Known as an Unmanned Aircraft System (UAS) or Unmanned Aerial Vehicle (UAV), a drone is basically any aircraft flying in the sky without a pilot, whether it be flying autonomously or with a remote control on the ground. As you’ve probably noticed, they are becoming increasingly common as technology rapidly advances.
In fact, sales of drones are expected to rise from 2.5 million in 2016 to 7 million in 2020, a staggering 180% increase. This means newer and more varied versions of them are constantly hitting the market, making it difficult to keep up with the different types of models.
To make things even more confusing, there are currently no official main categorization or set standards for the different types of drones! We’ll make things easier to understand. We have classified drones into three main categories and discuss the main advantages and disadvantages of each type of drone, as well as the typical uses.
Here are the 3 main types of drones from which most are developed from:
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Most freestyle quadcopters I have seen are specifically designed to fly with the motors facing upward and have the arms of the drone underneath the propellers like this:
As you can see in the picture ^ , the arms of the drone are fairly wide (as is common in lots of quadcopters of this type) and it seems to me that the arms would block a portion of the air coming from the props. I imagine that having the arms like this would reduce efficiency or top speed and maybe cause some amount of prop wash.
There are significantly less quadcopters which have the motors mounted under the arms like this:
(and almost all of them are home-made projects like this one which modified an existing frame to work upside down)
What I am wondering is, why are so many manufacturers and hobbyists making so many drones with upward-facing motors as it seems that downward-facing motors would be better in many ways? What are the advantages and disadvantages of upward-facing motors vs downward-facing motors?