eCTOLs: Five Reasons to be Excited
Electrification and automation are revolutionizing ground transportation, and we have every reason to expect the same to occur in air transportation. We all have visions of what the “Jetson’s Lifestyle” might be in 50 years, though it’s less obvious what the stepping stones between here and there will be, allowing innovative companies to have viable business models along the way. Over the past few years, eVTOL companies have captured our imagination of the future, with promises of “urban air mobility” becoming a mainstream reality. Without taking away from the incredible work of the UAM community, I think it’s worthwhile considering a less flashy development that may in fact have nearer-term impact: eCTOLs. While eVTOLs refer to electrically-powered vertical-takeoff-and-landing aircraft, eCTOLs are electrically-powered conventional-takeoff-and-landing aircraft. In other worlds, eCTOLs are good-old airplanes where the fossil-fuel engine and fuel tank are replaced by an electric motor and battery modules.
Why is it exciting to consider the near-term future of eCTOLs? Let’s consider five good reasons:
1. The operating cost of an eCTOL is less than half of a comparable fossil fuel aircraft
Discounting the obvious environmental benefits of going electric, the economic benefits are enormous. The required maintenance cost for an electrically propelled airplane will be a fraction of piston-powered airplanes, because electric motors are inherently more reliable than piston engines. Fuel costs are also dramatically reduced, because the electricity necessary to power an electric airplane is a fraction of the cost of aviation gas or jet fuel. While these factors are apparent for automobiles, and many of us enjoy the benefits of driving a Tesla, the impact is even greater for aircraft, due to the extreme reliability requirements for airborne travel, and pushing internal combustion engines to their design limits for power-versus-weight.
2. The path to certification is shorter and less costly than for eVTOLs
Unless you are working in the industry, this one is less obvious. Unlike traditional helicopters, eVTOLs are inherently “fly-by-wire” aircraft. In simple terms, fly-by-wire means that computers sit between the flight controls and the rotors and control surfaces. eVTOLs have to be fly-by-wire, because there is no combination of direct controls and flight training that will allow a pilot to adjust the RPM and pitch of six rotors (e.g. Joby), ailerons, elevator and rudder. The human brain just cannot juggle that many balls at the same time. Moreover, the obvious benefit of a fly-by-wire design is taking the pilot out of the aircraft stabilization, and allowing him or her to focus on getting from Point A to Point B. Anyone who has seen a helicopter pilot making small movements of the cyclic, collective and pedals knows that traditional helicopters are inherently unstable and challenging to hover. Though anyone who owns a $100 drone knows that a computer and an inertial sensor can make the process of hovering no more difficult than pushing upward on a control stick.
It may come as a surprise, but there is not a single commercially available fly-by-wire helicopter today. The closest attempt is Bell Helicopter with the Bell 525 “Relentless.” Bell filed for type certification with the FAA in December of 2011. While an incredibly impressive helicopter, Bell has suffered many program setbacks over the past decade, including a fatal crash during a flight test in 2016. The NTSB report of the accident concluded that the aircraft had suffered from severe inflight vibrations, which resulted in a loss of rotor RPM, subsequent rotor flapping and rotor impact with the tailboom, causing an inflight break-up. The root cause was determined to be biomechanical feedback to the collective control. While the cyclic control was equipped with a low-pass filter to remove unintended inputs from the pilot’s hand, the collective control was not, resulting in a feedback loop which worsened the 6 Hz vibration of the rotor system. Translation: The fly-by-wire controls were not perfect yet. Bell Helicopter appears to be back on-track, and the company has forecast type certification before December 31, 2021, almost exactly ten years since they started the certification process.
With billions invested in eVTOL companies, I have no doubt that type certification will be achieved, and hopefully with fewer setbacks and loss of life than Bell has experienced. However, it will be costly and time consuming, because the eVTOL innovators are paving the way for generations of fly-by-wire aircraft to come. In contract with eVTOL developments, companies pursuing eCTOLs are specifically trying to avoid fly-by-wire designs for their first developments. By mechanically connecting the flight controls with the ailerons, elevator and rudder, an eCTOL looks much like the hundreds of airplanes that have been certified over the past 100 years, though with a more reliable electric motor replacing the piston engine. Autopilot actuators can be connected in parallel with the flight controls, so these eCTOLs do not forego the opportunity for flight automation. Thus, we observe a distinction between aircraft that are inherently fly-by-wire, and those that are capable of progressive improvements toward fully autonomous flight. We see the same to be true for cars today. To avoid a long and painful certification process of putting a computer between critical mechanical systems, the steering wheel of cars are mechanically connected to swivel the wheels, though parallel actuators allow the steering wheel to be controlled by a computer.
