Flying cars have been announced in popular
science and technology magazines for 70 years. So have jet-back-packs
to fly individuals. Why hasn't technology achieved this great and colorful goal?
There are two answers to this question. First is that an airplane is all about gaining lift from the design of its body shape and controlling the airplane in three dimensions. Airplanes do not have any extraneous objects on their surface nor are they too short or too long for the purpose of flying. The design object that can fly and be controlled effectively is wildly irrelevant to the squat motorized piece of material that carries people on the 2 dimensional road surface. Everything that makes an object airworthy is irrelevant to a car.
The second issue is equally important. At speeds under 60 miles an hour, of any moving object, even one foot off the ground the multiple shear layers of air, moving in different directions, will destabilize virtually any object, whether the object is a person with a jet-back-pack or even a vertical lift-off 5 ton jet.
Air
shear, that is wind going different directions within a few feet of
each layer is a phenomenon most people never notice. But it is real
and it makes flying a jet-back-pack like running on a surface covered
with marbles. The technology to accomplish this was built into several
V/STOL aircraft, generally designated Harriers. A few are in service,
most have a high accident rate and all have terribly complex
electronics designed to cope with the dangerous volatility of air shear at low speeds.
Most auto-planes could never maneuver in this air shear danger zone... which is why we land small planes at 50-60 mph.