Wide-body aircraft

The Airbus A380 is the world's largest and widest passenger aircraft.

Size comparison between a British Airways Airbus A320 (narrow-body) and an Air Canada Boeing 777-300ER (widebody aircraft)

A wide-body aircraft is a jet airliner having a fuselage wide enough to accommodate two passenger aisles, also known as twin-aisle aircraft, with seven or more seats abreast.^[1] The typical fuselage diameter is 5 to 6 m (16 to 20 ft).^[2] In the typical wide-body economy cabin, passengers are seated seven to ten abreast,^[3] allowing a total capacity of 200 to 850^[4] passengers. The largest wide-body aircraft are over 6 m (20 ft) wide,^[5] and can accommodate up to eleven passengers abreast in high-density configurations.

By comparison, a typical narrow-body airliner has a diameter of 3 to 4 m (10 to 13 ft), with a single aisle,^[1][6] and seats between two and six people abreast.^[7]

Wide-body aircraft were originally designed for a combination of efficiency and passenger comfort and to increase the amount of cargo space. However, airlines quickly gave in to economic factors, and reduced the extra passenger space in order to maximize revenue and profits.^[8]

Wide-body aircraft are also used for the transport of commercial freight and cargo^[9] and other special uses, described further below.

The biggest wide-body aircraft are known as jumbo jets due to their very large size; examples include the Boeing 747 ("jumbo jet"), Airbus A380 ("superjumbo jet"), and upcoming Boeing 777X ("mini jumbo jet").^[10][11] The phrase, "jumbo jet", derives from Jumbo, a famous circus elephant in the 19th century.^[12][13]

7-abreast aircraft seats typically 160 to 260 passengers, 8-abreast 250 to 380, 9 and 10-abreast 350 to 480.^[14]

History

Boeing 747, the first widebody passenger aircraft, operated by Pan American World Airways

Following the success of the Boeing 707 and Douglas DC-8 in the late 1950s and early 1960s, airlines began seeking larger aircraft to meet the rising global demand for air travel. Engineers were faced with many challenges as airlines demanded more passenger seats per aircraft, longer ranges and lower operating costs.

Early jet aircraft such as the 707 and DC-8 seated passengers along either side of a single aisle, with no more than six seats per row. Larger aircraft would have to be longer, higher (such as a double deck), or wider in order to accommodate a greater number of passenger seats. Engineers realized having two decks created difficulties in meeting emergency evacuation regulations with the technology available at that time. During the 1960s, it was also believed that supersonic airliners would succeed larger, slower planes. Thus, it was believed that most subsonic aircraft would become obsolete for passenger travel and would be eventually converted to freighters. As a result, airline manufacturers opted for a wider fuselage rather than a taller one (the 747, and eventually the DC-10 and L-1011). By adding a second aisle, the wider aircraft could accommodate as many as 10 seats across, but could also be easily converted to a freighter and carry two eight-by-eight freight pallets abreast.^[15]

The engineers also opted for creating "stretched" versions of the DC-8 (61, 62 and 63 models), as well as longer versions of Boeing's 707 (-320B and 320C models) and 727 (-200 model); and Douglas' DC-9 (-30, -40, and -50 models), all of which were capable of accommodating more seats than their shorter predecessor versions. The full length double-deck solution was not realized until the twenty-first century, in the form of the Airbus A380.

The McDonnell Douglas DC-10 (Right) and MD-11 (Left) wide-body trijets.

The widebody age began in 1970 with the entry into service of the first widebody airliner, the four-engined, partial double-deck Boeing 747.^[16] New trijet widebody aircraft soon followed, including the McDonnell Douglas DC-10 and the Lockheed L-1011 TriStar. The first widebody twinjet, the Airbus A300, entered service in 1974. This period came to be known as the "widebody wars".^[17]

After the success of the early widebody aircraft, several successors came to market over the next two decades, including the Boeing 767 and 777, the Airbus A330 and A340, and the McDonnell Douglas MD-11. In the "jumbo" category, the capacity of the Boeing 747 was not surpassed until October 2007, when the Airbus A380 entered commercial service with the nickname Superjumbo.^[18]

In the mid-2000s, rising oil costs in a post-9/11 climate caused airlines to look towards newer, more fuel efficient aircraft. Two such examples are the Boeing 787 Dreamliner and Airbus A350 XWB. The proposed Comac C929 and C939 may also share this new widebody market.

Cross-section comparison of Airbus A380(Full length double deck) and Boeing 747-400(Only the front section is double deck)

Design considerations

Fuselage

Airbus A300 cross-section, showing cargo, passenger, and overhead areas

Although widebody aircraft have a larger frontal area (and thus greater form drag) than a narrow-body aircraft of similar capacity, they have several advantages over their narrow-body counterparts:

• Larger volume of space for passengers, giving a more open feeling to the space
• Lower ratio of surface area to volume, and thus lower drag on a per-passenger/cargo basis. The only exception to this would be with very long narrow-body aircraft, such as the Boeing 757
• Twin aisles that accelerate loading, unloading, and evacuation compared to a single aisle (widebody airliners typically have between 3.5 and 5 seats per aisle, compared to 5-6 on most narrow-body aircraft)^[19]
• Reduced overall aircraft length for a given passenger or cargo capacity, improving ground maneuverability and reducing the risk of tail strikes.
• Greater under-floor freight capacity
• Better structural efficiency for larger aircraft than would be possible with a narrow-body design

British and Russian designers had proposed widebody aircraft similar in configuration to the Vickers VC10 and Douglas DC-9, but with a widebody fuselage. The British Three-Eleven project never left the drawing board, while the Russian Il-86 widebody proposal eventually gave way to a more conventional wing-mounted engine design, most likely due to the inefficiencies of mounting such large engines on the aft fuselage.

