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Capital city of the United Arab Emirates

 

This article is about the city. For the municipal region, see Abu Dhabi Central Capital District. For the emirate, see Emirate of Abu Dhabi. For other uses, see Abu Dhabi (disambiguation).

Capital city and metropolis in United Arab Emirates

Abu Dhabi

Abu Dhabi (Asia)

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Abu Dhabi أبوظبي
Capital city and metropolis
Abu Dhabi's skyline Emirates Palace Louvre Abu Dhabi Sheikh Zayed Grand Mosque Ferrari World
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Abu Dhabi Location of Abu Dhabi within the UAE Show map of United Arab Emirates

Coordinates: 24°28′N 54°22′E / 24.467°N 54.367°E / 24.467; 54.367Country United Arab EmiratesEmirate Abu DhabiMunicipal regionCentral Capital District^[1]Government

 • TypeMunicipality • BodyAbu Dhabi City Municipality • Director-General of City MunicipalitySaif Badr al-QubaisiArea

972 km² (375 sq mi)Elevation

27 m (89 ft)Population

2,189,860 • Rank2nd • Density2,250/km² (5,840/sq mi)DemonymsAbu Dhabian, DhabyaniGDP

 • TotalUS$ 118.4 billion (2023) • Per capitaUS$ 75,600 (2023)Time zoneUTC+4 (UAE Standard Time)Websitewww.tamm.abudhabi

Abu Dhabi^[a] is the capital city of the United Arab Emirates (UAE). The city is the seat of the Abu Dhabi Central Capital District, the capital city of the Emirate of Abu Dhabi, and the UAE's second-most populous city, after Dubai. The city is situated on a T-shaped island, extending into the Persian Gulf from the central-western coast of the UAE.

Abu Dhabi is located on an island in the Persian Gulf, off the Central West Coast. Most of the city and the Emirate reside on the mainland connected to the rest of the country. As of 2023^[update], Abu Dhabi's urban area had an estimated population of 2.5 million,^[5] out of 3.8 million in the emirate of Abu Dhabi.^[6] The Abu Dhabi Investment Authority (ADIA), headquartered in the city, is estimated to manage approximately US$1 trillion in assets, making it the world's third-largest sovereign wealth fund after Norway's Government Pension Fund Global and China's CIC.^[7][8] Abu Dhabi itself has over a trillion US dollars' worth of assets under management in a combination of various sovereign wealth funds headquartered there.^[9]

Abu Dhabi houses local and federal government offices and is the home of the United Arab Emirates Government and the Supreme Council for Financial and Economic Affairs. The city is home to the UAE's president, a member of the Al Nahyan family. Abu Dhabi's rapid development and urbanisation, coupled with the massive oil and gas reserves and production and relatively high average income, have transformed it into a large, developed metropolis. It is the country's centre of politics and industry, and a major culture and commerce centre. Abu Dhabi accounts for about two-thirds of the roughly $503 billion UAE economy.^[10]

The area surrounding Abu Dhabi abounds in archaeological evidence from historical civilisations, such as the Umm Al Nar Culture, which dates back to the third millennium BC. Other settlements were also found farther outside the modern city of Abu Dhabi, including the eastern^[11] and western regions of the Emirate.^[12] On December 2, 1971, Abu Dhabi, along with five other emirates, formed the United Arab Emirates (UAE).^[13] This union was marked by the establishment of a federal government and the appointment of Sheikh Zayed bin Sultan Al Nahyan as the first President of the UAE.

"Abu" is Arabic for father, and "Dhabi" is the Arabic word for gazelle. Abu Dhabi means "Father of Gazelle."^[14]

The Bani Yas, the tribe from which the Al Nahyan family are drawn, was originally settled in the Liwa Oasis in the Emirate's western region. This tribe was the most significant in the area, having over 20 subsections. In 1761, the discovery of fresh water by a hunting party led by Sheikh Dhiyab bin Isa Al Nahyan near the coast saw a settlement established there.^[14] A popular story is that the hunters were pursuing a gazelle, hence the name of the settlement. The Al Bu Falah subsection of the tribe were the first to establish the new settlement and remained the source of the tribal rulers.^[15] Originally consisting of a fort and twenty houses, within two years the town consisted of a settlement of some 400 houses. The fort remains at the centre of Abu Dhabi today, the Qasr Al Hosn.^[14]

The pearl diving business was a key industry prior to the discovery of oil reserves. According to a source about pearling, the Persian Gulf was the best location for pearls.^[16] The pearl industry boomed from the late 19th century through to the second decade of the 20th century, however it is believed to date back around 7,000 years. Pearl divers dive for one to three minutes and would have dived as many as thirty times per day. Air tanks and any other sort of mechanical device were forbidden. The divers had a leather nose clip and leather coverings on their fingers and big toes to protect them while they searched for oysters.^[17] The divers were not paid for a day's work but received a portion of the season's earnings.^[18] There are three main journey of pearl divers, happening between the 5th and 9th month each year. Summer was the busiest time. Pearl divers made very deep dives, about 50 dives were made a day, each about 3 minutes long.^[19]

In the 19th century, as a result of treaties (known as "truces" which gave the coast its name) entered into between Great Britain and the sheikhs of the Arab States of the Persian Gulf, Britain became the predominant influence in the area.^[20] The main purpose of British interest was to protect the trade route to India from pirates, hence, the earlier name for the area, the "Pirate Coast". After the suppression of piracy, other considerations came into play, such as a strategic need of the British to exclude other powers from the region. Following their withdrawal from India in the year 1947, the British maintained their influence in Abu Dhabi as interest in the oil potential of the Persian Gulf grew.^[21]

In the mid to late 1930s, as the pearl trade declined, interest grew in the oil possibilities of the region. On 5 January 1936, Petroleum Development Trucial Coast Ltd (PDTC), an associate company of the Iraq Petroleum Company, entered into a concession agreement with the ruler, Sheikh Shakhbut bin Sultan Al Nahyan, to explore for oil. This was followed by a seventy-five-year concession signed in January 1939. However, owing to the desert terrain, inland exploration was fraught with difficulties. In 1953, D'Arcy Exploration Company, the exploration arm of BP, obtained an offshore concession which was then transferred to a company created to operate the concession: Abu Dhabi Marine Areas (ADMA) was a joint venture between BP and Compagnie Française des Pétroles (later Total). In 1958, using a marine drilling platform, the ADMA Enterprise, oil was discovered in the Umm Shaif field at a depth of about 2,669 metres (8,755 ft). This was followed in 1959 by PDTC's onshore discovery well at Murban No.3.^[22]

ADMA discovered the Bu Hasa oil field in 1962 and the Lower Zakum oil field in 1963. Today, in addition to the oil fields mentioned, the main producing fields onshore are Asab, Sahil and Shah, and offshore are al-Bunduq, and Abu al-Bukhoosh.^[22]

Perceived mismanagement of the emirate's oil revenues, as well as fears of a pan-Arab uprising, led to the British backing a bloodless coup by Shakhbut's younger brother Zayed Al Nahyan on August 6, 1966.^[23]

This section needs expansion. You can help by adding missing information. (December 2025)

The city of Abu Dhabi is on the southeastern side of the Arabian Peninsula, adjoining the Persian Gulf. It is on an island less than 250 metres (820 ft) from the mainland and is joined to the mainland by the Maqta and Mussafah Bridges. A third, Sheikh Zayed Bridge, designed by Zaha Hadid, opened in late 2010. Abu Dhabi Island is also connected to Saadiyat Island by a five-lane motorway bridge. Al-Mafraq bridge connects the city to Reem Island and was completed in early 2011. This is a multi-layer interchange bridge and it has 27 lanes which allow roughly 25,000 automobiles to move per hour. There are three major bridges in the project, the largest has eight lanes, four leaving Abu Dhabi city and four coming in.^[24]

Most of Abu Dhabi city is located on the island itself, but it has many suburban districts on the mainland, for example, Khalifa City A, B, and C; Khalifa City Al Raha Beach;^[25] Al Bahia City A, B, and C; Al Shahama; Al Rahba; Between Two Bridges; Baniyas; Shamkha; Al Wathba and Mussafah Residential.

Gulf waters of Abu Dhabi holds the world's largest population of Indo-Pacific humpbacked dolphins.^[26][27][28] To the east of the island is the Mangrove National Park, located on Al Qurm Corniche. Al-Qurm (ٱلْقُرْم) is Arabic for "The Mangrove".^[29]

Abu Dhabi has a hot desert climate (Köppen climate classification BWh). Sunny blue skies can be expected throughout the year. The months of May through September are generally extremely hot and humid with maximum temperatures averaging above 40 °C (104 °F), mainly occurring during the peak summer months of July and August. During this time, sandstorms occur intermittently, in some cases reducing visibility to a few metres.^[30] Due to high humidity, especially in coastal areas, the heat index (or "feels-like" temperature) can be significantly higher than the actual air temperature.^{[citation needed]} Dust storms are common during the hot, dry months, affecting air quality and visibility.^{[citation needed]}

The cooler season is from November to March, which ranges between moderately hot to mild. This period also sees dense fog on some days and a few days of rain. On average, January is the coolest month of the year, while August is the hottest. Since the Tropic of Cancer passes through the emirate, the southern part falls within the Tropics. However, despite the coolest month having an 18.8 °C (65.8 °F) average, its climate is far too dry to be classed as tropical.

For its geography, Abu Dhabi has been twinned with:

Abu Dhabi City is the capital of the Emirate of Abu Dhabi, and the local government of Abu Dhabi is directly led by the Ruler of Abu Dhabi. Abu Dhabi is the largest and wealthiest of the seven emirates, and it plays a crucial role in the UAE's governance and economy. The Ruler has the executive authority to issue local laws, create or merge government departments, and appoint heads of departments. The Ruler of Abu Dhabi appoints the Abu Dhabi Executive Council to lead the day-to-day management of government affairs. The Department of Municipal Affairs is responsible for municipal affairs for the entire emirate. Abu Dhabi is part of the Central Capital District,^[b] which is separate from the eastern and western municipal regions of the Emirate of Abu Dhabi. The main settlement of the eastern region, officially "Al Ain Region" since a decree by Sheikh Khalifa in March 2017, is Al Ain City, and that of the western region, officially "Al Dhafra Region" as per the same decree,^[39][40] is Madinat Zayed.^[1][12]

The Government of the Emirate of Abu Dhabi officially leads both the city and greater emirate with agencies operating out of Abu Dhabi with branches in other cities. The Abu Dhabi Government has various agencies and organisations operating across the emirate such as the Abu Dhabi Urban Planning Council and the Regulation and Supervision Bureau, which are responsible for infrastructure projects in the city.

