VTOL UAVs (Unmanned Aerial Vehicles) or Vertical Take-Off and Landing drones have the ability to take-off, fly and land vertically as well as hover in place. A typical VTOL UAV may be based around a helicopter design or may feature a multirotor design that incorporates four or more propellers. The propellers create both lift and propulsion for the UAS (Unmanned Aerial System).
Types of VTOL unmanned aircraft include:
Also known as helicopter drones, these can be purpose built or converted from a previously piloted system. Helicopter UAS are rugged, often built to withstand harsh maritime environments and easily launched from the deck of a ship. They are used extensively for a variety of harsh environment, maritime, military and coastal operations.
Similar to single rotor UAS, as the name suggests tandem rotor drone configurations feature two rotor sets, enabling them to carry heavy cargo and equipment. Favored for delivery and logistics applications, tandem rotors are often used to distribute equipment, medicines, tools and critical supplies in hard to access regions.
Coaxial technology is used to drive counter-rotating propellers. This has been employed effectively on cylindrical drones, resulting in a smaller surface area than traditional multirotors and so making them an easily transportable and deployable solution for tactical applications.
Typically named with reference to the number of rotors in the configuration, the most common types of multrotor are:
Generally the greater the number of rotors, the more the UAS can lift, therefore hexacopters and octopters are usually chosen to carry heavier payloads such as high specification cameras for filming and cinematography work.
Indoor or Caged
These are effectively multirotor UAS with a roll cage fitted around the entire drone to protect people and the drone itself from damage due to collision. Ideally suited to working indoors they are often selected for inspection work in enclosed spaces such as tunnels, mine shafts and warehouses.
Connected to a ground station by a physical cable or ‘tether’ which provides secure power and communications. Whilst altitude and distance is constricted by the cable, tethered drones are able to stay airborne for long periods of time making them ideal suited to surveillance and situation awareness applications.
Combining VTOL capability with the standard forward propulsion of a fixed wing UAV many hybrid VTOL UAS incorporate rotary lift propellers into the unmanned aircraft’s wings, which then transition for forward flight, combining the advantages of vertical take-off and landing with the endurance capabilities of fixed wing drones.
The majority of VTOL drones are eVTOL (electric vertical take-off and landing) powered by Lithium-Polymer (Li-Po) and Lithium-Ion (Li-ion) drone batteries. Although liquid fuels provide a higher energy density than batteries, they are typically only used by larger helicopter drones due to the weight of the fuel and the internal combustion engine. Hybrid fuel-electric systems are being developed that will combine the advantages of both methods.
Hydrogen fuel cells are available that provide a higher energy density than batteries and thus a greater endurance, while being lighter than combustion-based technologies. Solar cells are usually not used on multirotor VTOL UAV due to the relatively large surface area required to generate sufficient power.
VTOL UAS and multirotors may be equipped with a wide variety of payloads, including high-resolution cameras, multispectral sensors, LiDAR and environmental monitoring sensors such as CO2 and radiation detectors.
VTOL drones have several advantages over fixed-wing unmanned aircraft. They require much less space to launch and recover, as they do not need to use a runway. They are suited to applications such as inspection and monitoring where the drone must maintain a fixed position for a period of time. They are generally more maneuverable than fixed-wing unmanned aircraft due to the ability to vary the relative speed of each rotor, thus creating changes in thrust and torque.
The main disadvantage compared to fixed-wing UAVs is the lower endurance. This is due to the fact that VTOL UAVs use their rotors to generate both lift and thrust, therefore requiring more power, whereas fixed-wing aircraft only require their propulsion system to generate thrust, as the lift is generated by the wings.
UAS with vertical take-off and landing capabilities are used extensively in commercial applications such as logistics & cargo delivery to oil rigs, ships and offshore installations. They are also used in powerline inspection as well as mapping and surveying work, environmental inspection, agritech and cinematography projects.
Many types of VTOL UAV are employed by law enforcement and public safety bodies to ensure the safety of personnel and the smooth running of public events. They can be used by surveillance teams to monitor traffic, airports and public gatherings such as festivals and demonstrations, as well as by search and rescue teams and first responders to deliver emergency & disaster relief, communications and medical supplies. Other civil applications include the monitoring of environmental disasters such as oil spills and wildfires.
Rugged, reliable and easily transported and deployed, VTOL UAS are used tactically by armies, navies and marines worldwide. Capable of carrying multiple payloads such as cameras, thermal imaging equipment and LiDAR, they are ideally suited to ISTAR (Intelligence, Surveillance, Target Acquisition and Reconnaissance) operations. Tactical VTOL drones are also used in border and coastal patrol and anti piracy missions, as well as to deliver vital equipment and emergency supplies, and to provide advantageous situational awareness.