Personal aviation is about to get interesting
FAA is getting one enormously consequential thing right
Aviation is a poster child for economic stagnation. Yes, airline travel has gotten cheaper and safer—great. But every other aspect of aviation has struggled or even regressed. As I’ve noted many times, we had supersonic travel across the Atlantic from 1976 to 2003. Today, not even the world’s richest travelers can fly that fast.
Another part of aviation that has suffered over the last half-century is general aviation, particularly its low-end segment, personal aviation, in which people fly themselves to their destinations instead of hiring a private pilot to do it. Aviation is simply not practical personal transportation today. Where, one might ask, is my flying car?
Lately I have become obsessed with the Federal Aviation Administration’s new MOSAIC rulemaking on light-sport aircraft. The agency’s proposed rule is smart, counterintuitive, and potentially transformative. If not literal flying cars, it could make personal aviation in general much more viable. It’s an action that deserves both applause and careful study.
The safety continuum
FAA is primarily a safety regulator. In 1996, in order to address perceived conflicts of interest after a handful of airliner crashes, Congress removed the agency’s authorization to promote the development of civil aviation, saying that safety was the highest priority. FAA takes its safety mandate very seriously. Importantly, consistent with Congressional direction, it doesn’t apply the same safety standards to all activities, but instead explicitly adopts a “safety continuum,” which is worth reviewing before we get to the content of the MOSAIC rule.
The safest form of aviation is on type-certified Part 25 airliners flying on Part 121 airlines by highly trained, licensed commercial airline pilots. The explicit safety target that FAA and other regulators have settled on is that catastrophic events should be “extremely improbable,” meaning one per billion flight-hours. The regulation of this kind of aviation is nothing short of maniacal. Consequently, it can cost billions of dollars to develop a Part 25 airliner through type certification.
Next along the safety continuum come type-certified Part 23 aircraft. These include most general aviation aircraft, and they can be up to 19,000 pounds of maximum takeoff weight and include seating for up to 19 passengers, although many of them are small four-seaters. To fly a Part 23 aircraft, you must have a private or recreational pilot’s license. In 2017, FAA modernized the Part 23 rules to be less prescriptive, allowing the use of consensus standards (most commonly, ASTM’s).
The third spot on the continuum are light-sport aircraft (LSAs). This was a category FAA created in 2004 to fill a spot on the safety continuum between Part 23 aircraft and experimental amateur-built aircraft. No type certification is required, but the aircraft must still be built according to consensus standards. Under today’s rules, LSAs are subject to a number of restrictions to limit the size of the category: maximum speed is 120 knots, maximum weight is 1,320 pounds, the aircraft can only have 2 seats, and it can be powered only by one engine, which must be reciprocating. If you only want to fly LSAs, you don’t need a full private pilot’s license. FAA created a sport pilot certificate that can qualify you to fly an LSA with half the flight training.
Next along the safety continuum come experimental aircraft. This is America. You can build any aircraft you like, and if you can build it, you can fly it, subject to rules designed to limit the risk to the rest of the airspace and people on the ground. You can also buy a kit aircraft from a manufacturer and build it yourself. These aircraft are not only not type certified, they are not necessarily built according to any particular standards. You must be at least a private pilot to fly an experimental aircraft.
Rounding out the unsafe end of the safety continuum come ultralights. It turns out that FAA is perfectly willing to let you kill yourself in a flying vehicle as long as that vehicle weighs less than 254 pounds and can’t exceed 55 knots, and you do it in the daytime and in an unpopulated area. You need zero pilot training, the aircraft doesn’t have to be registered, and it doesn’t have to be built according to any particular standards.
The safety continuum makes sense. US airlines carry hundreds of millions of paying passengers per year. Those passengers have high safety expectations, particularly because some of them feel out of control on an airliner in a way that they don’t in a car they’re driving or riding in.1 The airline business doesn’t work without a high safety bar. Furthermore, flying big vehicles poses a bigger risk to people on the ground, who are more likely to be harmed by a crash. It is worth reducing that externality through policy measures to ensure safety.
At the other end of the safety continuum, there are some pretty big benefits to allowing experimentation. The system of permissionless innovation under which the Wright brothers worked is directly responsible for us having aviation at all. We made rapid progress in the early days of aviation by sacrificing a lot of test pilots. Even today, new aviation technology often starts out in the experimental and light-sport world and works its way up to airliners over time as safety regulators figure out how to certify it as safe. Composite materials are one example—they were used in experimental aircraft for decades before the 787 became the first majority-composite airliner.
Another benefit of the safety continuum is that it provides an onramp for aviation engineering. Let’s say you were starting a company to build airliners. You could have trouble finding engineers with Part 25 experience—you might have to hire them away from Boeing or Airbus. But fortunately, it’s relatively easy to find engineers who have built experimental or Part 23 aircraft before. The Part 25 rules are more strict, but the basic principles of aviation engineering are the same no matter the size of the plane. If the lower end of the continuum were not there, Part 25 development would suffer.
