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Ukcaa M14 Propulsion > Engine indicating systems > Flashcards

Engine indicating systems Flashcards

1
Q

What does N1 and N2 indicate in a gas turbine engine?

A

N1 indicates the speed of the low-pressure rotor, and N2 indicates the speed of the high-pressure rotor.

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2
Q

What are the three main parts of a rotor speed indication system?

A

The sensor, the data transmission, and the indication.

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2
Q

How is rotor speed expressed in gas turbine engines?

A

Rotor speed is expressed as a percentage of the 100% design speed.

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3
Q

How does a variable reluctance sensor generate a signal?

A

Changes in the magnetic flux cause variations in induced voltage, which is then amplified and conditioned to provide a usable output signal.

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3
Q

What is the role of a variable reluctance sensor in speed indication?

A

It detects changes in magnetic flux between a magnet and a ferromagnetic target to measure rotor speed.

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4
Q

Where is the variable reluctance sensor typically positioned?

A

It is positioned on the compressor casing in line with either a phonic wheel or the actual fan blades.

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5
Q

What does a tachometer generator do in older aircraft systems?

A

`It generates a 3-phase AC voltage proportional to the N2 rotor speed, which is directly used to drive rotor speed indicators.

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6
Q

How is the tachometer generator used in modern aircraft systems?

A

It sends 3-phase AC voltage to the FADEC computer for calculating speed and also supplies electrical power to the computer.

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7
Q

What additional function can a tachometer generator or speed probe serve during engine start?

A

It can provide a signal to illuminate a warning lamp indicating that the engine is turning and whether it’s turning in the correct direction.

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8
Q

What are the three types of rotor speed indication displays?

A

A display with a clock-type scale, a moving vertical bar, and the classical electromechanical indicator.

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8
Q

What happens when the N1 speed exceeds the redline limit?

A

The display indications turn red, warnings are issued, and the overspeed event is recorded for maintenance inspection.

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9
Q

What is the significance of the redline limit on rotor speed indications?

A

It represents the maximum permitted rotor speed to prevent engine damage.

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10
Q

How do modern engines handle N1 overspeed events?

A

The speed and duration of the overspeed are recorded, and a report is generated for maintenance to assess necessary inspections.

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11
Q

What principle does the variable reluctance sensor operate on?

A

It operates on the principle of magnetic reluctance, which is the opposition of a magnetic circuit to the flow of magnetic flux.

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12
Q

What is the role of the air gap in a variable reluctance sensor?

A

The air gap changes due to the target’s motion, affecting magnetic reluctance and thus inducing voltage changes in the sensor coil.

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13
Q

What is the primary purpose of the Exhaust Gas Temperature (EGT) indication in a gas turbine engine?

A

To monitor high temperatures in the turbine engine to prevent thermal damage and indicate when a limit is exceeded.

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14
Q

Why is it impractical to measure Turbine Inlet Temperature (TIT) directly in most engines?

A

Because the TIT can be higher than 1400 °C (2550 °F), making it difficult to measure directly.

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15
Q

Where is the highest temperature in a gas turbine engine measured, and what is it called?

A

The highest temperature is measured directly behind the combustion chamber, where the hot gas hits the high-pressure turbine. It is called the Turbine Inlet Temperature (TIT).

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16
Q

Where is the Exhaust Gas Temperature (EGT) typically measured in a gas turbine engine?

A

The EGT is measured at a colder location in the engine, either between the high- and low-pressure turbine or directly behind the low-pressure turbine.

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17
Q

What is the relationship between Exhaust Gas Temperature (EGT) and Turbine Inlet Temperature (TIT)?

A

The EGT has a direct relationship to the TIT, making it possible to use EGT as an indicator of the TIT.

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18
Q

Where are thermocouples typically placed in a gas turbine engine for temperature measurement?

A

Thermocouples are usually spaced at intervals around the perimeter of the engine exhaust duct near the turbine exit.

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18
Q

Why is temperature monitoring important in gas turbine engines?

A

Temperature monitoring is crucial for checking the mechanical integrity of the turbines and ensuring the engine operates within safe conditions.

19
Q

What are the typical temperature ranges for Exhaust Gas Temperature (EGT) indications?

A

Maximum EGT indications can range between 600 °C and 900 °C (1100 °F and 1650 °F).

20
Q

What are some of the different relative temperatures used to monitor gas turbine engines?

A

Exhaust Gas Temperature (EGT), Turbine Inlet Temperature (TIT), Turbine Gas Temperature (TGT), Interstage Turbine Temperature (ITT), and Turbine Outlet Temperature (TOT).

