Carl Copeland is the founder of Möbius Aero, an electric air race team, and MμZ Motion, a developer of custom, high-performance electric motors. Carl has built various engineering teams and led innovation in the fields of IT, mechanical, magnetic, and electrical design. He has founded four companies and holds over 25 patents, and his most recent innovation, the Field Modulation Motion System, is a novel electric motor design that is significantly lighter and smaller than established electric motors of similar power and torque ratings.
The Field Modulation Motion System achieves its high performance by using 18-phase field modulation rather than the three-phase modulation used in standard motors, essentially emulating six separate three-phase motors attached to a single shaft. Carl is putting his new engine design to the test in a new air racing series for electric aircraft known as Air Race E.
In contrast to typical air racing series, in Air Race E aircraft race against each other on a course rather than flying isolated time trials. In the past, air races have been an invaluable means of developing aerospace technology in a competitive setting and Air Race E is re-awakening the spirit of competition by launching the first fully electric airplane race series. In this episode of the Aerospace Engineering Podcast, Carl and I talk about:
his unique and auto-didactic background in engineering
his goal of finding practical solutions to humanity’s problems
the Air Race E competition and the origin story of Carl’s racing team Möbius Aero
the technical details and benefits of his new electric motor
Marc Ausman is the co-founder and CEO of Airflow, a California-based startup that is building an electric short-haul cargo aircraft. Marc holds a commercial pilot license, and among other endeavours, was previously the Chief Strategist for Airbus’ all-electric, tilt-wing vehicle demonstrator known as Vahana. Alongside four other former Vahana team members, Marc and the team at Airflow are building an aerial logistics network to move short-haul cargo quickly and cost effectively by using unused airspace around cities.
Key to Airflow’s vision is electric short takeoff and landing (eSTOL). Airflow’s eSTOL aircraft require only a few hundred feet for takeoff and landing—about the length of a football field—which means that runways can be built almost anywhere, even under existing regulations. What is more, even larger rooftops that can fit more than three conventional helipads could feasibly be used as a runway. Given the aerodynamic efficiency advantages of fixed-wing aircraft over rotary vertical take-off and landing (VTOL) aircraft, Airflow have come-up with an interesting alternative concept to many other companies in the growing urban mobility sector.
So in this episode of the Aerospace Engineering Podcast, Marc and I talk about:
Airflow’s vision of building the urban logistics network of the future
some of the misconceptions of eSTOL and eVTOL
the advantages of electric powertrains beyond reducing emissions
the technology Airflow is developing and challenges that need to be overcome
and striking a balance between financial and engineering incentives
The following is a guest post by Jason D’souza, a recent MSc Graduate in Aerospace Vehicle Design from the University of Cranfield in the UK. Jason is a long-term reader of the blog and reached out to me about the idea of a guest post on electric aviation. As I have covered the prospects of electrification on my podcast, and believe that electrification will have profound effects on the aviation industry just like the jet engine did post-WWII, I thought this would be a great opportunity to get a young engineer with fresh ideas to write about this exciting area. And, of course, if you have any questions or want to discuss the topic matter, please feel free to reach out to Jason directly.
Introduction – The Need for Electric Propulsion
In the automotive industry,
electrification is developing at a fast rate. In the UK, both electric and
hybrid cars are becoming a common sight on roads and electric charging ports
are ever-more common in car parks. Electric vehicles offer a better solution
towards a cleaner, greener environment than their diesel/petrol counterparts, as
well as reducing noise pollution for those living in busy residential areas.
So, when will air travel and air freight follow this electric journey?
Certainly, aircraft emissions degrade air quality and have an increasing effect on global warming as most emissions occur at high altitudes. According to the European Union [1], aviation accounts for approximately three percent of the EU’s total greenhouse gas emissions, and more than two percent of global emissions. Although air travel currently accounts for only a small portion of global emissions, air travel is recognized as one of the fastest growing contributors, as elucidated in a recent study in the Atmospheric Chemistry and Physics journal. But by what mechanisms is aviation actually effecting the climate?
