WIDE-BODY AIRCRAFT

A 'wide-body aircraft' is a large airliner with a fuselage diameter of 5 to 6 metres (16 to 20 ft). In common terms, it refers to an aircraft with twin aisles inside the cabin. 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.

Contents

History

Design considerations

Operating considerations

References

History

Following the success of the Boeing 707 and Douglas DC-8 in the late 1950s, airlines began asking for larger aircraft to meet the rising demand for air travel. Engineers were faced with many challenges as airlines wanted more seats, more range, and lower operating cost. One of the most significant difficulties was selecting a fuselage configuration suitable for more than 200 passengers.
Early jet aircraft like the 707 and DC-8 seated passengers either side of a single aisle, with no more than 6 seats per row. Larger aircraft would have to be longer, higher (ie double-deck) or wider in order to accommodate the proposed passenger numbers. Engineers realized that lengthening the fuselage would have resulted in aircraft that would be too long to be handled by airports, while having two decks caused difficulties meeting emergency evacuation regulations which were extremely challenging with the technology available at the time. This left a wider fuselage as the best option: by adding a second aisle as many as 10 seats across could be accommodated.^[1]

The first true wide-body airliner was the four-engined Boeing 747; it debuted in 1969 and remains the largest in passenger service, seating over 400 passengers. The main deck of the 747 features twin aisles and seating 10-abreast, while the upper deck "hump" seats 6-abreast along a single aisle.
Other wide-bodies soon followed, including the McDonnell Douglas DC-10 and the Lockheed L-1011 Tristar. In 1974, Airbus introduced the Airbus A300, first twin-engined wide-body. 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:

★ Airbus A380 (2007) - the world's largest passenger aircraft

★ Boeing 787 (2008) - first aircraft to utilize monolithic composite fuselage, replacement for the Boeing 767

★ Airbus A350 (2012-2013) - replacement for the Airbus A330/A340 line

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.

★ Twin aisles accelerate loading and unloading/evacuation relative to a single aisle

★ Wider fuselage reduces the overall length of the aircraft, improving ground maneuverability and reducing the risk of tail strikes.

★ Greater under-floor freight capacity.

★ More structurally efficient than narrow-bodies for large aircraft

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 300,000 lb (136,000 kg) or more are classed as Heavy, those between 15,500 lb and 300,000 lb (7,000 kg and 136,000 kg) are classed as Medium, and those below 15,500 lb (7,000 kg) are classed as Light. Due to their weight, all current wide-body aircraft are categorised as Heavy.
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, flight UAL342 operated by United Airlines using a wide bodied aircraft would use the call sign "United 342 Heavy" while in the USA.

References

1. Wide Body: The Making of the Boeing 747, , Clive, Irving, Coronet, , ISBN 0 340 59983 9