An unmanned aerial vehicle (UAV) is defined as a powered, aerial vehicle that does not carry a human operator, uses aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload. An unmanned aerial vehicle (UAV) is commonly known as a drone.

Must read: Applications of Drones

Specific features such as design, size, power source or use case, classify UAVs and drones into specific types. Here are some of those categories:

Classification of Drones and UAVs on the Basis of Structure of the Lift-Producing Surfaces

Fixed wing drones:

Fixed wing drones have wings that do not move, they are bound to the body of the drone. They may have control surfaces that turn and rotate, such as ailerons and rudder, but the wings themselves are fixed.

Pros of fixed wing drones are that their aerodynamic shape allows them to remain airborne for long periods of time, so they can cover large areas and are energy efficient. This is ideal for missions that require the drone to be airborne for hours or days, such as surveillance and climate monitoring.

The main cons are the steep learning curve for operators, the ample space required for take-off and landing, and the fact that they cannot hover in place.

Rotary wing drones:

For rotary-wing drones, the rotor-blades rotate around a central mast, forcing air downwards and creating the vertical lift required for the aircraft to become airborne. All vertical take-off and landing (VTOL) aircraft fall into this category, including small and large helicopters and multicopters. Rotary-wing drones may have a single rotor or even up to 16+ rotors generating thrust.

Pros of rotary-wing drones are that they are simpler to operate initially and can hover in place, allowing them to fulfill a wide variety of roles. Basic models are also relatively inexpensive.

The main cons relate to their short flight time, as generating upward and forward thrust requires a lot of energy, thus restricting the range and endurance of the vehicle.

VTOL drones, or Vertical Take-Off and Landing drones

VTOL drones, or Vertical Take-Off and Landing drones, combine the versatility of rotary-wing aircraft with the efficiency of fixed-wing UAVs. These innovative unmanned aerial systems (UAS) can take off and land vertically without the need for a runway, making them ideal for complex and constrained environments. Whether for military, commercial, or civil applications, VTOL UAVs offer unique advantages over traditional drones, including flexibility, range, and operational efficiency.

Powered-lift drones:

Powered-lift drones occupy a fascinating middle ground between fixed wing and rotary drones, using elements of both to complete a flight.

Rotors are used for VTOL-style take-offs and landings, then once airborne, the aircraft transitions to forward, fixed-wing-style propulsion. As such, they benefit from the low space requirements of rotary drones, while also having the improved aerodynamics and efficiency of fixed-wings.

There are several types of powered-lift drones, namely tiltrotors, tiltwings, and drones with two perpendicular sets of rotors.

While seeming to make the best of both worlds, powered-lift drones are quite complicated to design, which explains why they are not more common. Designing a system that can transition between configurations while remaining stable is challenging, though once achieved, the result is a highly versatile aircraft.

Classification of Drones and UAVs on the Basis of Number of Rotors or Arms

Tricopters:

As the name suggests, this type of tricopter drone has 3 arms. In this case, each of the front arms has a rotor that rotates in opposite directions to generate power. The rear rotor acts as a servomotor to provide stability in flight.

Quadcopters:

This is probably the most common type of drone on the market. It is an aerial vehicle with four arms, each of which has a rotor. Thanks to their equidistant configuration they offer great stability.

Hexacopters:

Hexacopters are drones with 6 arms and 6 rotors. These are the most used in the professional field to achieve high quality aerial shots, thanks to their excellent stability, which allows cameras to be installed and professional level recordings to be made.

Another advantage of this type of drone is that they offer greater safety, since in case of failure of any of the engines, it is possible to land the drone without major problems only with the propulsion of the other engines.

Octocopters:

As the name suggests, these drones have 8 arms and 8 rotors. Their stabilisation capacity is even greater than that offered by haxacopters, however, they have the disadvantage that they are larger and heavier because they have more components. This is why they can be difficult to control in small spaces.

Coaxials:

Coaxial drones are drones that each have 2 rotors. Thanks to this feature they are much more powerful, so they can transport objects or rise to great heights more easily.

They are also widely used in the professional field, to take high quality aerial shots or to perform specific tasks that require the movement of objects. Without a doubt, the coaxial drone is one of the most versatile drones.

Helicopter Drones:

Operating on the same principle as manned helicopters, heli-drones use a single or coaxial rotor to generate vertical lift, partnered with a tail rotor to counter torque. Like multirotor drones, a perk of helicopters is that they can take-off and land virtually anywhere.