Because Abu Dhabi is the capital of the UAE, it also serves as the headquarters of the Federal government of the United Arab Emirates, the office of the President of the United Arab Emirates, and seat of the Federal Supreme Council.^[41]

The Abu Dhabi Government Media Office (ADGMO) was formed in 2019 and is responsible for representing the government in the media, organising press conferences for the emirate and monitoring local and international media. It is a state-sponsored organisation that communicates the latest developments in the capital, and the emirate's vision, values and traditions.^{[42][43][44][45]}

 

Abu Dhabi skyline as seen from the Marina

The city was planned under the guidance of Sheikh Zayed by Japanese architect Katsuhiko Takahashi in 1967 initially for a population of 40,000.^[46] The density of Abu Dhabi varies, with high employment density in the central area, high residential densities in central downtown and lower densities in the suburban districts. In the dense areas, most of the concentration is achieved with medium- and high-rise buildings. Abu Dhabi's skyscrapers such as the notable Burj Mohammed bin Rashid (World Trade Center Abu Dhabi), Etihad Towers, Abu Dhabi Investment Authority Tower,^[47] the National Bank of Abu Dhabi headquarters,^[48] the Baynunah (Hilton Hotel) Tower,^[49] and the Etisalat headquarters are usually found in the financial districts of Abu Dhabi.^[50] Other notable modern buildings include the Aldar Headquarters, the first circular skyscraper in the Middle East^[51] and the Emirates Palace with its design inspired by Arab heritage.^[52]

The development of tall buildings has been encouraged in the Abu Dhabi Plan 2030, which will lead to the construction of many new skyscrapers over the next decade, particularly in the expansion of Abu Dhabi's central business district such as the new developments on Al Maryah Island and Al Reem Island.^[53] Abu Dhabi already has a number of supertall skyscrapers under construction throughout the city. Some of the tallest buildings on the skyline include the 382 m (1,253.28 ft) Central Market Residential Tower, the 324 m (1,062.99 ft) The Landmark and the 74-story, 310 m (1,017.06 ft) Sky Tower, all of them completed. Also, many other skyscrapers over 150 m (492.13 ft) (500 ft) are either proposed or approved and could transform the city's skyline. As of July 2008^[update], there were 62 high-rise buildings 23 to 150 m (75.46 to 492.13 ft) under construction, approved for construction, or proposed for construction.^[54]

The Sheikh Zayed Grand Mosque represents a key fixture of the city's architectural patrimony. Its construction was initiated under the administration of the late President Sheikh Zayed bin Sultan Al Nahyan, a key figure in the foundation of the modern United Arab Emirates.^[55]

The mosque was constructed with materials from countries around the world, including Italy, Germany, Morocco, Pakistan, India, Turkey, Iran, China, the United Kingdom, New Zealand, Greece, and the United Arab Emirates.^[56] More than 3,000 workers and 38 contracting companies took part in the construction of the mosque. Consideration of durability motivated the choice of many materials specified in the design of the structure. These materials include marble, stone, gold, semi-precious stones, crystals, and ceramics. Construction began on 5 November 1996. The building is large enough to safely contain a maximum of approximately 41,000 people. The overall structure is 22,412 square metres (241,240 square feet). The internal prayer halls were initially opened in December 2007.^[55]

As one of the most visited buildings in the UAE, the Sheikh Zayed Grand Mosque Center was established to manage the day-to-day operations, as a place of worship and Friday gathering and as a centre of learning and discovery through its education and visitor programs.^[57]

In July 2019, the Grand Mosque was listed among the top global attractions by TripAdvisor. As a part of its Travelers Choice Awards, the travel website placed the architectural masterpiece on number three out of the 750 landmarks considered from 68 countries.^[58]

In May 2021, the Sheikh Zayed Grand Mosque Center attended the Arabian Travel Market 2021 exhibition. This was part of the centre's core strategy to be active in the religious and cultural aspects of society.^[59]

The Founder's Memorial, a monument and visitor centre in Abu Dhabi, United Arab Emirates (UAE) is a memorial to Sheikh Zayed bin Sultan Al Nahyan, the first President of the United Arab Emirates, who died in 2004. The memorial consists of an open Heritage Garden and Sanctuary Garden at the centre of which is a cubic pavilion housing The Constellation, an artwork dedicated to Zayed's memory.^[60]

The UAE Presidential Palace, Qaṣr Al-Waṭan ("Palace of the Nation"),^[61] opened to the public in March 2019.^[62][63] It was built on the grounds of Ladies beach and construction was finished in 2018. Historically, 'barza' refers to a majlis session during which important matters can be brought to the attention of a Sheikh. After the Great Hall, it is the largest space in the UAE's Presidential Palace which holds up to 300 guests.^[64]

The Abrahamic Family House, a multi-faith complex on Saadiyat Island, includes the Imam Al-Tayeb Mosque, St. Francis Church, and the Moses Ben Maimon Synagogue—the UAE's first purpose-built synagogue. The project was inaugurated on 16 February 2023 and officially opened to the public on 1 March 2023.^[65][66][67]

On 22 September 2019, the Department of Community Development (DCD) in Abu Dhabi held a ceremony to grant licenses to 17 churches and the first-ever traditional Hindu temple. The listed churches were Catholic, Orthodox and Protestant churches, including St Joseph's Cathedral. The initiative was taken under the slogan "A Call for Harmony", to allow people from all religions and cultures to practice their faith in the country.^[68]

Qasr Al Hosn is the oldest building in the Emirate of Abu Dhabi, built by the Bani Yas tribe in 1761. It was once the seat of the government and the palace of the ruling Al Nahyan family. Today, it is a museum open to all visitors portraying the history of Abu Dhabi and early lifestyles. It is where the visitors will notice the art Talli, a traditional form of decorative embroidery done by women, and the making of Al Sadu patterns which represent symbols of daily life. A three-screen mini-theatre is available which describes the traditional form of weaving practised by Bedouin women.^[69]

Abu Dhabi has several parks, gardens, a zoo, and more than 400 kilometres (249 miles) of coastline, of which 10 kilometres (6 miles) are public beaches.^[70]

• 
  The Lake Park
• 
  Mangroves at Mangrove National Park, near Al Qurm Corniche on Sheikh Zayed Bin Sultan Street in the eastern part of the city^[29]
• 
  Giraffe at Emirates Park Zoo in Al Bahiyah, near the Abu Dhabi–Dubai highway

The UAE's large hydrocarbon wealth gives it one of the highest GDP per capita in the world and Abu Dhabi owns the majority of these resources—95% of the oil and 92% of gas.^[71] Abu Dhabi thus holds 9% of the world's proven oil reserves (98.2bn barrels) and almost 5% of the world's natural gas (5.8 billion cubic metres or 200 billion cubic feet). As of April 2022, oil production in the UAE was about 3.0 million barrels per day (BPD).^[72] The UAE is looking to expand its maximum production capacity from approximately 4 million BPD to 5 million BPD by 2030.^[73] In recent years, the focus has turned to gas as increasing domestic consumption for power, desalination and reinjection of gas into oil fields increases demand. Gas extraction is not without its difficulties, however, as demonstrated by the sour gas project at Shah where the gas is rich in hydrogen sulfide content and expensive to develop and process.^[22]

In 2009, the government diversified its economic plans. Served by high oil prices, the country's non-oil and gas GDP outstripped that attributable to the energy sector. Non-oil and gas GDP now constitutes 64% of the UAE's total GDP. This trend is reflected in Abu Dhabi with substantial new investment in industry, real estate, tourism and retail. As Abu Dhabi is the largest oil producer of the UAE, it has reaped the most benefits from this trend. It has taken on an active diversification and liberalisation program to reduce the UAE's reliance on the hydrocarbon sector. This is evident in the emphasis on industrial diversification with the completion of free zones, Industrial City of Abu Dhabi, twofour54 Abu Dhabi media free zone and the construction of another, ICAD II, in the pipeline. There has also been a drive to promote tourism and real estate with the Abu Dhabi Tourism Authority and the Tourism and Development Investment Company undertaking several large-scale development projects. These will be served by improved transport infrastructure, with a new port, an expanded airport and a proposed rail link between Abu Dhabi and Dubai all in the development stages.^[74]

Abu Dhabi's Emirate is the wealthiest of the UAE in terms of Gross domestic product (GDP) and per capita income. More than $1 trillion is invested worldwide in the city. In 2010, the GDP per capita reached $49,600, which ranks ninth in the world. Taxation in Abu Dhabi, as in the rest of the UAE, is nil for a resident or a non-bank, non-oil company. Abu Dhabi is also planning many future projects sharing with the Cooperation Council for the Arab States of the Gulf (GCC) and taking 29% of all the GCC future plannings. The UAE has a fast-growing economy: in 2006 the per capita income grew by 9%, providing a GDP per capita of $49,700 and ranking third in the world at purchasing power parity.

Abu Dhabi's government is looking to expand revenue from oil and gas production to tourism and other things that would attract different types of people. This goal is seen in the amount of attention Abu Dhabi is giving its International Airport. The airport experienced a 30%+ growth in passenger usage in 2009.^[75] This idea of diversifying the economy is also seen in the Abu Dhabi Economic Vision 2030^[76] planned by the Abu Dhabi Urban Planning Council. In this plan, Abu Dhabi's economy will be sustainable and not dependent on any single source of revenue. More specifically the non-oil portion of income is planned to be increased from about 40% to about 70%.^[77] As of July 2019, Abu Dhabi allocated $163 million to finance global entertainment partners as part of its plan to diversify the economy and wean it off oil.^[78]

Many Hollywood and other national film production teams have used parts of the UAE as filming locations. Neighbouring Dubai gets a lot of attention, but in recent years Abu Dhabi has become a popular destination. The Etihad Towers and Emirates Palace Hotel were some of the city's landmarks used as filming locations for the movie Furious 7, in which cars rush through the building and smashed through the windows of the towers.^[79]

In 2018, Abu Dhabi launched Ghadan 21, a string of initiatives to diversify the economy. The total injection is AED 50 billion.^[80] There are four main areas these initiatives must fall under: business and investment, society, knowledge and innovation, and lifestyle. The first phase includes over 50 initiatives that reflect the priorities of citizens, residents and investors.^[81]

The desalinated water supply and power production are managed by the Abu Dhabi Water and Electricity Authority (ADWEA). As of 2006^[update], it supplied 560.2 MiGD (million imperial gallons per day) of water,^[82] while the water demand for 2005–06 was estimated to be 511 MiGD.^[83] The Environment Agency of Abu Dhabi (EAD) states that groundwater is the most significant source of water, as well as desalinated potable water, and treated sewage effluent. At 40.6 MiGD, the Umm Al Nar storage is the largest water source for Abu Dhabi, followed by the rivers Shuweihat and Taweelah.^[84] With falling groundwater level and rising population density, Abu Dhabi faces a severely acute water shortage. On average each Abu Dhabi resident uses 550 litres (120 imp gal; 150 US gal) of water per day.^[85] Abu Dhabi daily produces 1,532 tonnes of solid wastes which are dumped at three landfill sites by the Abu Dhabi Municipality.^[86][87] The daily domestic wastewater production is 330 MiGD and industrial waste water is 40 MiGD. A large portion of the sewerage flows as waste into streams and separation plants.^[87]

The city's per capita electricity consumption is about 41,000 kWh and the total supplied is 8,367 MW as of 2007^[update].^[88] The distribution of electricity is carried out by companies run by SCIPCO Power and APC Energy. As part of UAE's Energy Strategy 2050 to reduce the carbon emission of power generation by 70%, Noor Abu Dhabi solar park project which is the largest solar project in the world was completed on 2 July 2019.^[89][90][91] The Abu Dhabi Fire Service runs 13 fire stations that attend about 2,000 fire and rescue calls per year.

State-owned Etisalat and private du communication companies provide telephone and cell phone service to the city. Cellular coverage is extensive, and both GSM and CDMA (from Etisalat and Du) services are available. Etisalat, the government-owned telecommunications provider, held a virtual monopoly over telecommunication services in Abu Dhabi prior to the establishment of other, smaller telecommunications companies such as Emirates Integrated Telecommunications Company (EITC – better known as Du) in 2006. The Internet was introduced into Abu Dhabi in 1995. The current network is supported by a bandwidth of 6 GB, with 50,000 dialup and 150,000 broadband ports.

Etisalat announced implementing a fiber-to-the-home (FTTH) network in Abu Dhabi during the third quarter of 2009 to make the emirate the world's first city to have such a network.^[92]

Waterfront park

View of the Beach Rotana

A public park

Abu Dhabi in the 1960s and 70s was planned for a predicted topmost population of 600,000. Following the urban planning ideals of the time period, the city has high-density tower blocks and wide grid-pattern roads.^[93] The population density is at its apex on the most northerly part of the island. At this point, the main streets have a large amount of 20- to 30-story towers. These towers are in a rectangular pattern, and inside is an ordinary grid pattern of roads with low rise buildings such as 2-story villas or 6-story low-rise buildings.

