From the materials used to the tip designs, most propeller features are backed with pretty straightforward explanations. The pitch, on the other hand, is generally considered to have a lot more depth.
Its importance is relevant to several types of industries. In my experience, you’ll come across a new concept every time you study it.
In this post, you’ll be finding out why the pitch is highlighted so often by understanding what the dimension has to do with a drone’s performance. The guide includes introductions to the more technical parts.
And interestingly enough, you’ll also end up having a fair idea of where drone development might be heading in the future.
The pitch is defined in the same way regardless of the system the propeller is used in. But there are a few things that are only relevant to drones.
The pitch is the drone propeller’s theoretical traveling distance in one complete spin of 360°. It’s measured in inches and roughly controls speed (of the air leaving the propeller) and turbulence. Drone propellers with different pitches also draw different amounts of current.
For example, a propeller with a 4-inch pitch will move 4 inches forward every time a blade starts from a position and rotates back to it.
The same concept is used for other mechanical devices as well. Similar to propellers, screws also have pitches that describe how far they will move through a material as they are turned by screwdrivers.
Here’s one thing to remember: whether you pick a higher or lower pitch, tradeoffs are always made.
The actual effects of a propeller pitch are discussed in the following sections.
A good amount of thrust boosts flight stability and gives room for additional payloads. And if the propeller pitch heavily affects the thrust generated, drone pilots have another point to consider.
But how much, if any, of an effect does it have? Here’s the answer.
The effect of propeller pitch on thrust can be described as a roughly proportional relationship. Generally, a high-pitch propeller generates more thrust compared to a low-pitch propeller. However, this effect is not particularly significant as other properties make more of a contribution to thrust.
The thing is, a higher pitch does result in more thrust per revolution. But when it comes to maximizing lift, the pitch isn’t the first concern.
Generating thrust is all about how much air is in contact with the propeller blades. And this is particularly relevant to the diameter of the propeller. In turn, the effect of the propeller pitch is rendered somewhat insignificant.
Thrust is also affected by how many blades per propeller you have so make sure to check out more info about that.
It’s important to note that both, the pitch and diameter, are limited by the drone’s motors and battery. So, they can’t be unreasonably increased to get more thrust.
In the upcoming sections, you’ll notice the pitch is more often related to speed than thrust.
There are some parts of drone flight that are actually affected. You may already have a fair idea of them by using the core definition, but here are the details.
Increasing the propeller pitch moves more air and results in greater top-end speed. At the same time, low-end speed is decreased and more turbulence is created. The motors work harder and more current is drawn, making the propeller more energy-intensive and reducing flight times.
So, there are a few things to unpack here.
It’s important to understand what the terms above are putting across. When we talk about less low-end speed, we’re referring to slower acceleration.
This is why a drone with low-pitch propellers generally feels more responsive.
On the other hand, the consequence of more turbulence isn’t particularly noticeable. This does, however, lead to slightly less control.
Drone pilots who opt for high-pitch propellers generally intend to fly in open areas where sharp turns or maneuvers aren’t needed.
And as I mentioned before, the propeller pitch can only be increased if the other components allow for it. A high-pitch propeller requires more powerful motors and demands more from the battery.
The pitch setting is a fairly common term in the aircraft industry. Therefore, you may have come across it as an enthusiastic drone pilot. Here’s what it means according to the FAA regulations.
The pitch setting refers to the propeller blade setting determined by the blade angle. The blade angle is the angle between the chord of the blade and the plane of rotation. It’s measured in degrees and at a radius specified by the instruction manual of the propeller in question.
One thing to note is that the pitch is not the same as the blade angle. But since they’re so closely linked, the terms are sometimes used in place of each other.
These principles mostly come into use with larger propellers. Ones that are designed for airplanes instead of drones.
This part is directly related to the discussion above. Here’s how the FAA defines pitch distribution in one of their circulars.
Pitch distribution refers to the gradual change in pitch angle from the root of a propeller blade to its tip. A propeller blade can have normal distribution where the pitch is nearly constant or its pitch could vary. The latter means a change of pitch in certain sections with respect to the others.
You might be wondering why the twist in the propeller blade is necessary in the first place.
To put it simply, it’s because the tip travels faster than the inner portion of the propeller.
The twist is there to decrease the angle and this change from the hub to the tip allows for a consistent lift to be produced over the full length of the propeller blade.
