in groups in parallel junction
boxes. All signals are then combined in the main junction box and transferred
to the FADEC system.
You may recall that special wiring is needed from the probes to the cold
junction. In our example the cold junction is located in the FADEC system
computer.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|EGT Probes|L2|B1/B2 Page 46

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Figure 23 EGT Indication Components

HAM US/F SwD 01.04.2008 02|EGT Probes|L2|B1/B2 Page 47
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ENGINE INDICATION SYSTEMS EGT Indication
M15.14 | M14.02

EGT Indication
You are now going to look at 3 different types of EGT indication:
S the display with a clock type scale,
S a display with a moving vertical bar, and
S the classical electromechanical indicator.
All 3 indications show the actual exhaust gas temperature in degrees Celsius in
both analog and digital.
They also always show the temperature limit, usually as a red line. This is the
maximum permissible EGT that should never be exceeded.
When an EGT red limit exceedance occurs in modern systems, then you get
information which is basically the same as you get when a rotor speed
exceedance occurs.
On each display there is also an amber line that shows the maximum EGT for
the maximum continuous thrust setting. The EGT is only allowed to exceed the
amber line value for a short time when the engines run at take-off or go around
thrust.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|EGT Indication|L1|A/B1/B2 Page 48

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Figure 24 EGT Indications

HAM US/F SwD 01.04.2008 03|EGT Indication|L1|A/B1/B2 Page 49
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ENGINE INDICATION SYSTEMS Vibration Monitoring
M15.14 | M14.02

VIBRATION MONITORING

Introduction
A very important secondary engine indication is the indication for engine
vibration. It enables you to identify a rotor imbalance, which can be the first
sign of engine damage.
The main parts of the engine vibration monitoring system are, as follows:
S the indication in the cockpit which you have just identified. This shows the
level of vibration usually in units from 0 to about 6.
S Then on the engine there are 1 or 2 vibration sensors, which deliver
electrical signals to a computer.
S This computer collects and filters the vibration data for indication and engine
trend monitoring. The computer is, for example, sometimes called the
engine vibration monitoring unit or EVMU for short.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 50

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Figure 25 Vibration Monitoring

HAM US/F SwD 01.04.2008 01|Intro|L1|A/B1/B2 Page 51
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M15.14 | M14.02

Vibration Sensor
The engine vibration sensors are accelerometers that measure the radial
acceleration of the rotor system.
You usually find 2 sensors on each engine.
S 1 sensor is located in the compressor area, for example near the N1 rotor
shaft, and
S a second sensor is in the turbine area, for example on the turbine frame.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|Vibrations Sensor|L1|A/B1/B2 Page 52

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Figure 26 Vibration Sensors

HAM US/F SwD 01.04.2008 02|Vibrations Sensor|L1|A/B1/B2 Page 53
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Accelerometer
2 different types of accelerometer are used on engines.
S 1 type is the electromagnetic accelerometer and the other
S 1 is the piezoelectric−crystal type sensor.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|Accelerometer|L2|B1/B2 Page 54

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Figure 27 Vibration Sensors 2

HAM US/F SwD 01.04.2008 03|Accelerometer|L2|B1/B2 Page 55
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Accelerometers cont.
The electromagnetic sensor has a permanent magnet that is hold in the
center by 2 springs. A fixed coil surrounds the magnet.
When there is a vibration, the coil moves up and down together with the sensor
housing. However, the magnet stays almost still due to its inertia force.
The difference in motion between the coil and the magnetic field induces an
AC voltage in the coil, like in a generator.
A piezoelectric crystal generates a voltage when you apply a force to the
crystal. In this sensor the force is applied by an inertia mass, which presses the
crystal against the base plate when the sensor is accelerated.
The vibration sensors give a signal to the monitoring unit with a voltage that is
proportional to the level of acceleration and a frequency that is equivalent to
the vibration frequency.
The monitoring unit filters and analyzes these signals from the accelerometers
for indication and trend monitoring.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 04|Accelerometer|L2|B1/B2 Page 56

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Figure 28 Operation of Vibration Sensors

HAM US/F SwD 01.04.2008 04|Accelerometer|L2|B1/B2 Page 57
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M15.14 | M14.02

Vibration Indication Selection

In older aircraft types there is 1 engine vibration indicator for each engine.
The indicated value depends on the selection of 2 switches. One switch selects
the turbine or inlet vibration sensor and the other switch selects a filter for a
high or a low frequency.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 05|Vib Ind Selection|L2|B1/B2 Page 58

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Figure 29 Vibration Indication

HAM US/F SwD 01.04.2008 05|Vib Ind Selection|L2|B1/B2 Page 59
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M15.14 | M14.02

Vibration Indication
The vibration indication on modern aircraft is automatically controlled by the
monitoring unit.
In this example of an ECAM display there are 2 indications for each engine.
S 1 indication shows units of vibration for the N2 rotor system and
S 1 for the N1 rotor system
The monitoring unit generates the 2 indications from a single sensor signal.
This can be done by comparing the frequency of the vibration signal and the 2
rotor speed signals.
Usually only the forward sensor is used for this indication, but the monitoring
unit is able to switch to the aft sensor when the forward sensor fails.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 06|Vibration Indication|L1|A/B1/B2 Page 60

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Figure 30 Vibration Indication on ECAM

HAM US/F SwD 01.04.2008 06|Vibration Indication|L1|A/B1/B2 Page 61
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Detailed Vibration Indication

