Ignition Systems and Components Flashcards
Describe the general operation of turbine engine ignition systems.
Turbine engine ignition systems operate briefly during the engine starting sequence and do not require precise timing. The igniter ignites the fuel in the combustion chamber and is then switched off. Continuous ignition, used at a lower voltage, is utilized during flight conditions where there is a risk of engine flame out.
When is continuous ignition used in turbine engines?
continuous ignition is used during conditions such ads take-off, landing and in abnormal or emergency situations like flying through hailstorms or volcanic clouds to prevent engine flame out
What type of ignition system is commonly found in turbine engines, and how is it cooled?
Most turbine engines are equipped with a high-energy, capacitor-type ignition system that is air-cooled by fan airflow. Air is ducted to the exciter box, igniter lead, and igniter, then flows back into the nacelle area.
how does a capacitor type ignition system work in turbine engines
The capacitor-type ignition system stores energy in capacitors. A high voltage is provided to arc across a wide igniter spark gap, ensuring reliable ignition under varying conditions. The system typically includes two exciter units, two transformers, and ignition leads, and it operates from a low voltage DC power source.
What are the power sources for a typical turbine engine ignition system?
The ignition system typically operates from a common low voltage DC electrical power source, which may include the aircraft battery, 115 AC, or a permanent magnet generator driven by the engine.
Explain the role of the exciter unit in a capacitor-type ignition system.
The exciter unit receives low voltage power, filters it, and uses it to charge capacitors. When charged, these capacitors discharge, creating a high-intensity spark at the igniter plug. The exciter is a dual unit, producing sparks at both igniter plugs, and is air-cooled to prevent overheating.
What is the function of igniter plugs in turbine engines?
Igniter plugs in turbine engines generate high-intensity sparks to ignite the fuel-air mixture in the combustion chamber. They differ from spark plugs in reciprocating engines by withstanding much higher energy currents and having a larger electrode gap.
What are the primary maintenance tasks for turbine engine ignition systems?
Maintenance tasks include inspection, testing, troubleshooting, and replacement of components such as igniter plugs, ignition leads, and exciter units. Always refer to the manufacturer’s manuals before performing any maintenance.
What are the two types of igniter plugs used in turbine engines?
The two types are the annular gap igniter plug, which projects slightly into the combustion chamber liner, and the constrained gap plug, which operates at a cooler temperature by arcing beyond the face of the combustion chamber liner.
Describe the process for inspecting an igniter plug.
Disconnect the ignition lead from the igniter plug, wait for energy dissipation, remove the igniter plug, inspect it for damage or erosion, clean if necessary, and replace if damaged. Ensure proper clearance and torque when reinstalling.
What should be inspected during an ignition lead inspection?
Inspect the lead terminal for arcing, carbon tracking, and cracks. Check the wire insulation for flexibility and signs of arcing. Inspect connectors for corrosion and damage. Perform continuity checks and reinstall leads after cleaning.
How can you perform a function test on a turbine engine ignition system?
A function test can be performed by listening for a clicking noise as the engine begins to turn or by removing the igniter and visually confirming a spark during the start cycle.
What safety precautions should be taken when servicing turbine engine ignition systems?
Wait at least 20 minutes after shutdown before working on high voltage components due to residual charges. Ground ignition leads to discharge stored energy before removal. Always follow manufacturer instructions and safety guidelines.
What could cause no igniter spark when the ignition system is turned on?
Possible causes include issues with the ignition relay, transformer unit, high tension lead, or a damaged igniter plug. Troubleshooting involves checking power inputs, outputs, continuity, and replacing faulty components.
What are the symptoms and remedies for a weak spark in a turbine engine ignition system?
A weak spark could be caused by a weak battery or cracked ceramic insulation in the igniter plug. Remedies include recharging the battery and replacing the faulty igniter plug.
