How Does an Air Starter Work?

For instance, an air starter supplies the necessary power to engines to start the initial rotation. Two types of motors dominate the industry, those of which are vane motors and turbine motors. Each type operates on similar principles, but utilize air very differently. With this in mind, we will discuss how vane and turbine rotors take advantage of air starters.

Vane Rotor

A  vane rotor consists of five major components: a rotor, vanes, the motor housing, the internal cylinder, and a set of end plates. When the start cycle is initiated, air is directed into the motor housing via an inlet that channels air through a series of grooves in the internal cylinder of the motor housing and small inlet holes in the end plates. The holes direct the air so that as it is being introduced into the system, it causes the vanes inserted in the grooves to be displaced from their resting position.

As the vanes are forced out of the rotor by the introduction of air, they come into contact with the internal cylinder and no longer extend. Once they have fully extended, the air moving through the slots in the internal cylinder builds pressure behind the vanes. As the housing is filled with air, the increasing pressure on the vanes forces them to move the rotor. This process changes the force of the air into rotational torque and power. The vanes act as paddles and catch the air, which turns the rotor and gears of the air starter.

It is important to note that the vane motor works on the principle of positive displacement. As the vanes are pushed against the side of the internal cylinder by the air pressure, they create pockets of trapped air. With increases in pressure behind the vane, pressure cannot be released until it does some positive work in order to move the vane past the outlet slots. This design allows air to move into the rotor with ease.

Turbine Rotor

A turbine motor consists of four major components: a nozzle, turbine wheel, central shaft, and a motor housing. As air flows into the housing, it is directed toward the turbine wheel via slots in the outside edge of the nozzle. The slots channel air into the rotor at specific angles so that the turbine wheel’s ability to capture the air’s potential energy is maximized. The turbine wheel is also equipped with slots that catch the air and force the turbine wheel to turn. Each slot is bucket-shaped to catch the air before it makes it way through the slot and exhausts out of the starter.

Meanwhile, the central shaft runs through the center of the rotor so that as the rotor begins to spin, the central shaft turns the rotor, creating torque and power. Unlike vane rotors, turbine rotors do not work on the principle of positive displacement. Instead, air is provided constant access to an outlet while its potential energy is captured by directing air flow.


NSN Fulfillment is a leading distributor of rotor assemblies, turbines, valves, and more. With over 2 billion ready-to-purchase items in our inventory, we are equipped to fulfill even the most complex part requirements. More than that, we operate  with AS9120B, ISO 9001:2015, and FAA AC 00-56B accreditation, alongside a strict NO CHINA SOURCING pledge, so that our customers are guaranteed offerings of the highest caliber. Kickoff the procurement process with a competitive quote and see why customers rely on NSN Fulfillment time and time again. 


July 14, 2023

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