This example of an EICAS display shows the vibration in an analog and digital
format. There is only 1 value for each engine.
The monitoring unit usually selects the highest vibration signal for the
indication. The display also shows the sensor and filter functions that are used
for the indication.
4 different modes of indication are possible in this example.
The first one shows FAN and means that the forward sensor is measuring the
vibration of the N1 rotor.
LPT stands for Low Pressure Turbine and means that the aft sensor measures
the vibration of the N1 rotor.
N2 means that the vibration of the N2 rotor system is measured by the aft
sensor.
BB means broad band and shows the unfiltered vibration signal from the aft
sensor. This signal is used, for example, when a rotor speed signal is not
available.
When a vibration reaches a certain critical level, in some aircraft types the
corresponding vibration indication starts pulsing. Now the pilot must react to
find the reason for the vibration, for example by scanning other engine
indications or even by power reductions or engine shut-down.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 07|Detailed Vib Ind|L2|B1/B2 Page 62

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Figure 31 Vibration Indication on EICAS

HAM US/F SwD 01.04.2008 07|Detailed Vib Ind|L2|B1/B2 Page 63
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Fan Balancing
For some engines you can also use the vibration monitoring system for ”on
wing fan balancing”.
It helps to find the highest imbalance with its exact location on the rotor.
The location is given by the so-called rotor phase angle. This is the position on
the rotor, measured in degrees from a fixed reference point.
You can measure the reference point for example with a ”trim balance sensor”.
This works like a rotor speed sensor but gives only 1 pulse for each rotation.
You can find the phase angle indication for example on an EICAS maintenance
page, together with all vibration signals.
On other aircraft you will find it on the print-out from the ACMS.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 08|Fan Balancing|L2|B1/B2 Page 64

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Figure 32 Phase Angle Measurement

HAM US/F SwD 01.04.2008 08|Fan Balancing|L2|B1/B2 Page 65
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ENGINE INDICATION SYSTEMS Fuel Indication
M15.14 | M14.02

FUEL FLOW INDICATION

System Architecture
The fuel flow indicating system provides 2 different indications for the pilot:
S The actual fuel flow to the engines, which is in kg or tons per hour, and
S the fuel used since the engine was started. This is in kg or tons.
The fuel flow indication allows you to monitor the performance and economic
operation of the engines. The engines usually have the same power setting
and therefore each flow indicator should also show identical fuel flow.
The fuel used indication shows the mass of fuel which was burned since the
last engine start on ground. This allows to compare the performance of the
different engines. It also gives a redundant information for the actual fuel
quantity.
You can calculate the actual fuel quantity by subtracting the amount of used
fuel from the amount of fuel in the tanks at take-off. The fuel used indication is
usually automatically reset to 0 when the engine master switch is switched to
ON and the aircraft is on the ground.
To generate the fuel flow and fuel used indications there needs to be a fuel flow
transmitter on each engine and then a calculation has to be done.
The calculation in modern systems is usually done by the FADEC system
computer.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|System Arch|L1|A/B1/B2 Page 66

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Figure 33 Fuel Flow Indication System

HAM US/F SwD 01.04.2008 01|System Arch|L1|A/B1/B2 Page 67
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ENGINE INDICATION SYSTEMS Fuel Indication
M15.14 | M14.02

Fuel Flow Transmitter Introduction

The fuel flow transmitter measures the mass flow of fuel between the fuel
control unit and the fuel nozzles.
There are different types of fuel flow transmitter, but their operation is always
based on a basic law of Physics:
Force is equal to mass times acceleration.
All transmitter types measure the force, which is applied by the mass of fuel.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|Fuel Flow Transm|L1|A/B1/B2 Page 68

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Figure 34 Powered Fuel Flow Transmitter

HAM US/F SwD 01.04.2008 02|Fuel Flow Transm|L1|A/B1/B2 Page 69
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ENGINE INDICATION SYSTEMS Fuel Indication
M15.14 | M14.02

Fuel Flow Transmitter Types

In the transmitter type shown here the fuel mass turns a turbine against a
spring and the deflection angle is measured.
To get the force you must accelerate the fuel. This is done here by an impeller
that rotates continuously, driven by an electric motor.
The mass of fuel is proportional to the turbine angle, because the acceleration
of the fuel is constant.
A position transducer, such as synchro or RVDT, measures the turbine angle
and sends it to the indicator.
The indicator shows the fuel flow directly and also calculates the fuel used
value by an integration of the fuel flow rate.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|Fuel Flow Transm. Page 70

Types|L2|B1/B2
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Figure 35 Powered Fuel Flow Transmitter 2

HAM US/F SwD 01.04.2008 03|Fuel Flow Transm. Page 71
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Fuel Flow Transmitter Types cont.

Modern fuel flow transmitters do not need an electric motor with a power
supply. They use the fuel itself to generate the acceleration.
In this transmitter type the fuel flow turns a small turbine. The rotating turbine
also drives a drum and an impeller, which is located inside the drum. Both are
coupled by a spring.
The fuel drives the turbine, drum, and impeller with a speed that is proportional
to the volume of fuel.
Behind the turbine the fuel passes through a fixed straightener that stops all
possible fuel spin. The straightened fuel then passes through the rotating drum
without affecting the rotation of the drum. Then the fuel hits the impeller blades.
The force of the fuel delays the rotation of the impeller, until this braking force
is compensated by the force of the spring.
The angle between the rotating drum and the rotating impeller is proportional to
the mass fuel flow.
The transmitter measures this angle with 2 coils in combination with 4
permanent magnets.
S 2 magnets are located on the drum and
S 2 are located on the impeller.
When a magnet passes the coil, it induces a voltage pulse in the coil. In our
example this happens twice for each rotation.
With no fuel flow the angle is zero and therefore the magnets on the drum and
the impeller pass the coils at the same time.
When there is fuel flow, the impeller magnet is delayed by an angle in
proportion to the fuel mass. When this happens, the pulse from the impeller coil
is also delayed.
FOR TRAINING PURPOSES ONLY!