For contrast, consider nuclear regulation. Although NRC is currently doing a supposedly risk-informed rulemaking for advanced reactors, it doesn’t really operate according to a safety continuum. Texas A&M has an on-campus reactor that produces 5 watts of thermal energy—similar to a chemical hand-warmer—and that reactor is nevertheless licensed as a utilization facility under the same framework used for all research and energy-producing reactors. This heavy regulation means that few new reactors are being built, which in turn means that if you are starting a new nuclear company, you’re going to have mostly engineers who have never built a nuclear reactor of any kind before. This lack of space for experimentation, as I discussed with Last Energy CEO Bret Kugelmass recently, is one reason for stagnation in the nuclear industry.
Less safe is more safe
There are two ways—one relatively obvious, one counterintuitive—that less stringent safety rules along the safety continuum can make us more safe over time.
Let’s start with the obvious one. If the compliance costs of safety regulation get too high, it will shut down iteration and innovation in the industry. These innovations include safety enhancements. After all, pilots and passengers generally want, other things equal, to be safe, so an unfettered free market will deliver cost-effective safety-improving innovations over time. It’s possible by some lights that the market will not produce the optimal amount of safety at all relevant margins, and so regulation persists. Yet everyone should recognize that there is such a thing as overregulation.
FAA does recognize this. The graphic below comes from a document in which they explain the safety continuum doctrine. “If certifcation [sic] requirements and oversight are overly stringent,” they write, “safety can be jeopardized because the burden of certification will prevent the adoption of safety enhancing technologies.” It’s hard to get more clear than that.
There is second way that less rigorous safety standards can improve safety, one that is more paradoxical or at least counterintuitive. FAA can adjust the boundaries of the different points on the safety continuum. If through deregulation it can increase the attractiveness of being in a safer part of the continuum, it can increase overall system safety while in a static sense only decreasing safety standards.
Amazingly, FAA explicitly recognizes this too, and is now through the MOSAIC rulemaking expanding the light-sport category in a deregulatory manner to induce pilots to upgrade their spot on the safety continuum from experimental to light-sport.
Since the 2004 rule, light-sport category aircraft have shown a lower accident rate than experimental amateur-built airplanes. The FAA considers that the successful safety record of light-sport category aircraft validates certification requirements established in the 2004 final rule and provides support for expanding the scope of certification for light-sport category aircraft and operations. As a result, the FAA identified this proposed rule as an opportunity to expand the 2004 final rule to include a wider variety of aircraft, increase performance, and increase operating privileges to extend these safety benefits to more aircraft. The FAA intends for these expansions to increase safety by encouraging aircraft owners, who may be deciding between an experimental aircraft or a light-sport category aircraft, to choose aircraft higher on the safety continuum and, therefore, meet higher aircraft certification requirements.
The data they are referring to are below. The y-axis measures the number of fatal accidents per 100,000 flight-hours. TC/Personal refers to Part 23 (type certified) aircraft used for non-commercial personal purposes. EAB is experimental amateur-built, and SLSA stands for special light-sport aircraft. These kinds of aircraft are all used by similar people and for similar purposes. The SLSA data is more volatile because of a low number of flight-hours compared to the other categories, but in most years, experimental aircraft are about twice as deadly as light-sport aircraft.
There are about 6 times as many EAB flight-hours as SLSA flight-hours, so if we move a large chunk of the EAB activity to SLSA, it could result in a net reduction in aviation fatalities, holding total flight-hours constant. To induce people to upgrade their spot on the safety continuum from experimental to light-sport, FAA needs to make the light-sport category more attractive, and boy are they delivering on that.
MOSAIC could be transformative
Modernization of Special Airworthiness Certification (MOSAIC) is the name of the new rulemaking initiative from FAA to expand the definition of light-sport aircraft. As discussed above, the explicit goal here is to make the new category so attractive that many recreational pilots switch from more dangerous experimental amateur-built aircraft to light-sport aircraft that are designed according to consensus standards. The changes are sweeping. Let’s walk through the relevant sections of the NPRM to see how FAA is expanding the category.
Additional Aircraft Classes
Under current rules, light-sport aircraft explicitly exclude helicopters and powered-lift aircraft (e.g., tilt-rotors and eVTOL aircraft). MOSAIC proposes to allow any kind of aircraft to be considered a light-sport aircraft if it meets the other criteria. This means we could see helicopters and eVTOLs come to market under light-sport rules—designed under consensus standards and not type certified.