Due to this planning, a modern city with tall offices, apartment buildings, broad boulevards, and busy shops is present. Principal thoroughfares are the Corniche, Airport Road, Sheikh Zayed Street, Hamdan Street, and Khalifa Street. Abu Dhabi is known in the region for its greenery; the former desert strip today includes numerous parks and gardens. The design of the inner city roads and main roads are quite organised. Starting from the Corniche, all horizontal streets are oddly numbered, while all vertical streets are evenly numbered. Thus, the Corniche is Street No. 1, Khalifa Street is Street No. 3, Hamdan Street is Street No. 5, Electra Street is Street No. 7, and so on. Conversely, Salam Street is Street No. 8.^[94]

Mail is generally delivered to post-office boxes only; however, there is door-to-door delivery for commercial organisations. There are many parks throughout the city. Entrance is usually free for children, however, there is often an entrance fee for adults. The Corniche, the city's seaside promenade, is about 10 kilometres (6.2 mi) in length, with gardens, playgrounds, and a BMX/skateboard ring.^[95]

In 2007, the Abu Dhabi Urban Planning Council (UPC) was established, which is the agency responsible for the future of Abu Dhabi's urban environments and the expert authority behind the visionary Plan Abu Dhabi 2030 Urban Structure Framework Plan that was published in September 2007.^[53] The UPC is also working on similar plans for the regions of Al-Ain and Al-Gharbia.

Because of the rapid development of Abu Dhabi, a number of challenges to the city's urban organisation have developed, among them:

• Today, the city's population far surpasses the original estimated maximum population when it was designed. This causes traffic congestion, a shortage of car parking spaces, and overcrowding.
• Although there is an addressing system for the city, it is not widely used, causing problems in describing building locations. Directions must often be given based on nearby landmarks.
• However, there is a new naming system under the name of Onwani which is overhauling the entire addressing system of the entire Abu Dhabi Emirate. Its phases have already been implemented and are a success. The addressing system is up to international standards.

Human rights organisations have heavily criticised violations of human rights in Abu Dhabi. As with other parts of the UAE, foreign workers are not given proper treatment^[96] and many companies (both government and private) have yet to improve working conditions.^[97]

In 2025, Abu Dhabi was ranked as the safest city in the world for the ninth year running by the statistical analysis website Numbeo.^[98]

Abu Dhabi ranks as the 67th most expensive city in the world and the second-most in the region behind Dubai.^[102]

As of 2014^[update], 477,000 of 2,650,000 people living in the emirate were UAE nationals. Approximately 80% of the population were expatriates.^[103] The median age in the emirate was about 30.1 years. The crude birth rate, as of 2005^[update], was 13.6%, while the crude death rate was about 2%.^[104]

Article 7 of the UAE's Provisional Constitution declares Islam the official state religion of the UAE.^[105]

The majority of the inhabitants of Abu Dhabi are migrant workers from Nepal, India, Pakistan, Russia, Ethiopia, Somalia, Bangladesh, Sri Lanka, the Philippines, China, Uganda, Vietnam, the United Kingdom, France, Italy, Tanzania and various countries from across the Arab world. Some of these expatriates have been in the country for decades with only a few of them awarded citizenship.^[106] Consequently, English, Hindi-Urdu (Hindustani), Malayalam, Tamil, Telugu, Gujarati, Marathi, Tulu, Somali, Tigrinya, Amharic and Bengali are widely spoken.^[107]

The native-born population are Arabic-speaking Arabs who are part of a clan-based society. The Al Nahyan family, part of the al-Falah branch of the Bani Yas clan, rules the emirate and has a central place in society.^[108] There are also Arabs who are from other parts of the Arab world.

Rapidly developing transportation in Abu Dhabi city is anchored by vast systems of highways connecting various islands and suburbs together alongside expanding public and private transport options.^[109]

The main Abu Dhabi island is connected by three vast highways with their own bridges, the oldest of which is Al Maqta Bridge, built in 1968 as the first connection to the previously small fishing village on the island,^[110] now part of the E22 highway. The second Mussafah Bridge was opened in 1977,^[111] now part of the E20 highway that transforms into Khaleej Al Arabi Street, and the third bridge was the Sheikh Zayed Bridge opened in 2010, now part of the E10 highway and Sheikh Zayed Road, all of which connect the entire island to the Corniche Road, the 8 km promenade and beach at the tip of the island that overlooks the Persian Gulf.^[29] As the city expands, new bridges and roads have been constructed, or are currently under construction to link the main island with Al Maryah Island, Al Reem Island, Saadiyat Island, and other previously undeveloped islands.^[109] For example, in 2023, Sheikh Khaled bin Mohamed Al Nahyan inaugurated the Umm Yifeenah Bridge, an 11 km highway connection between Al Reem Island and Sheikh Zayed bin Sultan Street.^[112] This change, and many other, are a part of Abu Dhabi's 2030 Urban Structure Framework Plan.^[113]

Zayed International Airport (AUH) is the city's main aviation hub and the second busiest airport in the UAE. Passenger numbers at Zayed International Airport rose by 17.2 percent in 2015, with more than 23 million travelers passing through its terminals during that year. A second runway and new terminal was also built recently.^[114] In July 2024, it was reported that the airport launched the world's first-of-its-kind "Smart Travel" biometric.^[115]

On 30 June 2019, the Department of Community Development (DCD) in Abu Dhabi officially inaugurated a multi-faith prayer room at Zayed International Airport. Located away from the main airport, the prayer room aims at enhancing the country's "position as an international hub for tolerance".^[116]

Abu Dhabi City is additionally served by the Al Bateen Executive Airport, situated on the main Abu Dhabi island, which was the old international airport for Abu Dhabi until AUH opened in 1982. The airport underwent renovation and expansion in 2022 to accommodate twin-aisle jets and resumed operation to private, business, and VIP traffic in addition to hosting an Abu Dhabi Police search and rescue base.^[117]

On December 5, 2024, Zayed International Airport in Abu Dhabi (AUH) won the title of "World's Most Beautiful Airport" at the Prix Versailles, a prestigious award for architecture and design. The award recognised its impressive architectural design in the Airports category. (WAM)^[118]

Abu Dhabi City is connected to the second phase of the Etihad Rail network, completed in 2023, for freight operations across the seven emirates. Passenger traffic has been confirmed and will allow for travel from Abu Dhabi city to other emirates on the network, however no date on commencement of operation has been set.^[119]

Public transport systems in Abu Dhabi include public buses, taxis, ferries, and hydroplanes.^[120] A massive expansion of public transport is anticipated within the framework of the government's Surface Transport Master Plan 2030.^[121] The expansion was expected to see 130 km (81 mi) of metro and 340 km (210 mi) of tramways and bus rapid transit (BRT) routes. The city has nonetheless planned for further smart public transport options in various areas within the city, such as Yas Island and Saadiyat Island, in addition to expected rail service to other nearby cities.^[122]

The first town bus entered service in about 1969 but this was all part of a very informal service. There are other inter-city buses departing the Abu Dhabi central bus station; these inter-city buses are not only intra-emirate buses, but also inter-emirate services. On 30 June 2008, the Department of Transport began public bus service in Abu Dhabi with four routes.^[123] There are also public buses serving the airport. In an attempt to entice people to use the bus system, all routes were zero-fare until the end of 2008.^[124] The four routes, which operate between 6 am and midnight every day, run at a frequency of 10 to 20 minutes.^[124] Within the first week of service, the bus network had seen high usage. Some of the buses, which have a maximum capacity of 45 passengers, only had room for standing left. Some bus drivers reported as many as 100 passengers on a bus at one time.^[125] Due to the new, zero-fare bus service success, many taxi drivers were losing business. Taxi drivers have seen a considerable decrease in the demand for taxis while lines were forming for the buses.^[126]

As of 2021, the Abu Dhabi public bus system had completed 53.3 million passenger trips, with a fleet of 583 buses for the city of Abu Dhabi.^[127]

In 2022, Abu Dhabi launched autonomous self-driving public transport options in Yas Island and Saadiyat Island. The route in Saadiyat Island stops at cultural and tourist stops such as Louvre Abu Dhabi, NYU Abu Dhabi, and Sorbonne University Abu Dhabi whereas the Yas Island route focuses on the attractions in the island such as Ferrari World Abu Dhabi. The expansion include autonomous trams (Automated Rapid Transit or "ART"), taxis, and minibuses.^[6][128]

During October 2023, the Integrated Transport Centre (ITC) launched the ART Service on mainland Abu Dhabi as a pilot phase as part of the Smart Mobility project. It spans approximately 27 kilometres from Reem Mall, Al Reem Island, until Marina Mall, serving 25 stations in total.^[129]

In 2025, WeRide and Uber announced the launch of Level 4 fully driverless Robotaxi commercial operations. Public commercial operations commenced on 26 November without a vehicle specialist inside the AV, starting with Yas Island. This initiative is supported by Abu Dhabi's Integrated Transport Centre.^[130]

The Emirate has many ports. One is Port Zayed. The others are Musaffah Port and Khalifa Port, which opened in 2012.^[131] They are owned by Abu Dhabi Ports Company and managed by Abu Dhabi Terminals.^[132] Water transport includes water taxis which can accommodate up to 12 passengers, and ferries which can carry up to 100 passengers on board. Water taxis can be hired for point-to-point travel across the city's waterways, offering a convenient option for shorter trips, and ferry transport system is a convenient and scenic way to travel between the city's islands and mainland.^[133]

In 2021, the number of passengers who used public ferries reached 114,093.^[127]

Abu Dhabi introduced four toll gates in 2021 on all bridges (Sheikh Zayed Bridge, Maqtaa Bridge, Mussafah Bridge, and Sheikh Khalifa Bridge) entering the main Abu Dhabi island that only operate during peak hours, and by year-end had over 1.8 million registered cars in the system. Drivers must manually create an account to add balance to their toll gate allowance. Crossing the toll gate costs 4 AED.^[127] Abu Dhabi's toll gate system, known as Darb, is aimed at reducing traffic congestion and promoting smoother traffic flow. Drivers must register their vehicles on the Darb app or the official website. The system automatically deducts the toll charges from a prepaid account.^[134]

Abu Dhabi's first flying taxi vertiport will open at the Zayed Port Cruise Terminal by late 2025.^[135] It will serve helicopters and eVTOLs, offering direct access to Saadiyat Island, the Corniche, and the Louvre Abu Dhabi.

Abu Dhabi has a diverse and multicultural society.^[136] The city's cultural imprint as a small, ethnically homogeneous pearling community was changed with the arrival of other ethnic groups and nationals—first by the Iranians in the early 1900s, and later by various African, Asian, European, and Middle Eastern ethnicities in the 1950s and 1960s. Abu Dhabi has been criticised for perpetuating a class-based society, where migrant workers are in the lower classes, and suffer abuse which "is endemic to the system".^[137]

Major holidays in Abu Dhabi include Eid al Fitr which marks the end of Ramadan, Eid ul-Adha which marks the end of Hajj, and National Day (2 December) which marks the formation of the United Arab Emirates.^[138]

This unique socioeconomic development in the Persian Gulf has meant that Abu Dhabi is generally more tolerant than its neighbours, including Saudi Arabia.^[139] Emiratis have been known for their tolerance; Christian churches, Hindu temples, Sikh gurdwaras (with the first synagogue commencing construction in 2020), and Buddhist temples can be found alongside mosques. The cosmopolitan atmosphere is gradually growing; as a result, there are a variety of African, Asian, European, Middle Eastern, and Western schools, cultural centres, and themed restaurants.

