Editing Flying car (section)

==Design==
A flying car must be capable of safe and reliable operation both on public roads and in the air. Current types require manual control by both a driver and a pilot. For mass adoption, it would also need to be environmentally friendly, able to fly without a fully qualified pilot at the controls, and come at affordable purchase and running costs.<ref>{{cite journal |last1=Pan |first1=Gaofeng |last2=Alouini |first2=Mohamed-Slim |title=Flying Car Transportation System: Advances, Techniques, and Challenges |journal=[[IEEE Access]] |date=2021 |volume=9 |pages=24586–24603 |doi=10.1109/ACCESS.2021.3056798 |doi-access=free|arxiv=2005.00832 |bibcode=2021IEEEA...924586P }}</ref>

Design configurations vary widely, from modified road vehicles such as the [[AVE Mizar]] at one extreme to modified aircraft such as the [[Plane Driven PD-1 Roadable Glastar|Plane Driven PD-1]] at the other. Most are dedicated flying car designs. While wheeled propulsion is necessary on the road, in the air lift may be generated by fixed wings, helicopter rotors or [[powered lift|direct engine power]]. The [[Alef Aeronautics|Alef Model A project]] offers an unusual configuration in which the body of the car is hollow and the sides are slabs; in the air it rolls sideways so that the slabs become a biplane wing. The cabin remains upright.<ref>{{Cite web|url=https://www.cnet.com/roadshow/news/alef-debuts-model-a-flying-car-and-hopes-to-sell-it-starting-in-2025/|title=Alef Debuts Model A Flying Car and Hopes to Sell It Starting in 2025|date=19 October 2022}}</ref>

===Lift===
Like other aircraft, lift in flight is provided by a [[fixed wing]], spinning [[rotorcraft|rotor]] or direct [[powered lift]]. The powered [[helicopter rotor]] and direct lift both offer [[VTOL]] capability, while the fixed wing and [[autogyro]] rotor take off conventionally from a runway.

The simplest and earliest approach was to take a driveable car and attach removable flying surfaces and propeller. However, when on the road, such a design must either tow its removable parts on a separate trailer or leave them behind and drive back to them before taking off again.

Other conventional takeoff fixed-wing designs, such as the [[Terrafugia Transition]], include folding wings that the car carries with it when driven on the road.

Vertical takeoff and landing (VTOL) is attractive, as it avoids the need for a runway and greatly increases operational flexibility. Typical designs include [[rotorcraft]] and ducted fan [[powered lift]] configurations.<ref>{{cite web|url= https://www.theregister.co.uk/2013/05/13/terrafugia_tfx_followup/|title=Your Flying Car? Delayed again, but you WILL get it, says Terrafugia|website=theregister.co.uk|date=13 May 2013|access-date=15 September 2013}}</ref> Most design concepts have inherent problems.

Rotorcraft include [[helicopter]]s with powered rotors and [[autogyro]]s with free-spinning rotors. For road use, a rotor must, like many naval helicopters, be either two-bladed or foldable. The [[quadcopter]] requires only a simple control system with no tail. The autogyro relies on a separate thrust system to build up airspeed, spin the rotor and generate lift. However, some autogyros have rotors that can be spun up on the ground and then disengaged, allowing the aircraft to jump-start vertically. The [[PAL-V Liberty]] is an example of the autogyro type.

Ducted-fan aircraft such as the [[Moller Skycar]] tend to easily lose stability and have been unable to travel at greater than 30–40 [[knot (unit)|knots]].<ref>{{cite web|url= http://www.haaretz.com/weekend/week-s-end/when-cars-fly-1.341214|title=When cars fly|website=haaretz.com|date=4 February 2011|access-date=18 October 2013}}</ref>

===Power===
The flying car places unique demands on the vehicle power train. For a given all-up weight, an aero engine must deliver higher power than its typical road equivalent. However, on the road the vehicle must handle well and not be overpowered. Power must also be diverted between the airborne and road drive mechanisms. Some designs therefore have multiple engines, with the road engine being supplemented, or even replaced by, additional flight engines.

As with other vehicles, power has traditionally been supplied by [[internal combustion engine]]s, but electric power is undergoing rapid development. It is coming into increasing use on road vehicles, but the weight of the batteries currently makes it unsuited to aircraft. However its low environmental signature makes it attractive for the short trips and dense urban environments envisaged for the flying car.

