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In order for any vehicle larger than a bicycle to be street legal, it must be registered under the state/province's Department/Bureau of Motor Vehicles as a highway vehicle. There already exist light sport airplanes that have folding wings so they can be parked in a standard automobile parking spot, though the tail might stick out a few feet. However, they are intended to be towed to the airfield and not taxied themselves there.

If one simply slaps turn signals, rear parking lights, brake lights, reversing lights, and side mirrors on such an airplane, does it make it road legal to the point where it can be registered under the DMV or BMV? Since FMVSS crashworthiness only applies to auto manufacturers, it does not apply to custom vehicles like Batman cars and Wienermobiles. That is why custom vehicles can be registered under DMV. Also, the tail number of the aircraft satisfies the FMVSS license plate requirement because it is more conspicuous than a license plate. USPS and other US Federal vehicles use large printed numbers to satisfy that requirement.

If such an aircraft is road legal, it is effectively flying car. This would be super useful for road trips, where the drive to the destination can be a conventional drive on the highway, but the return trip can be a flight in order to save time, all with the same vehicle. Furthermore, one can save a lot of money from not having to rent a hangar space by parking at home.

I live in California, where the vehicle safety and pollution laws are strictest in the USA, and want to know about that specifically. What about the Canadian provinces of British Columbia, Ontario, and Quebec, which are possibly even stricter than California?

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    $\begingroup$ Welcome to Aviation Stack Exchange! There will be many roadworthiness requirements that airplanes won't meet if they aren't specifically designed to. The propeller will also be problematic for safety reasons. Also, it might be better to ask this on law.stackexchange.com; even though this question is about airplanes, it technically isn't about aviation because it's about the use of airplanes on the ground. $\endgroup$
    – Someone
    Dec 18, 2023 at 23:37
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    $\begingroup$ @Someone - This started at law.se. I recommended here. But yes, it does fall into both realms. $\endgroup$
    – WPNSGuy
    Dec 18, 2023 at 23:45
  • $\begingroup$ @WPNSGuy oh okay, thank you. I hadn't seen it there. @ CoastCityLapse00crashtest in that case, please disregard my prior suggestion of asking on Law SE. $\endgroup$
    – Someone
    Dec 18, 2023 at 23:47
  • $\begingroup$ Some people are trying to make the aircraft/car combo work: PAL-V website $\endgroup$
    – ROIMaison
    Dec 19, 2023 at 8:47
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    $\begingroup$ The biggest problem isn't mechanical. It's what do you do when someone runs their car into your $100K+ aircarplane. Can you afford the collision coverage for it? $\endgroup$ Dec 20, 2023 at 2:25

5 Answers 5

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When driving on roads there is no such category as flying car. You must meet the regulations for the vehicle class in question, and if the vehicle can also fly that is a separate matter.

The most expedient way to do this is to classify the vehicle as a motorcycle. This is defined as a vehicle with no more than three wheels such as this vehicle, the 1800lb Aptera, considered a trike. This is a normal configuration for most aircraft.

enter image description here

The regulations are far less stringent: no crash testing, no EPA (or CARB) emissions/fuel economy testing required, etc. In fact, here is the entire list of FMVSS regs that apply to motorcycles, mopeds or motor driven cycles, including three wheeled vehicles:

  1. FMVSS No. 106, Brake Hoses
  2. FMVSS No. 108, Lamps, Reflective Devices, and Associated Equipment
  3. FMVSS No. 111, Rearview Mirrors
  4. FMVSS No. 116, Motor Vehicle Brake Fluids
  5. FMVSS No. 119, New Pneumatic Tires for Vehicles Other Than Passenger Cars
  6. FMVSS No. 120, Tire Selection and Rims for Vehicles Other Than Passenger Cars
  7. FMVSS No. 122, Motorcycle Brake System
  8. FMVSS No. 123, Motorcycle Controls and Displays
  9. FMVSS No. 205, Glazing Materials
  10. 49 CFR 565, Vehicle Identification Number Content Requirement
  11. 49 CFR 574, Tire Identification and Recordkeeping
  12. 49 CFR 575.6(a)(2)(I), Consumer Information
  13. 49 CFR 576, Record Retention

So slap some wings on an Aptera (if they ever go into production) and go flying. Emissions paranoid places will love you because the aptera is electric, at least on the ground. You might be able to use the included battery for flight with a suitable electric motor and prop.