Abu Dhabi is home to several cultural institutions, including the Cultural Foundation and the National Theater. The Cultural Foundation, while closed for reconstruction as of spring 2011, is home to the UAE Public Library and Cultural Center.^[140] Various cultural societies such as the Abu Dhabi Classical Music Society have a strong and visible following in the city. The recently launched Emirates Foundation offers grants in support of the arts and to advance science and technology, education, environmental protection, and social development. The International Prize for Arabic Fiction (IPAF) will be based in Abu Dhabi. The city also stages hundreds of conferences and exhibitions each year in its state-of-the-art venues, including the Abu Dhabi National Exhibition Centre (ADNEC), which is the Persian Gulf's largest exhibition centre and welcomes around 1.8  million visitors every year.^[141]

The Red Bull Air Race World Series has been a spectacular sporting staple for the city for many years, bringing tens of thousands to the waterfront.^[142] Another major event is the Abu Dhabi International Petroleum Exhibition and Conference (ADIPEC).^[143]

The diversity of cuisine in Abu Dhabi reflects the cosmopolitan nature of society. Arab food is trendy and is available everywhere in the city, from the small shawarma to the upscale restaurants in the city's many hotels. Fast food and South Asian cuisine are also trendy and are widely available. The sale and consumption of pork, though not illegal, is regulated and sold only to non-Muslims in designated areas.^[144] Similarly, the sale of alcoholic beverages is regulated. A liquor permit is required to purchase alcohol; however, alcohol is^{[further explanation needed]} available in bars and restaurants within four or five stars hotels. Shisha and qahwa boutiques are also popular in Abu Dhabi.

Poetry in Abu Dhabi and the UAE is highly regarded and often centres around satire, religion, family, chivalry, and love. According to an article from an Abu Dhabi tourism page, sheikhs, teachers, sailors, and princes make up a large bulk of the poets within the UAE. al-Khalil ibn Ahmad al-Farahidi formed a unique form of poetry to the UAE in the 8th century and was written in 16 metre. Another Emirati poet, Ibn Daher, is from the 17th century. Daher is important because he used Nabati poetry (AKA Bedouin poetry), a type of poetry written in the vernacular instead of classical/religious Arabic. Other important poets from the UAE are Mubarak Al Oqaili (1880–1954), Salem bin Ali al Owais (1887–1959), and Abdulla bin Sulayem (1905–1976). These poets made headway in Classical Arabic poetry as opposed to the Nabati poetry of the 17th century.^[145]

Today in Abu Dhabi, a group called the Abu Dhabi Cultural Foundation works to preserve the art and culture of the city. According to an article from the English Pen Atlas, Al Jawaher wal la'li was the first manuscript to come out of the UAE. According to another article, this book was written in the 1990s and was banned in the city for some time for making accusations about the ruling family.^[146]

For cultural influences, Abu Dhabi, since 2010, has become one of the major shooting spots for many film companies, including Hollywood. Some of the most famous films featuring Abu Dhabi are: The Kingdom (2007), Arrambam (2013), Baby (2015),^[147] Furious 7 (2015), Star Wars: The Force Awakens (2015), Dishoom (2016), War Machine (2017), Tiger Zinda Hai (2017), Race 3 (2018), Saaho (2019), Six Underground (2019), The Misfits (2021), Dune (2021), Vikram Vedha (2022), Crew (2024), Bade Miyan Chote Miyan (2024) and War 2 (2025).

In 2024, the Madison Square Garden Company confirmed that a second Sphere venue, identical to the Sphere in Las Vegas would be built in Abu Dhabi.^[148] The following year in 2025 it was confirmed that Disney would build a theme-park in Abu Dhabi called Disneyland Abu Dhabi. It will be located on Yas Island.^[149]

Abu Dhabi University

New York University Abu Dhabi campus on Saadiyat Island

Abu Dhabi is home to international and local private schools and universities, including government-sponsored INSEAD, New York University Abu Dhabi, Khalifa University, Higher Colleges of Technology, Sorbonne University Abu Dhabi, and Abu Dhabi University. New York University opened a government-sponsored satellite campus in Abu Dhabi in September 2010.^[150]

All schools in the emirate are under the authority of the Abu Dhabi Education Council. This organisation oversees and administers public schools and licenses and inspects private schools. From 2009, the council has brought over thousands of licensed teachers from native English speaking countries to support their New School Model Program in government schools.

Every year in the season of admissions, an exhibition is launched in Abu Dhabi Exhibition Center under government supervision.^[151] Universities from every corner of the world exhibit their career programs and scholarship programs. Heriot-Watt University, University of Bolton, Cambridge University, Oxford University, the Petroleum Institute, Khalifa University, and Abu Dhabi University attend.

In October 2019, Abu Dhabi announced the world's first graduate-level AI research institution, Mohamed bin Zayed University of Artificial Intelligence (MBZUAI). It enables graduation for students, businesses and governments to advance artificial intelligence. The university began accepting applications for masters and PhD programmes a year before the classes, which are scheduled to begin in September 2020.^[152]

Abu Dhabi has a diverse and expanding sporting culture underpinned by investments in sporting infrastructure and the hosting of global sporting events. Liwa Motorsport and traditional sports such as camel racing and equestrian sports have developed alongside popular modern sports such as Jiu-jitsu and football. Abu Dhabi follows the UAE's National Sport Strategy 2031 which aims to increase general participation in sports and expand the types and frequency of sport facilities available in the city.^[153]

Zayed Sport City (ZSC) is a large free zone complex in the heart of Abu Dhabi city with a mixed-use of properties and sporting facilities to encourage sport participation. ZSC offers practice facilities for basketball, billiards, football, paintball, and a dedicated ice rink.^[153] The complex is also home to the Zayed Sports City Stadium, the largest in the UAE with a seating capacity of 45,000 and is the headquarters of the Abu Dhabi Sports Council, which is responsible for hosting events in the city and Mubadala Arena, the home of the UAE Jiu Jitsu team.

Jiu Jitsu is a popular sport in the city with a dedicated complex in the Mubadala Arena. It is a 'Soft Art' originated from the ancient martial art of the Samurai in Japan several centuries ago and it has been adopted by Brazil in the early 1900s. Jiu Jitsu does not include punches or kicks, but it applies the techniques such as throws, control positions and locks.^[154] Abu Dhabi government's Abu Dhabi Education Council (ADEC) maintains a comprehensive after-school program for interested and talented jiujitsu students.^[155] The Abu Dhabi Jiujitsu Schools Program began in 2008 under the patronage of crown prince (now President) Mohammed bin Zayed Al Nahyan, a keen Brazilian jiu-jitsu competitor. The program launched in 14 schools for pupils in grades 6 and 7 and has since expanded to 42 government schools, with 81 Brazilian coaches brought in as instructors.^[156]

9 to 13-year-old students are taught Brazilian jiu-jitsu as part of the curriculum. The plan is for up to 500 schools to be participating in the school-Jitsu program by 2015. The project was set up by special request of Sheikh Mohammad bin Zayed Al Nahyan to the head coach of the Emirates jiu-jitsu team, Carlos "Carlão" Santos, now also the managing director of the School-Jitsu Project.^[157]

Football is the most popular sport in the city and the city has four football stadiums, namely Al Jazeera Stadium, Al Wahda Stadium, Sheikh Zayed Football Stadium (Zayed Sports City) and Hazza Stadium.^[158] The city hosts the Al Jazira Club, Al Wahda FC, and Baniyas Club, all of which compete at the UAE Pro League. In addition to local tournaments, the city has hosted international football events including five FIFA Club World Cup and the 2019 AFC Asian Cup.^[159]

The city hosts the Abu Dhabi Grand Prix of Formula One, which has been held at the Yas Marina Circuit since 2009.^[160] The race takes place late in the Formula One season in November or December, and it is usually the last race of the season. The Yas Marina Circuit is one of the most expensive racing tracks built and regularly hosts various other local races and tours.^[161] The circuit has also hosted other events such as the V8 Supercars series of Dubai.

Abu Dhabi regularly hosts the International Judo Federation Abu Dhabi grand slam. Engendering some criticism, the International Judo Federation refused to allow the Israeli flag and the Israeli national anthem at the international games in 2017. Some referred to this action as anti-Semitic.^[162][163] The ban on Israeli symbols was lifted in 2018 and Israeli flag and the national anthem was allowed to be displayed.^[164] Israeli minister of sports Miri Regev was also allowed to attend the event.^[164]

In March 2019, Abu Dhabi hosted the first Special Olympics World Games in the Middle East. The event took place from 14 to 21 March 2019 and featured more than 7,500 athletes participating in 24 sporting disciplines. The official World Games Flame of Hope was lit in Athens and flown to Abu Dhabi, where it then embarked on the torch run, visiting all seven emirates of the UAE.^[165] It was the first time the Special Olympics World Games were hosted in the Middle East and North Africa region, with Abu Dhabi being the host city. More than 2,500 coaches and 20,000+ volunteers were available in the Olympics.^[166]

The city has hosted multiple international cricket tournaments, such as the ICC Men's T20 World Cup,^[167] and tennis events such as the Mubadala World Tennis Championship.It has also hosted many UFC events.

Abu Dhabi has many sites and attractions that include the Sheikh Zayed Grand Mosque, Mariam Umm Eisa Mosque, Emirates Palace, Qasr Al Watan, Six Flags Qiddya City Yas Marina Circuit, The Corniche, Hayyatii Towers, Etihad Towers, Yas Marina, Yas Waterworld Abu Dhabi, Ferrari World Abu Dhabi, Louvre Abu Dhabi, Yas Island, Saadiyat Island, Warner Bros. World Abu Dhabi, SeaWorld Abu Dhabi and Jubail Mangrove Park.^[168]

On 29 April 2022, Abu Dhabi announced a 100% capacity for commercial activities, tourist attractions and events in the emirate.^[169]

The Walt Disney Company announced on 7 May 2025 that it plans to build its seventh worldwide theme park resort in Abu Dhabi on Yas Island.^[170]

• Abu Dhabi Fund for Development
• Abu Dhabi Investment Council
• Abu Dhabi Global Market
• Abu Dhabi Vegetable Market
• Abu Dhabi Mall
• Archaeology of the United Arab Emirates
• Department of Municipal Affairs (Abu Dhabi)
• Dubai-Abu Dhabi Highway
• Marawah
• National Center for Documentation and Research
• Postage stamps and postal history of Abu Dhabi

• Abu Dhabi Government Services
• Department of Urban Planning and Municipalities. Archived 3 April 2019 at the Wayback Machine.

Type of rotorcraft

For other uses, see Helicopter (disambiguation).

 

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Helicopter" – news · newspapers · books · scholar · JSTOR (August 2025) (Learn how and when to remove this message)

A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally.^[1] These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing (STOL) or short take-off and vertical landing (STOVL) aircraft cannot perform without a runway.

The Focke-Wulf Fw 61 was the first successful, practical, and fully controllable helicopter in 1936, while in 1942, the Sikorsky R-4 became the first helicopter to reach full-scale production. Starting in 1939 and through 1943, Igor Sikorsky worked on the development of the VS-300, which over four iterations, became the basis for modern helicopters with a single main rotor and a single tail rotor.

Although most earlier designs used more than one main rotor, the configuration of a single main rotor accompanied by a vertical anti-torque tail rotor (i.e. unicopter, not to be confused with the single-blade monocopter) has become the most common helicopter configuration. However, twin-rotor helicopters (bicopters), in either tandem or transverse rotors configurations, are sometimes in use due to their greater payload capacity than the monorotor design, and coaxial-rotor, tiltrotor and compound helicopters are also all flying today. Four-rotor helicopters (quadcopters) were pioneered as early as 1907 in France, and along with other types of multicopters, have been developed mainly for specialized applications such as commercial unmanned aerial vehicles (drones) due to the rapid expansion of drone racing and aerial photography markets in the early 21st century, as well as recently weaponized utilities such as artillery spotting, aerial bombing and suicide attacks.