On the road, most flying cars drive the road wheels in the conventional way. A few use the aircraft propeller in similar manner to an [[airboat]], but this is inefficient.

In the air, a flying car will typically obtain forward thrust from one or more propellers or ducted fans. A few have a powered [[helicopter rotor]]. Jet engines are not used due to the ground hazard posed by the hot, high-velocity exhaust stream.

===Safety===
In order to operate safely, a flying car must be certified independently as both a road vehicle and an aircraft, by the respective authorities. The person controlling the vehicle must also be licensed as both driver and pilot, and the vehicle maintained according to both regimes.

Mechanically, the requirements of powered flight are so challenging that every opportunity must be taken to keep weight to a minimum. A typical airframe is therefore lightweight and easily damaged. On the other hand, a road vehicle must be able to withstand significant impact loads from casual incidents while stationary, as well as low-speed and high-speed impacts, and the high strength this demands can add considerable weight. A practical flying car must be both strong enough to pass road safety standards and light enough to fly. Any propeller or rotor blade also creates a hazard to passers-by when on the ground, especially if it is spinning; they must be permanently shrouded, or folded away on landing.

For widespread adoption, as envisaged in the near future, it will not be practicable for every driver to qualify as a pilot and the rigorous maintenance currently demanded for aircraft will be uneconomic. Flying cars will have to become largely [[autonomous vehicle|autonomous]] and highly reliable. The density of traffic will require automated routing and collision-avoidance systems. To manage the inevitable periodic failures and emergency landings, there will need to be sufficient designated landing sites across built-up areas. In addition, poor weather conditions could make the craft unsafe to fly.<ref>{{cite web|url=http://auto.howstuffworks.com/5-reasons-you-dont-want-flying-car.htm|title=Top 5 Reasons You Don't Want a Flying Car|website=howstuffworks.com|date=3 October 2011 |access-date=10 October 2013}}</ref>

Regulatory regimes are being developed in anticipation of a large increase in the numbers of autonomous flying cars and [[personal air vehicle]]s in the near future, and compliance with these regimes will be necessary for safe flight.{{citation needed|date=May 2023}}{{Where|date=May 2023}}

===Control===
A basic flying car requires the person at the controls to be both a qualified road driver and aircraft pilot. This is impractical for the majority of people and so wider adoption will require computer systems to de-skill piloting. These skills include aircraft manoeuvring, navigation and emergency procedures, all in potentially crowded airspace. The onboard control system will also need to interact with other systems such as air traffic control and collision-risk monitoring. A practical flying car may need to be capable of full [[autonomous vehicle|autonomy]], in which people are present only as passengers.

===Environment===
A flying car capable of widespread use must operate acceptably within a heavily populated urban environment. The lift and propulsion systems must be quiet enough not to cause a nuisance, and must not create excessive pollution. For example, pollution emissions standards for road vehicles must be met.

The clear environmental benefits of electric power are a strong incentive for its development.

===Cost===
The needs for the propulsion system to be both small and powerful, the vehicle structure both light and strong, and the control systems fully integrated and autonomous, can only be met at present, if at all, using advanced and expensive technologies. This may prove a significant barrier to widespread adoption.<ref>{{cite book |title=The Millennium Book: Your Essential All-purpose Guide to the Year 2000|author=Gail Collins|author2=Dan Collins|date=1 December 1990|publisher=Main Street Books|isbn=978-0-385-41165-3|url=https://books.google.com/books?id=aZGZPAAACAAJ}}</ref>

Flying cars are used for relatively short distances at high frequency. They travel at lower speeds and altitudes than conventional passenger aircraft. However optimal fuel efficiency for aeroplanes is obtained at higher speeds and altitudes, so a flying car's energy efficiency will be lower than that of a conventional aircraft.<ref>Barney L. Capehart (2007). ''Encyclopedia of Energy Engineering and Technology'', Volume 1. CRC Press. {{ISBN|0-8493-3653-8}}, {{ISBN|978-0-8493-3653-9}}.</ref> Similarly, the flying car's road performance is compromised by the requirements of flight and the need to carry around the various extra parts, so it is also less economical than a conventional motor car.