If you’re just getting into drones, you might think the number of propeller blades is based on aesthetics.
Perhaps drone manufacturers simply pick a propeller that goes along with their drone model?
The more experienced pilots know that’s not the case. There’s intent behind the different ways drone components are designed, and propellers are no different.
Still, the number of blades remains a topic for discussion. No one can really point a finger at which number is the best.
But don’t get me wrong: experts have a pretty good idea which propeller type works for specific groups of people.
In this post, I’ll be helping you figure out which group you fall into using several examples. You’ll also find the pros and cons to each type and answers to a few pretty interesting questions.
The drone propellers in the title of this post are the most popular options. However, propellers having even more blades is well within the realm of possibility.
But like anything else, there is a limit.
A propeller can generally have up to eight blades. To keep the performance of flight balanced, drones commonly make use of two, three, or four blades per propeller. A few applications may require five or six blades per propeller. 8-blade propellers, while available on the market, are rarely used.
According to an aerospace engineer and NASA scholar, the maximum number of blades used per propeller, for aircraft in general, is likely eight. The HQProp 89MMX8 is an 8-blade example. It’s used for FPV drone racing.
On the other hand, the minimum number of blades a drone propeller can have is two. Single-blade models have been suggested in the past (by Amazon in particular) to save energy, but they’ve yet to become reality.
Now, let’s get to the heart of the matter. Do propellers simply get better as more blades are added? Here’s the answer.
More blades on a propeller are not necessarily better. A propeller with more blades doesn’t vibrate as much and, hence, makes less noise. And it produces more thrust at a given RPM. However, it will also be heavier and, more importantly, less efficient than a propeller with fewer blades.
The main talking points here are thrust and efficiency. The former is also why the number of blades moderately affects flight time, but we’ll get into that later in this post.
Drones using powerful motors are generally paired with propellers with a higher number of blades. And there’s a good reason why.
These motors drain the drone’s battery quicker and the extra blades make sure the energy is efficiently utilized. This allows more thrust to be produced at a given RPM value.
In other words, the drone would be consuming the same amount of energy yet generating less lift if the propellers had fewer blades.
The extra thrust ultimately results in a more stable flight as well.
Now, here’s the main reason why we don’t consider more blades per propeller better in every situation. As a general rule, the efficiency of a propeller decreases as more blades are added to it.
Some applications, like delivery, require more blades per propeller as drones are solely operated to carry heavy payloads.
However, the compromise made in propeller efficiency isn’t always worth the extra lift created. This is why 6-blade and 8-blade propellers aren’t particularly common.
Drone enthusiasts often opt for propellers that offer a balance of thrust and efficiency.
Speaking of what’s common, 2-blade propellers are incredibly popular. You’ll find most consumer drones sporting them.
And this is due to a combination of reasons. Take a look.
Drones typically have 2-blade propellers because of their efficiency and portability. They’re easy to carry around and their flexibility allows them to be surprisingly durable in case of collisions. They also have a low price which is why they’re considered the go-to option for drone pilots.
Since single-blade propellers aren’t practical in drones, 2-blade propellers are essentially the most efficient option.
It’s important to note how important portability is to consumer drones. It’s part of their appeal. And 2-blade propellers can be designed to fold, so they can simply be packed away.
One feature that’s often overlooked is their responsiveness. As 2-blade propellers are super lightweight, they respond quicker to changes made to the RPM.
Put simply, the drone pilot can swiftly change directions. This feature is commonly used in races and tight spaces in general.
When you throw a 3-blade propeller into the mix, you might be wondering which one is faster. The answer is pretty simple.
A 2-blade propeller is, indeed, faster than a 3-blade propeller. While a 3-blade propeller creates lift faster, it’s also heavier and slower in operation. This is why pilots who prioritize speed generally opt for using 2-blade propellers for their drones.
As suggested in the answer, this question does not refer to the speed of the lift.
A 2-blade propeller clocks in at a higher top speed but a 3-blade propeller will always sweep through more air and lift off quicker.
Let’s get to our first comparison. How do 3-blade and 2-blade propellers fare against each other? Here’s what I think.
3-blade propellers are better than 2-blade propellers for drones when it comes to flight stability. They generate more thrust and are less affected by wind. The 3-blade propellers also don’t have vibration issues. However, 2-blade propellers take the edge if we consider efficiency and portability.
The lack of vibration issues gives way to two plus points:
3-blade propellers are often used with (and are better for) heavier drones.
A well-known example is the DJI FPV. The quadcopter is noticeably better at resisting wind compared to other DJI models.
But there’s a catch.
While the DJI FPV has beginner-friendly features, it’s targeted towards somewhat experienced pilots.