It doesn’t mean that sport pilots would be allowed to fly all of these new light-sport aircraft. MOSAIC is decoupling the definition of light-sport aircraft from sport pilot privileges (that is, sport pilots cannot necessarily fly all light-sport aircraft by default). By doing this decoupling, FAA can be aggressive in deregulating the vehicles (not requiring them to be type certified) while being more cautious about expanding the privileges of pilots. Sport pilots can expand their privileges through additional ratings, although a rating does not necessarily exist for every aircraft considered an LSA.
To fly light-sport helicopters, sport pilots would have to get a helicopter rating, which they could only get for a helicopter that has simplified flight controls, about which more below. No rating would initially exist for light-sport powered-lift aircraft. FAA says this area is rapidly developing, and it expects that future rulemakings could expand privileges to cover these aircraft. This means that a two-seat eVTOL aircraft could come to market as an LSA, but you’d still need to have a private pilot’s license to fly one initially.
Maximum Takeoff Weight
MOSAIC would allow light-sport aircraft to not be so light. Current rules limit LSAs’ maximum takeoff weight to 1,320 pounds, except for seaplanes, which get to be up to 1,430 pounds. Under the new rule, FAA is scrapping the weight requirement entirely. The agency notes that other requirements like maximum stall speed implicitly limit the weight of aircraft, so perhaps LSAs will top out at around 3,000 pounds.
From a safety perspective, they also argue that a weight limit is counterproductive. It discourages a more robust airframe design. It results in more jostling during turbulence, which could increase pilot workload. And it could preclude the installation of additional safety equipment like ballistic recovery systems. Under MOSAIC, then, LSAs will be able to about double in size and be safer as a consequence.
Maximum Airspeed in Level Flight
Another big change is to maximum cruise speed. Current light-sport rules limit LSAs to 120 knots. The MOSAIC NPRM notes that even student pilots, who are less experienced than sport pilots, are allowed to go faster than that. Furthermore, there is no evidence that there is a safety benefit from such a low speed limitation. “FAA has not noted any definitive data that links cruise speed as a contributing factor in accidents involving light-sport category aircraft.” Consequently, FAA is more than doubling the LSA speed limit to 250 knots.
Relatedly, current LSA rules require aircraft to have fixed landing gear. With the speed limit more than doubling, that no longer makes sense as it would wildly increase drag at cruising speeds. Under MOSAIC, FAA will allow LSAs to have retractable landing gear. It doesn’t link that change to higher speeds, but I think it’s only logical that if you are allowing 250 knots you have to allow retractable gear. Sport pilots would require an additional rating to operate retractable landing gear, since it’s important to remember to extend the landing gear before you land.
Maximum Stalling Speed
The other speed limit that is relevant is the clean stall speed. Under today’s rules, LSAs must have a stall speed of no more than 45 knots. MOSAIC proposes to raise this limit to 54 knots for airplanes only. Stall speed is relevant because it affects the speed at which an aircraft comes in for a landing. Since kinetic energy increases with velocity squared, this is a parameter that affects the amount of energy involved in a landing accident. FAA says that since the creation of LSAs in 2004, there have been 501 landing accidents involving an LSA, and only 7 of them were fatal. Consequently, there is room to go up from 45 knots.
While an increase to 54 knots is welcome, this is one of the few parameters in the MOSAIC rule that could generate some objection from stakeholders, who will want it to be higher still. If it were increased to the low 60s knots, the category could include planes like the forthcoming Pipistrel Panthera.
Maximum Seating Capacity
Another instance of decoupling of sport pilot privileges and aircraft specifications is passenger capacity. Today’s light-sport rules limit everything to two seats (the pilot plus one passenger). MOSAIC would allow airplanes (but not other kinds of LSAs) to be manufactured with up to four seats. Sport pilots would still be limited to transporting one passenger. This is consistent with FAA taking aim at four-seat experimental airplanes flown by non-sport private pilots, trying to make it attractive for private pilots to “upgrade” their spot on the safety continuum to a standards-based aircraft. Undoubtedly, a lot of sport pilots will comment on this change, asking to be allowed to also carry additional passengers rather than flying with empty seats.
Engine and Motors
Under today’s light-sport rules, LSAs are limited to a single reciprocating (piston) engine. What this has meant in practice is that turboprops are not allowed. MOSAIC eliminates this limitation, prescribing no limit on the number or type of powerplant on the aircraft. FAA justifies this elimination by noting that modern turbines are simpler to operate than piston engines because of fancier firmware on the turbines.
While a turboprop LSA sounds awesome (a mini PC-12, anyone?), this change allows far more than turboprops. A big movement in the eVTOL space is distributed electric propulsion. While batteries aren’t good enough to yield good range yet, there are a lot of advantages to electric motors—simplicity, fast spin-up, reliability. Distributed propulsion also yields redundancy and noise reduction.
Without a limitation on propulsion technology, there is no rule stopping a manufacturer from using a turbogenerator and using it to power a slew of electric motors. It’s up to the market to figure out whether something like this would be practical, but FAA rules won’t stand in the way.