The FADEC system computer now calculates the time between the 2 pulses,
which is proportional to the mass fuel flow.
An integration of the fuel flow value gives the required fuel used information.

HAM US/F SwD 01.04.2008 04|Fuel Flow Transm. Page 72

Types|L2|B1/B2
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Figure 36 Fuel Flow Indication

HAM US/F SwD 01.04.2008 04|Fuel Flow Transm. Page 73
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ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02

ENGINE OIL MONITORING SYSTEM

Oil Quantity Indication

The oil quantity transmitter in the tank sends the information via a computer,
which performs the measurement, in this example called the engine interface
unit (EIU), to the display units in the cockpit.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 01|Oil Qty Indic|L1|A/B1/B2 Page 74

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Figure 37 Oil Quantity Indicating Schematic

HAM US/F SwD 01.04.2008 01|Oil Qty Indic|L1|A/B1/B2 Page 75
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Oil Quantity Indication cont.

The oil quantity transmitter is normally installed at the top of the oil tank.
This allows the transmitter to be changed without draining the tank.
2 types of transmitter are used
S the capacitance type transmitter and
S the reed switch type transmitter.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 02|Oil Qty Indic|L1|A/B1/B2 Page 76

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Figure 38 Different Types of Quantity Transmitter

HAM US/F SwD 01.04.2008 02|Oil Qty Indic|L1|A/B1/B2 Page 77
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Oil Quantity Indication cont.

Here you see the capacitance type transmitter. The upper part has the
electronic components for the capacitance measurement and an electrical
connector.
The lower part, which is immersed in the oil, has 2 concentric tubes. These are
the 2 plates of the capacitor.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 03|Oil Qty Transmtr|L2|B1/B2 Page 78

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Figure 39 Capacitance Type Transmitter

HAM US/F SwD 01.04.2008 03|Oil Qty Transmtr|L2|B1/B2 Page 79
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Oil Quantity Indication cont.

The reed type transmitter has a metal tube with a float inside and a multi switch
assembly.
The metal tube has holes to let the oil in from the tank so that the float can
move up and down with the oil level in the tank. The float assembly has
permanent magnets, which activate an internal switch assembly.
The multi switch assembly has a ladder of reed switches connected by
resistors. The magnet in the float always closes the switch nearest to it.
When, for example, the oil tank is full, then the float is at the upper limit of its
travel. The magnet in the float assembly causes the top switch in the ladder to
close. In this situation the resistance in the electrical circuit is at its minimum,
and this gives maximum output voltage from the transmitter.
You have seen that when the oil level falls, the float also falls. The switch
nearest to the float closes and all other switches open.
The electrical resistance in the circuit changes with the switch that is closed
and this gives a corresponding output voltage from the transmitter.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 04|Oil Qty Transmtr|L2|B1/B2 Page 80

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Figure 40 Reed Switch Type Transmitter

HAM US/F SwD 01.04.2008 04|Oil Qty Transmtr|L2|B1/B2 Page 81
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ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
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Oil Pressure Indication

The oil pressure transmitter is connected to the oil supply line and to the oil
tank vent line.
The transmitter senses the pressure difference between the total oil pressure in
the oil supply line and the vent pressure in the oil tank.
Oil pressure information is sent from the oil pressure transmitter to the engine
interface unit, which performs the measurement and then to the display unit in
the cockpit.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 05|Oil Press Indic|L1|A/B1/B2 Page 82

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Figure 41 Oil Pressure Indication System Schematic

HAM US/F SwD 01.04.2008 05|Oil Press Indic|L1|A/B1/B2 Page 83
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Oil Pressure Sensor

There are two main types of oil pressure transmitter:
S the bourdon tube type and
S the strain gage type.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 06|Oil Press Sensor|L2|B1/B2 Page 84

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Figure 42 Oil Pressure Sensors

HAM US/F SwD 01.04.2008 06|Oil Press Sensor|L2|B1/B2 Page 85
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Low Oil Pressure Switch

An additional pressure switch is used in the engine oil system to initiate a low
oil pressure warning.
The pressure switch is also connected to the oil supply line and the oil tank
vent line.
If the oil pressure decreases below the limit, the low oil pressure switch closes,
a signal is sent to the flight warning computer, and a warning message appears
on the display unit in the cockpit.
Note also, that the engine low oil pressure warning is always accompanied by
an acoustic warning in the cockpit.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 07|Low Oil Press Switch|L1|A/B1/B2 Page 86

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Figure 43 Low Oil Pressure Switch

HAM US/F SwD 01.04.2008 07|Low Oil Press Switch|L1|A/B1/B2 Page 87
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Low Oil Pressure Switch cont.

Here you can see the location of the oil pressure transmitter and the low oil
pressure switch on an engine.
In this example they are installed on the fan case in the ten o’clock position.
You can see where each is connected to the oil supply line and the oil tank
vent pressure line.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 08|Low Oil Press Switch|L1|A/B1/B2 Page 88

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Figure 44 Pressure Transmitter & Low Pressure Switch Location

HAM US/F SwD 01.04.2008 08|Low Oil Press Switch|L1|A/B1/B2 Page 89
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02

Oil Temperature Indication

The location of the oil temperature sensor in the lubrication system depends on
the engine type.
The sensor can be found in the scavenge system, where it senses the hot oil
temperature upstream of the oil cooler, or it can be found in the pressure
system, where it senses the temperature of the cooled oil.
Oil temperature information is sent from the oil temperature sensor to a
computer, which performs the measurement and then to the display unit in the
cockpit.
There are 2 main types of oil temperature sensor:
S the thermocouple and
S the thermistor.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 09|Oil Temp Indic|L1|A/B1/B2 Page 90

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02
FOR TRAINING PURPOSES ONLY!