Entry-level to mid-range drone models — that are ideal for novice pilots — almost always make use of 2-blade propellers. And this is primarily because they’re durable and cheap to replace.
You might be wondering how the inexpensive option generally lasts longer.
Well, it’s simply down to their configurations. A 2-blade propeller is more likely to rotate out of the way in case the drone goes down, whereas a 3-blade propeller is prone to damage in any kind of crash.
I also previously highlighted the flexibility of 2-blade propellers. This plays a role in their overall durability as the blades bend (and don’t easily shatter) when a little force is applied.
Thus, dual-blade propellers are generally the better option for simple and small drones like the DJI Mini.
Next up are the 4-blade propellers. You may not see them paired with your usual, hobby drones but they’re still important to drone enthusiasts. Here’s how these propellers are different.
The differences between a 3-blade and 4-blade propeller mainly relate to their top speed and thrust. 3-blade propellers are faster and push to a higher top speed performance. On the other hand, 4-blade propellers provide more thrust. This gives them greater acceleration and stability.
Needless to say, a 4-blade has a greater surface area and, hence, is in contact with more air. The effect of this is particularly noticeable during lift-off; 4-blade propellers ensure a smooth start to the flight.
They also come with different price tags. More blades per propeller result in a higher cost.
So, we’ve established that a 3-blade and a 4-blade propeller are different in particular aspects. But do those differences make for a clear winner? Here’s my opinion.
4-blade props are better than 3 for applications that require more control. They offer a vibration-free flight with more grip in the air, making them popular for commercial use. However, 3-blade props have a balance of everything and they’re definitely more suitable for drones using smaller motors.
The extra grip in the air may not sound like much, but it ensures the drone is able to maintain its direction. This is important as not every setting is perfectly suitable for drone flight.
You may spot 4-blade propellers being used with drones in the filmmaking, construction, and agriculture industries among others. They’re better for drones that carry payloads.
On the flip side, 3-blade propellers come in a larger variety of designs and are relatively efficient.
One thing to remember is that there isn’t a stark contrast between the effects of both types of propellers.
For example: 3-blade and 4-blade propellers are almost equally popular in drone racing and freestyling.
So, it essentially boils down to how well each propeller integrates into a system. The goal is to effectively pair the motors (based on their ratings) to the propellers.
As you read through this post, you might think adding more blades to a propeller increases its RPM value. In reality, though, the effect is quite different.
Here’s what happens to the RPM if you switch a 3-blade to a 4-blade propeller.
A 4-blade propeller will not increase RPM, assuming you’re coming from a 3-blade propeller. In fact, the RPM will decrease if you’re only changing the number of blades and not touching the size and pitch of the propeller. If you do change at least one of them, the RPM may remain unchanged.
As a general rule, the RPM value may stay the same if you add a blade to the propeller while also decreasing its pitch length.
In case you’re not sure what the pitch length is, I explain its concept in a different article. It’s entirely focused on breaking down terms commonly associated with propellers.
This one’s not only interesting but also important. A propeller’s effect on the drone’s efficiency is often the decisive factor for many pilots. Particularly those who’re looking to prioritize their drone’s flight time.
Here’s what you can expect with a 4-blade propeller.
A 4-blade propeller is said to be less efficient compared to ones with fewer blades. A higher number of blades draws more current. As a result, the propeller turns out to be more intensive on the battery. However, there are other properties, like the shape, that also affect the efficiency.
A common idea in the drone community is that more blades leave more turbulence in their wake, resulting in less efficiency. The validity of this statement is open to doubt.
You may learn more about how the calculations can be made in this in-depth piece on propeller efficiency.
This post was focused on 2, 3, and 4-blade propellers. Before wrapping it up, let’s touch on the advantages you may get if you choose to add one more blade.
The advantages of a 5-blade drone propeller mainly include flight smoothness and more control, especially while cornering. You may also notice the propellers creating less noise. These advantages are only valid if you switch from a dual-blade or tri-blade propeller.
Since there is a clear pattern being followed, you may have already known the answer before reading it. However, you probably haven’t seen a 5-blade propeller set in action.
This YouTube video shows a pilot using the fairly uncommon propellers with his FPV drone.
In conclusion, there is no definitive answer to this question. It depends on what works with your drone and what you’re looking to get out of it.
2 blades are best for a drone propeller if you want to prioritize efficiency, portability, and durability. 4 blades work best if you want to create more thrust and maximize your control on the drone. However, 3 blades are considered ideal for a propeller by many pilots since they provide a balance.
To make an informed decision, it’s necessary to factor in your skill level as well.
Propellers don’t really have hefty price tags. Still, they’re a component that needs to be changed regularly which means the costs add up.
In my opinion, it’s best to work your way up to the more fragile propellers and then find a suitable balance based on your applications.
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