Aircraft engines do not only
produce plenty of CO2, but also exhaust nitrous oxides, NOX,
fine particulate matter, PM25, and ozone, O3. CO2 emissions
are the most significant contributor to climate change and have the same effect
regardless of altitude emission. However, at higher altitudes, NOX emissions
are particularly effective in forming O3, thereby causing a greater
global warming effect than would be the case at lower altitudes.
To put this into perspective, if you’ve ever played with a Carbon Footprint Calculator and plugged in a return trip from London to New York, this trip balloons your carbon footprint by more than 2000 pounds of CO2, nearly equivalent to the level of emissions incurred by heating an average European household for an entire year [2]. Reducing the CO2 impact of aircraft should be addressed as early as possible, as future regulations may impart even stricter regulations on environmental targets that will only be achieved by the use of the latest, and hence most expensive, technologies.
Average fuel burn for new jet aircraft, 1960-2010. Large reductions in fuel burn are seen from 1960 up to 1990s. Since then, further reductions have been modest, despite the development costs of new aircraft continuing to rise [3].
Hence, there is a clear incentive
for cleaner, greener air mobility: the reduction of CO2, NOX,
PM25 and O3 emissions, reduced noise and better fuel consumption.
Currently, we have reached a plateau in terms of improving aircraft fuel
efficiency and reducing emissions. By introducing electric battery-powered
aircraft, an opportunity exists to reduce potentially harmful emissions even
further and to make air travel quieter in urban areas. But is electric flight
actually possible given the technological challenges?
Electric Innovations: Past, Present and Future
Many industry giants are researching
and developing new prototypes and concepts for electrification. Commercially,
the Airbus A350 and Boeing 787 increasingly use battery power for several of
their on-board systems to form an approach described as the ‘More-Electric
Aircraft’ (MEA). At the same time, both Airbus and Boeing are actively
developing methods to progress towards full electric propulsion. The strategy
is to begin with a hybrid option first, with energy still provided by
hydrocarbon fuels, and then progress to an all-electric system with batteries
to provide energy for propulsion.
History of Electric Aircraft [4].
In technical terms, the main challenge that hybrid or electric aircraft, such as the Airbus E-Fan X, Zunum Aero and Wright Electric, are faced with is power-to-weight ratio or specific power. To make an all-electric system a reality, a battery with greater energy density than currently available, with a longer service life and improved reliability is needed. However, historic trends and current understanding of aircraft development cycles suggest that battery technology will not reach the required technical level and production rates until the 2030s to support even current aircraft scales.
Potential Propulsion System Architectures
In the short term, we will
probably witness a ‘More Electric-Hybrid’ commercially sized aircraft rather
than an ‘All-Electric’ alternative. This ‘More Electric-Hybrid’ version could
deliver real benefits through reduced emissions and allow for the development
of motors and power electronics for the transition to fully electric operation.
Let’s examine, on a system level, what a hybrid powered solution might look
like.
Three potential system architectures are shown with a progression from ‘More Electric – Hybrid’ to ‘Full – Hybrid’ to ‘All – Electric’. There are varying development needs for each system component and a large integration challenge for the complete systems. While other proposals for hybrid systems exist, those presented here are considered the most feasible at present [5].
Using an existing gas turbine
with traditional jet fuel (kerosene) mixed with biofuels to drive an electric
generator creates a simple and well-understood solution. However, new power
electronics systems are likely to be required to control and transfer the electrical
energy to electric motors to provide the requisite thrust.
If only batteries are used to
power the remaining systems on the aircraft, then the architecture is known as
a ‘More Electric-Hybrid’ solution. However, the power available from the
generator and batteries can also be combined to power all aircraft systems to
form a ‘Fully-Hybrid’ solution with each energy supply augmenting the other in
different ratios during various flight phases. But, if kerosene is still the source
of energy, then where does the reduction in emissions come from?
