What Are Aircraft Spark Plugs?

Spark plugs are essential for igniting piston engines. Designed to deliver a pulse of electric current from the ignition system to the combustion chamber, internal combustion engines require the use of a spark plug to set alight aerosolized fuel. In aviation, a spark plug is typically housed out of sight at the top of a cylinder head and can easily go unchecked if maintenance is irregular. Resulting in poor engine performance, loss of power, or a critical accident if the component is failing, it is imperative that routine spark plug inspections are not dismissed. To better understand how spark plugs function in aircraft, we will dive into their application types, how each works, and their common errors.

Available in two types, massive electrode and fine wire spark plugs (Iridium spark plug), each come with their own individual characteristics that can determine their placement. Providing a lifespan of approximately 300 to 500 hours, massive electrode spark plugs make up roughly 90 percent of all aircraft spark plugs sold.

Unlike the aforementioned spark plug, fine wire spark plugs contain thin lengths of Iridium wire along their electrode tips, and can cost upwards of three times the amount of massive electrode spark plugs. However, this is a factor contributed by implementing Iridium, the hardest metal available to this date. Welded to the electrode tips for secure measure, Iridium erodes three times slower than materials used to construct massive electrodes. As such, it can withstand up to 1000 hours of operation, and potentially more.

When identifying the current state of a spark plug, it is imperative that the electrodes are examined for their level of wear and tear. The continued use of worn electrodes can impede the connection needed to bridge the gap between a spark plug and a cylinder for a spark of electricity to successfully cross over. To avoid premature wear of spark plugs, they must be evaluated after every 100 hours of operating time. Additionally, spark plugs should also be periodically rotated to allow an even distribution of electrode wear on both ends of the plug. Capable of simultaneously carrying a positive and negative charge, these forces can eat away at the metals forming internal and external spark plug components. Inevitably lengthening the gap already present in spark plug assemblies, these gaps will continue to lengthen until the part is replaced or rotated.

Inspected with a specialized, industrial-quality gapping tool, it is imperative that the gap between electrodes and a cylinder core are regularly measured. To ensure an appropriate distance between all parts has been achieved, it is recommended that the gap be anywhere from 16/1000th to 21/1000th of an inch. If too vast of a distance, the spark attempting to jump the gap will require excess voltage to bridge a connection. When left uninterrupted, this excess electricity can travel through the network, damaging an aircraft's ignition system over time.

Vital for primary function of aircraft, in the event that you require an impromptu replacement, rely on Complete Sourcing Solutions for any one of your needs. For any necessary plane parts, we invite you to browse our inventory for numerous components ready for application. Whether you require an aircraft magneto, fine wire spark plug, ignition system, and more, Complete Sourcing Solutions is here to streamline and expedite any one of your orders for immediate procurement. Due to our quality control and export compliance, we operate with AS9120B, ISO 9001:2015, and FAA AC 00-56B certification and accreditation, alongside our NO CHINA sourcing pledge. If you would like to request a quote for your comparisons, you can submit an RFQ form as provided on our website. Upon receipt, a dedicated account manager will quickly review and respond with a personalized solution to your needs in just 15 minutes or less, 24/7x365.


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