Above All: Autonomy
Why autonomy is the essential enabler of widespread access to personal air travel
Part 1: Personal On-Demand Transportation Options
To get to the point where travel by small aircraft is as safe and affordable as car travel is today, autonomy will be the key technology to bring the needed substantive step change.
Cars and their dominance
Getting around by car is convenient, fast, and affordable. The automobile has been a popular and universal means of conveyance for decades, hinging on the fact that, for many, it usually checks all three of those boxes.
Cars are very convenient. After a few steps from my front door I am off to my destination at a pace that is plenty quick for trips to work, running errands, and most everyday activities. The trip usually ends right next to where I want to go, making for quick and seamless overall journeys. But is it affordable? The short answer is “yes.” The simple evidence for this is that a majority of the population in large parts of the world can, and does, afford to regularly use a personal car of their own (at about 56 cents per mile — see below) or some sort of on-demand taxi or ride service (varying greatly from a bit over $1 to over $4 per mile in the US).
AAA and others have crunched the numbers to get a full bottom-up picture of costs for personal car travel. At a typical 56 cents per mile, if you had your own coin-operated car, you would have to deposit a quarter every 800 yards or so. Here is the breakdown of what that money pays for:
Due to fixed costs (costs depending more on calendar time than miles traveled), a personal car also becomes less affordable when it isn’t being utilized on a regular basis. We call costs that scale more with usage (primarily fuel and maintenance) variable costs, in that these operating costs for a given year vary depending on how much the vehicle is used.
One interesting takeaway is that fuel plays only a minor role in the cost, which is dominated by costs tied directly or indirectly to the purchase price and value of the vehicle (depreciation, financing, etc.), or in the case of a service, driver-related costs. Fuel is only a small part of the full picture, and yet, in the United States, gasoline prices are a daily topic of discussion, and there is a disproportionate focus on vehicle gas mileage.
Automobiles are an excellent baseline for examining the pros and cons of transportation methods because most of us are intimately familiar with the experience as owners, drivers, and passengers. This provides a common ground for discussing the economics of personal travel not on the ground, but in the air.
Aircraft: the affordably fast alternative
Looking at personal air travel against convenience, speed, and affordability, the clear reason to choose it is the speed. It is also clear that, since almost all aircraft journeys will be multimodal due to the necessary additional travel to and from airports, it is not as convenient as door-to-door car travel — it’s only worth it when the distances and travel times are long enough that the speed makes a real difference.
Examining the operating costs, we will use as a baseline the Cirrus SR22, a representative contemporary personal airplane. Aircraft vary much more than passenger cars in their utility, performance, and, therefore, cost, but the Cirrus models make sense for this series because they are common, are relatively simple, were developed recently (by airplane standards), have added acceptance due to the whole-aircraft parachute, and are widely used in a range of roles from private planes to rental fleets to air taxis.
Flying in a personal airplane is similar to the costs of an on-demand ride service.
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The common practice when discussing aircraft operating costs is to refer to hourly instead of per-mile costs. The variable costs for operating a recent SR22 come to about $185 per hour the engine is running. The average fuel burn is about 17 gallons per hour, and at $5 per gallon for aviation fuel, that means $85 is for fuel. The remaining $100 is for costs like repairs, engine overhauls, and other maintenance.
Given that a flight in the Cirrus will average nearly 200 mph from takeoff to landing, variable costs come to 93 cents per mile — not bad for getting where you’re going at several times highway speeds, and more directly to boot (road journeys are on the order of 25% longer than the straight-line distance).
But what about those pesky fixed costs that were so dominant with the car? Airplanes have them too, but because there is so much variation in how they are used, stored, financed, and flown, it is harder than with cars to say what the typical fixed costs are. At one extreme, where a brand new airplane barely gets flown at all, the fixed costs can dwarf the variable costs. More commonly, airplane users will work hard to make sure aircraft are flown as much as possible via shared ownership or renting.
Since many who fly do so via renting, we can let the FBOs (fixed-base operators — typical airplane rental facilities) do the math for us and determine fixed costs using the difference between typical rental rates and the more known variable costs discussed earlier. The rental rates with fuel range from just under $300 per hour up to $475 per hour, so split at $385 and subtracting the $185 variable cost from above, we get a nice round $200 per hour, or $1 per mile, in fixed costs for the relatively high-utilization rental aircraft. The total cost comes to $1.93 per mile, or, to use our coin-operated vehicle analogy, depositing a quarter every couple hundred yards.
