How to make your ideas fly?

There are a lot of innovative ideas coming up but most of the innovators are stuck at a point where they are not able to check if their concept will work in real-life conditions. One of the main challenges is that innovators struggle to calculate the power consumption since it varies based on the diameter, thrust, etc. We are always welcoming innovative ideas and trying to support you technically up to our limits. To know how the power consumption changes based on the diameter (for multicopter) please read our previous blog posts.

How to make your ideas fly?

So how do we know that if your ideas will fly?

In this post, we will discuss only the hover condition. We are not discussing anything about the fixed-wing configuration.

Unfortunately, all the ideas will not be able to fly now with the current technology we have. Since we are limited by some inefficiencies in the propeller, motor, batteries, etc.

With this blog post, we can help you to do some rough calculations to check the feasibility of your design. For this task, we need to know one important factor called disk loading.

What is disk loading?

The formula for disk loading is simple: 

Let’s consider an example:

The estimated weight of the aircraft is 50 kg and the aircraft has 4 propellers.

Therefore, each rotor must produce 50/4= 12.5 kg (122.6N) of thrust to hover.

Let’s assume the diameter of the propeller is 34 inches (which is 0.86 meters),

Now we can calculate the area using the formula 

if we calculate the disk loading it will be 209 N /m^2

Pretty simple, right?

Why is disk loading important?

If you reduce the diameter of the propeller you can see that the disk loading goes up, and if we increase the diameter of the propeller the disk loading goes down.

Lower the disk loading is, the more efficient the system will be, which means you can fly longer.

As mentioned in the previous blog post you can also see how the power consumption changes with the diameter of the prop

What should be my Disk loading range?

Helicopters have disk loading of approximately 200-500 N/m^2. But as the disk loading gets higher the endurance of the aircraft reduces.

If we are building a multicopter powered by Lipo battery the disk loading should be around 200N/

There are a lot of fighter aircraft like F35B or Harrier which can take off vertically with disk loading of ~2000-5000 N/m^2, But in reality, if they take off vertically, there will be less fuel left for them to do the mission, which shows how much power they need to spend if the disk loading is high.

Since in this post, we are discussing mainly the aircraft with hover characteristics, we must make sure that the disk loading is as low as possible.

Anyone with aircraft design where disk loading is exceeding 250 N/m^2
must consider making some modifications to get closer to this number. If not, you will have to wait, until the technology improves to meet your ideas.

Demircan, Osman & Demir, Oguzhan & Demirsoy, Elif & Sahin, Selim & Kılıç, Burak & Coskun, Onur & Dökme, Ramazan. (2017). Design of an Unmanned Rotorcraft with 24 Hours of Hovering Endurance. 10.13140/RG.2.2.11691.03366.https://www.researchgate.net/figure/Power-loading-as-a-function-of-disk-loading-2_fig2_312531897Accessed on 16/12/2019

What will happen if we have a very high disk loading?

There are two possibilities:

  1. The aircraft will be too heavy and will not be able to take off
  2. The aircraft will be very inefficient that will only be able to fly for a few minutes.

Does all the aircraft have to follow this disk loading range?

Of course, there are exceptions. Not all the aircraft have to be in this range of disk loading.

1. If the power source has a higher power density than standard Lipo batteries.

2. If the aircraft has a variable payload, you will have to work out how the payload changes with time and optimize the setup efficiently to match the required endurance.

3. There are exceptions where the vertical takeoff or the hover phase is for a very short time. In this case, the disk loading can be slightly higher but remember higher the disk loading lesser the battery power remaining for the cruise flight.

4. Or if you want your aircraft to fly only for a very short duration then the disk loading can be changed accordingly.

Most common Idea that is unattainable with the current technology

Here we would like to share one of the most common queries that we get quite often. Unfortunately, we are not able to help with the currently available technology.

Having a high takeoff weight with a small propeller diameter. Although it is very fascinating to imagine having such a compact system, the current technology has inefficiencies and does not support it. But we wouldn’t be surprised if this happens in the future as we believe there are so many advancements and Research going on in this field to increase the efficiency of the subsystems. But right now, as of early 2020, the answer for this is, unfortunately, a no.

Does your idea fall within the discussed disk loading?

Get in touch with us, we can try to help you further.