I'm not a fan of electric aircraft due to weight and flying cars have to make a lot of compromises, but this shows that a road legal vehicle can be aerodynamic and lightweight enough to use as a fuselage. Use of electric wheel motors on the ground means you don't have to have a spinning prop in traffic, and cutting back on battery capacity to accommodate local ground use only might have some chance of working.

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    $\begingroup$ Nah, with the included battery good luck getting a 1.5 ton body to fly. by adding wings and fuselage - a cessna skyhawk weighs 1.1 tons dry all inclusive. The Aptera would be 80% dead weight. $\endgroup$
    – Trish
    Dec 19, 2023 at 15:33
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    $\begingroup$ @Trish The Aptera was intended as an example only, but you are mistaken in stating that it weighs 3000lb. With the 60kw battery it is 1800lb, less than your skyhawk. That does not include any wings, propulsion or tail. I'm not a fan of electric aircraft and flying cars have to make a lot of compromises, but this shows that a road legal vehicle can be aerodynamic and lightweight. Use of electric wheel motors on the ground means you don't have to have a spinning prop in traffic, and cutting back on battery for local ground use only might have some chance of working. $\endgroup$
    – Pilothead
    Dec 19, 2023 at 17:49
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    $\begingroup$ @Pilothead The basic empty weight of a Skyhawk is less than 1700 pounds. It will be heavier with a pilot of course but the same is true of the Aptera. And 60 kWh is the equivalent of about 10 pounds of avgas. Per the POH a Skyhawk uses about that just for engine start, taxi, and takeoff. $\endgroup$
    – Chris
    Dec 19, 2023 at 18:31
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    $\begingroup$ @Chris LOL no, 60kWh is equivalent to the energy in 10 lbs of gas only for silly comparisons like burning the gas in a space heater vs. powering an electric heater with the battery. ICEs are horrifically inefficient at turning fuel into motion. 60 kWh into a motor is equivalent to more like 30 or 40 lbs of gas into an engine. $\endgroup$
    – nobody
    Dec 19, 2023 at 23:18
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    $\begingroup$ @nobody 10 lbs or 30 lbs, the point is it's very little for a Skyhawk. With 30 lbs of fuel you'd be around the legal VFR limit just to do one lap around the pattern! $\endgroup$
    – Chris
    Dec 20, 2023 at 4:10
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Unlikely. Some problems:

  • Putting additional lights on vehicles is illegal per CVC 24003 (California Vehicle Code). You'd need an aircraft with no navigation lights, landing light, etc.
  • Per CVC 26311, every wheel needs brakes.
  • Smog testing is probably an issue unless the airframe is old enough to be exempted.
  • CVC 27200 prescribes noise limits, which many aircraft would not comply with.
  • CVC 27400 forbids drivers from wearing headphones. This kind of fits in with the last one- pilots wear headsets for a reason!
  • Brakes are likely a problem. Motor vehicles are required to have service brakes and parking brakes, and they must be redundant in specific ways that aircraft brakes may not be. The maximum stopping distances may also be problematic.
  • You need windshield wipers.
  • You need a windshield constructed of "safety glazing material." Yours may or may not be already, but aircraft windshields are not required to be.

I'm sure this list is not exhaustive.

From a practical standpoint it would be a bad road vehicle, since it would be slow, have poor gas mileage, kick up rocks something awful, and have a spinny blade of death on it that will badly damage anything it touches but also can do thousands of dollars worth of damage to itself if it so much as hits a rock.

