AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

What Is an Aircraft Propeller?

Propellers are designed to provide a method of propulsion for various vessels, and with aircraft, they provide the means for certain planes to move forward when in the air. To achieve this, propellers usually consist of two or more blades connected together on the engine shaft by a central hub. Shaped similarly to wings, propeller blades take advantage of an engine’s rotational power to produce enough lift for takeoff.

Generally, propellers function by displacing air, pulling it behind all present blades which results in the aircraft being pushed forward by the generation of a pressure difference. In other words, the more air that is pulled behind the propeller, the more the propeller can produce thrust or forward propulsion. In terms of their construction to accommodate different model aircraft, propellers are typically made with one to six in-line blades based on the efficiency requirements of different vehicles.

Aircraft performance requirements and engine power are two major determining factors in the number of propeller blades employed. When engine power increases, additional blades are necessary to efficiently take advantage of the increased level of power. Moreover, the angle of a propeller’s blades and their overall size and shape has a tremendous effect on the amount of thrust generated.

As mentioned before, propeller blades are designed in a similar way to aircraft wings, meaning they are subject to some of the same aerodynamic forces like drag and lift. It is important to note that the only difference between wings and propellers is that a propeller has the additional forces of rotational speed and forward acting momentum. Apart from centrifugal forces, in addition to centrifugal and aerodynamic twisting, propellers also experience vibration, torque, and thrust bending.

Propeller Basics

Aircraft propellers are made up of four fundamental components, those of which we will cover below.

  • Chord Line: The chord is an imaginary line that goes through the center of the blade from its leading edge to its trailing edge.
  • Pitch: The pitch is the measure of how far the propeller can move forward in one revolution, and it is used to control the speed of the air leaving the back of the propeller. In addition, the pitch of a propeller blade changes as you move along its surface from one end to the other.
  • Blade Angle: The blade angle is found between the chord line and plane of rotation, and it is measured at a specific point along the length of the blade. The terms blade angle and pitch are often used interchangeably, but they are not the same. However, they do affect each other.
  •  Angle of Attack: The angle of attack is the angle at which air strikes the propeller blade. Put more simply, it can be described as the difference between where a wing is pointing and where it is going. Keep in mind that increasing the angle of attack results in an increase in lift and induced drag up to the point of a stall.

Aircraft Propeller Materials

The basic engineering behind how propeller blades work has not seen many changes over the years. Nonetheless, there have been a number of significant modifications in the materials used to build them. To begin, wood was the primary material used to make propellers prior to WWII, but is only seen in hobby or vintage aircraft today. Next, aluminum alloys surfaced shortly after, rendering the use of wooden propellers obsolete. Aluminum alloy blades are lighter and easier to repair, making them a popular choice. Lastly, composite blades are taking over the propeller market, most of which are made from carbon fiber. These blades offer reduced weight, less noise, lower vibration, and are easier to repair than their counterparts.

Types of Aircraft Propellers

There are three basic types of aircraft propellers, those of which are fixed-pitch, constant speed, and ground-adjustable propellers.

  • Fixed-Pitch Propellers are constructed with the pitch built into the propeller; thus, the pitch cannot be adjusted or changed. They are often found on single-engine aircraft that fly at low speeds with limited range or altitude.
  • Constant Speed Propellers, also called controllable-pitch propellers, are designed with a variable pitch that can be altered during flight while the propeller is rotating.
  • Ground-Adjustable Propellers can be adjusted only while they are not in use and on the ground.

Conclusion

Alpha Industrial Parts is a leading distributor of aircraft propellers and their related parts, all of which have been vetted for fit, form, and function. With countless ready-to-purchase items on our database, customers have a plethora of options to choose from. Get started today and see why customers continuously rely on Alpha Industrial for all of their operational needs, no matter the time constraint. 


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