3. The acquisition cost of eCTOLs will be less than half of an eVTOL per passenger.
As with any product development, the resulting sales price has to reflect both the cost of manufacturing the product, as well as a recovery of the development cost. Because eVTOLs are much more complicated than eCTOLs, the development cost will be higher, and the manufacturing cost will be higher. Based upon anecdotal information at this early stage of the electric aircraft market, it appears that a four passenger eCTOL will be sold for about $800k, while a four passenger eVTOL will be about $2.0M. Interestingly, the price for an eCTOL will closely track the cost-per-passenger for a piston-powered airplane. However, the price of eVTOLs will be about 50% higher than the cost-per-passenger for a turbine helicopter.
4. eCTOLs don’t need new vertiports, they can operate between 5,000 public airports in the US.
Perhaps the greatest challenge to the adoption of Urban Air Mobility is the development of new infrastructure to allow thousands of passengers to travel to and from major cities. While there are more than 5,000 heliports in the US alone, most of these are restricted to emergency use only, due to concerns for noise and safety. eVTOLs will be much quieter than helicopters, and we can anticipate improved safety as well. However, it will take years to build thousands of new vertiports, and reopen restricted heliports. Companies like Skyports have already begun the effort of building vertiports, and many of the eVTOL manufacturers intend to develop their own infrastructure and operate as service providers.
In contrast, eCTOLs avoid the requirement for new infrastructure by operating from existing small airports. In the US, we have 5,000 public airports, and more than 14,000 private airports, mostly serving a declining population of General Aviation users. Since airline deregulation made commercial air travel more affordable in the 1980s, General Aviation has become less and less competitive on purely a cost basis, shifting the motivation toward hobby activities. This trend may reverse itself with the emergence of eCTOLs. With low operating costs, no carbon emissions, and quiet operations, eCTOLs can be both practical and fun at the same time. With the installation of electric chargers, thousands of existing airports suddenly become the home bases for eCTOL operators.
5. eCTOLs have compelling business cases, both for carrying humans as well as cargo
Commercial air travel over distances of 300 miles or more have become affordable, thanks to worldwide competition amongst airlines. Traveling by car is affordable and convenient for trips of 50 miles or less. Between these two ranges, normal people face a less-than-convenient choice of driving by car, bus or rail, or a combination of these modes of travel. For the uber rich, private aviation between small airports has always been an option, though financially impractical for the average consumer. With the emergence of eCTOLs, the cost-per-passenger-mile is low enough that taking a trip, of say 200 miles, may involve a hop from one GA airport to another, with short legs by ground transportation on either side. Multi-mode transport may be facilitated by service providers such as Uber and Lyft, whereby the three legs of the trip can be coordinated to avoid lost time. One nice thing about small airports is avoiding TSA lines. For a future eCTOL flight, you will simply show your ID to the pilot, and then jump in the airplane for immediate takeoff.
Shipping companies like UPS and FedEx utilize small airports, often through third-party service providers, to move cargo into less densely populated areas of the country. One of the workhorse aircraft of the cargo industry is the venerable Cessna 208 Caravan, a turbo-prop airplane introduced in 1984. As we begin to see the emergence of automation, pilots flying cargo airplanes will move to the ground, and operate several aircraft simultaneously. Eventually, even the ground-based pilots will be replaced by computers. In parallel, eCTOLs will appear as alternatives to conventional fossil-fuel powered aircraft, like the Caravan. Combining automation and electrification, costs for “feeder route” air transport will drop dramatically, allowing people living in remote areas to receive their shipments overnight and affordably, as those of us living in cities have enjoyed for many years. Thus, eCTOLs will serve important roles for both cargo delivery and human transport, and on similar timelines.
Conclusions:
eCTOLs may not be as sexy as the “flying car” eVTOLs, but their time-to-market is imminent, and the business cases are compelling. Keep an eye out for near-term announcements from electric aircraft manufacturers, as there will be electric airplanes landing near you within the next three years.
