Uber recently unveiled plans to launch flying taxis by 2020. To remove the need for runways, these cars will rely on vertical take-off and landing technology, known as VTOL. While Uber's plans may be somewhat ambitious, VTOL technology is increasingly making its way into more aircraft, from small recreational drones up to the traditional systems in helicopters and military jets.
What is VTOL?
VTOL stands for vertical take-off and landing and, as the name suggests, refers to aircraft that can take off, hover, and land vertically. The best-known example is the helicopter, but the F35B fighter jet can also take-off and land from a standing start off the back of an aircraft carrier.
Are there different types of VTOL?
Yes, broadly speaking, there are two different types of VTOL technology: rotorcraft and powered-lift.
Rotorcraft, or rotary wing aircraft, are those that use lift generated by rotor blades spinning around a central mast, so helicopters, quadcopters and gyrocopters.
Powered-lift vehicles are those that take off and land vertically but perform differently from rotorcraft when in flight. They typically have a more conventional fixed wing plane design. Examples include convertiplanes such as the Bell Boeing V-22 Osprey, which takes off and lands vertically but uses fixed wing lift in normal flight.
Vectored thrust planes, such as the Harrier Jump Het series also used powered-lift by manipulating the thrust from the engine or motor to control the flight of the aircraft.
Lockheed Martin's F-35A Lightning II jet which can use vectored thrust to take off and land
Most powered-lift planes in use today, including the Harrier, V-22 Osprey and the new F-35B, are considered to be V/STOL (vertical and/or short take-off and landing) vehicles. They tend to make a rolling takeoff from a runway when possible as this requires less thrust. This is especially useful for a military plane loaded up with heavy weapons.
What are the advantages of VTOL?
VTOL technology means aircraft can theoretically take off and land almost anywhere, making them far more flexible. They're also able to perform various manoeuvres not possible with a conventional plane; a significant advantage for aircraft in combat situations.
What's more, VTOL aircraft, such as drones, that use electric motors are more energy efficient than those using jet engines.
What is the future of VTOL?
A number of firms are developing aircraft that use a VTOL system. Despite a flood of recent controversies, ride-sharing app firm Uber has pledged to launch its first flying taxis in 2020 using VTOL.
Meanwhile, Munich-based aviation startup Lilium aims to offer an on-demand flying taxi service that it claims will be five times faster than travelling in a car. The current prototype is a two-seater aircraft shaped like a conventional plane that uses a VTOL system.
And, at the 2017 Geneva Motor Show, Airbus showcased a prototype flying hybrid car. The modular vehicle can disconnect from it wheels, after which it is picked up by a flying set of rotors.
What's more, Nasa has developed the battery-powered GL-10, which take off and land vertically but flies efficiently like a conventional plane.