The aircraft’s flight is
affected by the varying thrust requirements needed for take-off, climb, cruise,
and altitude changes. Current jet engines are designed to operate in all
conditions but do not always function optimally and efficiently in all flight
segments. In a hybrid solution, the gas turbine can be isolated from changes in
operational conditions and continuously run at an optimized speed to power an
electric generator, which then drives the power electronics that provide
electrical energy.
The main danger in this
scenario is relying on unproven power distribution systems and electric motors.
Indeed, one of the stated objectives of the Airbus E-Fan X program is to
address this uncertainty with regards to electric power systems. Further advancements
can be made by switching the kerosene-powered gas turbine and generator to
battery power, thereby forming an ‘All-Electric’ system. In this case, the
power electronics used for the hybrid solution will need to be adapted, but the
propulsive element could remain the same.
Electric Motor Development
To date, Siemens has developed
a 50 kg electric motor SP260D that delivers 260 kW power output—five times more
than comparable hybrid electric propulsion systems of equal weight. However, this
is still a long way away from the power required for a commercial aircraft to
fly at acceptable speeds (2-50 MW). Nonetheless, Siemens has established its
electric propulsion systems business through the development of the eAircraft
program, now acquired by Rolls Royce.
So, with improved technology,
can enough power be generated? Currently, the answer to this question isn’t
clear, keeping in mind changes to the overall aircraft weight, safety considerations
for electrical systems, wiring routes, electrical interference, and thermal
environment created by batteries.
A High Aspect-Ratio Wing Design
Aircraft wings are designed to withstand aerodynamic loads and carry jet fuel distributed across the span. For an electric aircraft, would there be any benefit of carrying batteries within the wings instead?
High aspect ratio wing [7].
One positive side-effect of
electrification would be that the wing’s mass remains constant during flight (unless
using lithium air batteries), creating novel opportunities for aeroelastic
tailoring and aerodynamic optimization by allowing wings to become longer and
thinner (better lift-to-drag ratio). A current challenge of designing long and
slender wings for conventionally fueled is the onset of ‘aeroelastic flutter’,
an unstable interaction between airflow and the wing’s elasticity that causes a
buildup of oscillations and potential wing failure. With strategically placed
batteries, thinner and longer wings could emerge as a viable design that doesn’t
succumb to flutter, thereby improving aerodynamics and paving the way for
radically different aircraft configurations.
The Need to Reduce Aircraft Mass
What happens to the weight of
the airframe in a move towards hybrid or full electrification? In a hybrid
system, the full propulsion and electrical system, combined with all the
technical operation equipment inside the aircraft, will probably increase the
mass of the airframe. Furthermore, as the aircraft is no longer shedding mass
via fuel burn during flight, the landing weight of aircraft is likely to be
higher than it is today. To compensate for these effects, reductions in the
airframe mass are probably required to facilitate a fully electric system. Indeed,
designing lighter airframes is a huge challenge, putting great requirements on
future research on materials science to determine the full capabilities of next-generation
metallic alloys and fiber-reinforced plastics.
Funding Resources
The best solutions often come
from coordinated efforts to ensure a collaborative, knowledge-sharing approach
that leads to conformity in standards. The UK is a major player in Aerospace
Research & Development and is involved in extensive research networks, partnerships,
and bids to numerous funding bodies working on developing the technology for the
future of air travel.
Lastly, the largest European research program developing innovative technologies aimed at aircraft emission and noise reductions, known as the Clean Sky Initiative, has a €4 billion budget and has backed several projects like Airbus’ BLADE and Safran’s Contra Rotating Open Rotor engine.
Regulation
There is a need for new
regulations addressing emerging technologies, platforms and systems related to
electrification. Firstly, as new technologies are created in the field of
electric aviation, each technology will need regulatory backing to determine
the airworthiness of the technology. This is critical to establish broad
regulatory acceptance for enabling technologies like high-power batteries,
voltage distribution systems and boundary layer ingestion.
