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What Is the Ignition Harness

Within a variety of internal combustion engines, the ignition of fuel and air mixtures is made possible through magnetos, spark plugs, and other related components. In order for electrical energy to be transported from the magneto to the spark plug, a component known as an ignition harness is implemented. With wire connections leading from the magneto distributor block to a spark plug, the ignition harness can both serve as a conductive path for energy transfer and for the shielding of components from the stray magnetic fields resulting from standard operations. With the importance that the ignition harness serves for combustion and flight operations, it can be very useful to understand how such components function as well as how to best care for them.

As a magneto is a high frequency radiation emanating device, a large amount of wave oscillations may be produced within the system across a wide range of frequencies. Without the shielding provided by the aircraft ignition harness, the magneto and ignition leads would all begin picking up frequencies as if they were antennas. To sufficiently protect the lead from this, the component is fully encapsulated within a mesh braid so that the radiation of energy is mitigated.

For the energy handling characteristics of the ignition lead, the component acts as a capacitor as it can store electrostatic charges. As such, the magneto will produce enough energy to charge the capacitance of the ignition lead while ensuring that there is sufficient energy remaining to fire the plug. As capacitance means that more energy is required for a spark to travel across gaps, the magneto must meet demands for proper operations and firing. Within the lead under layers of coating, shielding, and an insulator, conducting materials are placed within the core of the ignition harness so that high-voltage can be transferred while ensuring the component is protected from outside environmental factors.

In order to protect the ignition harness from hot spots resulting from exhaust or to avoid damage from vibration, the leads require specific routing and clamping from the magneto to the cylinders. With threading, the spark plugs and lead can be attached to one another while the magneto is hard connected. With all-weather ignition harness types commonly available, such components can provide optimal insulation to protect the assembly from dangers such as moisture.

Despite the simplicity of the ignition harness, such components are consistently exposed to numerous elements sourcing from the engine and atmosphere. With consistent exposure, the insulation of the ignition harness will break down and gap erosion will increase over time. At a certain point, voltage may be able to break down insulation and leak through the component to the shielding. If this occurs, energy cannot be supplied to the spark plug for efficient combustion, thus leading to a loss in power and damage through improper stroke timing.

High-voltage leaks are the most common issue faced by ignition harnesses and high-tension ignition systems, though they are very difficult to detect. The presence of moisture can significantly worsen damages, as high-voltage stress can result in the formation of an arc that burns areas where moisture is collected. With the presence of fluids such as oil, grease, or gasoline, the burning from arcs can create a carbon track that should be removed when maintenance and repair is conducted.

In order to test the insulation of a particular ignition harness, a specific voltage is induced to each lead, and a sensitive measuring device is used to measure the amount of current leaking between the lead and harness. Based on the reading garnered from such devices, one can discern whether an ignition harness requires service, repair, or replacement. If harnesses are fairly new, their rate of insulation breakdown should be quite slow. With older components, however, more inspection and maintenance may be required to ensure the safety of such assemblies.

When it comes time to begin procuring the actuator ignition components, armature ignition parts, actuator ignition switches, and other aircraft parts that you need for your operations, NSN Gamut is your sourcing solution. As a leading distributor of aviation tools, we can help customers find everything they require for carrying out quality aircraft maintenance. Explore our robust part catalog at your leisure, and our team of industry experts is readily available to assist you through the purchasing process as necessary, 24/7x365. To receive a personalized quote on parts that you wish to purchase, submit an Instant RFQ form as provided on our website and a dedicated account manager will be in touch in 15 minutes or less.


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