Figure 45 Oil Temperature Indication

HAM US/F SwD 01.04.2008 09|Oil Temp Indic|L1|A/B1/B2 Page 91
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02

Oil Temperature Indication cont.

There are 2 main types of oil temperature sensor:
S the thermocouple and
S the thermistor.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 10|Oil Temp Indic|L1|A/B1/B2 Page 92

Lufthansa Technical Training
GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02
FOR TRAINING PURPOSES ONLY!

Figure 46 Oil Temperature Sensor Location

HAM US/F SwD 01.04.2008 10|Oil Temp Indic|L1|A/B1/B2 Page 93
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02

Oil Contamination Monitoring cont.

The scavenge oil filter element catches larger particles which are of a size of
more than 0.015 mm. These particles can be removed and sent for analysis.
The problem with this is that the filter element is not changed very often and
each filter inspection takes time.
Magnetic chip detectors are an easier and less time consuming method to get
information about the condition of the oil.
Magnetic chip detectors catch metal particles which are attracted to the
magnet. They can be easily removed and the condition can be checked.
The magnetic chip detectors can be manually checked at fixed intervals or on
some modern aircraft they can be electronically monitored and removed when
necessary.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 12|Oil Contam Monitorg|L1|A/B1/B2 Page 94

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02
FOR TRAINING PURPOSES ONLY!

Figure 47 Magnetic Chip Detectors

HAM US/F SwD 01.04.2008 12|Oil Contam Monitorg|L1|A/B1/B2 Page 95
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02

Oil Contamination Monitoring cont.

Here you see an electronically monitored chip detector, installed in the
scavenge oil line.
This chip detector has 2 magnets at its tip. The resistance between the 2 chip
detector magnets is monitored by the electronic control unit. The resistance
decreases when particles connect with the magnets. When the resistance
between the magnets gets below the limit, the electronic control unit sends a
maintenance message for the post flight report.
FOR TRAINING PURPOSES ONLY!

HAM US/F SwD 01.04.2008 14|Oil Contam Monitorg|L1|A/B1/B2 Page 96

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Engine Oil Monitoring System
M15.14 | M14.02
FOR TRAINING PURPOSES ONLY!

Figure 48 Electronic Magnetic Chip Detectors

HAM US/F SwD 01.04.2008 14|Oil Contam Monitorg|L1|A/B1/B2 Page 97
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Manifold Pressure
M15.14 | M14.02

MANIFOLD PRESSURE
Manifold Pressure
The manifold pressure gauge shows for carburettor engines the pressure of the
fuel/air mixture and, for injection engines, the pressure of the charge air.
In the case of a commonly used type of manifold pressure gauge, there is a
bellows system, whereby one capsule has a vacuum while the other is under
manifold pressure. A bell-crank lever connects the two sets of bellows and at
the same time the pointer of the instrument is moved. The indication is the
result of the two bellows systems working together and is the sum of
atmospheric pressure and the higher pressure produced by the charger. When
the aircraft is on the ground and the engine is not running, the manifold
pressure gauge must indicate current atmospheric pressure.
Manifold pressure is thus an absolute, i.e. a pressure relative to a vacuum.
Manifold air pressure (MAP) is normally indicated in inch/Hg.
A rule of thumb is that MAP in inch/Hg must not exceed the corresponding
RPM divided by 100.
Example: At 2100 RPM manifold air pressure should not be greater than 21
in/Hg.
Exact values must however be taken from the flight manual.
FOR TRAINING PURPOSES ONLY!

Figure 49 Load indication digital

FRA US/O DaC Sep.15,2012 01|manifold pressure|L1/A/B1/B2 Page 98

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ENGINE INDICATION SYSTEMS Manifold Pressure
M15.14 | M14.02

POINTER
GEAR

LINK

SECTOR AND PINION

HAIR SPRING

BOURDON
TUBE
FOR TRAINING PURPOSES ONLY!

SOCKET

PRESSURE
CONNECTION

Figure 50 bourdon tube

FRA US/O DaC Sep.15,2012 01|manifold pressure|L1/A/B1/B2 Page 99
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

TORQUE AND POWER

Introduction
All aircraft certification authorities require a torque indication system for
engines which produce indirectly a propulsive force by generating a shaft
power for the physical thrust generator.
Accordingly, such systems are for following engine types required:
S turboprop engines (TPE)
S turboshaft engines (TSE)
For these engine types are the typical synonyms of turbojet and turbofan
engine thrust indications (rotor speed and EPR) not useable.
S Due to the propeller or rotor blade adjustment a different performance can
be generated at the same speed at TPE and TSE.
In general the available rotor speed range for powering the propulsion
generator is less than the range at TJE and TFE.
At some single−shaft TPE with single−lever operation (see figure) the fuel
flow rate is altered by moving the control lever, but the the propeller
regulator prevents by changing the propeller blade pitch angle ö a rotor
speed changement. That means that the braking torque of the popeller is
increased or decreased to keep a constant propeller speed.
So the speed indication of the rotor system(s) is required for monitoring
TPE and TSE, but does not make any statement about the sufficient
performance of the engine.
S The engine pressure ratio (EPR) is also unsuitable for the performance
indicator in TPE and TSE, because of the small difference of the pressure
indications which are set in relation.
FOR TRAINING PURPOSES ONLY!

The torque indicator is therefore the primary performance indicator in the

cockpit.