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    $\begingroup$ One can just turn off the navigation lights in order to comply with CVC 24003. Just installing them isn't a problem because commercial vehicles have other lights, especially advertisement screens on top of taxis and ride hailing vehicles. Aren't all wheels braked on an airplane, thus complying with CVC 26311? Airplanes obviously have service brakes for landing. Don't they also have parking brakes for the apron and hangar? $\endgroup$ Dec 19, 2023 at 4:54
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    $\begingroup$ @CoastCityLapse00crashtest Most aircraft have brakes on the mains but not on the nosewheel/tailwheel. Airplanes are quieter while taxiing slowly but they're still pretty darn loud and extremely loud at freeway speeds. Airplanes may or may not have a lower drag coefficient but using a propeller to drag yourself across the ground is really, really inefficient. The propeller can easily kick up rocks even at taxi throttle, but in any case you're going to be at quite a bit higher throttle to be at "reasonable road vehicle" speeds. $\endgroup$
    – Chris
    Dec 19, 2023 at 6:06
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    $\begingroup$ @CamilleGoudeseune I take offense to that. It is a spinny blade of life...for the pilot! $\endgroup$
    – DKNguyen
    Dec 19, 2023 at 15:40
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    $\begingroup$ @CoastCityLapse00crashtest "So, shouldn't they get better gas mileage when taxiing/driving?" No. Slow taxi speeds make the drag advantage of airplanes relative to cars irrelevant. Propellers also have inferior coupling for momentum transfer on the ground compared to driven wheels. Airplane engines and propellers are also optimized for high efficiency at flight speeds with little attention, if any, on the efficiency while taxiing. Indeed, taxxing efficiency is gladly sacrificed for flight efficiency. $\endgroup$
    – DKNguyen
    Dec 19, 2023 at 17:27
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    $\begingroup$ @CoastCityLapse00crashtest In other words, airplanes have terrible TERRIBLE efficiency on the ground. $\endgroup$
    – DKNguyen
    Dec 21, 2023 at 15:38
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It looks like someone is seriously underestimating the complexity of this enterprise.

I wouldn't be surprised if Aptera just attaches wings, propeller

Aptera can also just slap antennas integrated into the windshield that connects directly to the infotainment system

If we consider the above mentioned Aptera car, and a similar weight Cessna 172...

The wingspan of the Skyhawk is 11 meters. Subtract the fuselage from that, and you end up with wings about 4.5 meters. Which is the full length of the Aptera at 4.5 meters. So where do you put these when driving around town? Remember, they can't obstruct visibility.

In both realms, the vehicle is hauling around extra weight. On the ground, the flight control surfaces and prop. In the air, roadable suspension. A car can generally withstand a big pothole at 50mph. Not good for the car, but not critical. Go ahead and hit that same pothole at 50mph with the front wheel of the Cessna.

Crashworthiness? I can render your Cessna illegal to fly with a hammer. A couple of bashes in the wing, and you'll need, at the least, an inspection. Probably replace the applicable surfaces. Do the same with a car, and...meh. It still drives OK.

Can this be done? Probably. But it will NOT be cheap or easy.

A flyable Aptera will be significantly heavier than its road counterpart.

FAA, NHTSA, state inspections, all will come into play.

In response to the comment on 'visibility', here is a pic of an Aptera, and the Aptera with an overlay of a Cessna 172 wing. Pretty much to scale, both at 4.5m long.

A wing that size is needed to get an aircraft of that weight and power in the air.

enter image description here

Aptera pic from TheVerge. Wing planform from WikiPedia

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  • $\begingroup$ Yes, a few bashes of the flight control surfaces will render the plane inoperable. However, bashes that are hard enough to dent structural metal are uncommon enough that it isn't a problem. If they were such a huge problem, then bush planes wouldn't exist because they need to land on open fields. $\endgroup$ Dec 20, 2023 at 18:58
  • $\begingroup$ Also, the wings on an Aptera won't obstruct the legally required visibility because even with them folded up on the side, the visibility is still better than with people with 2.5 and 3.5 ton lifted pickup trucks. $\endgroup$ Dec 20, 2023 at 19:00
  • $\begingroup$ Arranged with intent you could obstruct the view with a school lunch tray.) $\endgroup$
    – Pilothead
    Dec 20, 2023 at 20:41
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    $\begingroup$ @Pilothead - Just going by the commenters statement of "folded up on the side". A lunch tray, you could put anywhere. A thing that is larger than the car...not so much. $\endgroup$
    – WPNSGuy
    Dec 20, 2023 at 20:44
  • $\begingroup$ @CoastCityLapse00crashtest Not sure that I understand your comments about lifted trucks. You can see quite well to the sides from those. It's everyone else who has a problem seeing past you. $\endgroup$
    – reirab
    Dec 21, 2023 at 22:54
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Sure, the CAA (FAA precursor) certified the Aerocar in 1956 and 6 examples were actually produced with folding wings and a road capable car body. There is still at least one that is airworthy. Granted the road regulations at the time we not quite the same as today.

