Electric aircraft
An electric aircraft is an aircraft powered by electricity.
Electric aircraft are seen as a way to reduce the environmental effects of aviation, providing near zero emissions and quieter flights.
Electricity may be supplied by a variety of methods, the most common being batteries.
Most have electric motors driving propellers or turbines.
Crewed flights in an electrically powered airship go back to the 19th century, and to 1917 for a tethered helicopter.
Electrically powered model aircraft have been flown at least since 1957, preceding the small unmanned aerial vehicles or drones used today. Small UAS could be used for parcel deliveries, and larger ones for long-endurance applications: aerial imagery, surveillance, telecommunications.
The first crewed free flight by an electrically powered aeroplane, the MB-E1, was made in 1973, and most crewed electric aircraft today are still only experimental prototypes. The world's first serially produced self-launching, manned electric aircraft with EASA type certification since 2006 and a patented wing-integrated battery system, the Lange E1 Antares, completed its maiden flight in 1999; since 2004, more than 100 aircraft of this type have been delivered, totalling more than 165,000 electric flight hours to date.
Between 2015 and 2016, Solar Impulse 2 completed a circumnavigation of the Earth using solar power.
Electric VTOL aircraft or personal air vehicles are being considered for urban air mobility.
Electric commercial airliners could lower operating costs.
History
By May 2018 almost 100 electric aircraft were known to be under development.This was up from 70 the previous year and included 60% from startups, 32% from aerospace incumbents, half of them major OEMs and 8% from academic, government organizations and non-aerospace companies, mainly from Europe and the U.S.. Mostly urban air taxis and general aviation aircraft, a majority are battery-powered, while some are hybrid-electric, most of these being larger airliners. By May 2019, the number of known electric aircraft development programmes was closer to 170, with a majority of them aimed at the urban air taxi role.
By 2022, about 100 electric aircraft designs were under development worldwide.
By 2023, the number of sustainable aircraft concepts under development was estimated at up to 700.
Airships
The use of electricity for aircraft propulsion was first experimented with during the development of the airship in the latter part of the nineteenth century. On 8 October 1883, Gaston Tissandier flew the first electrically powered airship. The following year, Charles Renard and Arthur Krebs flew La France with a more powerful motor. Even with the lifting capacity of an airship, the heavy accumulators needed to store the electricity severely limited the speed and range of such early airships.Fully electric airships are expected to be available again by the 2030s.
Unmanned aircraft
In 1909, an electric free flight model was claimed to have been flown eight minutes, but this claim has been disputed by the builder of the first recorded electric radio-controlled model aircraft flight in 1957. Power density for electric flight was problematic even for small models.File:Pathfinder Plus solar aircraft over Hawaii.jpg|thumb|The NASA Pathfinder Plus electric-powered unmanned aerial vehicle
NASA's Pathfinder, Pathfinder Plus, Centurion, and Helios were a series of solar and fuel cell system–powered unmanned aerial vehicles developed by AeroVironment, Inc. from 1983 until 2003 under NASA's Environmental Research Aircraft and Sensor Technology program. On September 11, 1995, Pathfinder set an unofficial altitude record for solar-powered aircraft of during a 12-hour flight from NASA Dryden. After further modifications, the aircraft was moved to the U.S. Navy's Pacific Missile Range Facility on the Hawaiian island of Kauai. On July 7, 1997, Pathfinder raised the altitude record for solar–powered aircraft to, which was also the record for propeller–driven aircraft.
On August 6, 1998, Pathfinder Plus raised the national altitude record to for solar-powered and propeller-driven aircraft.
On August 14, 2001, Helios set an altitude record of – the record for FAI class U, and FAI class U-1.d as well as the altitude record for propeller–driven aircraft. On June 26, 2003, the Helios prototype broke up and fell into the Pacific Ocean off Hawaii after the aircraft encountered turbulence, ending the program.
In 2005, AC Propulsion flew an unmanned airplane named "SoLong" for 48 hours non-stop, propelled entirely by solar energy. This was the first such around-the-clock flight, on energy stored in the batteries mounted on the aircraft.
The QinetiQ Zephyr is a lightweight solar-powered unmanned aerial vehicle. As of 23 July 2010 it holds the endurance record for an unmanned aerial vehicle of over 2 weeks. It is of carbon fiber-reinforced polymer construction, the 2010 version weighing with a span of . During the day it uses sunlight to charge lithium-sulphur batteries, which power the aircraft at night. In July 2010 a Zephyr made a world record UAV endurance flight of 336 hours, 22 minutes and 8 seconds and also set an altitude record of for FAI class U-1.c.