So, is $1.93 per mile affordable? Flying in a personal airplane is similar to the costs of an on-demand ride service (though driving a personal car, even for painfully long journeys, remains much more popular). Besides the benefits of a lifestyle with less time spent in cars (or airport security lines), flying in small aircraft begins to make even more economic sense when considering the value of our time.
A 200-mile journey in the SR22 might take an hour and $385. In a car (which might need to cover 250 miles for the same origin and destination, but we’ll discount that to account for ground travel to and from the airports and some time for planning, preflight checks, taxiing, etc.), it would take about four hours and $113 dollars for a personal car (and about $300 for an equally-slow low-cost car service like Uber or Lyft). So, flying costs up to an extra $272 but saves three hours of time, or about $90 per hour (for any length of journey). Is it worth it? It depends on who you are and your situation. For business travel where you could spend that extra time working, for example, it usually is.
When we load each vehicle option closer to capacity, that time savings is realized by up to four people, driving that number for the minimum value of one’s time down to $23 per hour. Now we’re into territory where a significant portion of the population would see that time and convenience savings as worth the moderate extra cost — especially considering secondary benefits such as saving hotel and meal costs.
Why we don’t fly
If personal air travel in small airplanes is a financially sound choice for so many situations, then why is personal air travel so uncommon that so many people have never even been in a small aircraft, let alone considered it as a viable option for a given journey?
Let’s first look at what it takes to get the training needed for both basic pilot qualifications and additional ratings necessary to safely fly in more weather conditions (even then, weather is often a factor in considering flying for a given journey). The total time and cost might be roughly 250 hours and $25,000. If we imagine that this is more of a chore than an enjoyable experience and we value time at $50 per hour, that totals $37,500 to spread over all miles flown in a lifetime. Conservatively, waiting on training to age 40 and making only a few dozen small round trips per year (10,000 miles per year on average) until age 70, the flying costs in the worst case increase by only about 6.5% from $1.93 per mile to $2.05 per mile.
Could safety concerns, real or perceived, explain why we don’t fly, then? They probably are a strong contributor. Here are some representative safety numbers for different transportation modes:
General aviation is right in the middle of the group of transportation modes for which we tolerate greater risk for the sake of personalized mobility and on-demand convenience. If safety alone fully explained why personal aircraft are so uncommon, we would not expect motorcycles to be so much more popular.
There is also the multimodal issue. Unless you find yourself in the extremely rare circumstance that your actual origin and destination are both airports, every journey will be multimodal (requiring more than one type of conveyance, which may or may not even be available at your destination airport). Multimodal is inconvenient, especially if you get stuck moving yourself and luggage from one mode to another in a downpour. It is easier to settle into the car once with the baby and the dog for a weekend getaway instead of repeating the hassle multiple times.
Another factor reducing convenience for light users of aircraft is that, without a frequent routine, the effort and safety get worse. Short round trips spanning multiple days (a large set of journeys) are also less feasible with aircraft rental because many rentals charge a minimum amount of flying per full day of use.
Autonomy to the rescue
Given the title of this series, it is tempting to stop here and say that making small aircraft autonomous addresses or completely solves many of the issues with aircraft mentioned above. It’s true: an autonomous small aircraft in the same class as the Cirrus SR22 would do away with the pilot training barrier and would make air travel more convenient and worry-free. It would also be significantly safer than the status quo for personal aviation (where accidents, as with cars, are much more often caused by human error rather than mechanical failures).
Such a product has the potential for far more commercial success than any light aircraft before. The market for personal aircraft would suddenly explode to include all those who could afford airplanes but were not buying them because of safety concerns, disqualifying medical conditions, flight training barriers, or general lack of interest in the minutiae of aviation.
While this alone is a good argument for the merits of making personal aircraft autonomous, next we will look at air taxis as a mechanism for more widespread access to personal on-demand air travel and how autonomy is a true game-changer in the air taxi realm.
Part 2: Air Taxis
So far, we have established that flying can be fast and affordable (similarly priced to on-demand car ride services) and that there are currently a great deal of pain points of small aircraft travel that autonomy could address. Now we will look at how drastically different the economics of flying become with air taxis and charters as opposed to personally-flown aircraft. We will also show how autonomy is the most powerful technology that can influence the affordability of personal air travel for the masses, be it with regional journeys in airplanes or with short urban hops to and from helipads and vertiports.
