It seems inevitable that large, electric multirotors are going to play a key role in the coming decades, and not just as flying cars. Much simpler, cheaper and easier to fly than helicopters, these jumbo drones are going to revolutionize all sorts of transport, delivery and cargo industries. Not yet, though, because of the same thing that's holding electric cars, trucks and motorcycles to the top end of the market – batteries are still too expensive, too slow to charge, and too heavy for long range utility in aircraft.
And gasoline engines don't look like a very effective substitute at this stage. While they can deliver terrific power, endurance and allow quick refueling, multirotor airframes need to be able to make lots of motor speed changes in quick succession to remain stable in the air. Gasoline engines are slow to react, and complex to manage since they deliver differing amounts of power depending on how fast they're spinning. That's why multirotor drones never really took off, if you'll excuse the pun, until lithium batteries became ubiquitous.
All of this is what makes bridging technology like the SKYF all the more interesting. Russia's ARDN Technology has built a large multirotor platform that uses a hybrid propulsion system to deliver heavy-lift capacity and long-endurance flights, right now, using proven equipment.
The SKYF airframe takes advantage of the lifting power and endurance of a gasoline engine to drive its two main lift props, and then uses four sets of coaxial twin props with electric motors at the corners of its boxy frame to stabilize and steer it. By separating the lift from the control, the advantages of both motors can shine.
According to ARDN, this combination allows a 400-lb (181-kg) payload capacity and a range up to 350 km (217 mi) or eight hours in the air, for a decent-sized multirotor that's suitable for a range of industrial jobs, from precise, automated crop dusting to fire fighting and cargo work where wheels can't take you.
You won't be sitting people on this one, at least not flying carpet style, thanks to those two large props. But there's no reason it couldn't be fitted with an undercarriage in the future to become a manned aircraft. For the moment, though, flights of a prototype are automated, with the airframe receiving encrypted instructions from a flight dispatch center.
In practical terms, the company claims the SKYF costs around US$150 an hour to run, which is an order of magnitude less than a helicopter. It can also fold down small enough that two will fit in a 20-ft cargo container. Setup takes around 10 minutes and the overall dimensions work out at 5.2 x 2.2 m (17 x 7.2 ft). The operational ceiling is around 10,000 ft, and its autonomous flight controller operates within a precision of around 30 cm (11.8 in).
An airframe like the SKYF gives companies the chance to get a head start on long-range, heavy-lift multirotor development while the rest of the world waits for batteries to catch up. Seems like a solid idea to us.
Here's a video explaining the tech, and showing early flight tests.