A Research Blog about Multidisciplinary Design Optimization

A quick look at the proposed EASA eVTOL rule

October 16th, 2018, by Ben Brelje

EASA dropped big news on Monday, announcing a proposed special condition under which electric VTOL aircraft under 2000kg may be certified in the European Union. This is the most concrete pathway to certification from a major western regulator and is sure to be followed closely by the FAA (which tends to keep regulations in sync with Europe for the most part, and vice versa). I'll take a quick look at the updated rule and identify the novel issues raised. Several of the points are sure to be contentious, and I expect the public comment period to be quite lively.

More »
No comments

Aerodynamics of the Winter Olympics - Part One (Speed Skating)

January 29th, 2018, by Ben Brelje

The Olympics are about both training the human body to its highest potential and harnessing creative engineering to gain a competitive edge. At the Winter Olympics in particular, technology plays a key role in athletes' competitiveness. As I have time, I hope to write a quick post on how aerospace engineering principles apply to athletic performance at Winter Olympic sports. Today's topic: speed skating.

Full disclosure: I'm an aerodynamicist and a cyclist but I can barely skate. 

More »
No comments

E-flight Roundup: New Flight Tests, New Entrants, and New Hype

January 20th, 2018, by Ben Brelje

Two months of eVTOL developments in one post!


  • Erik Lindbergh (yes, that Lindbergh) launches VerdeGo
  • Bell Helicopter shows cabin mockup
  • Hopflyt goes public with eVTOL craft based on Custer Channelwing concept
  • Detroit Aircraft shows mockup at Detroit auto show
  • Vimana, the worst eVTOL concept yet (now with BLOCKCHAIN and 100% NATURAL AUTO-STABILIZATION!)
Test flights

  • Vahana (apparently) misses targeted 2017 first flight
  • Workhorse Surefly accomplishes tethered flight at Consumer Electronics Show
  • Boeing reveals multirotor, heavy-lift cargo drone
  • Zee Aero shows some old flight test footage on CNN

Industry developments

  • Uber makes strange request of City of LA government
  • Uber hires away Tesla's top battery expert
  • AHS holds sold-out eVTOL technical meeting in San Francisco

More »
No comments

E-Flight Roundup: Airbus internal competition heating up

November 18th, 2017, by Ben Brelje
  • The CityAirbus eVTOL demonstrator completes propulsion system ground testing in preparation for first flight in 2018
  • XTI Trifan announces a major redesign and 60% scale flight test demonstrator
  • Aurora Flight Sciences joins The Boeing Company
  • STARC-ABL rev B to be externally assessed by Aurora

More »
No comments

Have electric aircraft reached the peak of inflated expectations?

November 17th, 2017, by Ben Brelje

It’s common knowledge that most new technologies are overhyped during early development. Technology advisory firm Gartner terms this process the hype cycle and suggests that there are five stages. Sure, it's made up and it's not really a cycle, but we'll go with it:

  1. Technology trigger: Laboratory or theoretical results suggest a promising new area known mostly to topical experts. Industry and the press largely have not picked up the story yet
  2. Peak of inflated expectations: Popular press and industrial leaders learn of the technology and appreciate the potential benefits but not the technical risks and limitations. Some early demonstrators may be revealed as successes; the bugs may not be publicly known.
  3. Trough of disillusionment: Commercial implementations produce mixed results once customers put the technology into use and expose flaws. Major early projects may fail.
  4. Slope of enlightenment: Problems are fixed in second-generation products following in-service experience. Industry begins to change its ways of doing business to take full advantage of the new technology.
  5. Plateau of productivity: The technology becomes mainstream in industry; incremental improvement maximizes performance. 
Where is electric aircraft propulsion in the hype cycle?

More »
No comments

Deriving the modified Breguet range equation for a hybrid-turboelectric aircraft

September 8th, 2017, by Ben Brelje


  • Modifications to the Breguet range equation considering hybridization of energy storage are proposed
  • Payload-range charts are constructed to illustrate the impact of hybridization on airplane performance for a TBM 700-sized design using two different non-dimensionalizations
  • Simple, analytical expressions for the impact of technology and mission requirements on airplane weight are derived and explained

More »
No comments

Progress in hybrid-electric drivetrain components

September 6th, 2017, by Ben Brelje

I just moved back to Ann Arbor and started school, so the last several weeks have seen a large number of important stories pile up. Let's address some of them here:

  • NASA forms partnerships for development of electric propulsion system components, focusing on power density and efficiency
  • GE announces hybrid-electric progress
  • Aviation Week publishes eVTOL issue
  • Hybrid-electric UAS offered for sale
  • Airbus Vahana flight test plans
  • eVTOL odds and ends

More »
No comments

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

More »
No comments

Weekly Roundup: Airbus Vahana is number-crunching away

June 21st, 2017, by Ben Brelje
  • Airbus A^3's Vahana team is renting the heavy iron with Rescale Cloud HPC
  • Israeli firm EViation makes its Paris debut
  • XTI Aviation announces first three orders in Paris
  • Zunum secures another round of funding from the Washington State clean energy fund

More »
No comments

Electric Flight at AIAA AVIATION 2017

June 20th, 2017, by Ben Brelje

AIAA recently posted a live stream from the "Aircraft Electric Propulsion: Transforming Aviation" track at AIAA AVIATION 2017. I wasn't able to attend in person, so it was great to be able to review the panel discussion and questions.

The panel featured speakers from E/S Aero, the American Helicopter Society, NASA Glenn, CALSTART, and Zunum Aero.

More »
No comments