How To Start A Reciprocating Engine

Modern aircraft engines are immensely powerful, utilizing the combustion of fuel and compressed air to achieve heavier-than-air flight that allows pilots and passengers to traverse the world with speeds never before thought possible. If you work with aircraft or pilot them, it can be extremely important to have a general understanding of how various engine operations work. In this blog, we will briefly cover the starting process for a reciprocating engine, ensuring that you are familiar with how it works for standard flight and for troubleshooting.

The starting process for any modern engine is carried out by the ignition system, that of which will generally contain a battery, a flywheel, magnetos, and spark plugs. The battery is crucial for basic power necessities, supporting the starter with energy. Meanwhile, the flywheel is connected to the propeller assembly. Lastly, a pair of spark plugs will be situated within each cylinder, and a magneto set will be mounted to the accessory case of the aircraft engine. To begin the starting process, the pilot will prime the engine by putting fuel into the intake manifold. Then, the crankshaft will begin spinning with the assistance of the starter, and once the magnetos are rotating, current will be directed to the spark plugs. This process results in the movement of the pistons until the spark plugs initiate combustion, and from there, the combustion process should continue unabated until the engine is shut off.

Magnetos are one of the most important elements of the ignition system, providing the current necessary for spark plugs to ignite fuel mixtures. Magnetos base their operation on electromagnetic induction, meaning that they are a magnet spin within a coil of wire to produce electricity. On the ignition switch within the cockpit, pilots will often notice that there are options for activating the left or right magneto by itself, or both at the same time. Having two magnetos in an aircraft with selectable options is important for redundancy as if one magneto fails, the pilot can rely on the second one for continued operations. Additionally, two magnetos promote more even fuel mixture combustion, enhancing the overall power output of the engine.

The starter, meanwhile, is tasked with driving the flywheel for the means of kick-starting piston movement. From the starter, a small gear extends out and engages the flywheel, ensuring that it is able to spin for as long as energy is supplied to the starter by the battery. It is important that the starter is actuated with care, as too much operation can cause it to overheat and lead to damage.

While this starting process is applicable for reciprocating engines, other engine types follow a somewhat similar process. If you are facing issues with the starting process, it is important to be aware of common causes so that you know how to best address the issue. In hotter months, vapor lock may occur, which is when fuel enters gaseous state due to heat. Additionally, overpriming and flooding are both issues a pilot wants to avoid, those of which result from adding too much primer which can lead to a fire if overpriming is excessive. To avoid the most common starting issues, pilots should read their applicable owner’s manuals to determine safe practices, and aging and defective parts should be replaced as soon as possible. If you are in need of spare engine components and are looking for a reputable distributor, we have you covered at NSN Orbit.

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May 17, 2023
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