Uber is reportedly looking beyond driverless cars to an even faster, more futuristic way to ride: VTOL (vertical takeoff and landing) drones for use in crowded cities. Such vehicles are still years away, but the news focuses attention on a technology that’s only recently started to emerge: the hybrid multi-rotor/fixed-wing drone. Because of the confined spaces they would have to work in, and the premium on flying fast, hybrid drones are the only vehicles that could fit Uber’s requirements.
The most familiar hybrids flying today are probably tiltrotors like the MV-22 Osprey, a fusion of a tandem rotor helicopter (like the CH-47 Chinook) and a fixed-wing aircraft. While a tiltrotor is a true VTOL craft, it has only two rotor systems, which have to be large enough to lift the whole contraption. That makes them unsuitable for Uber’s needs, due to size and safety considerations.
The technology for smaller rotor systems isn’t ready yet, but it’s just over the horizon. Recently, DARPA announced the release of its VTOL X-Plane Phase 2 design, with a concept video showing just how a drone like Uber wants might look and perform.
With a line of small ducted fans integrated into both main and canard wings, the aircraft—best described as a “tilt multi-rotor”—can generate enough lift to launch and land vertically. Once airborne, it can shift into “airplane mode” to propel it faster than any helicopter or multi-rotor could fly. Because the rotors are housed in ducts in the wings, they’re much safer than helicopters, tilt-rotors, or fixed-wing aircraft. Advancements in battery technology could make these electric drones quiet and clean; they might even use hybrid-electric power systems.
While the rapid pace of technology advancement could make Uber’s concept a reality within (the company believes) 10 years, a working model doesn’t yet exist that can carry a human. There are, however, commercially available multi-rotor/fixed-wing hybrid drones, including the Firefly6, from BirdsEyeView Aerobotics. The Firefly6 (which can lift a 1.5-pound payload) fuses a main wing with wing-tip winglets and a Y-6 multi-rotor. The Y-6 design (with three thrust points, each composed of two counter-rotating, coaxial rotors) provides power and redundancy for vertical launching and landing, as well as high speed for forward airplane mode flight. The Transition drone, from Alti Unmanned Aerial Systems (which can lift a payload of around 2.2 pounds), fuses a fixed electric-powered quad with a fixed-wing aircraft that has a fixed, gasoline powered pusher motor.
Many other hybrid designs are in the works, so that “dropping in for a bite to eat downtown” may soon take on a much more literal meaning.