A propeller blade with the same pitch angle over its length is considered to have poor efficiency.
All light drones make use of fixed pitch propellers. Here’s a full description of what gives them that name.
A fixed pitch propeller is a propeller that has its pitch set during its manufacturing stage. It cannot be changed during flight. The set pitch is thoroughly tested and is generally a value that provides balance. However, a fixed pitch propeller may also prioritize either climbing or cruising.
The drawback of such a propeller is the compromise made in the efficiency. Think of it like driving a vehicle with a single gear — it isn’t particularly ideal.
But here’s the deal: the alternative solutions currently come with their own set of complexities. Drones, like quadcopters, are designed to work with less mechanical parts.
With the twist distribution of blades, small drones already deliver good performances to the point where complex solutions seem relatively unattractive.
The “complex” solution to a fixed pitch propeller is a variable pitch propeller. Now, what is its purpose and how does it work? Here’s the answer.
A variable pitch propeller is designed to give the pilot the freedom of being able to adjust the pitch during flight. The pitch can also be adjusted automatically in a system that uses a mechanical governor. Some older propellers, however, can only be adjusted on the ground.
The point is this: for optimal all-round performance, propellers need to be able to change their pitch based on the flying conditions.
Taking off, climbing, and cruising all require a different propeller pitch. And a variable pitch propeller allows the ideal orientation to be maintained.
These propellers are used in airplanes and commercial aircraft. As I mentioned before, they’re yet to properly break through into the drone industry.
However, with the limited battery capacity of drones, experts continue to carry out experimental tests in order to find a feasible solution. Their goal is to improve overall power efficiency so the demands of the global market can be met.
Following the theme of large aircraft propellers, these terms are used to categorize blade pitch. Here’s what they mean exactly.
Fine pitch refers to a low pitch angle while coarse pitch refers to a high pitch angle. For aircraft that use variable pitch propellers, fine pitch is used for takeoff as it delivers faster acceleration and coarse pitch is used during cruise flight due to better high-speed performance.
As you may have noticed, the effects of propeller pitch play a significant role in these applications.
A commonly asked question is where the terminology comes from.
Well, I previously mentioned the link between propeller pitch and screw pitch. The words “fine” and “coarse” are also used in screw threading.
Fine-thread screws, compared to coarse-thread screws, need to be turned more times to travel the same distance.
Say you’re in the market for a propeller that prioritizes speed. What propeller pitch should you go for? Here’s a little guidance.
As a general rule, a high pitch is better for delivering greater speed as more thrust is created per revolution. A quadcopter propeller with a 4-inch pitch is often considered a balanced option. Therefore, a 5-inch propeller may suit applications that require more speed.
The values used above are simply an example. Heavier drones make use of larger propellers that can have longer pitch lengths.
So, it’s always a good idea to do a little research with your drone components in mind and then follow the rule of picking a high-pitch propeller.
And again, make sure you don’t confuse top-end speed for acceleration.
At this point, you’ve gone through everything to do with the pitch of a drone propeller. But what if you need to know the pitch length of a specific model? It’s pretty simple.
You can find the pitch of a propeller using the model’s propeller number. Similarly, the pitch is always highlighted in the product description and the user manual of the propeller. In case you do not have any information to go off of, you may try calculating it yourself.
The calculation method involves making certain measurements and then using a formula to find the theoretical pitch. It is, however, not exactly an easy method to follow. The margin of error is high.
Therefore, I recommend researching the propeller’s model to find its propeller number. The pitch length typically follows the diameter and is the second value in the number.
But in case you do come across a different format, I’ve done a separate article explaining how to decipher various drone propeller numbers.
To round off this post, there isn’t a particular pitch length for drone propellers that reigns supreme.
The best pitch for a propeller depends on the application and the rest of the components in the system. A high-pitch propeller is ideal for lifting force and speed while a low-pitch propeller is better for fine control and acceleration. However, it’s usually smart to go for the balanced option.
You may be asking yourself what makes a propeller “balanced”.
A balanced propeller is one that provides a fair compromise between climb and cruise. Again, there is no specific value for a balanced pitch as it also depends on the propeller size.
For example, it’s safe to opt for a pitch of 4 inches when considering 5-inch propellers.
The best pitch for you may ultimately boil down to a few different values. In that case, I suggest feeling them out individually to gain hands-on experience.
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