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The most common type of propeller in sport aviation is the fixed pitch propeller. Although cheap, this is one of the crudest propulsion devices you could use, and has been superseded by a variety of more advanced options, now readily available on the market. But, how do you know how each type of propeller operates and what advantages the different types offer? How are you going to choose between the different types available for your aircraft, especially considering that a more capable propeller is also more expensive?

There are four common families of propeller, which I will introduce to you. They are fixed pitch, ground adjustable, in flight adjustable and constant speed. The last two are both examples of variable pitch propellers.

In order to appreciate the advantages which are characteristic of the different families of propeller, we must first consider the most fundamental characteristic of a propeller – the pitch. Pitch is important, as it is the manner in which pitch is controlled that allows us to differentiate between one family of propeller and another.

A useful analogy when considering the affect of pitch is that of an automobile gearbox. By comparing a propeller's pitch to a gear ratio, and considering the function of a gearbox, we will gain an appreciation of the different families of propellers.
What is pitch?
Propeller theory includes a variety of concepts that may at times be called pitch. Pitch can refer to the blade angle with respect to a flat plane, the distance that a propeller will advance through the air for each rotation or the amount of "bite" that the blade has on the air. Essentially these concepts all describe the same thing. To use our automobile analogy, pitch is like the gear ratio of the gearbox. The important thing to note with pitch, is that it is available in a wide variety of degrees, or 'amounts', much like different gear ratios. To demonstrate, consider the following examples:

* A fine pitch propeller has a low blade angle, will try to move forward a small distance through the air with each rotation, and will take a 'small' bite of the air. It requires relatively low power to rotate, allowing high propeller speed to be developed, but achieving only limited airspeed. This is like having a low gear in your automobile.


* A coarse pitch propeller has a high blade angle, will try to advance a long distance through the air with each rotation, and will take a big 'bite' of the air. It requires greater power to rotate, limiting the propeller speed that can be developed, but achieving high airspeeds. This is like having a high gear in your automobile.