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Flying Cars

What is with the obsession with people trying to build flying cars? Yes, cars and planes are both vehicles, but that is where the comparison ends. A washing machine and a dishwasher are both appliances that use water to clean things you put inside them, but you would never try to build a machine that does both tasks.
Flying through the air requires a special mix of features, and a century of experimentation has taught us how to optimize these. Similarly, a good car requires a different set of optimized attributes. Planes are designed to be in the air. Cars are designed to drive on roads.
For an aircraft, lightness is essential. Put too many non-critical items on a plane and it’s either going to be too massive to ever get off the ground, or require so much power that it will have no payload capacity (never mind be ridiculously inefficient even if it could make it into the air).
Aerodynamically, planes need wings to fly efficiently - the bigger the wingspan the better. Even with a lifting body design, you can’t make a wing efficient enough to lift a car like object anywhere inside the width restrictions of a traffic lane, and if your flying car is going to be four lanes wide, it’s not going to be very practical as a car. Just give it wings, and make it a plane, and call it a plane.
Cars need large wheels for stability and comfort (again the bigger the better), and soft spongy suspensions to soak up the bumps. They need brakes to be able to stop quickly, and they only need controls to navigate in two dimensions, not three.
If your car has a mechanical problem, it’s inconvenient, but not life threatening. You can pull off to the side of the road and call for help. You don’t have that option when in the air. Car engines can therefore be tuned for performance (and cost) over reliability.
Cars are built strong to both protect the occupants in a crash, and also to be resilient to minor bangs, scratches, knocks, and bumps. Cosmetically a particular car might not look great, but it will (probably) get you from A to B. Aircraft are fragile with critical safety alignments; any one of which could be catastrophic if tolerances are out. Whilst aircraft designers want you to be safe and do all they can, planes are not fitted with airbags and crumple zones and don’t undergo side impact studies because, well, being brutally honest, other than a heavy landing, ditching in water, or collision with a few birds, it’s hard to imagine how to engineer a plane to be ‘safe enough’ for any other kind of accident that might occur.
Planes require long runways to accelerate and decelerate from rest to their flying speeds and back again. We make dedicated locations for these maneuvers, they are called airports, and the space around these locations is carefully controlled. Even if you could build a flying car, the infrastructure around most roads (bridges, telegraph poles, buildings, wires, fences, lamp posts, signs, trees … ) are not compatible. Even skilled helicopter pilots prefer to use dedicated helipads and only land in non-optimal locations if there really is no other choice. Trying to get into the air with your car/plane from your local high street would be a recipe for disaster.
For stability, a car needs downforce to keep it safely on the road, and also for traction to transfer power to the road. Planes, need upforce! Engineers design cars to stick to the road and not lift at speed. Cars have voluminous passenger cabins to transport people in comfort, and this is aerodynamically inefficient. It’s not just the killer of frontal drag, there is the issue of weathercocking stability from the drag associated with the side profile in cross-winds.
We have rules of the road (laws) and flow controls (traffic lights, roundabouts, stop signs, speed limits) to help avoid collisions (and motor vehicles can stop on a dime, relatively speaking). We have air traffic control to shepherd many orders of magnitude fewer aircraft, but this would not scale to the number of cars (and remember, you can’t just ‘stop’ a plane in mid-air to pause it, and even slowing it down requires forward planning). Anything more than a small number of flying personal vehicles means we’re going to have to turn all control over to AI.
Stop this madness. Stop trying to make car/plane hybrids. Even if you could build such a Frankenstein Monster, it would be a very bad car, and a very bad plane. It would be so full of compromises and constraints that it would be terrible in both roles. Any remotely comparable dedicated single mode device would be orders of magnitude better (and a fraction of the price). Buy one of each!
Even hybrid car/drones are not the answer. There’s science why you can’t simply scale up a drone into a passenger carrying vehicle.
Just because it sounds cool, it does not mean it’s practical. Also, why stop with a car/plane hybrid? Anyone for a submarine/plane, or a boat/snowmobile? How about a combination toaster/rice machine to go with your vacuum/hair-dryer?
A century from now, we’re still going to have ‘regular’ cars, driving on conventional roads. We’re still going to have dedicated planes that arrive and depart from dedicated airports. Yes, we’ll have more lightweight delivery drones, and even some scaled up personal airborne (vaguely drone like) transportation devices, but these devices will be dedicated devices just for these tasks and will not drive on the road like conventional cars when they are not in the air (though they will allow take off and landing from locations other than airports).
I don’t think there’s a more quintessential view of the future than a flying car, but it’s not going to happen. Don’t get me wrong, I love cars, and I love planes, but I also love soup and chocolate pudding; some things don’t mix. This is not an article to put anyone down, I’m an engineer. This is all about celebrating the unique requirements and designs for both, and how to optimize them. A Bugatti is a fantastic piece of engineering and pretty close the pinnacle of what is possible for an automobile. Putting a set of wings on it would be as silly as mounting a set of four 21” alloy rims and racing slicks to the side of an F-18 fighter jet.

This is not a car. You could not park it in my garage. You could not drive it down the road. You could not drive it on the freeway. You could not take it to the supermarket. You could not park it downtown. It needs a runway to take off and land. It’s not a flying-car it’s a “flying car” <- Yes, I just used “air quotes”. It’s a plane with a fuselage made from Ford Pinto. Tragically, it also killed the designers when the starboard wing strut buckled in flight from being over stressed due to the excessive weight of the vehicle.
“Mark my words – a combination aeroplane and motor car is coming.”
– Henry Ford, 1940
In 1940, Henry Ford is quoted as saying, “Mark my words – a combination aeroplane and motor car is coming.” He was a great man, but wrong on this one. 80 years later, we’ve broken the sound barrier, walked on the moon, created the internet, and over half of humanity now has a smart phone, but we still don’t have flying cars. It’s not that we don’t know how to build planes, or build cars, it’s just there is no need to combine them.