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Questions and Answers
What is the main reason for performing continuous operation with low joule HEIUs?
What is the main reason for performing continuous operation with low joule HEIUs?
- To save energy consumption
- To increase igniter plug life (correct)
- To improve aircraft performance
- To decrease igniter plug life
In which scenario would the persistent operation of high joule units be recommended?
In which scenario would the persistent operation of high joule units be recommended?
- To maximize energy consumption
- To minimize maintenance costs (correct)
- For short flights
- All of the above
What is the primary drawback of using high joule units for continuous operation?
What is the primary drawback of using high joule units for continuous operation?
- Decreased igniter plug life (correct)
- Improved safety measures
- Enhanced fuel efficiency
- Increased aircraft performance
Why is it common to use low joule HEIUs for continuous operation?
Why is it common to use low joule HEIUs for continuous operation?
Which of the following is a possible consequence of using high joule units for continuous operation?
Which of the following is a possible consequence of using high joule units for continuous operation?
What impact does persistent operation of high joule units have on igniter plug life?
What impact does persistent operation of high joule units have on igniter plug life?
What receives power from the DC bus through the fuel shut-off valve circuit breaker?
What receives power from the DC bus through the fuel shut-off valve circuit breaker?
Which switch energises the ignition relay in the example discussed?
Which switch energises the ignition relay in the example discussed?
Where is the ignition relay usually located?
Where is the ignition relay usually located?
What controls fuel scheduling during engine start and deceleration?
What controls fuel scheduling during engine start and deceleration?
What supplies electrical power to the HEIU?
What supplies electrical power to the HEIU?
What de-energises the ignition relay in the speed sensitive control system?
What de-energises the ignition relay in the speed sensitive control system?
What is the main function of an aircraft bus?
What is the main function of an aircraft bus?
How can circuit breakers protect aircraft electrical circuits?
How can circuit breakers protect aircraft electrical circuits?
What advantage do circuit breakers have over fuses?
What advantage do circuit breakers have over fuses?
What happens when the white collar becomes exposed in a circuit breaker?
What happens when the white collar becomes exposed in a circuit breaker?
What type of power supply do low tension current ignition systems receive?
What type of power supply do low tension current ignition systems receive?
How are high tension current ignition systems powered?
How are high tension current ignition systems powered?
What is the main difference between low tension and high tension current ignition systems?
What is the main difference between low tension and high tension current ignition systems?
In terms of duty cycles, what defines an intermittent duty cycle ignition system?
In terms of duty cycles, what defines an intermittent duty cycle ignition system?
What does the term 'duty cycle' refer to in relation to ignition systems?
What does the term 'duty cycle' refer to in relation to ignition systems?
Where does a high tension current ignition system draw its power from?
Where does a high tension current ignition system draw its power from?
What is a key advantage of a continuous duty cycle ignition system for aircrew?
What is a key advantage of a continuous duty cycle ignition system for aircrew?
What is the main difference between AC and DC igniter systems?
What is the main difference between AC and DC igniter systems?
Which component is typically found in a dual high energy ignition system for gas turbine engines?
Which component is typically found in a dual high energy ignition system for gas turbine engines?
What is the purpose of the 'fuel control relay' in an ignition system?
What is the purpose of the 'fuel control relay' in an ignition system?
In a typical ignition system, what component protects against circuit overloads?
In a typical ignition system, what component protects against circuit overloads?
What is the significance of 'ignition and relight switches' in an ignition system?
What is the significance of 'ignition and relight switches' in an ignition system?
What is the purpose of the ignition and relight switches in an aircraft?
What is the purpose of the ignition and relight switches in an aircraft?
What is the role of the relight switch in the ignition system?
What is the role of the relight switch in the ignition system?
Which component generates the high voltage necessary for engine ignition?
Which component generates the high voltage necessary for engine ignition?
What happens when the relight switch is turned on in an aircraft?
What happens when the relight switch is turned on in an aircraft?
Why is it necessary to have both AC and DC voltage options for the HEIU?
Why is it necessary to have both AC and DC voltage options for the HEIU?
Which part of an aircraft's ignition system receives power directly from the HEIU?
Which part of an aircraft's ignition system receives power directly from the HEIU?
How do intermittent duty cycle systems differ from continuous duty cycle systems?
How do intermittent duty cycle systems differ from continuous duty cycle systems?
What is the main concern addressed by implementing a duty cycle for ignition systems?
What is the main concern addressed by implementing a duty cycle for ignition systems?
How does high joule unit operation impact igniter plug life in an intermittent duty cycle system?
How does high joule unit operation impact igniter plug life in an intermittent duty cycle system?