Subsequently, regulation will be critical to enable new platforms. Regulation and certification procedures for radically new architectures such as distributed fans will be required to enable the full potential of Electrical Propulsion. As a first step, both the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) are currently opening doors for electrical propulsion. For example, a key change in FAA Part 23 and EASA CS23 came into effect in 2017, allowing larger classes of general aviation aircraft to legally fly non-traditionalengine types. This not only opens revenue potential for developers in general aviation, but this platform category is a key stepping stone to even larger architectures. There is, however, a long journey ahead and regulation must keep a-pace with the technological evolution of electric aircraft.
In April 2018, these new regulations provided the opportunity for Siemens to test the Magnus eFusion at Matkópuszta airfield in Hungary, using a Siemens SP55D electric motor and a FlyEco diesel engine to allow for silent take-off and landing with an extended range. The full electrical propulsion system is developed by the Siemens eAircraft program. Furthermore, a Los Angeles-based company Ampaire recently demonstrated its electric hybrid propulsion system at Camarillo Airport in California with its maiden flight test in June 2019. Their technology was adapted to the Cessna 337 Skymaster and is already considered by some as the largest hybrid-electric aircraft to have ever flown.
There’s Turbulence Ahead
Certainly, the biggest
challenge is integration. For example, when designers and engineers have new
technologies ready for flight, how does the industry support in-service
operation? As an aviation company, how will business models need to adapt over
the next twenty years? When is the best time to start thinking about how to
integrate these new business models with the shift in aircraft architecture? Even
though some of these changes are still years away, it pays to contemplate the
disruptive nature of these changes now, and to consider strategies of how the
industry can ready itself to face up to these coming challenges.
Additional Thoughts
Keeping in mind the
potentially great opportunity aircraft electrification presents, Maintenance
and Servicing Organizations (MRO’s) should be reconsidering their operations to
address questions like what kind of physical infrastructure will be needed going
forward? Topics for consideration range from how many spare batteries will need
to be stored at airports and the most optimal location of recharging points, to
how long it will take for the batteries to be charged or changed in between
flights. The latter will be a considerable consideration for airlines, as an
electric aircraft will not be earning money when it is recharging.
With regards to traffic
control, what happens in the case of diversions and re-routing? Will regional
electric aircraft take priority over long-range gas-powered aircraft? Or could
quieter aircraft lead to additional airports in closer vicinity to cities, such
that regional and long-range aircraft won’t share the same airspace? Finally, a
major challenge will be instilling confidence in passengers about the safety of
this new technology.
Conclusion – Where Do We Stand?
The continuing growth of the
aviation sector has buoyed production rates and has led Airbus and Boeing to
establish themselves as the key players in the aviation market. This duopoly
has only been reinforced by recent mergers and acquisitions of smaller
operations (Bombardier and Embraer). The shift to electrification poses a risk
to incumbents, as this new paradigm in propulsion levels the playing field for
new entrants entering the market.
At the same time, both
incumbents and new players will face key technical barriers, such as improving
the current energy storage capacity per unit weight of batteries, as well as light
and efficient electrical generators, motors and power electronics able to
convert, condition and switch to high voltage power.
On the regulatory side,
airworthiness authorities will have to find approaches to certify novel
aircraft architectures as for over fifty years commercial aircraft have not
deviated from the gas turbine powered architecture. The Advisory Council for
Aeronautics Research (ACARE) has brought about a united sense of purpose across
the European aviation sector to shift towards greener solutions and has set
challenging goals, such as achieving seventy-five percent CO2
emission reductions per passenger.
These challenges mean that we
will probably witness a ‘More Electric-Hybrid’ commercially sized aircraft in
the near future rather than an all-electric alternative. This could, however,
still deliver real benefits through reduced emissions and allow for the
development of motors and power electronics for the switch to fully electric
operation in the far-reaching future.
Michael Darcy is the Chief Commercial Officer of the British eVTOL (electric vertical-takeoff-and-landing) company Vertical Aerospace. Vertical Aerospace has set out to change the way we fly short-haul distances and to reduce the time required for end-to-end journeys. Their vision is to develop an intercity air taxi service that gives customers the freedom to fly from local neighbourhood directly to the final destination.
