Arizona’s Rotor X wants to step up from being the world’s biggest kit helicopter manufacturer and get into the e-VTOL game.
Their design is “dramatically more efficient and less expensive than all other e-VTOL concepts being proposed or developed today.” Its huge blades could also make it one of the safest e-VTOLs in the sky, since they give it the capacity to autorotate in the case of motor failure.
Rotor X’s design is called the RX e-Transporter. It’s a relatively simple quad-rotor multi-copter, with a helicopter-like cabin that seats up to nine, including pilots, or carries up to 1,600 lb (726 kg) of cargo. These guys are not interested in the complexities of tilt-rotor design or the hover inefficiency of small-diameter rotors; this thing offers four of the biggest rotors you’ll see in the e-VTOL space, extended out from the cabin on long poles.
Where most transitioning vectored-thrust or lift-and-cruise e-VTOLs rock a large wing for efficient forward flight, the e-Transporter has a T-tail and a small top wing. This looks to us like a clever way of compensating for some of each rotor’s retreating blade stall as airspeed increases, but this still won’t be one of the faster air taxis in the sky. Cruise speed is listed at 140 mph (225 km/h), with a max speed “over 160 mph” (257 km/h) – vectored thrust designs are aiming at more like 200 mph (322 km/h).
The e-Transporter will be among the most efficient e-VTOLs on the market in a hover – indeed, Rotor X says it’ll be able to hover on the spot for more than 45 minutes if necessary on a single charge. Moving through the air at speed will develop enough lift from the small wings and the body design to double its endurance figure to more than 1.5 hours, and the company is claiming a max range up to 230 miles (370 km) running on battery power. That’s an incredibly impressive figure for a straight-up multi-copter, and a testament to just how efficiently larger rotors like this can produce lift.
There are some possible downsides to this approach. One could be blade tip noise, which could prove a limiting factor for a given e-VTOL’s ability to operate in densely populated spaces. That said, Rotor X president Don Shaw tells us that the company is currently working on quiet rotor technology, and expects this design to make less whooshy downwash than small-rotor competitors. Another is footprint, although Shaw says the e-Transporter’s four wide arms will fold in to make it easier to garage.
Lose one of the rotors on a typical quad-copter and you’ve got yourself a one-way ticket to tumble town. According to Shaw, however, each of the e-Transporter’s rotors is powered by multiple electric motors, allowing multiple failures before you lose a single prop. And even if you do completely lose power to a rotor, these large blades will also make the e-Transporter one of the very few e-VTOL market entrants capable of autorotation, a process in which an unpowered rotor can be spun up by the ambient air as the aircraft descends, effectively allowing the pilot to use a dead rotor a bit like a parachute, making for a controlled and cushioned landing.
In forward flight, Shaw says the total failure of a single rotor will be even less of an issue; the pilot will be able to choose to continue the flight or land, whatever’s safest. “The e-Transporter,” he says, “will be one of the safest means of transportation by far in the e-VTOL air taxi market.”
Rotor X says a number of mining companies, for example, are “already showing serious interest” in pilot-optional cargo lift versions. The company is working on this project with Advanced Tactics (AT), makers of the Black Knight VTOL “flying truck” for the US Military. AT will be developing a military version of this aircraft as part of the US Air Forces AFWERX/Agility Prime programs. There will also be a longer-range, heavier-lift version built using either a fully combustion-fueled or hybrid powertrain.
Rotor X says it expects to start testing an experimental-class prototype in Alaska next year. It’s expecting commercial FAA air taxi certification by 2024.
(Source: Rotor X)