Engines

Mechanic working on a Rolls Royce Trent 900 engine during testing. The Trent is a typical type of high bypass turbofan used in widebody airliners.

As jet engine power and reliability have increased over the last decades, most of the widebody aircraft built today have only two engines. A twinjet design is more fuel-efficient than a trijet or four-engined aircraft of similar size. The increased reliability of modern jet engines also allows aircraft to meet the ETOPS certification standard, which calculates reasonable safety margins for flights across oceans. The trijet design has been effectively dismissed due to higher maintenance and fuel costs compared to a twinjet. The vast majority of aircraft designs today have two engines, with only the heaviest widebody aircraft built with four engines (the Airbus A340, Airbus A380 and Boeing 747).^[20][21]

The Boeing 777 twinjet features the largest and most powerful^[22] jet engine in the world, the General Electric GE90, which is 134 inches (3.40 m) in diameter.^[23] This is almost as wide as the entire fuselage of a Boeing 737 at 148 inches (3.76 m).

The massive maximum takeoff weight of the Airbus A380 (560 tonnes (1,200,000 lb)) would not have been possible without the engine technology developed for the Boeing 777 (such as contra-rotating spools).^[24] The Trent 900 engine pictured, used on the Airbus A380, has a fan blade diameter of 116 inches (2.95 m), only slightly smaller than the GE90 engines on the Boeing 777. An interesting design constraint of the Trent 900 engines is that they are designed to fit into a Boeing 747-400F freighter for relatively easy transport by air cargo.^[25]

Interior

The interiors of aircraft, known as the aircraft cabin, have been undergoing evolution since the first passenger aircraft. Today, between one and four classes of travel are available on wide-body aircraft.

Bar and lounge areas which were once installed on wide-body aircraft have mostly disappeared, but a few have returned in first class or business class on the Airbus A340-600,^[26] Boeing 777-300ER,^[27] and on the Airbus A380.^[28] Emirates Airline has installed showers for first-class passengers on the A380; twenty-five minutes are allotted for use of the room, and the shower operates for a maximum of five minutes.^[29][30]

Depending on how the airline configures the aircraft, the size and seat pitch of the airline seats will vary significantly.^[31] For example, aircraft scheduled for shorter flights are often configured at a higher seat density than long-haul aircraft. Due to current economic pressures on the airline industry, high seating densities in the economy class cabin are likely to continue.^[32]

In some of the largest single-deck widebody aircraft, such as the Boeing 777, the extra space above the cabin is utilized for crew rest areas and galley storage.

A comparison of interior cabin widths and economy class seating layouts is shown below under widebody specifications. Further information can be found under external links.

• 

  Cubana's Ilyushin Il-96 economy-class cabin

• 

  Avianca Airbus A330 business-class seats

• 

  First-class seats on a Cathay Pacific 747-400

Wake turbulence and separation

This picture from a NASA study on wingtip vortices illustrates wake turbulence.

Aircraft are categorized by ICAO according to the wake turbulence they produce. Because wake turbulence is generally related to the weight of an aircraft, these categories are based on one of four weight categories:^[33] light, medium, heavy, and super.^[34]

Due to their weight, all current widebody aircraft are categorized as heavy, or in the case of the A380 in U.S. airspace, super.

The wake-turbulence category also is used to guide the separation of aircraft.^[35] Super and heavy-category aircraft require greater separation behind them than those in other categories. In some countries, such as the United States, it is a requirement to suffix the aircraft's call sign with the word "heavy" (or super) when communicating with air traffic control in certain areas.

Special uses

A U.S. Space Shuttle mounted on a modified Boeing 747

Widebody aircraft are used in science, research, and the military. Two specially modified Boeing 747 aircraft, the Shuttle Carrier Aircraft, were used to transport the U.S. Space Shuttle. Some widebody aircraft are used as flying command posts by the military, such as the Boeing E-4, while the Boeing E-767 is used for Airborne Early Warning and Control. New military weapons are tested aboard widebodies, as in the laser weapons testing on the Boeing YAL-1. Other widebody aircraft are used as flying research stations, such as the joint German-U.S. Stratospheric Observatory for Infrared Astronomy (SOFIA). Airbus A340,^[36] Airbus A380,^[37] and Boeing 747^[38] four-engine widebody aircraft are used to test new generations of aircraft engines in-flight. A few aircraft have also been converted for aerial firefighting, such as the DC-10-based^[39] Tanker 910 and the 747-based Evergreen Supertanker.^[40]

Some widebody aircraft are used as VIP transport. Canada uses the Airbus A310, while Russia uses the Ilyushin Il-96 to transport their highest leaders. Germany replaced their Airbus A310 by an Airbus A340 in spring 2011. Specially-modified Boeing 747-200s (Boeing VC-25s) are used to ferry the President of the United States. When one of these aircraft is in use by the President, its call sign is Air Force One. More information can be found under: Air transports of heads of state and government.

Comparison of wide-body aircraft civilian and military passenger and freight

See also

• Aircraft seat map
• Competition between Airbus and Boeing
• Large aircraft
• List of large aircraft
• Narrow-body aircraft

References

External links

Look up widebody in Wiktionary, the free dictionary.

Wikimedia Commons has media related to Aircraft cabins.

• Official Airbus website
• Official Boeing website
• Airplane seat pitch and width information from eskyguide.com, in table form
• WidebodyAircraft.nl information and chronology
• Etihad Airways document of their A340-600 interior.