Etymology

[edit]

The English word helicopter is adapted from the French word hélicoptère, coined by Gustave Ponton d'Amécourt in 1861, which originates from the Greek helix (ἕλιξ), genitive helikos (ἕλῐκος), "helix, spiral, whirl, convolution"^[2] and pteron (πτερόν) "wing".^[3][4] In a process of rebracketing, the word is often (erroneously, from an etymological point of view) perceived by English speakers as consisting of heli- and -copter, leading to words like helipad and quadcopter.^[5][6] English language nicknames for "helicopter" include "chopper", "copter", "heli", and "whirlybird". In the United States military, the common slang is "helo" pronounced /ˈhiː.loʊ/.

Design

[edit]

A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more horizontally-spinning rotors.^[7] By contrast the autogyro (or gyroplane) and gyrodyne have a free-spinning rotor for all or part of the flight envelope, relying on a separate thrust system to propel the craft forwards, so that the airflow sets the rotor spinning to provide lift. The compound helicopter also has a separate thrust system, but continues to supply power to the rotor throughout normal flight.^{[citation needed]} U.S. federal regulations state that "helicopter" means a rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.^[8]

Rotor system

[edit]

The rotor system, or more simply rotor, is the rotating part of a helicopter that generates lift. A rotor system may be mounted horizontally, as main rotors are, providing lift vertically, or it may be mounted vertically, such as a tail rotor, to provide horizontal thrust to counteract torque from the main rotors. The rotor consists of a mast, hub and rotor blades.^{[citation needed]}

The mast is a cylindrical metal shaft that extends upwards from the transmission. At the top of the mast is the attachment point for the rotor blades called the hub. Main rotor systems are classified according to how the rotor blades are attached and move relative to the hub. There are three basic types: hingeless, fully articulated, and teetering; although some modern rotor systems use a combination of these.^{[citation needed]}

Most helicopters have a single main rotor, but torque created by its aerodynamic drag must be countered by an opposed torque. The design that Igor Sikorsky settled on for his VS-300 was a smaller tail rotor. The tail rotor pushes or pulls against the tail to counter the torque effect, and this has become the most common configuration for helicopter design, usually at the end of a tail boom.^{[citation needed]}

Some helicopters use other anti-torque controls instead of the tail rotor, such as the ducted fan (called Fenestron or FANTAIL) and NOTAR. NOTAR provides anti-torque similar to the way a wing develops lift through the use of the Coandă effect on the tail boom.^[9]

The use of two or more horizontal rotors turning in opposite directions is another configuration used to counteract the effects of torque on the aircraft without relying on an anti-torque tail rotor. This allows the power normally required to be diverted for the tail rotor to be applied fully to the main rotors, increasing the aircraft's power efficiency and lifting capacity. There are several common configurations that use the counter-rotating effect to benefit the rotorcraft:

• Tandem rotors are two counter-rotating rotors with one mounted behind the other.^[10]
• Transverse rotors are pair of counter-rotating rotors transversely mounted at the ends of fixed wings or outrigger structures. Now used on tiltrotors, some early model helicopters had used them.
• Coaxial rotors are two counter-rotating rotors mounted one above the other with the same axis.
• Intermeshing rotors are two counter-rotating rotors mounted close to each other at a sufficient angle to let the rotors intermesh over the top of the aircraft without colliding. An aircraft utilizing this is known as a synchropter.
• Multirotors make use of three or more rotors. Specific terms are also used depending on the exact amount of rotors, such as tricopter, quadcopter, hexacopter and octocopter for three rotors, four rotors, six rotors and eight rotors respectively, of which quadcopter is the most common. Multirotors are primarily used on drones and use on aircraft with a human pilot is rare.^{[citation needed]}

Tip jet designs let the rotor push itself through the air and avoid generating torque.^[11]

The number, size and type of engine(s) used on a helicopter determines the size, function and capability of that helicopter design. The earliest helicopter engines were simple mechanical devices, such as rubber bands or spindles, which relegated the size of helicopters to toys and small models. For a half century before the first airplane flight, steam engines were used to forward the development of the understanding of helicopter aerodynamics, but the limited power did not allow for manned flight. The introduction of the internal combustion engine at the end of the 19th century became the watershed for helicopter development as engines began to be developed and produced that were powerful enough to allow for helicopters able to lift humans.^{[citation needed]}

Early helicopter designs utilized custom-built engines or rotary engines designed for airplanes, but these were soon replaced by more powerful automobile engines and radial engines. The single, most-limiting factor of helicopter development during the first half of the 20th century was that the amount of power produced by an engine was not able to overcome the engine's weight in vertical flight. This was overcome in early successful helicopters by using the smallest engines available. When the compact, flat engine was developed, the helicopter industry found a lighter-weight powerplant easily adapted to small helicopters, although radial engines continued to be used for larger helicopters.^{[citation needed]}

Turbine engines revolutionized the aviation industry; and the turboshaft engine for helicopter use, pioneered in December 1951 by the aforementioned Kaman K-225, finally gave helicopters an engine with a large amount of power and a low weight penalty. Turboshafts are also more reliable than piston engines, especially when producing the sustained high levels of power required by a helicopter. The turboshaft engine was able to be scaled to the size of the helicopter being designed, so that all but the lightest of helicopter models are powered by turbine engines today.^{[citation needed]}

Special jet engines developed to drive the rotor from the rotor tips are referred to as tip jets. Tip jets powered by a remote compressor are referred to as cold tip jets, while those powered by combustion exhaust are referred to as hot tip jets. An example of a cold jet helicopter is the Sud-Ouest Djinn, and an example of the hot tip jet helicopter is the YH-32 Hornet.^{[citation needed]}

Some radio-controlled helicopters and smaller, helicopter-type unmanned aerial vehicles, use electric motors or motorcycle engines.^[12] Radio-controlled helicopters may also have piston engines that use fuels other than gasoline, such as nitromethane. Some turbine engines commonly used in helicopters can also use biodiesel instead of jet fuel.^[13][14]

There are also human-powered helicopters.

The transmission is a mechanical system that transmits power from the engine(s) to the rotors. The transmission is a system of gears, bearings, clutches and shafts that performs several functions (1) Translates the alignment of the drive shaft to match the alignment of the rotor shafts; (2) Reduces the RPM of the drive shaft to the lower RPMs of the rotors; and (3) Enables the engine to engage or disengage from the rotors. For helicopters with tail rotors, the transmission drivetrain forks into two paths: one leading to the main rotor, and one leading to the tail rotor.^{[15]: 4-10 to 4-13 [16][17]}

The drive shafts of helicopter engines are typically not aligned with the rotor shafts, so the transmission must translate the alignment of the drive shaft to match the shafts of the rotors. Many engine drive shafts are aligned horizontally, yet the main rotor shaft ("mast") is usually vertical, and the tail rotor shaft is often perpendicular to the engine's drive shaft. The transmission contains a series of gears, usually bevel gears, that translate the alignment of the drive shaft to the alignment of the rotor shafts.^{[15]: 4–12 [18]}

The transmission also reduces the RPMs of the engine to the lower RPMs required by the rotors. The output drive shaft of the engine, before any gearing is applied, is typically between 3,000 and 50,000 RPM (turbine engines typically have higher RPM than piston engines). The main rotor typically rotates between 300 and 600 RPM. The tail rotor, if present, usually rotates between 1,000 and 5,000 RPM. (The RPMs of a given model of helicopter are usually fixed — the RPM ranges listed above represent a variety of helicopter models).^[19] The transmission contains a series of reduction gears to reduce the engine RPM to the rotor RPMs. Several types of reduction gears may be used, including bevel gears, planetary gears, helical gears, and spur gears. Most transmissions contain several reduction gears: the engine itself may contain reduction gears (often spur gears) between the engine's internal shaft and the output drive shaft; the main rotor may have a reduction gear at its base (typically a planetary gear); and there may be reduction gears at the tail rotor, and on the shaft leading to the tail rotor.^{[15]: 4–11}

The transmission often includes one or more clutches, which permit the rotors to engage or disengage from the engine. A clutch is required so the engine can start up and gain speed before taking the load of the rotors. A clutch is also required in the case of engine failure: in that situation, the rotors must disengage from the engine so that the rotors can continue spinning and perform autorotation. Helicopter clutches are usually freewheel clutches relying on centrifugal forces (sprag clutchs are commonly used), but belt drive clutches are also used.^{[15]: 4–7, 4-12 to 4-13}

A helicopter has four flight control inputs. These are the cyclic, the collective, the anti-torque foot pedals, and the throttle.

The cyclic control is usually located between the pilot's legs and is commonly called the cyclic stick or just cyclic or stick and moves forwards and backwards and side to side. On most helicopters, the cyclic is similar to a joystick. However, the Robinson R22, Robinson R44 and Robinson R66 have a unique teetering-bar cyclic control system and a few helicopters have a cyclic control that descends into the cockpit from overhead.^{[citation needed]}

The cyclic is called the cyclic because it cyclically changes the pitch of the main rotor blades. In a forward flight state, as the blades rotate, the blade rotating forward will see higher speed and a corresponding increase in lift compared to the retreating blade. As such, the angle of attack of the forward rotating blade has to be lower than the retreating blade or the helicopter will roll to the retreating blade side. This happens cyclically as the blades rotate through a complete rotation leading to the naming of this control as the cyclic. The cyclic controls this differential angle.

The cyclic controls the tilt of the rotor. In hover, the cyclic controls motion of the helicopter over the ground. In flight, the cyclic controls the pitch and roll of the helicopter.

In a hover, if the pilot pushes the cyclic forward, the rotor disk tilts forward, and the rotor produces a thrust in the forward direction. If the pilot pushes the cyclic to the side, the rotor disk tilts to that side and produces thrust in that direction, causing the helicopter to move sideways.^{[citation needed]}

Because of precession, the cyclic moves the swashplate 90 degrees before the desired main rotor tilt. This can be seen when the rotor is stopped. With the blades aligned fore/aft, moving the cyclic forward does not change the blade angle but moving the cyclic to the side will change the blade angle.

In flight, the cyclic acts like the stick in an airplane. Moving the cyclic forward pitches the nose down for more speed. Moving the cyclic aft lifts the nose to slow the aircraft. Moving the cyclic to the side rolls the helicopter in that direction which generally leads to turning in that direction, assuming coordinated flight.

The collective pitch control or collective is located on the left side of the pilot's seat with an adjustable friction control to prevent inadvertent movement freeing the pilot's left hand for other uses. The collective changes the pitch angle of all the main rotor blades collectively (i.e. all at the same time) and independently of their rotational position. Therefore, if an up collective input is made, all the blades increase angle of attack equally, and the result is additional lift (power) to the main rotor system which can increase helicopter speed or altitude.^{[citation needed]} Lowering the collective results in less lift from the main rotor system.

A swashplate controls the collective and cyclic pitch of the main blades. The swashplate moves up and down, along the main shaft, to change the pitch of the blades. The stick is connected to the swash plate through the collective and cyclic systems allowing both systems to independently control the angle of the blades.

The anti-torque pedals are located in the same position as the rudder pedals in a fixed-wing aircraft, and serve a similar purpose, namely to control the yaw or direction in which the nose of the aircraft is pointed. Application of the pedal in a given direction changes the pitch of the tail rotor blades, increasing or reducing the thrust produced by the tail rotor and causing the nose to yaw in the direction of the applied pedal. The pedals mechanically change the pitch of the tail rotor altering the amount of thrust produced.^{[citation needed]} Helicopters do not exhibit adverse yaw as seen in airplanes and the pedals are not generally required when turning in forward flight. Use of the pedals is closely related to the collective in hover. For example, increasing collective increases aerodynamic drag on the main rotor system causing a yaw of the helicopter. The pedals are used to counter that yaw.

Both the cyclic and collective can have a wide variety of toggles and switches available to the pilot to control such things as aerodynamic trim, engine speed trim, radio and intercom, hook release, water release, etc. This allows the pilot to control these functions without removing their hands from the controls.

