Types of Drones - Rotorcraft
There are two types of rotorcraft. One being a helicopter, consisting of a single rotor system. Another type being a multirotor. A multirotor can have up to 8 rotors on the platform. The added motors provide greater stability, redundancy, and greater lifting capacity.
The most popular rotorcraft platform is the quadcopter. This provides for a stable and simple to operate UAV that can carry a wide variety of payloads, landing and taking off in a small space, and being harder to detect than many of the other UAV configurations due to small size and quiet rotors. Examples of various rotorcraft are shown below:
How Does a Quadcopter Fly?
To calculate and mitigate risks associated with rotorcraft, it is helpful in having a basic understanding of how an aircraft operates. This allows the entity concerned with mitigating risks posed by UAVs to understand the aircraft's limitations.
Prior to analyzing a multirotor, one must realize that a multirotor is comprised up of three main components;
- Arms, that complete the multirotor structure.
- Propellers, this provides the multirotor with enough lift to overcome gravity.
- Motors, that provide thrust to the propellers.
In the most popular configuration, the quadrotor, the propellers 1 and 3 rotate clockwise and propellers 2 and 4 rotate counterclockwise. All the propellers are fixed pitch, with the counterclockwise propellers having the opposite pitch. This results in four rotors that have thrust in the same direction.
When controlling the multirotor, the gyroscope and control unit on the aircraft will determine which motors to slow down or speed up depending on the control input received from the pilot. The below figure explains the reactions seen on the quadrotor based on the inputs received from the pilot. The green rotors represent the motors slowing down, and the red represent the motors speeding up.
Can a quadcopter be used maliciously?
This category is one of the most versatile in the UAV industry. This is because this aircraft can take off and land vertically, meaning that it requires very little room for operation. This aircraft also can hover, switch directions almost instantly, and can carry relatively heavy objects. This makes the multirotor the most widely used platform in the UAV industry.
Quadcopter flight benefits:
- Take off and land vertically
- Can carry relatively heavy objects
- Switch directions almost instantly
Looking at this UAV from a security standpoint, this model could be used for various missions:
- Surveillance - Mounting a camera on the bottom of the multirotor provides a stable “point and shoot” platform for aerial videography.
- Flying Weaponry – This model can easily be retrofitted to carry a gun and programmed to fire at the command of the pilot.
- Dropping Supplies/Explosives – Due to the high thrust to weight ratios of the multirotor, it can carry heavy payloads. These payloads can consist of supplies such as drugs, explosives, weapons, or external means of communications like cell phones.
This is also the easiest category of aircraft to be programmed to fly autonomously, meaning the UAV has a “set” mission and there is no pilot behind the operation of the UAV. This is because of the ability to change direction and altitude quickly to avoid objects along the programmed route.