Which type of duty cycle system would be more suitable for an aircraft that requires frequent engine restarts?
Which type of duty cycle system would be more suitable for an aircraft that requires frequent engine restarts?
In an aircraft, what defines the duration an ignition system can operate without causing harm to its components?
In an aircraft, what defines the duration an ignition system can operate without causing harm to its components?
What is the duty cycle of the ignition system mentioned in the text?
What is the duty cycle of the ignition system mentioned in the text?
At what RPM range does the ignition system operate continuously?
At what RPM range does the ignition system operate continuously?
What is the action of the 'above 65%' switch in the ignition system?
What is the action of the 'above 65%' switch in the ignition system?
What happens when the ignition system is de-energised by the 'above 65%' switch?
What happens when the ignition system is de-energised by the 'above 65%' switch?
What component connects the high tension ignition leads to the igniter plugs?
What component connects the high tension ignition leads to the igniter plugs?
Which speed-sensitive control system is activated above 65% RPM according to the text?
Which speed-sensitive control system is activated above 65% RPM according to the text?
What is the primary reason for implementing intermittent duty cycle ignition systems in aircraft?
What is the primary reason for implementing intermittent duty cycle ignition systems in aircraft?
How are intermittent duty cycle ignition systems managed by aircrew?
How are intermittent duty cycle ignition systems managed by aircrew?
In intermittent duty cycle systems, what happens after the restricted duty cycle based on operating time?
In intermittent duty cycle systems, what happens after the restricted duty cycle based on operating time?
Which feature distinguishes intermittent duty cycle ignition systems from continuous duty cycle systems?
Which feature distinguishes intermittent duty cycle ignition systems from continuous duty cycle systems?
How do some aircraft enhance their intermittent duty cycle ignition systems for critical operations like take-off?
How do some aircraft enhance their intermittent duty cycle ignition systems for critical operations like take-off?
What distinguishes DC and AC igniter systems in terms of components, according to the text?
What distinguishes DC and AC igniter systems in terms of components, according to the text?
In a gas turbine engine, what is the purpose of the speed-sensitive control component in the ignition system?
In a gas turbine engine, what is the purpose of the speed-sensitive control component in the ignition system?
Which component in the typical ignition system ensures proper fuel scheduling during engine start and deceleration?
Which component in the typical ignition system ensures proper fuel scheduling during engine start and deceleration?
What protects aircraft electrical circuits from overload in an ignition system?
What protects aircraft electrical circuits from overload in an ignition system?
Which component is responsible for generating the high voltage required for engine ignition?
Which component is responsible for generating the high voltage required for engine ignition?
What is the primary function of the ignition leads in an aircraft's ignition system?
What is the primary function of the ignition leads in an aircraft's ignition system?
Where does a low tension current ignition system receive its power from?
Where does a low tension current ignition system receive its power from?
What determines whether an ignition system is classified as having an intermittent duty cycle or continuous duty cycle?
What determines whether an ignition system is classified as having an intermittent duty cycle or continuous duty cycle?
In an aircraft's ignition system, where are the high-voltage, high-amperage discharges across igniter plugs dissipated?
In an aircraft's ignition system, where are the high-voltage, high-amperage discharges across igniter plugs dissipated?
What is the primary function of the High Energy Ignition Unit (HEIU) in the ignition system?
What is the primary function of the High Energy Ignition Unit (HEIU) in the ignition system?
Which component varies in type and position within a combustion chamber in different engine designs?
Which component varies in type and position within a combustion chamber in different engine designs?
What is the source of power for high tension current ignition systems in aircraft?
What is the source of power for high tension current ignition systems in aircraft?
What is the duty cycle of the ignition system when operating above 65% RPM?
What is the duty cycle of the ignition system when operating above 65% RPM?
Which component de-energises the HEIU, paralleling valve, and manifold drain valve in the ignition system?
Which component de-energises the HEIU, paralleling valve, and manifold drain valve in the ignition system?
How does the ignition system differ when operating below 65% RPM compared to above 65% RPM?
How does the ignition system differ when operating below 65% RPM compared to above 65% RPM?
In the context of the text, what is the purpose of high tension ignition leads?
In the context of the text, what is the purpose of high tension ignition leads?
What effect does de-energising the ignition relay have on the parallel valve and manifold drain valve?
What effect does de-energising the ignition relay have on the parallel valve and manifold drain valve?
Which switch is responsible for halting the operation of the ignition system above 65% RPM?
Which switch is responsible for halting the operation of the ignition system above 65% RPM?
What is the purpose of the trembler mechanism in a DC HEIU?
What is the purpose of the trembler mechanism in a DC HEIU?
