Rotor X’s four-rotor eVTOL promises extreme efficiency and autorotation

Arizona’s Rotor X wants to go from being the world’s largest kit helicopter maker and into the eVTOL game, and to do so, it has put forward a design it claims to be “considerably more efficient.” and less expensive than any other eVTOL concept proposed or developed today. “Its huge blades could also make it one of the safest eVTOLs in the sky, since they give it the ability to self-propel itself in the event of a failure. engine.

The design of the Rotor X is called the RX eTransporter. It is a relatively simple four-rotor multicopter, with a helicopter-like cabin that can accommodate up to nine people, including pilots, or can carry up to 1,600 lbs (726 kg) of cargo. These guys do not care about the complexities of tilt rotor design or the inefficient hovering of small diameter rotors; this thing offers four of the biggest rotors you’ll see in eVTOL space, sprawled out of the cab on long poles.

Where most vector-thrust or lift-and-cruise eVTOLs flip a large wing for efficient forward flight, the eTransporter has a T-tail and a small top wing. Sounds like a nifty way to compensate for some of the stalling of the retreating blades of each rotor as speed increases, but it still won’t be one of the fastest air taxis in the sky. Cruising speed is listed at 140 mph (225 km / h), with a top speed “above 160 mph” (257 km / h) – vector thrust designs aim for more at 200 mph (322 km / h).

This is the opposite approach to the ultra-small rotor concept used by Lilium, and its pros, cons and mission profiles will tend towards the other end of the spectrum. The Lilium jet is horribly inefficient in hovering, but very efficient on the wing, so Lilium is looking to position itself as a longer distance intercity transport service.

Large diameter rotors produce very efficient lift, although there are other factors to consider

Rotor X

The eTransporter, on the other hand, will be among the most efficient hover eVTOLs on the market – indeed, Rotor X says it will be able to park in place for over 45 minutes if needed on a single charge. Moving through the air at high speed will develop enough lift thanks to the small fenders and body design to double its endurance to over an hour and a half, and the company claims a range of up to 230 miles (370 km). battery operated. That’s an incredibly impressive figure for an upright multicopter, and a testament to how efficiently larger rotors like this can produce lift.

There are a few possible drawbacks to this approach. One could be blade tip noise, which could be a limiting factor for a given eVTOL’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 produce less downwash than small rotor competitors. Another is the footprint, although Shaw says the eTransporter’s four wide arms will fold up to make parking easier.

And then there is the redundancy. Lose one of the rotors of a typical quadrocopter and you get a one-way trip down town. According to Shaw, however, each of the eTransporter’s rotors is powered by multiple electric motors, allowing multiple failures before losing a single attachment. And even if you completely lose the power of a rotor, these large blades will also make the eTransporter one of the very few market entrants of eVTOL capable of autorotation, a process in which an unpowered rotor can be driven. by ambient air such as an airplane. descends, effectively allowing the pilot to use a dead rotor much like a parachute, allowing for a controlled and cushioned landing.

In forward flight, Shaw says total failure of a single rotor will be even less of a problem; the pilot will be able to choose to continue the flight or to land, whichever is safer. “The eTransporter,” he says, “will be by far one of the safest forms of transportation in the eVTOL air taxi market.”

Rotor X will also build combustion versions of this airframe, and Advanced Tactics will develop it for military applications.
Rotor X will also build combustion versions of this airframe, and Advanced Tactics will develop it for military applications.

Rotor X

Nonetheless, it will be interesting to see how the four rotor setup plays out when it comes to certification, even though the rest of the design is much less complex than most of the bigger players in this field; redundancy over redundancy is the mantra with which other eVTOLs hope to put regulators (and their investors) to sleep.

Either way, an airplane designed for super efficient hovering could make a lot of sense for rapid transit between cities, deliveries, and industrial operations. Rotor X says that a number of mining companies, for example, “are already showing serious interest” in the optional pilot cargo lift versions of this thing.

The company is working on this project with Advanced Tactics (AT), the makers of the Black Knight VTOL “flying truck” for the US military. AT will develop 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 version built using a fully combustion or hybrid powertrain.

Rotor X says it plans to start testing an experimental class prototype in Alaska next year. He expects commercial air taxi certification from the FAA by 2024.

Editor’s Note: This article was modified on June 29, 2021 to include additional information provided by Rotor X President Don Shaw.

Source: Rotor X

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