Electric Flight Roundup: More details on the NASA X-57 Maxwell


July 27th, 2017, by Ben Brelje

Well, I may have been too ambitious with the idea of a "weekly" tempo for my last blog post. So much was announced at Paris but the following weeks were slow. I've been gathering updates since then and my plan is to post when I reach a critical mass of material or when a feature-worthy development comes along.

  • More details on the X-57
  • Turbine primes throw cold water on electrification potential
  • External analysis of Zunum
  • New FACEs and fresh configurations

Popular Mechanics highlights the X-57 Maxwell 

PM carried a great article outlining the plan for the X-57 program. The phased development approach seems well designed and feasible and progress is well underway. It sounds as though the battery weight is a bigger problem than original anticipated (no surprise there). 

Phase I was a truck-mounted testbed to prove out the distributed propulsion effect on high lift performance. Phase II is basically a drop-in replacement of the Tecnam testbed's gas engines with motors and the associated battery systems (testing set to start Winter/Spring 2018).


Phase III involves swapping the existing wing for a deliberately undersized composite wing, mounting the primary propulsive motors at the tips and dummy pylons where the distributed lift motors will eventually go. This high wing loading airplane will need a dry lakebed test environment due to high approach and takeoff speeds. 

Finally, in Phase IV, the distributed propulsion will be installed onto the airplane to determine the true impact on the high lift system. 

The concept is very energy limited but there is a potential follow-on project to replace the batteries with a diesel fuel cell to extend the range. I like it!

Established turbine manufacturers not ready to throw in the towel

Far from it - this AIAA hosted talk included representatives of the "Big Three" (RR, GE, Rolls) and Safran, who pointed out the inconvenient truth that electric concepts might result in a net increase in carbon emissions for equivalent missions, at least in the near term.

Rolls and Safran expressed interest in turbine-powered hybrid concepts. The GE representative pointed out technology issues with safety, high-voltage insulation, and power density (all potential show-stoppers; this was the first I've seen a discussion of insulators)

Zunum shares new details with industry press

Zunum, the Kirkland, WA based propulsion house developing regional jet competitors powered by ducted electric fans, was featured in recent articles in Aviation Week and Leeham News (an independent industry outlet). The Leeham content in particular is valuable because Bjorn Ferhm brings a good business mind and technical acumen to bear in his analysis. I haven't cross checked his rough sizing numbers. 

The AvWeek commenters picked up on a worrying sign - Zunum's stated hopes of achieving extensive NLF. Dealing with contamination on the many, low-altitude cycles per day will be a serious, perhaps insurmountable problem. Hopefully NLF isn't a make-or-break technology for the company. 

Interestingly, Zunum studied boundary-layer ingestion but did not select it, as it did not provide a benefit at the scale being considered or introduced issues. BLI is a very fashionable design paradigm right now and it's somewhat surprising to see a contrarian approach being taken here.

The periodic upgrades proposed by the company involve both flight software and hardware; certifiability seems like a big red flag here. 

Beautiful but unserious concepts 

The Portuguese/Brazilian newFACE consortium showed 3 new concepts at the 2017 Future of Transportation Conference in Cologne (h/t evtol.news)

(credit: AlmaDesign)

The interior designs are mocked up beautifully and the utility/STOL concept is sort of unique. However, the configurations are clearly the work of a design house and did not have much input from the Embraer industry partner with a number of puzzling technical design decisions (e.g. try getting a jetbridge to the mid-cabin boarding doors when a box wing tip is in the way). The aerospace industry could benefit from this type of design process based on user stories, much as the tech industry does.

Airbus had a mockup of the CityAirbus e-VTOL concept at Paris - note the noise-attenuating rotor shrouds. I'm not sure what the relationship is between this concept and the Vahana team but it seems like they may be internal competitors to some extent.

Ugly and unserious concept

And then there's the Neva Airquad. I won't be climbing on one of these any time soon.