Vertical flight
For a tethered device such as an air observation platform, it is possible to run the power up the tether. In an attempt to create a more practical solution than the clumsy balloons then in use, the Austro-Hungarian Petróczy-Kármán-Žurovec PKZ-1 electric-powered helicopter was flown in 1917. It had a specially designed continuous-rated electric motor made by Austro-Daimler that was powered by a cable connected to a DC generator on the ground. However, electric motors were not yet powerful enough for such applications and the motor burned out after only a few flights.In 1964, William C. Brown at Raytheon flew a model helicopter that received all of the power needed for flight by microwave power transmission.
The world's first large-scale all-electric tilt-rotor was the AgustaWestland Project Zero unmanned aerial vehicle technology demonstrator, which performed unmanned tethered fights on ground power in June 2011, less than six months after the company gave the official go-ahead.
The first free-flying electric helicopter was the Solution F/Chretien Helicopter, developed by Pascal Chretien in Venelles, France. It went from computer-aided design concept on September 10, 2010, to first flight in August 2011, in under a year.
In September 2016, Martine Rothblatt and Tier1 Engineering successfully tested an electric-powered helicopter. The five minute flight reached an altitude of with a peak speed of. The Robinson R44 helicopter was modified with two three-phase permanent magnet synchronous YASA Motors, weighing, plus 11 Lithium polymer batteries from Brammo weighing. It later flew for 20 minutes in 2016.
On December 7, 2018, Tier 1 Engineering flew an electric, battery-powered R44 over at and an altitude of, setting a Guinness World Record for the farthest distance.
In June 2017, Airbus presented its CityAirbus, an electrically powered VTOL aircraft demonstrator. The multirotor aircraft is intended to carry four passengers, with a pilot initially and to become self-piloted when regulations allow. Its first unmanned flight was scheduled for the end of 2018 with manned flights planned to follow in 2019. Type certification and commercial introduction are planned for 2023.
Ingenuity, the NASA small uncrewed aerial system which flew on Mars in 2021 to become the first extraterrestrial aircraft, has a single pair of coaxial rotors. The Dragonfly rotorcraft lander should be the second aircraft and rotorcraft to operate on another astronomical object than Earth. It should be flying in the atmosphere of Titan starting around 2034. The VTOL capabilities is incorporated in order to move the lander and its sensors at various locations farther from the landing site.
Experimental demonstrators
On 21 October 1973, the Militky MB-E1, a Brditschka HB-3 motor glider converted by Fred Militky and piloted by Heino Brditschka, flew for 9 minutes from Linz in Austria: the first electric aircraft to fly under its own power with a person on board, powered by Nickel–cadmium batteries. NiCad batteries have a higher energy density than lead–acid batteries, needed to power a heavier than air aircraft.Following successful human-powered flight, a relaunched Kremer prize allowed the crew to store energy before takeoff. In the 1980s, several such designs stored electricity generated by pedalling, including the MIT Monarch and the Aerovironment Bionic Bat.
The Boeing-led FCD project uses a Diamond HK-36 Super Dimona motor glider as a research test bed for a hydrogen fuel cell powered light airplane. Successful flights took place in February and March 2008.
The European Commission has financed many low TRL projects for innovative electric or hybrid propulsion aircraft. The ENFICA-FC is a project of the European Commission, to study and demonstrate an all-electric aircraft with fuel-cells as the main or auxiliary power system. During the three-year project, a fuel-cell based power system was designed and first flown in a Rapid 200FC ultralight aircraft on 20 May 2010.
The first NASA Green Flight Challenge took place in 2011 and was won by a Pipistrel Taurus G4 on 3 October 2011.
In 2013, Chip Yates demonstrated that the world's fastest electric airplane, a Long ESA, a modified Rutan Long-EZ, could outperform a gasoline-powered Cessna and other aircraft in a series of trials verified by the Fédération Aéronautique Internationale. The Long ESA was found to be less expensive, have a higher maximum speed, and higher rate of climb, partly due to the ability of the aircraft to maintain performance at altitude as low air density does not impair engine performance.
In 2017, Siemens used a modified Extra EA-300 acrobatic airplane, the 330LE, to set two new records: on March 23 at the Dinslaken Schwarze Heide airfield in Germany, the aircraft reached a top speed of around over and the next day, it became the first glider towing electric aircraft.
NASA was developing the X-57 Maxwell to demonstrate technology to reduce fuel use, emissions, and noise, but the program was cancelled due to problems with the propulsion system. Modified from a Tecnam P2006T, the X-57 will have 14 electric motors driving propellers mounted on the wing leading edges. In July 2017, Scaled Composites is modifying a first P2006T by replacing the piston engines with electric motors, to fly early in 2018, then will move the motors to the wingtips to increase propulsive efficiency and finally will install the high aspect ratio wing with 12 smaller props.
US/UK startup ZeroAvia develops zero-emissions fuel-cell propulsion systems for small aircraft, and tests its HyFlyer in Orkney supported by £2.7 million from the UK government.