Tiltrotors & the Future Transformative VTOL Aircraft: Opportunities and Challenges by Noor Nabi (ESR#3)
From first successful flight by Wright brothers to Airbus A380, and from first flight of Sikorsky’s VS-300 to Boeing’s AH-64 Apache, the aerospace industry has made huge advances in both fixed-wing and rotary-wing aircraft.
Fixed wing allows an airplane to fly by generating lift through vehicle’s forward airspeed. On the other hand, helicopters do not need the vehicle’s forward speed; the lift is generated by the spinning rotary wings. Helicopters have the ability to vertically takeoff and land that allows them to takeoff and land virtually anywhere and access remote areas, however, it has limited capability in speed and range when compared to a conventional fixed-wing airplane. The ambition to combine best of both worlds i.e., an aircraft that has VTOL (Vertical Takeoff and Landing) capability of a helicopter, and speed and range of a fixed-wing airplane, led to the development of several hybrid configurations. Tiltrotor is one such example and is the only rotary convertiplane in service.
Tiltrotors are the ultimate transformers, because not only they transform from one configuration to another during flight, they are also transforming the future of aviation industry. Most of the modern transformative VTOL aircraft, such as Uber Elevate, Lilium jet, Vahana from A3 by Airbus, Project zero by Leonardo helicopters, are inspired by tiltrotors in one way or another.
The hybrid configuration of these transformative VTOL aircraft allows them to operate over a broad flight envelope and thus present a lot of opportunities. The ability to hover like a helicopter and at the same time to fly at relatively high cruise speeds and range make them an effective point-to-point fast means of transportations. Their multi-role capability not only make them ideal for urban air mobility but also for energy & medical services and search & rescue missions.
However, the multi-role capability with large flight envelope pose various technical challenges in designing an aircraft to perform adequately over a wide range of aircraft configurations. These technical challenges include: dramatic change in control strategies with flight conditions and aircraft configurations, Rotorcraft Pilot Coupling (RPC) and structural loads.
In conclusion, the modern rotary VTOL aircraft will be half airplane and half helicopter that will fly long distances at higher speeds. In order to ensure safety and take full advantage of the hybrid capabilities of future transformative VTOL aircraft, various technical challenges need to be addressed at the design phase of the aircraft.