To achieve this, Vertical has assembled a world-class team with veteran engineers from Airbus, Boeing, Rolls Royce and leading Formula 1 teams to design a fully certified eVTOL aircraft starting from first principles. Since their founding in 2016, Vertical Aerospace has already built the UK’s first full-scale eVTOL aircraft, and is iterating quickly to build the next generation of larger aircraft. One aspect that really stands out in this conversation is that Vertical Aerospace focuses strongly on quickly iterating through the design, manufacture and test cycle to improve their design in the most efficient way. In this episode, Michael and I discuss:
Vertical’s particular approach to designing eVTOL aircraft
how Vertical Aerospace see the electric aviation sector developing
and which hurdles need to be overcome by the industry to build certifiable aircraft
Oliver Family is the Overall Aircraft Design Leader of the Airbus E-Fan X demonstrator. The E-Fan X is a hybrid-electric technology demonstrator being developed by Airbus, Rolls-Royce and Siemens based on a British Aerospace 146 regional airliner. The driver behind the E-Fan X demonstrator is that current aircraft designs have converged to a near-optimum, and with existing technologies, it is difficult to meet the stringent sustainability goals in terms of CO2/NOX emissions and reductions in noise. New technologies, such as electrification, are therefore required to achieve these goals.
As we have seen on other episodes of the podcast, electrification of aircraft is currently a hot topic with new start-up companies promising to disrupt and revolutionise the regional aircraft market. In this environment, one may assume that incumbents like Airbus are too slow to react to a changing technology landscape. As you will hear in this episode, nothing could be further from the truth. The E-Fan X project is structured as a separate entity within Airbus with the explicit mission of challenging Airbus’ legacy business. As you will hear, the consequences of integrating an electric propulsion system on a regional aircraft run much deeper than mere calculations about battery power density and battery longevity. In fact, it’s the secondary effects that we rarely think, hear and read about, such as thermal management of batteries; the interaction between pilots and new control systems; and the challenges of new certification protocols, that are especially challenging. So in this episode, Oliver and I discuss:
what exactly the E-Fan X demonstrator aims to achieve
the main technical and economic challenges of electric aircraft
and how electrification widens the design envelope for engineers
On this episode I am speaking to Nick Sills who is the founder of Contra Electric Propulsion Ltd. Nick’s engineering background is in developing underwater propulsion systems for the offshore oil and gas industry. He has designed products ranging from a hydraulically powered excavator for pipeline route trenching, to the world’s biggest deep water excavator. He received a Queen’s Award for Technological Achievement for the “Jet Prop” tool, a 5 m diameter propeller that is powered by ejecting high pressure seawater from its propeller blades.
Nick founded his most recent company, Contra Electric Propulsion, to develop a contra-rotating propeller system for the light aircraft market. Contra-rotating propeller systems typically use two propellers mounted in series that spin in opposite directions. The fact that props are spinning in both directions alleviates many of the attitude and control problems when flying aircraft.
Contra-rotation has rarely found its way onto modern, gas-powered aircraft because the variable-pitch requirement for efficient operation has made the system overly expensive, complex and maintenance intensive. By changing the power source from fossil fuels to electrons, however, many components of the modern aircraft can be designed differently. With new electric motors it is now possible to build a much simpler, fixed-pitch, contra-rotating propulsion system for light aircraft.
As an aerobatic pilot, Nick immediately realised the massive advantages of instantaneous torque delivery and reversible thrust that electric motors can provide. That’s why he believes that the next big advance in light aircraft propulsion will be a battery-powered, twin motor, contra-rotating system with fixed-pitch propellers. Since this has now become technically feasible, he is privately building one to prove it.
On this episode I am speaking to Thomas Pfammatter, who is the co-founder of the Swiss electric aircraft startup Dufour Aerospace. Dufour is currently designing an electric aircraft with vertical take-off and landing (VTOL) capabilities for the urban and rural transport market. The promise of their current aircraft, the aEro 2, is that with VTOL capabilities it can take-off and land pretty much anywhere, which can considerably reduce travel times, especially to places that are difficult to reach by car or train.