A significant societal benefit of helicopter drones is their potential to replace humans in dangerous missions.

Classification of Drones and UAVs on the Basis of Control Method

Autonomous drone:

These are drones that move autonomously according to a previous programming that guides it through the sites to be covered.

Drone operated by remote control:

This kind of drone flies remotely controlled by a pilot. It is the most common type of drone and can be controlled by a remote control with a camera, or through first-person view (FPV) goggles that transmit images in real time and in first person to the pilot.

Classification of Drones and UAVs on the Basis of Power or Energy Source

UAVs can be classified based on their power or energy source, which significantly impacts their flight duration, range, and environmental impact. The main categories include:

Battery-powered (electric): 

These UAVs use rechargeable batteries, offering quiet operation and lower maintenance but potentially limited flight times. The reduced noise levels make them suitable for urban environments and sensitive operations.

Fuel-powered (internal combustion): 

Utilizing traditional fuels like gasoline or diesel, these UAVs often have longer flight times but may be noisier and require more maintenance. They are typically used for applications requiring extended endurance or heavy payload capacity.

Hybrid: 

Combining electric and fuel power sources, hybrid UAVs aim to balance the benefits of both systems for improved performance and efficiency. This configuration could allow for versatility in mission profiles and adaptability to different operational requirements.

Hydrogen fuel cell: 

Hydrogen fuel cell offer the potential for longer flight times than batteries yet stealthier (no heat signature) operation than combustion engines. The high energy density of hydrogen makes it a promising option for future UAV propulsion systems.

Solar-powered: 

Equipped with solar panels, these UAVs can potentially achieve extended flight times by harnessing solar energy, especially at high altitudes. Solar-powered UAVs may be particularly suited for long-endurance missions and environmental monitoring applications.

Nuclear-powered: 

While nuclear power has been explored for larger aircraft, its application in UAVs remains largely theoretical due to safety concerns and regulatory challenges. Research in this area is ongoing but faces significant hurdles before practical implementation.

Classification of Drones and UAVs on the Basis of Range and Endurance

Very close range and short endurance UAVs:

This class includes UAVs that have a range of 5 km and endurance time of 20 to 45 minutes.

Close range UAVs:

This class includes UAVs that have a range of 50 km and endurance time of 1 to 6 hours. They are usually used for reconnaissance and surveillance tasks.

Short range UAVs:

This class includes UAVs that have a range of 150 km or longer and endurance times of 8 to 12 hours. Like the close range UAV, they are mainly utilized for reconnaissance and surveillance purposes.

Mid-range UAVs:

The mid-range class includes UAVs that have super high speed and a working radius of 650 km. They are also used for reconnaissance and surveillance purposes, in addition to gathering meteorological data.

Endurance UAVs:

The endurance class includes UAVs that have an endurance of 36 hours and a working radius of 300 km. This class of UAVs can operate at altitudes of 30,000 feet. They are also used for reconnaissance and surveillance purposes.

Classification of Drones and UAVs on the Basis of Size

Very small UAVs:

The very small UAV class applies to UAVs with dimensions ranging from the size of a large insect to 30-50 cm long. The insect-like UAVs, with flapping or rotary wings, are a popular micro design. They are extremely small in size, are very lightweight, and can be used for spying and biological warfare. Larger ones utilize conventional aircraft configuration.

The choice between flapping or rotary wings is a matter of desired maneuverability. Flapping wing-based designs allow perching and landing on small surfaces.

Small UAVs:

The Small UAV class (which also called sometimes mini-UAV) applies to UAVs that have at least one dimension greater than 50 cm and no larger than 2 meters. Many of the designs in this category are based on the fixed-wing model, and most are hand-launched by throwing them in the air.

Medium UAVs:

The medium UAV class applies to UAVs that are too heavy to be carried by one person but are still smaller than a light aircraft. They usually have a wingspan of about 5-10 m and can carry payloads of 100 to 200 kg.

Large UAVs:

The large UAV class applies to the large UAVs used mainly for combat operations by the military. Examples of these large UAVs are the US General Atomics Predator A and B and the US Northrop Grumman Global Hawk.

PRACTICE QUESTIONS

QUES . With reference to Unmanned Aerial Vehicles (UAVs), consider the following statements: UPSC PRELIMS 2025

I. All types of UAVs can do vertical landing.

II. All types of UAVs can do automated hovering.

III. Al types of UAVs can use battery only as a source of power supply.

How many of the statements given above are correct?

(a) Only one

(b) Only two

(c) All the three

(d) None

Show Answer