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ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

125

100 maximum power

ö = 25_

(%)

range of power regime

75
shaft power

ö = 20_

50

ö = 15_

25
ö = 10_
FOR TRAINING PURPOSES ONLY!

ö = 15_

ö = 0_
0
11000 12000 13000 14000 15000 16000
Idle engine rotor speed (min–1)

ö – blade angle of the propeller blades

Figure 51 Rotor Speed Characteristics

FRA US/O-5 DaC Jun 13, 2013 01|Torque&Power|L1|A/B1/B2 Page 101
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

Torque Indication
The display device receives its signal from the torque measurement system of
the engine; the display can be designed in different ways:
S Torque oil pressure
It takes place in ”pounds per square inch (PSI)” or, in older engines, even in
”newtons per square centimeter (kp/cm2)”.
For such systems, the availability of the propeller shaft power is calculated:
N TWńLS @ p MD
PW +
K
In this formula:
− NTW/LS – Engine speed of the propeller driving turbine
(min–1, rpm)
− pMD – Torque proportional oil pressure (PSI, kp/cm2)
− K – Constant factor which depends on the design
conditions of the reduction gear and the torque
measuring system; specified by the manufacturer
− PW – Power to the propeller shaft (SHP, PS oder kW)
S Direct representation of the torque [torque (TRQ or TQ)]
It is displayed in „feet-pounds (FT.LBS.)“ or − in older jet engines − in
”newtons−meters (kpm)” and allows the calculation of the available propeller
shaft power:
P W + K @ N TWńLS @ MD
In this formula:
FOR TRAINING PURPOSES ONLY!

− MD – displayed torque (ft.lbs., kpm)

− All other factors correspond to the first specified sizes.
S Torque proportional percentage display [torque percent (TRQ %)]
The display scaled in percent extends generally from 0 to 120%.
S Direct indication of shaft power [shaft (horse) power, horsepower output]
The display is in ”shaft horse power (SHP)” or ”horsepower (HP).”

FRA US/O-5 DaC Jun 13, 2013 02|Torque Indic.|L1|A/B1/B2 Page 102
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

PW123, Dash 8 Series 300

A
A

Use of digital displays in conjunction with a push button [momentary

switch] MAINT SELECT on a console next to the pilot for a
maintenance mode data
In this mode, errors are previously stored in an engine control
system established in the ECC coded and displayed on the digital
FOR TRAINING PURPOSES ONLY!

display.

PW123, Dash 8 Series 300

Figure 52 Torque Indicating System

FRA US/O-5 DaC Jun 13, 2013 02|Torque Indic.|L1|A/B1/B2 Page 103
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

Torque Measurement
Regarding the way of the torque measurement, two basic methods may be
distinguished:
1. Hydromechanical sensing systems can be designed in a very different
way - particular to its reduction gear - depending on the construction of the
engine.
They are based mainly on the measurement of an oil pressure, which
A. is proportional to the reaction torque which is transferred by certain
components of the reduction gear through a plurality of tangentially
arranged cylinder−piston assemblies of the torque meter to the
stationary transmission housing,
B. is corresponding to a proportional axial force to the torque which acts on
one or more cylinder−piston assemblies of the torque measuring
system.
These systems require the use of helical gears inside of the gearbox.
C. is proportional to the torque-proportional torsion of a torsion shaft
compared with a not twisted reference shaft.
These torque measuring devices are connected with the drive shaft
system between the engine and the reduction gearbox.
These systems are called „balanced oil piston systems“ .
2. Electronic torque sensing systems are generally based on the electronic
measurement of the under 1.C. described method of a proportional torsion
of a torsion shaft compared a not twisted reference shaft; they are
therefore called ”phase shift systems”.
These torque measuring systems are
A. either connected to the power shaft between the engine and the
FOR TRAINING PURPOSES ONLY!

reduction gear
B. or installed in the reduction gear.

FRA US/O-5 DaC Jun 13, 2013 03|Torque Meas.|L2|B1/B2 Page 104
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

TORQUE INDICATOR

BULL GEAR DRIVES PROPELLER REDUCTION GEAR

TRANSDUCER
TORQUE SENSOR

OIL PRESSURE RISES WITH POSITIVE TORQUE

SPLINE
FOR TRAINING PURPOSES ONLY!

TORSION SHAFT

HIGH SPEED PINION GEAR TIE BOLT SHAFT

Figure 53 Negative Torque System

FRA US/O-5 DaC Jun 13, 2013 03|Torque Meas.|L2|B1/B2 Page 105
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

Hydro-mechanical Torque Measurement

Hydro-mechanical torque measurement withe reaction torque
1. The reduction gear which is shown is a differential planetary gear, wherein
the planetary gear (B − B) a simple differential gear upstrem connected is
(A − A). It is also referred as a planetary mechanism.
The power transmission from the engine rotor to the reduction gear is done
by the drive shaft (1) with the speed of the rotor in the counterclockwise
direction (seen in the flight direction).
2. The torque meter operates on the principle of balance between the
stationary planet carrier (4) against the direction of rotation of the propeller
and the counteracting torque, which is generated by the cylinder−piston
assemblies.
This torque is generated by the oil pressure acting in the six modules, which
is esnured by the lubricant pump (9) of the torque measuring unit. This
pump is driven via the ring gear Z7 .
The balance between these moments is guaranteed by the respective oil
flow from the cylinders (6) over the drainage holes (8).
The cross section of the outflow openings is automatically changed during a
longitudinal displacement of the cylinder (6) relative to the the housing (12)
attached to the piston (7).
A. By reducing the braking torque on the propeller the torque acting in
clockwise direction on the stationary planet carrier (4) decreases.
The prevailing oil pressure in the six cylinder−piston units (5) causes
consequently a displacement of the cylinder (6) in the counterclockwise
direction, and thus an increase in the cross section of the outflow
openings (8).
FOR TRAINING PURPOSES ONLY!