Helicopter rotors are designed to operate in a narrow range of RPM.^{[20][21][22][23][19]} The throttle controls the power produced by the engine, which is connected to the rotor by a fixed ratio transmission. The purpose of the throttle is to maintain enough engine power to keep the rotor RPM within allowable limits so that the rotor produces enough lift for flight. The throttle control is a motorcycle-style twist grip mounted on the collective control.

A compound helicopter has an additional system for thrust and, typically, small stub fixed wings. This offloads the rotor in cruise, which allows its rotation to be slowed down, thus increasing the maximum speed of the aircraft. The Lockheed AH-56A Cheyenne diverted up to 90% of its engine power to a pusher propeller during forward flight.^[24]

There are three basic flight conditions for a helicopter: hover, forward flight and the transition between the two.

Hovering is the most challenging part of flying a helicopter. Required are constant control inputs and corrections by the pilot to keep the helicopter where it is required to be.^[25] Despite the complexity of the task, the control inputs in a hover are simple. The cyclic is used to eliminate drift in the horizontal plane, that is to control forward and back, right and left. The collective is used to maintain altitude. The pedals are used to control nose direction or heading. It is the interaction of these controls that makes hovering so difficult, since an adjustment in any one control requires an adjustment of the other two, creating a cycle of constant correction.^{[citation needed]} In addition, the center of lift of the main rotor system is significantly above the center of gravity (CG) of the helicopter. Thus, any lateral perturbation of the helicopter in a hover will tend to increase as the rotor lift will increasingly roll or pitch the helicopter in a positive-feedback rotor-lift versus helicopter CG situation. The lateral motion of the helicopter lags behind the roll induced by the rotor lift side vector which will lead an inexperienced pilot into a pilot induced oscillation (PIO) and eventual loss of control.

A hovering helicopter is surrounded by a vortex of air pushing the helicopter down. This can be a hover in ground effect or out of ground effect. Thus, when in a hover, the engine needs to provide enough power to both counter helicopter weight as well as counter this downward flow of air into the rotor system. As a helicopter moves from hover to forward flight it flies out of this downward flowing vortex and enters a state called translational lift which provides extra lift without increasing power. This state, most typically, occurs when the airspeed reaches approximately 16–24 knots (30–44 km/h; 18–28 mph), and may be necessary for a helicopter to obtain flight.^{[citation needed]} A maneuver called a running take off involves sliding the helicopter on the ground at increasing speed until sufficient lift is achieved for flight.

In forward flight a helicopter's flight controls behave more like those of a fixed-wing aircraft. Applying forward pressure on the cyclic will cause the nose to pitch down, with a resultant increase in airspeed and loss of altitude. Aft cyclic will cause the nose to pitch up, slowing the helicopter and causing it to climb. Increasing collective (power) while maintaining a constant airspeed will induce a climb while decreasing collective will cause a descent. Coordinating these two inputs, down collective plus aft cyclic or up collective plus forward cyclic, will result in airspeed changes while maintaining a constant altitude. Helicopters do not exhibit adverse yaw and the pedals are not generally needed for forward flight, even when turning.

If the engine fails or is disconnected from the rotor system, the helicopter will enter an autorotation, where the helicopter's main rotor turns due to air moving up through the rotor, instead of engine power driving the rotor.

Due to the operating characteristics of the helicopter—its ability to take off and land vertically, and to hover for extended periods of time, as well as the aircraft's handling properties under low airspeed conditions—it has proved advantageous to conduct tasks that were previously not possible with other aircraft, or were time- or work-intensive to accomplish on the ground. Today, helicopter uses include transportation of people and cargo, military uses, construction, firefighting, search and rescue, tourism, medical transport, law enforcement, agriculture, news and media, and aerial observation, among others.^[26]

A helicopter used to carry loads connected to long cables or slings is called an aerial crane. Aerial cranes are used to place heavy equipment, like radio transmission towers and large air conditioning units, on the tops of tall buildings, or when an item must be raised up in a remote area, such as a radio tower raised on the top of a hill or mountain. Helicopters are used as aerial cranes in the logging industry to lift trees out of terrain where vehicles cannot travel and where environmental concerns prohibit the building of roads.^[27] These operations are referred to as longline because of the long, single sling line used to carry the load.^[28] In military service helicopters are often useful for delivery of outsized slung loads that would not fit inside ordinary cargo aircraft: artillery pieces, large machinery (field radars, communications gear, electrical generators), or pallets of bulk cargo. In military operations these payloads are often delivered to remote locations made inaccessible by mountainous or riverine terrain, or naval vessels at sea.^{[citation needed]}

In electronic news gathering, helicopters have provided aerial views of some major news stories, and have been doing so, from the late 1960s. Helicopters have also been used in films, both in front and behind the camera.^[29]

The largest single non-combat helicopter operation in history was the disaster management operation following the 1986 Chernobyl nuclear disaster. Hundreds of pilots were involved in airdrop and observation missions, making dozens of sorties a day for several months.^{[citation needed]}

"Helitack" is the use of helicopters to combat wildland fires.^[30] The helicopters are used for aerial firefighting (water bombing) and may be fitted with tanks or carry helibuckets. Helibuckets, such as the Bambi bucket, are usually filled by submerging the bucket into lakes, rivers, reservoirs, or portable tanks. Tanks fitted onto helicopters are filled from a hose while the helicopter is on the ground or water is siphoned from lakes or reservoirs through a hanging snorkel as the helicopter hovers over the water source. Helitack helicopters are also used to deliver firefighters, who rappel down to inaccessible areas, and to resupply firefighters. Common firefighting helicopters include variants of the Bell 205 and the Erickson S-64 Aircrane helitanker.^{[citation needed]}

Helicopters are used as air ambulances for emergency medical assistance in situations when an ambulance cannot easily or quickly reach the scene, or cannot transport the patient to a medical facility in time. Helicopters are also used when patients need to be transported between medical facilities and air transportation is the most practical method. An air ambulance helicopter is equipped to stabilize and provide limited medical treatment to a patient while in flight. The use of helicopters as air ambulances is often referred to as "MEDEVAC", and patients are referred to as being "airlifted", or "medevaced". This use was pioneered in the Korean War, when time to reach a medical facility was reduced to three hours from the eight hours needed in World War II, and further reduced to two hours by the Vietnam War.^[31] In naval service a prime function of rescue helicopters is to promptly retrieve downed aircrew involved in crashes occurring upon launch or recovery aboard aircraft carriers. In past years this function was performed by destroyers escorting the carrier, but since then helicopters have proved vastly more effective.^{[citation needed]}

Police departments and other law enforcement agencies use helicopters to pursue suspects and patrol the skies. Since helicopters can achieve a unique aerial view, they are often used in conjunction with police on the ground to report on suspects' locations and movements. They are often mounted with lighting and heat-sensing equipment for night pursuits.

Military forces use attack helicopters to conduct aerial attacks on ground targets. Such helicopters are mounted with missile launchers and miniguns. Transport helicopters are used to ferry troops and supplies where the lack of an airstrip would make transport via fixed-wing aircraft impossible. The use of transport helicopters to deliver troops as an attack force on an objective is referred to as "air assault". Unmanned aerial systems (UAS) helicopter systems of varying sizes are developed by companies for military reconnaissance and surveillance duties. Naval forces also use helicopters equipped with dipping sonar for anti-submarine warfare, since they can operate from small ships.^{[citation needed]}

Oil companies charter helicopters to move workers and parts quickly to remote drilling sites located at sea or in remote locations. The speed advantage over boats makes the high operating cost of helicopters cost-effective in ensuring that oil platforms continue to operate. Various companies specialize in this type of operation.^{[citation needed]}

NASA developed Ingenuity, a 1.8 kg (4.0 lb) helicopter used to survey Mars (along with a rover). It began service in February 2021 and was retired due to sustained rotor blade damage in January 2024 after 73 sorties. As the Martian atmosphere is 100 times thinner than Earth's, its two blades spin at close to 3,000 revolutions a minute, approximately 10 times faster than that of a terrestrial helicopter.^[32]

In 2017, 926 civil helicopters were shipped for $3.68 billion, led by Airbus Helicopters with $1.87 billion for 369 rotorcraft, Leonardo Helicopters with $806 million for 102 (first three-quarters only), Bell Helicopter with $696 million for 132, then Robinson Helicopter with $161 million for 305.^[33]

By October 2018, the in-service and stored helicopter fleet of 38,570 with civil or government operators was led by Robinson Helicopter with 24.7% followed by Airbus Helicopters with 24.4%, then Bell with 20.5 and Leonardo with 8.4%, Russian Helicopters with 7.7%, Sikorsky Aircraft with 7.2%, MD Helicopters with 3.4% and other with 2.2%. The most widespread model is the piston Robinson R44 with 5,600, then the H125/AS350 with 3,600 units, followed by the Bell 206 with 3,400. Most were in North America with 34.3% then in Europe with 28.0% followed by Asia-Pacific with 18.6%, Latin America with 11.6%, Africa with 5.3% and Middle East with 1.7%.^[34]

The earliest references for vertical flight came from China. Since around 400 BC,^[35] Chinese children have played with bamboo flying toys (or Chinese top).^[36][37][38] This bamboo-copter is spun by rolling a stick attached to a rotor. The spinning creates lift, and the toy flies when released.^[35] The 4th-century AD Daoist book Baopuzi by Ge Hong (抱朴子 "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft.^[39]

Designs similar to the Chinese helicopter toy appeared in some Renaissance paintings and other works.^[40] In the 18th and early 19th centuries Western scientists developed flying machines based on the Chinese toy.^[41]

It was not until the early 1480s, when Italian polymath Leonardo da Vinci created a design for a machine that could be described as an "aerial screw", that any recorded advancement was made towards vertical flight. His notes suggested that he built small flying models, but there were no indications for any provision to stop the rotor from making the craft rotate.^[42][43] As scientific knowledge increased and became more accepted, people continued to pursue the idea of vertical flight.^{[citation needed]}

In July 1754, Russian Mikhail Lomonosov had developed a small coaxial modeled after the Chinese top but powered by a wound-up spring device^[41] and demonstrated it to the Russian Academy of Sciences. It was powered by a spring, and was suggested as a method to lift meteorological instruments. In 1783, Christian de Launoy, and his mechanic, Bienvenu, used a coaxial version of the Chinese top in a model consisting of contrarotating turkey flight feathers^[41] as rotor blades, and in 1784, demonstrated it to the French Academy of Sciences. Sir George Cayley, influenced by a childhood fascination with the Chinese flying top, developed a model of feathers, similar to that of Launoy and Bienvenu, but powered by rubber bands. By the end of the century, he had progressed to using sheets of tin for rotor blades and springs for power. His writings on his experiments and models would become influential on future aviation pioneers.^[42] Alphonse Pénaud would later develop coaxial rotor model helicopter toys in 1870, also powered by rubber bands. One of these toys, given as a gift by their father, would inspire the Wright brothers to pursue the dream of flight.^[44]

In 1861, the word "helicopter" was coined by Gustave de Ponton d'Amécourt, a French inventor who demonstrated a small steam-powered model. While celebrated as an innovative use of a new metal, aluminum, the model never lifted off the ground. D'Amecourt's linguistic contribution would survive to eventually describe the vertical flight he had envisioned. Steam power was popular with other inventors as well. In 1877, the Italian engineer, inventor and aeronautical pioneer Enrico Forlanini developed an unmanned helicopter powered by a steam engine. It rose to a height of 13 meters (43 feet), where it remained for 20 seconds, after a vertical take-off from a park in Milan.^[45] Milan has dedicated its city airport to Enrico Forlanini, also named Linate Airport,^[46] as well as the nearby park, the Parco Forlanini.^[47] Emmanuel Dieuaide's steam-powered design featured counter-rotating rotors powered through a hose from a boiler on the ground.^[42] In 1887 Parisian inventor, Gustave Trouvé, built and flew a tethered electric model helicopter.^{[citation needed]}