Which component in a DC HEIU extends the duration of spark by delaying the reservoir capacitor discharge?
Which component in a DC HEIU extends the duration of spark by delaying the reservoir capacitor discharge?
What does the reservoir capacitor do in a DC HEIU?
What does the reservoir capacitor do in a DC HEIU?
In a DC HEIU, what does the glass sealed discharge gap contain?
In a DC HEIU, what does the glass sealed discharge gap contain?
What is the role of the high voltage rectifier in a DC HEIU?
What is the role of the high voltage rectifier in a DC HEIU?
Which component in a DC HEIU converts AC voltage to DC voltage for charging the reservoir capacitor?
Which component in a DC HEIU converts AC voltage to DC voltage for charging the reservoir capacitor?
What is the function of the High Energy Ignition Unit (HEIU) in an aircraft's ignition system?
What is the function of the High Energy Ignition Unit (HEIU) in an aircraft's ignition system?
Where does an igniter lead connect to in an aircraft's ignition system?
Where does an igniter lead connect to in an aircraft's ignition system?
What determines whether the HEIU is supplied with DC or AC voltage?
What determines whether the HEIU is supplied with DC or AC voltage?
In an aircraft's ignition system, what component connects the igniter plug to the High Energy Ignition Unit (HEIU)?
In an aircraft's ignition system, what component connects the igniter plug to the High Energy Ignition Unit (HEIU)?
What is the purpose of supplying 28 volt DC directly to the HEIU when the relight switch is closed?
What is the purpose of supplying 28 volt DC directly to the HEIU when the relight switch is closed?
What occurs when the relight switch is selected to 'on' in an aircraft's ignition system?
What occurs when the relight switch is selected to 'on' in an aircraft's ignition system?
What differentiates low tension current systems from high tension current systems in terms of power source?
What differentiates low tension current systems from high tension current systems in terms of power source?
What role does the engine starting system play in relation to the High Energy Ignition Unit (HEIU)?
What role does the engine starting system play in relation to the High Energy Ignition Unit (HEIU)?
Which statement accurately describes how the HEIU interacts with igniter plugs during operation?
Which statement accurately describes how the HEIU interacts with igniter plugs during operation?
In what way does the High Energy Ignition Unit (HEIU) contribute to engine design variation?
In what way does the High Energy Ignition Unit (HEIU) contribute to engine design variation?
How do low joule High Energy Ignition Units (HEIUs) differ from high joule units in terms of operation?
How do low joule High Energy Ignition Units (HEIUs) differ from high joule units in terms of operation?
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Study Notes
Ignition System Types
- Two common types of gas turbine ignition systems:
- Low tension (DC voltage)
- High tension (AC voltage)
Ignition System Duty Cycles
- Two types of duty cycles:
- Intermittent duty cycle: used for short periods, usually during ground starting
- Continuous duty cycle: provides continuous engine relight capability during critical flight maneuvers
Ignition System Components
- Typical components of an ignition system:
- DC or AC bus
- Ignition circuit breaker
- High Energy Ignition Unit (HEIU)
- Fuel control relay
- Ignition relay
- Speed sensitive control
- Ignition leads
- Igniter plugs
- Ignition and relight switches
High Energy Ignition Unit (HEIU)
- Generates high voltage required for engine ignition
- Can be supplied with either DC or AC voltage
- Components of a DC HEIU:
- Induction coil
- Trembler mechanism
- Reservoir capacitor
- Glass sealed discharge gap
- High voltage rectifier
- Choke
Igniter Plugs
- Types of igniter plugs vary between engine designs
- Positioned within a combustion chamber
Ignition Relight Switches
- Located in the aircraft cabin, near the throttles
- Connect bus voltage to the HEIUs
- Allow pilots to regain combustion in case of in-flight flame-out### Ignition System Overview
- Each system is connected to a High Energy Ignition Unit (HEIU), which receives a voltage supply controlled by the engine starting system.
- The HEIU stores electrical energy until it reaches a predetermined value, then dissipates it as a high-voltage, high-amperage discharge across an igniter plug or plugs.
Igniter Plug
- Igniter plug types and their position within a combustion chamber vary between engine designs.
Ignition System Types
- There are two common types of gas turbine ignition systems: low tension (DC voltage) and high tension (AC voltage).
Low Tension Current (DC) System
- Receives power from the battery bus.
High Tension Current (AC) System
- Receives power from the aircraft AC bus.
Ignition System Duty Cycles
- There are two types of ignition system duty cycles: intermittent and continuous.
- The term 'duty cycle' refers to the time limit placed on the operation of the ignition system to prevent damage to its components.
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