21
Q

How does an Exhaust Gas Temperature (EGT) indicator function in the flight deck?

A

The EGT indicator shows the average temperature measured by individual thermocouples, with the tiny thermocouple voltages being amplified to drive the indicator pointer.

22
Q

What does a Turbine Inlet Temperature (TIT) indicating system provide?

A

It provides a visual indication at the instrument panel of the temperature of gases entering the turbine, using multiple thermocouples to represent the average TIT.

22
Q

Describe the range and features of a typical analogue EGT indicator.

A

The analogue EGT indicator ranges from 0 °C to 1200 °C (0 °F to 2190 °F) and includes a vernier dial, a power off warning flag, and is a hermetically sealed unit.

23
Q

What components are included in the analogue Turbine Inlet Temperature (TIT) indicating system?

A

It includes a bridge circuit, chopper circuit, two-phase motor, feedback potentiometer, voltage reference circuit, amplifier, power off flag, and over-temperature warning light.

24
Q

What is the function of dual thermocouples in a Turbine Inlet Temperature (TIT) system?

A

Dual thermocouples provide signals to both the flight deck indicator and engine monitoring/control systems, ensuring dual-system reliability.

25
Q

How does the digital flight deck instrumentation system differ from analogue systems in temperature monitoring?

A

Digital systems use sensor resistance and voltage values input to a computer, which processes and displays the information, and sends it to other systems for control and monitoring.

26
Q

What are the three main groups of engine indications?

A

Performance indications (primary), system indications (secondary), and engine trend monitoring.

27
Q

What is the purpose of performance indications?

A

To monitor engine performance, set thrust for different flight phases, and monitor engine limits.

28
Q

What are system indications used for?

A

To monitor the operation of engine systems like oil and fuel systems and to quickly detect malfunctions.

28
Q

What does engine trend monitoring aim to do?

A

Detect engine problems early by analyzing engine parameters recorded by the Aircraft Condition Monitoring System (ACMS).

28
Q

What types of displays are used for engine indications?

A

A combination of analogue gauge-type displays, digital readouts, and moving vertical bars.

29
Q

Where are performance indications typically located, and what do they measure?

A

Located at the top, they measure equivalent engine power using N1 or Engine Pressure Ratio (EPR).

30
Q

What parameters are monitored in the engine’s oil system through secondary indications?

A

Oil quantity, oil pressure, and oil temperature.

31
Q

What sensors are used for engine performance indications, and how is data transmitted?

A

Specific sensors or probes measure data, which is electrically transmitted to indicators, often via the FADEC system.

32
Q

What is the purpose of the nacelle temperature indication?

A

To monitor the temperature in the engine nacelle, which can increase due to hot air leakage.

33
Q

What additional indications are provided on the ECAM/EICAS system?

A

Warnings and cautions when limits are exceeded, such as low oil pressure or a clogged filter.

33
Q

How is engine trend monitoring data typically recorded and transmitted?

A

Recorded during flight by ACMS, printed out in the flight deck, and transmitted via ACARS to the ground for analysis.

34
Q

What are the three types of analysis used in engine trend monitoring?

A

Thermodynamic analysis, mechanic-dynamic analysis, and oil consumption analysis.

35
Q

What does the thermodynamic analysis in engine trend monitoring check?

A

Pressures, temperatures, and feedback from components like Variable Stator Vanes (VSV) and fuel flow.

36
Q

What triggers an alert in the oil consumption analysis?

A

When the oil consumption exceeds a certain level.

37
Q

What does the mechanic-dynamic analysis in engine trend monitoring primarily check?

A

Rotor system failures such as imbalances and bearing failures by monitoring vibration and rotor speed.

38
Q

What is Engine Pressure Ratio (EPR), and what does it measure?

A

EPR is a differential pressure gauge measuring the ratio of turbine discharge pressure to engine inlet pressure, indicating engine thrust.

39
Q

What additional features are shown on an EPR display?

A

An AMBER or RED line for maximum thrust, and a BLUE circle for the actual throttle position.

40
Q

How is EPR data generated and displayed?

A

Pressure measurements from engine inlet and turbine exhaust are sent to a differential pressure transducer, with the ratio displayed on the flight deck.

41
Q

What adjustments are made to EPR to ensure accurate thrust monitoring?

A

Adjustments for temperature, altitude, and other factors are made to reflect accurate thrust.

42
Q

What is the “Flexible Take-Off” (FLEX) setting, and when is it used?

A

FLEX is a reduced thrust setting based on an assumed temperature to preserve engine life, used unless conditions require full thrust (TOGA).

43
Q
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44
Q
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45
Q
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Ukcaa M14 Propulsion (14 decks)

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