A convertible aircraft is one that is capable of taking off and landing vertically, like a helicopter but which, once it has achieved enough height, can move horizontally like a conventional aircraft. It is also known as convertiplane or tilt rotor aircraft. This concept that allows the propellers-rotors to change their position by 90º with respect to the fuselage, acting as rotors in helicopter mode and as propellers in airplane mode with fixed wings, is called VTOL (Vertical Take-Off and Landing).
The development of the VTOL aircraft was driven by the need to shorten runways, as well as the possibility of having aircraft that can operate in any kind of terrain.
The development of this type of technology was driven by the need to shorten runways, as well as the possibility of having aircraft that can operate in any kind of terrain, even on aircraft carriers in the high seas.
The most famous convertible is perhaps the Bell Boeing V-22, better known as the Osprey. In this aircraft an attempt was made to unify the manoeuvrability of the helicopter, and the ease with which it takes off and lands vertically, with an airplane’s speed of travel. This is achieved by changing the position of its propellers. Unfortunately, this aircraft is very expensive to manufacture, and at the same time is expensive and complex to maintain. Operationally, although faster than other similar aircraft, it is also less efficient aerodynamically, which affects its manoeuvrability and safety.
There are other experimental models whose design and testing were used to develop the qualities of vertical take-off and landing in a tilt wing aircraft, including: Canadair CL-84 Dynavert, LTV XC-142 and the Vertol VZ-2 (Model 76).
Although initially these machines may seem somewhat fanciful, it was only a matter of time before they became a reality. A look at the new concepts in aircraft that are being developed by the different aerospace companies will give us some idea of the sort of aviation that awaits us in the years to come.
The flying car Terrafugia TF-X is a hybrid VTOL vehicle that runs on petrol and electricity, carries four people and has two folding wings, each with an engine at its tip. In 2015 it achieved the necessary documentation to make test flights with a dummy, although not with passengers or a pilot.
The American company Krossblade presented the SkyCruiser, a hybrid transport vehicle, 8.4 m long and 1.3 m high, that takes off and lands like a helicopter. To this end, it extends its 4 rotors as if it were a drone and, once at height, its rotors fold away and it starts to fly like an airplane propelled by rear propellers and reaching up to 500 km/h. When it is on the ground, it is transformed into a road vehicle, retracting and storing its wings in its own fuselage. The doors fold upwards to admit up to 5 passengers. At the moment, it is just a prototype and while it is being commercialised, the company is experimenting with SkyProwler, a scale model of the same concept.
Transformable drones are also nothing new. Google and NASA, for example, have their own drone projects for the transport of people based on this concept.
The EHang 184 AAV (Autonomous Aerial Vehicle) is a drone of Chinese origin with a high level of maturity and which is expected to be on the market very soon. It uses electric power, has 4 propellers and is large enough to accommodate a person of up to 100 kg inside its cabin. Although it cannot be piloted from the inside, it can move a passenger to a given location by means of a mobile application. Its range is approximately 20 minutes flight time at a speed of 100 km per hour, which means it only serves for short journeys, but this could be quite useful for medical emergencies or tourist travel.
Finally, Kitty Hawk’s Flyer has recently been presented. This ten-propeller drone, sponsored by one of the founders of Google, follows the same line as the previously mentioned vehicles. According to its manufacturers, you can learn to fly one in a few minutes and it will not be necessary to be licensed to pilot it (although this is something that will obviously have to be determined by the aviation authority).
In short, technology that until just a few years ago appeared to be a chimera, straight out of futuristic films, can now be seen as realistic to implement. Small advances and constant iteration will lead to manufacturers achieving, and even improving on, the initial concept.
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