Simplified flight controls
This is the part where my jaw hit the floor. MOSAIC makes specific provision for “simplified flight controls.” In today’s airplanes, pilots have direct control of flight surfaces and available power. Imagine if instead of moving flaps and rudders you could just tell the airplane to turn left. You could fly it like in an arcade game. The aircraft would be responsible for keeping itself in a safe flight envelope, and it would take suggestions from the pilot as to what to do.
FAA is non-prescriptive about what simplified flight controls could look like. The requirements if manufacturers want to opt into simplified flight controls are that:
The pilot cannot directly control flight surfaces or engine power.
The aircraft is designed to prevent loss of control regardless of pilot input.
The pilot has a means to discontinue the flight safely and quickly (triggering an emergency landing, return to starting point, course change, or a holding pattern).
These flight controls could range from arcade-style controls to full self-piloting. Because these simplified controls would vary from model to model, FAA is proposing a model-specific endorsement for pilots who wish to fly any aircraft with simplified flight controls.
Here’s your flying car
After World War II, expectations for general aviation were sky high. The war had driven significant advancements in aeronautics, navigation, and communication technologies. There were a large number of military surplus planes and a lot of trained pilots returning from the war. For someone alive in 1945, who had perhaps witnessed the social transformation wrought by the automobile, it would seem only natural that general aviation would be the next step in personal transportation.
Of course, it didn’t play out that way. The government significantly tightened certification requirements for general aviation in 1945 and 1965. With the market flooded with cheap, surplus military aircraft, it was hard for manufacturers to make money investing in new, more advanced models. And, of course, piloting an airplane using conventional flight controls is not as simple as driving a car, requiring significantly more skill, with lapses in attention more catastrophic.
If general aviation is to make a comeback, something like the MOSAIC rule is a prerequisite. By making a category of aircraft that doesn’t require type certification, is actually useful for transportation (250 knots and 4 seats), and can be flown with less skill via simplified flight controls, FAA is opening the door to a bigger market and vastly more innovation.
Without the need for type certification, manufacturers can iterate on their designs more rapidly without going through the costly supplemental type certification process. They can include cheaper uncertified avionics. They can do over-the-air software updates.
Meanwhile, simplified flight controls and making LSAs actually useful could greatly increase demand for these aircraft as transportation. That increased demand feeds directly into manufacturing investment and the pace of iteration. The more progress there is in making these small planes really great, the more the demand for them will increase, creating a flywheel effect.
If we can get LSAs into mass manufacturing, production costs of the airframe could go down further. Mass manufactured items tend toward the cost of inputs. Aviation manufacturing entails more burdensome supply chain integrity requirements than other industries, so LSAs will likely never get as cheap as a Toyota Camry despite having similar mass, but it could be a smaller multiple of the cost.
In the near term, I’d love to see a MOSAIC aircraft that had the following:
200+ knot cruise speed
Distributed electric propulsion (maybe vectorable) powered by a turbogenerator and small battery for buffer and reserves
1000 nmi range
STOL capability to maximize versatility. DEP helps with this, and you have to have low stall speed anyway
Ultra-simplified controls including autopilot and autoland
Starlink on board for passenger connectivity, over-the-air avionics updates, and maintenance monitoring
Weight-saving and performance-improving technologies like ethernet-based addressing of actuators instead of more traditional fly-by-wire
Active turbulence reduction
A ballistic recovery system
This is the kind of aircraft that could draw people into flying, kicking off the flywheel of innovation and making personal aviation relevant again.
Two cheers for FAA
One reason I wrote this post is because I wanted to publicly praise FAA for such an innovative and thoughtful action. FAA’s longstanding safety continuum philosophy makes eminent sense, and with MOSAIC they are applying it with rigor and insight. This rulemaking will indeed, over time, make general aviation safer, both by increasing safety innovation and by inducing experimental pilots to upgrade their spot on the safety continuum. This is the public sector operating at its finest.
Although I have nothing but applause for the civil servants behind the MOSAIC rule, the policy change also makes a darker point about the history of general aviation in the United States. There’s nothing magical about the current moment that makes it the right time to expand the class of aircraft that don’t need to be certified. If it is the right policy now, and it is, then it was likely the right policy decades ago. If we had never introduced type certification into four-seat aircraft, we could be in much better shape today. Our present stagnation in general aviation is a direct result of 70 years of the wrong policy choices being made by FAA and its predecessors. There are many other areas, both within aviation and in the economy overall, where we are similarly making the wrong policy choices. If we want both safety and prosperity, we need to root them out.
The comment period for the MOSAIC rulemaking closes on January 22, 2024. It will take several months after comments close for the rule to be finalized and take effect. When it does, we’re going to have to throw a big party.
Even if someone else is driving, you can at least see the driver.