eVTOLs Hitting the Airshow Circuit

 - August 6, 2018, 7:47 AM

Electric vertical takeoff and landing aircraft (eVTOLs) were all the rage at two of this summer's premiere airshows—Farnborough EAA AirVenture.

At Farnborough, super car maker Aston Martin unveiled the Volante Vision, a three-seat hybrid electric aircraft with three propellers about which few specific details were released. Rolls-Royce took the wraps off a slightly larger four- to five-seat model powered by the ubiquitous M250 helicopter turboshaft it says can reach speeds of 250 mph for up to two hours. The Rolls-Royce design is a concept vehicle designed to showcase the distributed electric power system it is developing based around the M250. Rolls-Royce engineers are developing complementary systems for the concept vehicle including algorithms for fly-by-wire controls. Boeing said it is allying with SparkCognition to form BoeingNeXt to work on urban air taxis as well as unmanned cargo and supersonic aircraft. At Farnborough, the UK government announced that it was investing $436 million in hybrid electric aircraft development and related projects.

At EAA AirVenture, Miami startup Assen Aeronautics showed off its A1 ducted fan “flying bike” tri-copter. The single-seater is speed limited to 63 mph, an altitude of 4,000 feet, and designed for the needs of the developing world. The hybrid electric power system gives the A1 a maximum endurance of 55 minutes (gasoline) and 20 minutes (batteries). The gas tank holds 4.9 gallons and recharging time is 40 minutes. Maximum sustained bank angle is 40 degrees and maximum bank angle (10 seconds) is 50 degrees. The vehicle as currently designed has a limited payload; maximum empty weight is 253 pounds and maximum gross weight is 463 pounds. The company plans to organize racing events to build an initial market for the vehicle and anticipates demonstration flights will begin next year. The company calls the A1 “the next revolution in sport transportation.”

Palo Alto, California-based Opener brought its BlackFly 2 and 3 vehicles to Oshkosh this year. The “personal aerial vehicles” (PAV) have a range of up to 25 miles at a restricted speed of 62 miles per hour. The aircraft features eight propulsors distributed across two wings, is amphibious, has automatic return-home, has a ballistic parachute, and is designed to fit on a small auto trailer and deploy within 30 minutes.

Workhorse brought its two-seat “SureFly” contra-rotating quadcopter to Oshkosh, but the demonstration flight was aborted. SureFly made its first, brief untethered flight in April and it appears the company has been expanding its flight envelope very slowly since then. The aircraft has a 400-pound payload capacity and a range of approximately 70 miles; target price is $200,000. The hybrid aircraft is powered by a fossil-fueled generator linked to a parallel bank of battery packs. Its electrical system powers motors linked to four propeller arms, each with two contra-rotating propellers. The batteries can power the motors if the generator fails. In addition, the airframe has a ballistic parachute.

NASA brought a model of its X-57 “Maxwell” all-electric X-plane to Oshkosh and several program experts to discuss the project. While not an eVTOL per se, it uses much of the same base technology included in distributed electric propulsion. The X-57 is a modified Tecnam P2006T under a NASA program called SCEPTOR—scalable convergent electric propulsion technology operations research. Tests beginning in 2015 evaluated the aircraft's electric propulsion high lift system. A wing fitted with 18 electric motors producing 300 horsepower was driven at speeds of up to 80 mph atop a modified semi truck to simulate wind-tunnel conditions. The test showed the wing generated double the lift at lower speeds compared to traditional propulsion. In 2015 NASA also collected baseline aircraft data from a stock Tecnam. The program aircraft arrived from Italy in 2016 and is being converted for NASA by Scaled Composites in Mojave. X-57 pilots already are practicing in a simulator at NASA Armstrong. The X-57 also will be fitted with a high-aspect ratio wing that will reduce wing area and increase wing loading from 17 pounds to 45 pounds per square foot to reduce friction drag and enable a smoother ride. The stock cruise main Rotax engines will be replaced by Joby 60-kilowatt motors that will be moved outboard, allowing those engines to recover energy otherwise lost to the wingtip vortices. The final configuration of the aircraft is designed to weigh 3,000 lbs, cruise at 9,000 feet, and have a cruise speed of 172 mph.