As a result, the oil pressure is reduced in the cylinder−piston assemblies

(5) and, consequently also the resulting moment.
When the moments are balanced, the system is again in balance. This
pressure will be displayed on the display device (11).
B. When increasing the braking torque, these processes occur oppositely.

FRA US/O-5 DaC Jun 13, 2013 04|Hydr−Mech|L2|B1/B2 Page 106

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

PTL 12
12 B
Ivchenko Progress 5
AI-20 LEGEND (Gears):
Z6 4 A 11
Z1 – Central Drive
(sungear)
Z7 Z2 Z2 – Planet Gear (6)
Z5
Z3 – Internal Toothed Ring
Z4 – Driving Wheel of the Planetary Gear
2 Z5 – Planetary Gears (6)
Z6 – Internal Toothed Ring
Z7 – Oil Pump Drive Gear
Z4 Z1 of the Torque Measuring System 12

3 1

5
Z3 10

9 9
7

A
ÉÉÉÉÉÉÉÉÉÉÉÉ
5 B–B

ÉÉÉÉÉÉÉÉÉÉÉÉ
B

ÉÉÉÉÉÉÉÉÉÉÉÉ
Z6 12 Z3

ÉÉÉÉÉÉÉÉÉÉÉÉ
Z2 8 LEGEND (OTHER COMPONENTS):
Z5 6

ÉÉÉÉÉÉÉÉÉÉÉÉ
Z2 Z2 1 – Driving Shaft
2 – Planet Carrier
FOR TRAINING PURPOSES ONLY!

Z5

ÉÉÉÉÉÉÉÉÉÉÉÉ
3 – Propeller Shafte
Z5 4 – Stationary Planet Carrier

ÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉ
Z4 Z1
Z2
5

6
–

–
Torque Transducer
(Cylinder-Pistonr-Assemblies)
Cylinder

ÉÉÉÉÉÉÉÉÉÉÉÉ
Z5 7 – Piston
Z2
4 8 – Outflow Opening of the Cylinder

ÉÉÉÉÉÉÉÉÉÉÉÉ
Z5 Z2 9 – Oil Pump of the Torque Measuring
System

ÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉ
Z5

4
A–A
Transmission Plan:
Direction of rotation of the gears and wreaths
10 –

11 –
Oil Loop of the Torque Measring
System
Display Device of the Torque

ÉÉÉÉÉÉÉÉÉÉÉÉ
Direction of propeller rotation Measuring System
Rotation of the counter torque 12 – Reduction Gear Housing

Figure 54 Hydro−mechanical torque measuring system with reaction torque measurement

FRA US/O-5 DaC Jun 13, 2013 04|Hydr−Mech|L2|B1/B2 Page 107
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

Hydro−mechanical torque measurement system with axial force

1. By the use of helical gears changes in the braking torque on the propeller
or rotor system of a helicopter axial forces act on these.
These are proportional to the change in torque and thus can be used for the
measurement.
2. In the shown example, a turboshaft engine powers the two stage power
turbine over the power turbine input gear and the torque meter gear the
power output gear, which is connected to the helicopter rotor system.
3. The shaft of the torque meter gears is supported on the support shaft by
two roller bearings, which enable its axial displacement.
The support shaft is used to supply lubricant to the bearings and the space
which is formed by the disc−shaped collar (with seal), the support shaft and
the piston.
− With increasing torque on the output shaft the forward axial force acting
on the torque meter gear increases. This is thereby shifted forward and
moves the piston via the ball bearing.
This increases the metering area (detail X), where the oil can flow
through a hole in the support shaft and a channel into the space between
the piston and piston shaft support. The oil pressure in this space − and
thus also on the display [torque meter gauge] − increases proportionally
to the increasing torque.
− At constant torque a constant pressure level will be constituted within the
torque transducer. (supply via X = outflow through hole in the piston to
lubricate the ball bearing)
− Due to a reduction of the torque on the axial force acting on the torque
meters gear decreases, and the oil pressure moves the piston and thus
also the torque meter gear to the rear position (on fig. to the right)
FOR TRAINING PURPOSES ONLY!

Thereby the metering area (X) is reduced and the supply flow of oil
pressure into the measuring transducer is decreased until the balance
between the (reduced) axial force and the (lower) oil pressure in the
transducer is reached again.

FRA US/O-5 DaC Jun 13, 2013 05|Hydr−Mech|L2|B1/B2 Page 108

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

GAS GENERATOR TSE Rolls-Royce/Allison Model 250

ROTOR
COMBUSTION
SECTION

SUPPORT PISTON BALL SEE DETAIL A

SHAFT BEARING POWER
TURBINE
OIL IN
TORQUEMETER
GEARSHAFT
NUT

X
FOR TRAINING PURPOSES ONLY!

TORQUEMETER
ACCESSORY SEE DETAIL B
GEARBOX
HOUSING ACCESSORY
GEARBOX
TO COVER
TORQUEMETER
GAUGE
DETAIL B DETAIL A

Figure 55 Hydro-mechanical Torquemeter (Axial Thrust Measurement)

FRA US/O-5 DaC Jun 13, 2013 05|Hydr−Mech|L2|B1/B2 Page 109
Lufthansa Technical Training
GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

Electronic Torque Measuring Systems

Torque measuring system as an integral part of the drive shaft system
The TPE engine PW123 (Bombardier Dash 8 Series 300, Power: 2150 shp,
1600 kW) consists of low and high pressure rotor two−shaft gas generator; the
propeller is driven by the two−stage (free) power turbine via the reduction
gear [reduction gearbox].
The reduction gearbox is a single module which is mounted to the inlet housing
[front inlet case] and can be removed as a complete unit.
On the reduction gearbox are
S the oil−cooled AC generator with an output of 30 kVA,
S the propeller (or: pitch) control unit, PCU],
S the hydraulic pump,
S the propeller oil pump and
S the overspeed governor
installed.
The reduction gearbox is via
S the power turbine shaft,
S the torque shaft,
S the reduction gearbox coupling shaft and
S the helical input gearshaft
driven by the power turbine.
The double−helical gear of the input Helical Gear Shaft acts on the analogy
designed gears of the first stage of the reduction gearing [first stage (double)
helical gear].
FOR TRAINING PURPOSES ONLY!