There is a long-standing compromise in aviation between taking-off vertically, and being able to travel fast horizontally. Dufour Aerospace believes that with electric propulsion it is possible to combine these two worlds. To achieve this, Dufour are using a tilt-wing design fitted with two propellers. The wing and attached propellers can pivot around a hinge between the horizontal and vertical planes, and thereby provide exceptional lift, stability and control characteristics even in slow flight. Dufour have proven their electrical aviation ambitions with the aEro1 aerobatic aircraft and are currently in the process of developing the tilt-wing aEro 2 airplane. In this episode you will learn about many of the details behind Dufour’s technology such as:
the tilt-wing concept and the tail fan used for pitch control
the aerodynamic importance of the vortex ring state
the future of regional travel and how Dufour hopes to influence this space
Dr Mark Cutler has a PhD in Robotics and Autonomous Systems from MIT. He has researched multiple aspects of UAV technology—from designing and building his own novel quadrotor for aerobatic flight to developing machine learning algorithms for autonomous systems. Mark is currently working for the California-based startup Kitty Hawk backed by Google founder Larry Page.
At Kitty Hawk, Mark is applying his expertise in rotorcraft to create the next generation of vehicles for everyday flight. Kitty Hawk are currently designing, testing and building all-electric vertical take-off and landing vehicles for work and play. Their first product, the Cora, is an air taxi that could one day bring us an UBER-like service for the sky, and Kitty Hawk is currently in the first stages of testing the Cora in New Zealand. In this episode of the Aerospace Engineering Podcast, Mark and I talk about:
his diverse background in UAV’s
the explosion of hobbyist rotorcraft
the promises of machine learning for autonomous flight
Neil Cloughley is the founder and managing director of Faradair, the UK’s leading hybrid aviation programme. Neil has a broad background in the aviation industry ranging from aircraft re-marketing and aircraft leasing to starting his own aircraft consultancy business, which found him working with the world’s major airlines, OEMs and trailblazing companies like Virgin Galactic. Neil’s father developed one of the most advanced unmanned aerial vehicles of the early 1990s, and had a flying prototype before the General Atomics MQ-1 Predator entered service in 1995. Unfortunately, as a result of being slightly ahead of its time, and due to a lack of funds and unfortunate timing, ASVEC UK had to close its doors.
Neil is now stepping into his father’s footsteps and building the bio-electric hybrid aircraft (BEHA) drawing from many of the lessons he learned from his father. The BEHA is a six-passenger aircraft with a hybrid gas and electric propulsion system, and is to be used for regional travel of around 200 miles. The BEHA has an unconventional design with a triple-staggered wing, an all-composite airframe and a ducted propeller. These design decisions reflect the three key specifications that need to be met to make regional inter-city flight a reality: minimising noise, emissions and operational costs. In this conversation, Neil and I talk about
the engineering behind BEHA
the challenging economics of new aviation businesses
his long-term vision for a regional Uber-like taxi service in the sky
“We need to get going into the future in terms of clean aviation” — Kim-Tobias Kohn
On this episode of the podcast I speak to Kim-Tobias Kohn who is a lecturer in Aerospace Engineering at the University of the West of England. Beside his main vocation, Kim is also an avid pilot and runs an electric skateboard startup company. Kim has garnered attention in the media and from aerospace societies in the UK for his unique university project of building an electric glider with his undergraduate students. For obvious reasons, building an electric passenger aircraft that can replace current fuel-powered airliners is significantly more challenging than replacing gasoline cars with electric vehicles. However, there is a growing grass-roots initiative developing in the UK that is attempting to solve some of the regulatory and technical challenges to realise this vision of electric aviation.
So in this episode Kim and I talk about:
the unique regulatory framework for experimental aircraft in the UK known as the E-conditions
the major technical hurdles that need to be overcome to make electric aviation a reality
how the UAV/drone sector is opening doors for larger-scale electric aviation
his university project of building an electric glider
his dreams for a student-led design, build and fly competition for electric aircraft