Air taxi costs
Costs for an air taxi include significant extras due to the way the network is operated. Most obvious is the pilot who has to be trained and paid, but who also has to either get home at night or be put up in a hotel. This is the breakdown of what a typical Cirrus SR22 air taxi costs on a per-mile basis:
Wow! The cost per mile ($5.35), nearly tripled from a personally-flown aircraft as we examined in Part 1 ($1.93 per mile). This is similar to the cost ratio for hired versus personal car travel. Why is this, and why are those new costs so dominant? First, because network densities are very low, a significant portion (around 50% for some operators!) of the miles flown by an air taxi or charter company are on deadhead flights. Deadheads are flights flown without clients on board and are just for relocation of the pilot or plane — for example to get to the client or to get the pilot home at night.
There is also the pilot pay. There are a variety of ways in which pilots are compensated, ranging from per flight hour to an annual salary. For this analysis, I took a simple $150 per flight hour rate (derived from typical commercial pilot annual salary and total flight hours). Keep in mind that the pilot has to be paid for all of those deadheads as well.
With the air taxi, instead of a 200-mile trip costing about $385 (the cost for a self-piloted trip), I would expect it to be closer to $1,070. As a rough check, fares on imagineair.com from Pensacola to Tuscaloosa (194 miles) are $1,269, with other options ranging from $1,078 (for members) up to $1,695.
Autonomy revolutionizes the air taxi
From the above, it’s clear that getting the pilot off the airplane using autonomy has some cascading benefits. The biggest will be a vast reduction in deadhead miles since it will be much more feasible to simply leave airplanes where they were last used until they are needed again at that location or somewhere relatively close by. The pilot costs (now ground-based personnel remotely monitoring multiple vehicles at once), both on revenue flights and on any remaining deadheads, will also be reduced.
The other huge benefit is the extra transportation value that is added by being able to carry more people and things on any given flight. We are not examining costs per seat-mile here, but it is worth a mention how expensive it is on such small aircraft to have the pilot occupying a potential revenue seat. In the extreme case of a two-seat aircraft, you pay double what you would if you could split the fare with a friend instead of paying for the pilot’s seat.
Add it all up, and the operating cost for an air taxi can get down much closer to the base operating cost of just the aircraft, especially on a per-seat basis, which, as discussed in Part 1, is quite reasonable — enough so that we can expect an air taxi to make economic sense in many situations for much of the population.
Autonomy and the future of aviation
It is difficult to discuss the future of aviation these days without two topics coming up: electric propulsion and (usually electric) vertical takeoff and landing (VTOL) short-range urban air taxis. I will end with an argument that autonomy deserves at least as much if not more attention than these two current technology pushes in aviation.
While operating costs can decrease with future electrification, the effect is clearly much smaller than what can be achieved by removing the pilot.
We can examine these emerging technologies simultaneously, comparing costs for several alternate modes of travel:
The Robinson R44 (pictured below) is a good baseline for a future urban air mobility air taxi and is representative of costs for four-seat VTOL vehicles, which tend to be more expensive, more complex, slower, and thirstier than airplanes. Because they operate from several vertiports throughout a city, urban air taxis can likely achieve denser networks and, we assume, half the deadhead miles (25% of the total instead of 50% with the SR22). The portion of deadhead miles is assumed to be halved in both cases for autonomous operations (down to 25% for SR22 air taxis and 12.5% for VTOL).
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While operating costs can decrease with future electrification, the effect is clearly much smaller than what can be achieved by removing the pilot. These are also all nominally four-seat vehicles — the benefits of autonomy are even more pronounced as aircraft become even smaller, as many proposed air taxi designs are in order to enable a true on-demand service as opposed to a much less convenient miniature airline.
Conclusions
Improving aviation and reducing the costs of personalized air travel are a multi-pronged effort that includes more efficient and high volume manufacturing to reduce fixed costs; simplified architectures to reduce maintenance and improve safety; developing grid and powertrain technologies to make electric propulsion feasible, cost-effective, and low-emissions; and novel vehicle concepts offering combined benefits.
While these advancements have the potential to provide incremental improvements to aviation, to get to the point where on-demand journeys by air are a similar per-mile cost as hired car travel is today, autonomy is the technology that will bring the requisite substantive step change in the costs of personal air travel and will truly enable the implementation of many of these other developments.
Note: Estimates are based off of data accessed primarily in early 2018 when the first version of this article was written.
