Wednesday, February 2, 2011

Wide-body aircraft

The Airbus A380 is the world's largest and widest passenger aircraft
A wide-body aircraft is a large airliner with two passenger aisles, also known as a widebody aircraft or twin-aisle aircraft. The typical fuselage diameter is 5 to 6 m (16 to 20 ft). In the typical wide-body economy cabin, passengers are seated seven to ten abreast, allowing a total capacity of 200 to 600 passengers. The largest wide-body aircraft are over 6 m (20 ft) wide, and can accommodate up to eleven passengers abreast in high-density configurations.
By comparison, a traditional narrow-body airliner has a diameter of 3 to 4 m (10 to 13 ft), with a single aisle, and seats between two and six people abreast.
Wide-body aircraft were originally designed for a combination of efficiency and 
Size comparison between a Boeing 737-300 (narrow-body) and a
Boeing 777 (widebody aircraft),..

passenger comfort. However, airlines quickly gave in to economic factors, and reduced the extra passenger space in order to maximize revenue and profits.
Wide-body aircraft are also used for the transport of commercial freight and cargo and other special uses, described further below.

Boeing 747, the first widebody passenger aircraft, operated by Pan American World Airways
The Bristol Brabazon was a widebody transatlantic design that first flew in 1949 but never reached production. Following the success of the Boeing 707 and Douglas DC-8 in the late 1950s, 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 the greater number of passenger seats. Engineers also realized that lengthening the fuselage would have resulted in aircraft that would be too long to be handled by airports, while having two decks created difficulties in meeting emergency evacuation regulations, which were extremely challenging provided the technology available at the time. These parameters left a wider fuselage as the best option: by adding a second aisle, the wider aircraft could accommodate as many as 10 seats across.
The widebody age began in 1970 with the entry into service of the first widebody airliner, the four-engined, double-deck Boeing 747. 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.
After the success of the early widebody aircraft, several successors came to market over the next two decades, including the Airbus A330-A340 Series and the Boeing 777. 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.

Design considerations

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 basis
Twin aisles that accelerate loading, unloading, and evacuation compared to a single aisle.
Wider fuselage that reduces the overall aircraft length, improving ground manoeuvrability 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 VC-10 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 a large engine on the aft fuselage.

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 comparable trijet or four-engined aircraft. 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 eliminated due to higher maintenance and fuel costs,[citation needed] and only the heaviest widebody aircraft today are built with four engines (the Airbus A340, Airbus A380 and Boeing 747-8).
The Boeing 777 twinjet features the largest and most powerful jet engine in the world, the General Electric GE90, which is 128 inches (3.25 m) in diameter. 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). 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.


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 widebody aircraft.
Bar and lounge areas which were once installed on the Boeing 747 have mostly disappeared, but a few have returned in first class or business class on the Airbus A340-600, Boeing 777-300ER, and on the Airbus A380. 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.
Depending on how the airline configures the aircraft, the size and seat pitch of the airline seats will vary significantly.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.
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.

Wake turbulence and separation

This picture from a NASA study on wingtip vortices illustrates wake turbulence
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: light, medium, heavy, and super.
Due to their weight, all current widebody aircraft are categorized as heavy, or in the 
case of the A380, super.

Separation (air traffic control)
The wake-turbulence category also is used to guide the separation of aircraft.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, are 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. Airbus A340, Airbus A380, and Boeing 747 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 Tanker 910 and the 747-based Evergreen Supertanker.
Some widebody aircraft are used as VIP transport. Germany uses the Airbus A310, while Russia uses the Ilyushin Il-96 to transport their highest leaders. The specially modified Boeing 747-200 used by the President of the United States is known as Air Force One, or the Boeing VC-25. More information can be found under: Air transports of heads of state and government.

Future development
The Boeing 787, the first large composite aircraft, expected in service in 2011
Airbus and Boeing are racing to market with two new widebody designs, currently in development. Both manufacturers have been under significant pressure to see which obtains the most orders.
Currently, the Boeing 787 has received more orders than Airbus, and will be first to enter into airline service. The 787 is also the first large commercial aircraft to utilize a monolithic composite fuselage.
The initial Airbus A350 design was only a minor upgrade to that of the A330/A340 series, but Airbus was forced to make significant design changes in response to feedback from the airlines. In addition to being a few inches wider than the Boeing, Airbus claims that the A350 final specifications will be better than that of the 787.
The article on competition between Airbus and Boeing further discusses the rivalry, while order counts between the two aircraft can be compared under Airbus A350 orders versus Boeing 787 orders.

Widebody specifications

Inside Diameter,
main passenger deck,
upper passenger deck
Outside Diameter,
main passenger deck
Number of seats across in economy,
main deck (seat width)
Airbus A3001974–20072132.0 tons
171.7 tons
208 inches (5.28 m)222 inches (5.64 m)8 across (17.0" wide) in 2-4-2 on TG
8 across (17.0" wide) in 2-4-2 on LH
Airbus A3101982–20072164.0 tons208 inches (5.28 m)222 inches (5.64 m)8 across (17.4" wide) in 2-4-2 on AI
Airbus A33019942233.0 tons208 inches (5.28 m)222 inches (5.64 m)8 across (17.5" wide) in 2-4-2 on EK
8 across (17.5" wide) in 2-4-2 on NW
Airbus A34019934380.0 tons208 inches (5.28 m)222 inches (5.64 m)8 across (17.3" wide) in 2-4-2 on EY 
Airbus A35020132298.0 tons221 inches (5.61 m) 235 inches (5.97 m) 8 across (19.0" wide) in 2-4-2 proposed
9 across (17.7" wide) in 3-3-3 proposed
Airbus A38020074560.0 tons259 inches (6.58 m)
233 inches (5.92 m) 
281 inches (7.14 m) 10 across (20.5" wide) in 3-4-3 on LH
10 across (18.1" wide) in 3-4-3 on QF
10 across (18.0" wide) in 3-4-3 on EK
Boeing 74719704412.8 tons240 inches (6.10 m)
136 inches (3.45 m)
256 inches (6.50 m) 10 across (17.7" wide) in 3-4-3 on TG
10 across (17.2" wide) in 3-4-3 on NW
Boeing 76719822204.1 tons186 inches (4.72 m)198 inches (5.03 m)7 across (18.0" wide) in 2-3-2 on UA
7 across (17.0" wide) in 2-3-2 on US
Boeing 77719952351.5 tons231 inches (5.87 m) 244 inches (6.20 m) 9 across (18.0" wide) in 2-5-2 on UA 
9 across (17.9" wide) in 3-3-3 on CO
10 across (17.0" wide) in 3-4-3 on AF
Boeing 78720112245.0 tons215 inches (5.46 m)227 inches (5.77 m)
8 across (18.5" wide) in 2-4-2 proposed
9 across (17.2" wide) in 3-3-3 proposed
Ilyushin Il-861980–19944208.0 tons224 inches (5.70 m) 239 inches (6.08 m) 9 across (18.0" wide) in 3-3-3
Ilyushin Il-9619924240.0 tons224 inches (5.70 m)239 inches (6.08 m) 9 across (18.0" wide) in 3-3-3 on SU
L1011 Tristar1972–19843231.3 tons225 inches (5.72 m)237 inches (6.02 m)9 across (17.0" wide) in 2-5-2 on SV
MD DC-101971–19883259.5 tons224 inches (5.69 m)237 inches (6.02 m)9 across (17.2" wide) in 2-5-2 on NW
MD MD-111990–20003286.0 tons224 inches (5.69 m)237 inches (6.02 m)9 across (17.5" wide) in 3-3-3 on KL 


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