The Mechanisms that Allow Aircraft to Start Their Engines

While aircraft engines are advanced apparatuses that are self-sustaining when in operation, they often require assistance to efficiently start up. While the process may seem mysterious to the average passenger, understanding the basics of how an aircraft starts its engines can provide a fascinating insight into the marvels of aviation technology. In this blog, we will explore the essential components and processes which permit a piston-powered engine to kick off operations.

The Aircraft Starter

The aircraft starter itself serves as the catalyst for engine ignition, and similar to a car's ignition key, it is responsible for initiating the rotation of the engine's crankshaft. Once activated, the starter motor engages with the engine assembly, setting the entire starting process in motion. Put simply, the starter is an electric motor that converts electrical energy into mechanical energy, enabling the rotation of the engine's crankshaft. Starter motors are usually powered by the aircraft's onboard battery and controlled by the pilot or automated systems. When activated, the starter motor engages with the engine's flywheel, a large gear attached to the crankshaft, initiating the engine's rotation.

Engine Crankshaft

The engine crankshaft is a fundamental component of an aircraft engine, serving to convert the linear motion of pistons into rotational motion. This rotational motion is then harnessed by a propeller assembly for thrust generation, allowing for flight to be made possible. In order for the crankshaft to be operated, it is engaged with the starter motor through a flywheel.


Pistons play a crucial role in general engine operations, and their functionality is paramount for the starting process. Pistons are cylindrical components that move up and down inside the engine's cylinders, and they are connected to the crankshaft via connecting rods. During the starting process, the pistons are positioned in a specific arrangement to facilitate the intake, compression, combustion, and exhaust strokes required for the engine to run smoothly. Once they begin their motion during the starting process, the standard combustion cycle will begin as the engine reaches a sustainable speed.

Engine Starting Process

Now that we have a basic understanding of the key components involved, let us explore the engine starting process with a brief overview of each step.

  1. Activation: The pilot or automated systems activate the aircraft starter, which engages the starter motor.

  1. Rotation Initiation: The starter motor engages with the engine's flywheel, providing the initial rotation to the crankshaft. As the crankshaft rotates, it moves the pistons up and down in their cylinders.

  1. Intake Stroke: During the first stroke, the intake valve of pistons opens, allowing a mixture of air and fuel to enter each cylinder. Pistons will then move downward, creating a vacuum that draws the mixture into the cylinder.

  1. Compression Stroke: The intake valve closes, and each piston moves upward, compressing the air-fuel mixture. This compression increases the mixture's temperature and pressure, preparing it for combustion.

  1. Ignition and Combustion: Once the air-fuel mixture is compressed, a spark plug will ignite it with the assistance of a magneto to initiate combustion. This combustion creates a rapid expansion of gasses, exerting force on each piston.

  1. Power Stroke: As the expanding gasses push a piston downward, it rotates the crankshaft to commence generating power. This rotational energy is transmitted to the aircraft's propellers or turbines, resulting in forward thrust or electrical power generation.

  1. Exhaust Stroke: The exhaust valve opens, allowing the combustion by-products to exit the cylinder. Finally, the piston moves upward, expelling the waste gas.


With a general understanding of the parts and processes that make engine operations possible, you can better appreciate the very apparatuses that allow countless aircraft models to achieve heavier-than-air flight. Here at ASAP NSN Hub, we can help you secure all the aircraft engine starter parts that you need to carry out your projects and operations. With our purchasing power and market expertise, we present highly competitive pricing options and rapid lead times for our customers, ensuring that we can fulfill all your requirements while meeting your restrictions alike. Feel free to explore our database as you see fit while taking advantage of our online RFQ system and around-the-clock customer service. Get started today and see why so many customers steadily depend on us for their operational needs.


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