In July 1901, the maiden flight of Hermann Ganswindt's helicopter took place in Berlin-Schöneberg; this was probably the first heavier-than-air motor-driven flight carrying humans. A movie covering the event was taken by Max Skladanowsky, but it remains lost.^[48]

In 1885, Thomas Edison was given US$1,000 (equivalent to $35,000 today) by James Gordon Bennett, Jr., to conduct experiments towards developing flight. Edison built a helicopter and used the paper for a stock ticker to create guncotton, with which he attempted to power an internal combustion engine. The helicopter was damaged by explosions and one of his workers was badly burned. Edison reported that it would take a motor with a ratio of three to four pounds per horsepower produced to be successful, based on his experiments.^[49] Ján Bahýľ, a Slovak inventor, adapted the internal combustion engine to power his helicopter model that reached a height of 0.5 meters (1.6 feet) in 1901. On 5 May 1905, his helicopter reached 4 meters (13 feet) in altitude and flew for over 1,500 meters (4,900 feet).^[50] In 1908, Edison patented his own design for a helicopter powered by a gasoline engine with box kites attached to a mast by cables for a rotor,^[51] but it never flew.^[52]

In 1906, two French brothers, Jacques and Louis Breguet, began experimenting with airfoils for helicopters. In 1907, those experiments resulted in the Gyroplane No.1, possibly as the earliest known example of a quadcopter. Although there is some uncertainty about the date, sometime between 14 August and 29 September 1907, the Gyroplane No. 1 lifted its pilot into the air about 0.6 metres (2 ft) for a minute.^[53][54] The Gyroplane No. 1 proved to be extremely unsteady and required a man at each corner of the airframe to hold it steady. For this reason, the flights of the Gyroplane No. 1 are considered to be the first manned flight of a helicopter, but not a free or untethered flight.^{[citation needed]}

That same year, fellow French inventor Paul Cornu designed and built the Cornu helicopter which used two 6.1-metre (20 ft) counter-rotating rotors driven by a 24 hp (18 kW) Antoinette engine. On 13 November 1907, it lifted its inventor to 0.3 metres (1 ft) and remained aloft for 20 seconds. Even though this flight did not surpass the flight of the Gyroplane No. 1, it was reported to be the first truly free flight with a pilot.^{[n 1]} Cornu's helicopter completed a few more flights and achieved a height of nearly 2.0 metres (6.5 ft), but it proved to be unstable and was abandoned.^[53]

In 1909, J. Newton Williams of Derby, Connecticut, and Emile Berliner of Washington, D.C., flew a helicopter "on three occasions" at Berliner's lab in Washington's Brightwood neighborhood.^[55]

In 1911, Slovenian philosopher and economist Ivan Slokar patented a helicopter configuration.^[56][57][58]

The Danish inventor Jacob Ellehammer built the Ellehammer helicopter in 1912. It consisted of a frame equipped with two counter-rotating discs, each of which was fitted with six vanes around its circumference. After indoor tests, the aircraft was demonstrated outdoors and made several free take-offs. Experiments with the helicopter continued until September 1916, when it tipped over during take-off, destroying its rotors.^[59]

During World War I, Austria-Hungary developed the PKZ, an experimental helicopter prototype, with two aircraft built.^{[citation needed]}

In the early 1920s, Argentine Raúl Pateras-Pescara de Castelluccio, while working in Europe, demonstrated one of the first successful applications of cyclic pitch.^[53] Coaxial, contra-rotating, biplane rotors could be warped to cyclically increase and decrease the lift they produced. The rotor hub could also be tilted forward a few degrees, allowing the aircraft to move forward without a separate propeller to push or pull it. Pateras-Pescara was also able to demonstrate the principle of autorotation. By January 1924, Pescara's helicopter No. 1 was tested but was found to be underpowered and could not lift its own weight. His 2F fared better and set a record.^[60] The British government funded further research by Pescara which resulted in helicopter No. 3, powered by a 250-horsepower (190 kW) radial engine which could fly for up to ten minutes.^[61][62]

In March 1923 Time magazine reported Thomas Edison sent George de Bothezat a congratulations for a successful helicopter test flight. Edison wrote, "So far as I know, you have produced the first successful helicopter." The helicopter was tested at McCook's Field and remained airborne for 2 minutes and 45 seconds at a height of 15 feet.^[63]

On 14 April 1924, Frenchman Étienne Oehmichen set the first helicopter world record recognized by the Fédération Aéronautique Internationale (FAI), flying his quadrotor helicopter 360 meters (1,180 ft).^[64] On 18 April 1924, Pescara beat Oemichen's record, flying for a distance of 736 meters (2,415 ft)^[60] (nearly 0.80 kilometers or .5 miles) in 4 minutes and 11 seconds (about 13 km/h or 8 mph), maintaining a height of 1.8 meters (6 feet).^[65] On 4 May, Oehmichen completed the first one-kilometer (0.62 mi) closed-circuit helicopter flight in 7 minutes 40 seconds with his No. 2 machine.^[53][66]

In the US, George de Bothezat built the quadrotor helicopter de Bothezat helicopter for the United States Army Air Service but the Army cancelled the program in 1924, and the aircraft was scrapped.^{[citation needed]}

Albert Gillis von Baumhauer, a Dutch aeronautical engineer, began studying rotorcraft design in 1923. His first prototype "flew" ("hopped" and hovered in reality) on 24 September 1925,^[67] with Dutch Army-Air arm Captain Floris Albert van Heijst at the controls. The controls that van Heijst used were von Baumhauer's inventions, the cyclic and collective.^[68][69] Patents were granted to von Baumhauer for his cyclic and collective controls by the British ministry of aviation on 31 January 1927, under patent number 265,272.^{[citation needed]}

In 1927,^[70] Engelbert Zaschka from Germany built a helicopter, equipped with two rotors, in which a gyroscope was used to increase stability and serves as an energy accumulator for a gliding flight to make a landing. Zaschka's aircraft, the first helicopter, which ever worked so successfully in miniature, not only rises and descends vertically, but is able to remain stationary at any height.^[71][72]

In 1928, Hungarian aviation engineer Oszkár Asbóth constructed a helicopter prototype that took off and landed at least 182 times, with a maximum single flight duration of 53 minutes.^[73][74]

In 1930, the Italian engineer Corradino D'Ascanio built his D'AT3, a coaxial helicopter. His relatively large machine had two, two-bladed, counter-rotating rotors. Control was achieved by using auxiliary wings or servo-tabs on the trailing edges of the blades,^[75] a concept that was later adopted by other helicopter designers, including Bleeker and Kaman. Three small propellers mounted to the airframe were used for additional pitch, roll, and yaw control. The D'AT3 held modest FAI speed and altitude records for the time, including altitude (18 m or 59 ft), duration (8 minutes 45 seconds) and distance flown (1,078 m or 3,540 ft).^[75][76]

Spanish aeronautical engineer and pilot Juan de la Cierva invented the autogyro in the early 1920s, becoming the first practical rotorcraft.^[77] In 1928, de la Cierva successfully flew an autogyro across the English Channel, from London to Paris.^[78] In 1934, an autogyro became the first rotorcraft to successfully take off and land on the deck of a ship.^[79] That same year, the autogyro was employed by the Spanish military during the Asturias revolt, becoming the first military deployment of a rotocraft. Autogyros were also employed in New Jersey and Pennsylvania for delivering mail and newspapers prior to the invention of the helicopter.^[80] Though lacking true vertical flight capability, work on the autogyro forms the basis for helicopter analysis.^[81]

In the Soviet Union, Boris N. Yuriev and Alexei M. Cheremukhin, two aeronautical engineers working at the Tsentralniy Aerogidrodinamicheskiy Institut (TsAGI or the Central Aerohydrodynamic Institute), constructed and flew the TsAGI 1-EA single lift-rotor helicopter, which used an open tubing framework, a four-blade main lift rotor, and twin sets of 1.8-meter (5.9-foot) diameter, two-bladed anti-torque rotors: one set of two at the nose and one set of two at the tail. Powered by two M-2 powerplants, up-rated copies of the Gnome Monosoupape 9 Type B-2 100 CV output rotary engine of World War I, the TsAGI 1-EA made several low altitude flights.^[82] By 14 August 1932, Cheremukhin managed to get the 1-EA up to an unofficial altitude of 605 meters (1,985 feet), shattering d'Ascanio's earlier achievement. As the Soviet Union was not yet a member of the FAI, however, Cheremukhin's record remained unrecognized.^[83]

Nicolas Florine, a Russian engineer, built the first twin tandem rotor machine to perform a free flight. It flew in Sint-Genesius-Rode, at the Laboratoire Aérotechnique de Belgique (now von Karman Institute) in April 1933, and attained an altitude of six meters (20 feet) and an endurance of eight minutes. Florine chose a co-rotating configuration because the gyroscopic stability of the rotors would not cancel. Therefore, the rotors had to be tilted slightly in opposite directions to counter torque. Using hingeless rotors and co-rotation also minimised the stress on the hull. At the time, it was one of the most stable helicopters in existence.^[84]

The Bréguet-Dorand Gyroplane Laboratoire was built in 1933. It was a coaxial helicopter, contra-rotating. After many ground tests and an accident, it first took flight on 26 June 1935. Within a short time, the aircraft was setting records with pilot Maurice Claisse at the controls. On 14 December 1935, he set a record for closed-circuit flight with a 500-meter (1,600-foot) diameter.^[85] The next year, on 26 September 1936, Claisse set a height record of 158 meters (518 feet).^[86] And, finally, on 24 November 1936, he set a flight duration record of one hour, two minutes and 50 seconds^[87] over a 44 kilometers (27 miles) closed circuit at 44.7 kilometres per hour (27.8 mph). The aircraft was destroyed in 1943 by an Allied airstrike at Villacoublay airport.^[88]

American inventor Arthur M. Young started work on model helicopters in 1928 using converted electric hover motors to drive the rotor head. Young invented the stabilizer bar and patented it shortly after. A mutual friend introduced Young to Lawrence Dale, who once seeing his work asked him to join the Bell Aircraft company. When Young arrived at Bell in 1941, he signed his patent over and began work on the helicopter. His budget was US$250,000 (equivalent to $5.3 million today) to build two working helicopters. In just six months they completed the first Bell Model 1, which spawned the Bell Model 30, later succeeded by the Bell 47.^[89]

Heinrich Focke at Focke-Wulf had purchased a license from Cierva Autogiro Company, which according to Frank Kingston Smith Sr., included "the fully controllable cyclic/collective pitch hub system". In return, Cierva Autogiro received a cross-license to build the Focke-Achgelis helicopters. Focke designed the world's first practical helicopter, the transverse twin-rotor Focke-Wulf Fw 61, which first flew in June 1936. It was demonstrated by Hanna Reitsch in February 1938 inside the Deutschlandhalle in Berlin.^[90] The Fw 61 set a number of FAI records from 1937 to 1939, including: maximum altitude of 3,427 metres (11,243 ft), maximum distance of 230 kilometres (140 mi), and maximum speed of 124 kilometres per hour (77 mph).^[91] Autogiro development was now being bypassed by a focus on helicopters.^[92]

During World War II, Nazi Germany used helicopters in small numbers for observation, transport, and medical evacuation. The Flettner Fl 282 Kolibri synchropter—using the same basic configuration as Anton Flettner's own pioneering Fl 265—was used in the Baltic, Mediterranean, and Aegean Seas.^[93] The Focke-Achgelis Fa 223 Drache, like the Fw 61, used two transverse rotors, and was the largest rotorcraft of the war.^[94] Extensive bombing by the Allied forces prevented Germany from producing helicopters in large quantities during the war.

