Wide-body aircraft

The Airbus A380 prototype on its first landing, April 27, 2005.

Boeing 747, the first wide-body, operated by Pan American.

Lockheed C-5 Galaxy, one of the world's largest aircraft, is an example of a military wide-body.

A wide-body aircraft is a large airliner with a fuselage diameter of 5 to 6 metres (16 to 20 ft) and twin aisles. Passengers are usually seated 7 to 10 abreast. For comparison, a traditional narrow-body airliner has a diameter of 3 to 4 metres (10 to 13 ft), a single aisle, and seats arranged 2 to 6 abreast. Typical wide-body aircraft can accommodate between 200 and 600 passengers, while the largest narrow-bodies carry about 280. Freight or cargo wide-bodies also exist.

History

The 1940s saw a significant growth in the size of aircraft for commercial service: to serve larger destinations on longer flights, a larger aircraft with more paying passengers would, in theory, be more efficient and profitable. Larger aircraft developed in the 1940s included the Boeing 377 Stratocruiser, the Lockheed Constitution, and the Bristol Brabazon (the latter two of which did not enter civilian service).

The first true wide-body airliner was the four-engined Boeing 747; it debuted in 1969 and remains the largest in passenger service. (The new Airbus A380 is larger; it is scheduled to enter service in 2007.)

Slightly smaller and shorter-ranged three-engined wide-bodies followed in the early 1970s—the McDonnell Douglas DC-10 and the Lockheed L-1011 Tristar—then the twin-engined Airbus A300 in 1974. Subsequent commercial wide-bodies include:
* Ilyushin Il-86 (1980)
* Airbus A310 (a shortened A300) (1982)
* Boeing 767 (1982)
* McDonnell Douglas MD-11 (1986)
* Ilyushin Il-96 (1992)
* Airbus A330/A340 family (1993)
* Boeing 777 (1995)

Three wide-body designs are in development or testing: the aforementioned Airbus A380, the Airbus A350 (a member of the A330/A340 family), and the 787 "Dreamliner," scheduled for 2008.

The United States and the Soviet Union/Russia have both produced dedicated military wide-body transports. These include:
* Lockheed C-5 Galaxy
* Ilyushin Il-76 "Candid"
* Antonov An-124/An-225
* Boeing C-17 Globemaster III

Two unorthodox freight aircraft, modified from more conventional designs, deserve mention, although these are "one-offs" and not production designs. The Boeing C-97 Stratofreighter design was transformed into the Pregnant Guppy or Super Guppy with bulbous upper fuselages, used for transporting spacecraft and rocket stages for the Apollo program. Airbus performed a similar operation on its A300 design to create the Beluga design, of which five are in operation. The Airbus design has, among other duties, a similar mission as its Boeing predecessor: transporting International Space Station components for the European Space Agency.

Design considerations

Although a wide-body aircraft has a larger frontal area than a narrow-body of equivalent capacity, and thus greater form drag, it has several advantages:
* Lower ratio of surface area to volume, and thus (for equal volume) lower frictional drag.
* Shorter twin aisles make loading and unloading/evacuation faster and reduce the difficulty of serving refreshments.
* Shorter overall length reduces difficulty in achieving desired take-off rotation angle without very long and heavy landing gear.
* Greater under-floor freight capacity.
* It is possible to make a wide-body aircraft much larger than a narrow-body and, all else being equal, the larger the aircraft, the lower the fuel-burn per passenger-mile and the lower the cost.

Operating considerations

Aircraft are categorised by ICAO according to the amount of wake turbulence they produce. Because wake turbulence is generally related to the weight of an aircraft, these categories are based on weight - aircraft with a maximum certificated take-off weight of 300,000lb (136,000kg) or more are classed as Heavy, those between 15,500lb and 300,000lb (7,000kg and 136,000kg) are classed as Medium, and those below 15,500lb (7,000kg) are classed as Light. Due to their weight, all current wide-body aircraft are categorised as Heavy (in addition, the narrowbody Boeing 757, while not being a Heavy by weight, is classed as Heavy due to the amount of wake turbulence it creates).

The wake turbulence category is used to guide the separation of aircraft - a Heavy category aircraft will require greater separation behind it than a Medium category, which in turn requires more separation than a Light category. In some countries, such as the USA, it is a requirement to suffix the aircraft's call sign with the word "heavy" when communicating with ATC in the Terminal Radar Area. If the aircraft is on an ARTCC (Center Freq) they are not required to say "heavy" at the end of the callsign. (for example UAL342 operated by a Heavy aircraft would use the call sign "United 342 Heavy" while in the USA).