If its gas or powerplant your worried about, the Porsche 3.2L Carrera engine was at one point certified for flight and there are MoGas conversions for common aviation engines out there. There are also aircraft running more modern Jet-A (read diesel) engines that you could use to build such a craft.

Dealing with the DOT to get it passed all the certifications for safety and keeping it light enough to be a functional airplane is going to be tricky at best but there is nothing explicitly preventing it.

However you might not be able to park it at home and you likely cant just land anywhere even if you "think" its for landing.

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  • $\begingroup$ Fortunately, keeping it light enough to fly while complying with even DOT crashworthiness regulations shouldn't be a problem. That is because DOT regulations are regarding property damage and occupant protection of the vehicle against a stationary object. Since the plane has to be so lightweight to fly anyway, it'll only have fairly small inertial forces that it has to resist at the speeds the 5-mph bumper and 30-mph crash tests are done at. Furthermore, since the 1990s, the bumper requirement has been lowered to 2.5 mph. I wouldn't be surprised if an unmodified airplane aces all crash tests. $\endgroup$ Dec 19, 2023 at 21:16
  • $\begingroup$ On the other hand, making a rail vehicle with folding wings that runs with freight trains that can also fly would be next to impossible without the chassis being completely made out of carbon fibre or titanium alloys. That is because the FRA has long required a buff strength of 800,000 pounds. Since 2020, however, the FRA has required PTC on all railroads, and the buff strength requirement with PTC is the EU standard of 300,000 lb. So, even a stainless steel airplane with folding wings can also be FRA-compliant under current engineering methods, though likely with poor gas mileage when flying. $\endgroup$ Dec 19, 2023 at 21:17
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Most foldable-wing aircraft aren't street legal, however, the Terrafugia Transition does have this as a design goal. It was announced in 2006 and its first flight was in 2009. Its first delivery was planned for 2011... and that still hasn't happened, nor is there even currently a firm delivery timeline. It did receive a Light-Sport Aircraft Airworthiness Certificate from the FAA in 2021, but then the company soon after announced that it was closing down its operations in the U.S. and moving to China. I haven't heard any updates on them since then.

Meeting the requirements to be legal to drive on streets in the U.S. while keeping its weight low enough to be reasonable for an airplane has been a huge challenge, to say the least.

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  • $\begingroup$ It could simply be that the company is not well-funded due to lack of investors rather than being an engineering challenge. After all, being able to start commercial production is way, way harder than engineering a hand-built one that works as intended. That is because production line equipment is super expensive. $\endgroup$ Dec 22, 2023 at 4:40
  • $\begingroup$ @CoastCityLapse00crashtest The problem for them has always been engineering, specifically, getting it to be street-legal while also able to fly with reasonable efficiency. Actually fabricating it is relatively cheap compared to designing it and getting it simultaneously certified for both flight and driving on roads. This is pretty much always the case with aviation, which is why manufacturers are still building aircraft based on designs originally certified in the 50s or 60s. (Engineer who has worked as such at one of the world's most capable aviation R&D testing facilities here.) $\endgroup$
    – reirab
    Dec 22, 2023 at 13:36
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    $\begingroup$ @CoastCityLapse00crashtest - It could also be that you are simply applying copious amounts of handwavium to the significant engineering and regulatory issues. No one has said this is "impossible". But it ain't easy or cheap. $\endgroup$
    – WPNSGuy
    Dec 22, 2023 at 13:56

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