These form the rear part of the countershaft [layshafts]; the double helical
gearing is used to avoid axial forces.
The normal gears of the second stage [second stage spur gears] are forming
the front part of layshafts and transmit the torque to the big spur gear of the
propeller shaft.

FRA US/O-5 DaC Jun 13, 2013 06|Elec−Measur.|L2|B1/B2 Page 110

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

REFERENCE POWER
SHAFT TURBINE
*) SHAFT POWER
FRONT TURBINE
PROPELLER INLET
MOUNTING CASE
FLANGE

ACCESSORY REDUCTION
DRIVE GEARBOX
HP ROTOR
GEAR SHAFTS COUPLING
SHAFT
PROPELLER LP ROTOR
SHAFT
TORQUE SHAFT
*)
SECOND STAGE
SPUR GEAR
HELICAL INPUT RIGID COUPLING
GEAR SHAFT *)
FOR TRAINING PURPOSES ONLY!

(20 000 RPM)

SECOND STAGE
SPUR GEARS

FIRST-STAGE
HELICAL GEARS
LAYSHAFT (L/H) NOTE: COMPONENTS OF THE TORQUE SYSTEM ARE MARKED WITH AN ASTERIX *)

Figure 56 Reduction Gearbox of a Three-Shaft Turboprop Engine (Pratt & Whitney Canada PW123)
FRA US/O-5 DaC Jun 13, 2013 06|Elec−Measur.|L2|B1/B2 Page 111
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02
The torque measuring system of the engine includes the following components:
S a torque shaft,
S a torque reference shaft with a fixed rigid coupling,
S a torque sensor with a variable reluctance sensor or magnetic pickup,
S a torque signal conditioner unit (TCU) and
S a characterization plug
FOR TRAINING PURPOSES ONLY!

FRA US/O-5 DaC Jun 13, 2013 06|Elec−Measur.|L2|B1/B2 Page 112

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

TORQUE
SENSOR TORQUE SHAFT

FRONT
INLET
CASE

REFERENCE
SHAFT FRONT
INLET
CASE RIGID
COUPLING
TORQUE SIGNAL
CONDITIONER UNIT
(TSCU)
FOR TRAINING PURPOSES ONLY!

ACTUAL TORQUE

CHARACTERIZATION
PLUGS
(WITH LANYARDS)

TORQUE GAGE

Figure 57 Electronic Torque Measuring System (Pratt & Whitney Canada PW123)
FRA US/O-5 DaC Jun 13, 2013 06|Elec−Measur.|L2|B1/B2 Page 113
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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02
The torque sensor is located in front of inlet case.
It projects downwards into the housing and receives its signals from two
sprockets.
These sprockets are located
S on the rear side of the connecting flange of the torque shaft, which
transmits the torque to the reduction gear via the reduction gearbox
Coupling Shaft and
S on the outside of the front end of the reference shaft, which is not claimed
by the torque.
Both shafts are only at their ends firmly connected together and are
connected via the fixed coupling [rigid coupling] with the power turbine
shaft.
The twisting of the torque shaft relative to the reference shaft is
proportionally to the transmitted torque value.
The sensor detects this phase shift [phase difference] between the two
sprockets and sends he appropriate signals to the TSCU and the main
electronic control of the engine [engine electronic control, EEC, or: engine
control unit, ECU].
The sensor also measures the temperature of the air in the vicinity of the shaft
system to compensate the torsional effects on the intensity or rate [rate of
twist] induced on the torque shaft cause by thermally influences
FOR TRAINING PURPOSES ONLY!

FRA US/O-5 DaC Jun 13, 2013 06|Elec−Measur.|L2|B1/B2 Page 114

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GAS TURBINE ENGINE/PROPULSION EASA PART-66 M15
ENGINE INDICATION SYSTEMS Torque and Power
M15.14 | M14.02

A
B
ENGINE
RUNNING

TORQUE HIGH TORQUE

REFERENCE
ROTATION SHAFT SHAFT

A
B

NO TORQUE

ENGINE
AT
REST
FOR TRAINING PURPOSES ONLY!

TORQUE TORQUE SHAFT

SENSOR
SECTION A – A REFERENCE
A SHAFT RIGID
COUPLING

Figure 58 Torque Measurement (Pratt & Whitney Canada PW123)