In the United States, Russian-born engineer Igor Sikorsky and Wynn Laurence LePage competed to produce the U.S. military's first helicopter. LePage received the patent rights to develop helicopters patterned after the Fw 61, and built the XR-1^[95] in 1941. Meanwhile, Sikorsky settled on a simpler, single-rotor design, the VS-300 of 1939, which turned out to be the first practical single lifting-rotor helicopter design. After experimenting with configurations to counteract the torque produced by the single main rotor, Sikorsky settled on a single, smaller rotor mounted on the tail boom.^{[citation needed]}

Developed from the VS-300, Sikorsky's R-4 of 1942 was the first large-scale mass-produced helicopter, with a production order for 100 aircraft. The R-4 was the only Allied helicopter to serve in World War II, used primarily for search and rescue (by the USAAF 1st Air Commando Group) in the Burma campaign;^[96] in Alaska; and in other areas with harsh terrain. Total production reached 131 helicopters before the R-4 was replaced by other Sikorsky helicopters such as the R-5 and the R-6. In all, Sikorsky produced over 400 helicopters before the end of World War II.^[97]

While LePage and Sikorsky built their helicopters for the military, Bell Aircraft hired Arthur Young to help build a helicopter using Young's two-blade teetering rotor design, which used a weighted stabilizer bar placed at a 90° angle to the rotor blades. The subsequent Model 30 helicopter of 1943 showed the design's simplicity and ease of use. The Model 30 was developed into the Bell 47 of 1945, which became the first helicopter certified for civilian use in the United States (March 1946). Produced in several countries, the Bell 47 was the most popular helicopter model for nearly 30 years.^{[citation needed]}

In 1951, at the urging of his contacts at the Department of the Navy, Charles Kaman modified his K-225 synchropter—a design for a twin-rotor helicopter concept first pioneered by Anton Flettner in 1939, with the aforementioned Fl 265 piston-engined design in Germany—with a new kind of engine, the turboshaft engine. This adaptation of the turbine engine provided a large amount of power to Kaman's helicopter with a lower weight penalty than piston engines, with their heavy engine blocks and auxiliary components. On 11 December 1951, the Kaman K-225 became the first turbine-powered helicopter in the world. Two years later, on 26 March 1954, a modified Navy HTK-1, another Kaman helicopter, became the first twin-turbine helicopter to fly.^[98] However, it was the Sud Aviation Alouette II that would become the first helicopter to be produced with a turbine-engine.^[99]

Reliable helicopters capable of stable hover flight were developed decades after fixed-wing aircraft. This is largely due to higher engine power density requirements than fixed-wing aircraft. Improvements in fuels and engines during the first half of the 20th century were a critical factor in helicopter development. The availability of lightweight turboshaft engines in the second half of the 20th century led to the development of larger, faster, and higher-performance helicopters. While smaller and less expensive helicopters still use piston engines, turboshaft engines are the preferred powerplant for helicopters today.^{[citation needed]}

There are several reasons a helicopter cannot fly as fast as a fixed-wing aircraft. When the helicopter is hovering, the outer tips of the rotor travel at a speed determined by the length of the blade and the rotational speed. In a moving helicopter, however, the speed of the blades relative to the air depends on the speed of the helicopter as well as on their rotational speed. The airspeed of the advancing rotor blade is much higher than that of the helicopter itself. It is possible for this blade to exceed the speed of sound, and thus produce vastly increased drag and vibration.^{[citation needed]}

At the same time, the advancing blade creates more lift traveling forward, the retreating blade produces less lift. If the aircraft were to accelerate to the air speed that the blade tips are spinning, the retreating blade passes through air moving at the same speed of the blade and produces no lift at all, resulting in very high torque stresses on the central shaft that can tip down the retreating-blade side of the vehicle, and cause a loss of control. Dual counter-rotating blades prevent this situation due to having two advancing and two retreating blades with balanced forces.^{[citation needed]}

Because the advancing blade has higher airspeed than the retreating blade and generates a dissymmetry of lift, rotor blades are designed to "flap" – lift and twist in such a way that the advancing blade flaps up and develops a smaller angle of attack. Conversely, the retreating blade flaps down, develops a higher angle of attack, and generates more lift. At high speeds, the force on the rotors is such that they "flap" excessively, and the retreating blade can reach too high an angle and stall. For this reason, the maximum safe forward airspeed of a helicopter is given a design rating called V_NE, velocity, never exceed.^[100] In addition, it is possible for the helicopter to fly at an airspeed where an excessive amount of the retreating blade stalls, which results in high vibration, pitch-up, and roll into the retreating blade.^{[citation needed]}

At the end of the 20th century, designers began working on helicopter noise reduction. Urban communities have often expressed great dislike of noisy aviation or noisy aircraft, and police and passenger helicopters can be unpopular because of the sound. The redesigns followed the closure of some city heliports and government action to constrain flight paths in national parks and other places of natural beauty.^{[citation needed]}

To reduce vibration, all helicopters have rotor adjustments for height and weight. A maladjusted helicopter can easily vibrate so much that it will shake itself apart. Blade height is adjusted by changing the pitch of the blade. Weight is adjusted by adding or removing weights on the rotor head and/or at the blade end caps. Most also have vibration dampers for height and pitch. Some also use mechanical feedback systems to sense and counter vibration. Usually the feedback system uses a mass as a "stable reference" and a linkage from the mass operates a flap to adjust the rotor's angle of attack to counter the vibration. Adjustment can be difficult in part because measurement of the vibration is hard, usually requiring sophisticated accelerometers mounted throughout the airframe and gearboxes. The most common blade vibration adjustment measurement system is to use a stroboscopic flash lamp, and observe painted markings or coloured reflectors on the underside of the rotor blades. The traditional low-tech system is to mount coloured chalk on the rotor tips, and see how they mark a linen sheet. Health and Usage Monitoring Systems (HUMS) provide vibration monitoring and rotor track and balance solutions to limit vibration.^[101] Gearbox vibration most often requires a gearbox overhaul or replacement. Gearbox or drive train vibrations can be extremely harmful to a pilot. The most severe effects are pain, numbness, and loss of tactile discrimination or dexterity.^{[citation needed]}

For a standard helicopter with a single main rotor, the tips of the main rotor blades produce a vortex ring in the air, which is a spiraling and circularly rotating airflow. As the craft moves forward, these vortices trail off behind the craft.^{[citation needed]}

When hovering with a forward diagonal crosswind, or moving in a forward diagonal direction, the spinning vortices trailing off the main rotor blades will align with the rotation of the tail rotor and cause an instability in flight control.^[102]

When the trailing vortices colliding with the tail rotor are rotating in the same direction, this causes a loss of thrust from the tail rotor. When the trailing vortices rotate in the opposite direction of the tail rotor, thrust is increased. Use of the foot pedals is required to adjust the tail rotor's angle of attack, to compensate for these instabilities.^{[citation needed]}

These issues are due to the exposed tail rotor cutting through open air around the rear of the vehicle. This issue disappears when the tail is instead ducted, using an internal impeller enclosed in the tail and a jet of high pressure air sideways out of the tail, as the main rotor vortices can not impact the operation of an internal impeller.^{[citation needed]}

For a standard helicopter with a single main rotor, maintaining steady flight with a crosswind presents an additional flight control problem, where strong crosswinds from certain angles will increase or decrease lift from the main rotors. This effect is also triggered in a no-wind condition when moving the craft diagonally in various directions, depending on the direction of main rotor rotation.^[103]

This can lead to a loss of control and a crash or hard landing when operating at low altitudes, due to the sudden unexpected loss of lift, and insufficient time and distance available to recover.^{[citation needed]}

Conventional rotary-wing aircraft use a set of complex mechanical gearboxes to convert the high rotation speed of gas turbines into the low speed required to drive main and tail rotors. Unlike powerplants, mechanical gearboxes cannot be duplicated (for redundancy) and have always been a major weak point in helicopter reliability. In-flight catastrophic gear failures often result in gearbox jamming and subsequent fatalities, whereas loss of lubrication can trigger onboard fire.^{[citation needed]} Another weakness of mechanical gearboxes is their transient power limitation, due to structural fatigue limits. Recent EASA studies point to engines and transmissions as prime cause of crashes just after pilot errors.^[104]

By contrast, electromagnetic transmissions do not use any parts in contact; hence lubrication can be drastically simplified, or eliminated. Their inherent redundancy offers good resilience to single point of failure. The absence of gears enables high power transient without impact on service life. The concept of electric propulsion applied to helicopter and electromagnetic drive was brought to reality by Pascal Chretien who designed, built and flew world's first man-carrying, free-flying electric helicopter. The concept was taken from the conceptual computer-aided design model on 10 September 2010 to the first testing at 30% power on 1 March 2011 – less than six months. The aircraft first flew on 12 August 2011. All development was conducted in Venelles, France.^[105][106]

In addition to regulatory measures, helicopter operators are also supported by voluntary safety teams that analyze accident data and promote specific countermeasures. In the United States, for example, the U.S. Helicopter Safety Team (USHST) publishes accident reviews and safety enhancements that address issues such as loss of control in flight, inadvertent flight into instrument meteorological conditions (IIMC), and low-altitude operations, encouraging improvements in training, operational decision-making, and the use of safety-enhancing technologies.^[107][108]

As with any moving vehicle, unsafe operation could result in loss of control, structural damage, or loss of life. The following is a list of some of the potential hazards for helicopters:

• Settling with power is when the aircraft has insufficient power to arrest its descent. This hazard can develop into vortex ring state if not corrected early.^[109]
• Vortex ring state is a hazard induced by a combination of low airspeed, high power setting, and high descent rate. Rotor-tip vortices circulate from the high pressure air below the rotor disk to low pressure air above the disk, so that the helicopter settles into its own descending airflow.^[109] Adding more power increases the rate of air circulation and aggravates the situation. It is sometimes confused with settling with power, but they are aerodynamically different.
• Retreating blade stall is experienced during high speed flight and is the most common limiting factor of a helicopter's forward speed.
• Ground resonance is a self-reinforcing vibration that occurs when the lead/lag spacing of the blades of an articulated rotor system becomes irregular.
• Low-G condition is an abrupt change from a positive G-force state to a negative G-force state that results in loss of lift (unloaded disc) and subsequent roll over. If aft cyclic is applied while the disc is unloaded, the main rotor could strike the tail causing catastrophic failure.^[110]
• Dynamic rollover in which the helicopter pivots around one of the skids and 'pulls' itself onto its side (almost like a fixed-wing aircraft ground loop).
• Powertrain failures, especially those that occur within the shaded area of the height–velocity diagram.
• Tail rotor failures which occur from either a mechanical malfunction of the tail rotor control system or a loss of tail rotor thrust authority, called "loss of tail-rotor effectiveness" (LTE).
• Brownout in dusty conditions or whiteout in snowy conditions.
• Low rotor RPM, is when the engine cannot drive the blades at sufficient RPM to maintain flight.
• Rotor overspeed, which can over-stress the rotor hub pitch bearings (brinelling) and, if severe enough, cause blade separation from the aircraft.
• Wire and tree strikes due to low altitude operations and take-offs and landings in remote locations.^[111]
• Controlled flight into terrain in which the aircraft is flown into the ground unintentionally due to a lack of situational awareness.
• Mast bumping in some helicopters^[112]

Wikimedia Commons has media related to Helicopters.

Look up helicopter in Wiktionary, the free dictionary.

• "Helicopterpage.com – How Helicopters Work" Complete site explaining different aspects of helicopters and how they work.
• "Planes That Go Straight Up". 1935 article about early development and research into helicopters.
• "Flights — of the Imagination". 1918 article on helicopter design concepts.
• "Twin Windmill Blades Fly Wingless Ship" Popular Mechanics, April 1936
• Silent (Russian-language intertitled) video about the Cheremukhin/Yuriev TsAGI 1-EA pioneer helicopter
• American Helicopter Society
• U.S. Helicopter Safety Team
• Helicopter Safety Enhancements
• Graham Warwick (17 June 2016). "How The Helicopter Has Developed". Aviation Week & Space Technology. Getting from idea to reality took far longer for the helicopter than for the fixed-wing aircraft.