FRA US/O-5 DaC Jun 13, 2013 06|Elec−Measur.|L2|B1/B2 Page 115
M15.14 B1 E

TABLE OF CONTENTS
M15 GAS TURBINE ENGINE . . . . . . . . . . . . . 1 FUEL FLOW TRANSMITTER INTRODUCTION . . . . . . . 68
FUEL FLOW TRANSMITTER TYPES . . . . . . . . . . . . . . . 70
M15.14 ENGINE INDICATION SYSTEMS . . . . . . . . . . . 1 ENGINE OIL MONITORING SYSTEM . . . . . . . . . . . . . . . 74
INDICATION SYSTEM LAY-OUT . . . . . . . . . . . . . . . . . . . 2 OIL QUANTITY INDICATION . . . . . . . . . . . . . . . . . . . . . . . 74
ENGINE INDICATION SYSTEM . . . . . . . . . . . . . . . . . . . . 2 OIL PRESSURE INDICATION . . . . . . . . . . . . . . . . . . . . . . 82
ENGINE PERFORMANCE INDICATIONS . . . . . . . . . . . . 6 OIL PRESSURE SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . 84
ENGINE SYSTEM INDICATIONS . . . . . . . . . . . . . . . . . . . 8 LOW OIL PRESSURE SWITCH . . . . . . . . . . . . . . . . . . . . 86
ENGINE TREND MONITORING . . . . . . . . . . . . . . . . . . . . 12 OIL TEMPERATURE INDICATION . . . . . . . . . . . . . . . . . . 90
ROTOR SPEED INDICATION . . . . . . . . . . . . . . . . . . . . . . 14 MANIFOLD PRESSURE . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 TORQUE AND POWER . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
TACHOMETER GENERATOR . . . . . . . . . . . . . . . . . . . . . . 16 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
VARIABLE RELUCTANCE SPEED SENSOR . . . . . . . . . 22 TORQUE INDICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
SPEED INDICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 TORQUE MEASUREMENT . . . . . . . . . . . . . . . . . . . . . . . . 104
LIMIT INDICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 HYDRO-MECHANICAL TORQUE MEASUREMENT . . . 106
ENGINE PRESSURE RATIO INDICATION . . . . . . . . . . . 34 ELECTRONIC TORQUE MEASURING SYSTEMS . . . . 110
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
PRESSURE SENSORS . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
EPR INDICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
ADDITIONAL INDICATIONS . . . . . . . . . . . . . . . . . . . . . . . 42
EXHAUST GAS TEMPERATURE INDICATION . . . . . . 44
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
EGT PROBES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
EGT INDICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
VIBRATION MONITORING . . . . . . . . . . . . . . . . . . . . . . . . 50
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
VIBRATION SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
ACCELEROMETER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
VIBRATION INDICATION SELECTION . . . . . . . . . . . . . . 58
VIBRATION INDICATION . . . . . . . . . . . . . . . . . . . . . . . . . . 60
DETAILED VIBRATION INDICATION . . . . . . . . . . . . . . . . 62
FAN BALANCING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
FUEL FLOW INDICATION . . . . . . . . . . . . . . . . . . . . . . . . . 66
SYSTEM ARCHITECTURE . . . . . . . . . . . . . . . . . . . . . . . . 66

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Figure 1 Engine Indication System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 36 Fuel Flow Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Figure 2 Engine Performance Indication . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 37 Oil Quantity Indicating Schematic . . . . . . . . . . . . . . . . . . . . . . . 75
Figure 3 Engine Performance Indication 2 . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 38 Different Types of Quantity Transmitter . . . . . . . . . . . . . . . . . . 77
Figure 4 Engine System Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Figure 39 Capacitance Type Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Figure 5 Engine System Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 40 Reed Switch Type Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Figure 6 Engine Trend Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Figure 41 Oil Pressure Indication System Schematic . . . . . . . . . . . . . . . 83
Figure 7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Figure 42 Oil Pressure Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Figure 8 Tachometer Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 43 Low Oil Pressure Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Figure 9 Direct Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 44 Pressure Transmitter & Low Pressure Switch Location . . . . . 89
Figure 10 FADEC Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 45 Oil Temperature Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Figure 11 Sensor and Phonic Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 46 Oil Temperature Sensor Location . . . . . . . . . . . . . . . . . . . . . . . 93
Figure 12 Variable Reluctance Speed Sensor . . . . . . . . . . . . . . . . . . . . . 25 Figure 47 Magnetic Chip Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Figure 13 Speed Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Figure 48 Electronic Magnetic Chip Detectors . . . . . . . . . . . . . . . . . . . . . 97
Figure 14 Exceedance Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Figure 49 Load indication digital . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Figure 15 Exceedance Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Figure 50 bourdon tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Figure 16 N1 Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Figure 51 Rotor Speed Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Figure 17 EPR Indication System Components . . . . . . . . . . . . . . . . . . . . 35 Figure 52 Torque Indicating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Figure 18 Sensors and Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Figure 53 Negative Torque System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Figure 19 Sensors and FADEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Figure 54 Hydro−mechanical torque measuring system
Figure 20 EPR Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 with reaction torque measurement . . . . . . . . . . . . . . . . . . . . . . 107
Figure 21 Additional Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Figure 55 Hydro-mechanical Torquemeter (Axial Thrust Measurement) 109
Figure 22 EGT Indication System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Figure 56 Reduction Gearbox of a Three-Shaft
Turboprop Engine (Pratt & Whitney Canada PW123) . . . . . . 111
Figure 23 EGT Indication Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Figure 57 Electronic Torque Measuring System (Pratt
Figure 24 EGT Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 & Whitney Canada PW123) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Figure 25 Vibration Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Figure 58 Torque Measurement (Pratt & Whitney Canada PW123) . . . 115
Figure 26 Vibration Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Figure 27 Vibration Sensors 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Figure 28 Operation of Vibration Sensors . . . . . . . . . . . . . . . . . . . . . . . . . 57
Figure 29 Vibration Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Figure 30 Vibration Indication on ECAM . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Figure 31 Vibration Indication on EICAS . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Figure 32 Phase Angle Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Figure 33 Fuel Flow Indication System . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Figure 34 Powered Fuel Flow Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . 69
Figure 35 Powered Fuel Flow Transmitter 2 . . . . . . . . . . . . . . . . . . . . . . . 71

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