Airliner
From Wikipedia, the free encyclopedia
An airliner is a large fixed-wing aircraft with the primary function of transporting paying passengers. Such aircraft are usually operated by an airline which owns or leases the aircraft.
The official definition of an airliner varies from country to country, but the common definition is an aircraft with seating for 20 or more passengers and/or an empty weight above 22,680 kg (50,000 lb.), with two or more engines.
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[edit] Types of airliners
[edit] Wide-body jets
The largest airliners are wide-body jets. In the aviation industry, these aircraft are frequently called twin-aisle aircraft because they generally have two separate aisles running from the front to the back of the passenger cabin. Aircraft in this category are the Boeing 747, Boeing 767, Boeing 777, Airbus A300/A310, Airbus A330, Airbus A340, Airbus A380, McDonnell Douglas DC-10, McDonnell Douglas MD-11, Ilyushin Il-86 and Ilyushin Il-96. These aircraft are usually used for long-haul flights between airline hubs and major cities with many passengers. Future wide-body models not yet flying include Boeing 787 and Airbus A350.
[edit] Narrow-body jets
A smaller, more common class of airliners are the narrow-body or single aisle aircraft. These smaller airliners are generally used for medium-distance flights with fewer passengers than their wide-body counterparts.
Examples include the Boeing 717, 737, 757, DC-9, MD80 series, and Airbus A320 family. Older airliners like the Boeing 727, DC-8, Fokker 70/100, VC10, Tupolev, and Yakovlev jets also fit into this category.
[edit] Regional airliners
Regional airliners typically seat fewer than 100 passengers and may be powered by turbofans or turboprops. These airliners, though smaller than aircraft operated by major airlines, frequently serve customers who expect service similar to that offered by crew on larger aircraft. Therefore, most regional airliners are equipped with lavatories and have a flight attendant to look after the in-flight needs of the passengers.
Typical aircraft in this category are the Bombardier CRJ series and "Q" (DASH-8) series, Embraer ERJ 145 family, ATR 42/72 and Saab 340/2000. Airlines and their partners sometimes use these for short flights between small hubs, or for bringing passengers to hub cities where they may board larger aircraft.
[edit] Commuter aircraft
Passenger aircraft with 19 or fewer passenger seats are called commuter aircraft or air taxis, depending on their size, engines, and seating configurations. The Beechcraft 1900, for example, has only 19 seats and thus, depending on local and national regulations, it may not qualify as an airliner and may not be subject to the regulations applied to larger aircraft.
Members of this class of aircraft normally lack such amenities as lavatories and galleys and typically do not carry a flight attendant.
Other aircraft in this category are the Fairchild Metro, Jetstream 31/41, IPTN CN-235, and Embraer EMB 110 Bandeirante. The Cessna Caravan, a single-engine turboprop, is sometimes used as a small airliner, although many countries stipulate a minimum requirement of two engines for aircraft to be used as airliners.
Twin piston-engined aircraft like the Cessna, Piper, Britten-Norman, and Beechcraft, are also in use as commuter aircraft.
[edit] Engines
Until the beginning of the jet age, piston engines were common on propliners like the Douglas DC-3. Now nearly all modern airliners are powered by turbine engines, either turbofans or turboprops. Gas turbine engines operate efficiently at much higher altitudes, are far more reliable than piston engines, and produce less vibration and noise.
[edit] Airliner variants
Some variants of airliners have been developed for carrying freight or for luxury corporate use. Many airliners have also been modified for government use as "VIP" transports and for military functions such as airborne tankers (for example, the Vickers VC-10, Lockheed L1011, Boeing 707), air ambulance (USAF/USN McDonnell-Douglas C-9), reconnaissance (Embraer ERJ 145, Saab 340, Boeing 737), as well as for troop-carrying roles.
[edit] Manufacturers
Historically, a few manufacturers have dominated the market for large airliners. These include:
- American companies
- Boeing
- Douglas Aircraft Company and later, McDonnell Douglas (now a part of Boeing)
- Lockheed Corporation (now part of Lockheed-Martin, and no longer involved in civil aviation)
- Russian companies (formerly Soviet-controlled)
- Europe
- Airbus Industrie (a multinational conglomeration of smaller European aerospace companies)
- Other major manufacturers include:
- Embraer (Brazil)
- Bombardier (Canada,includes the former De Havilland Canada)
- ATR (France/Italy)
- Fokker (The Netherlands, now defunct)
[edit] Notable disputes
The large (100 seat or greater) airliner market is dominated by two companies: Airbus, a Western European aviation conglomerate, and Boeing, based in the United States. With the emergence of Airbus as a competitor to Boeing, both companies, backed by their respective governments (the European Union and European governments on one side, the US government on the other side), have recently been engaged in various trade disputes. Each side accuses the other of being unfairly subsidized by their respective governments. Owing to its origin as a combination of state-owned aviation enterprises, Airbus receives a significant portion of its operating budget directly from various European governments, ostensibly as loans, but without the obligation to repay them. On the other hand, Boeing gets research and development funding from NASA and the US Department of Defense, various tax breaks (which all similar US companies receive), and a large volume of military orders, all of which Airbus views as indirect subsidies.
In addition to their main headquarters in Europe and the United States, both Airbus and Boeing use subcontractors from many countries. For example, Boeing has long had major components built by companies in Japan with various subsystems coming from Europe and Asia. Airbus aircraft are often equipped with engines, auxiliary power units, and electronic systems built in the US. Thus, while both companies may try to present themselves as strictly national entities, the airliners they build are composed of components manufactured across the globe.
[edit] Famous airliners
Below are some famous airliners:
- The Douglas DC-3 - Considered by many to be the first true airliner
- The triple-tailed Lockheed Constellation of the 1950s
- The De Havilland Comet - First jet airliner in service
- The Sud Caravelle - First sucessful jet airliner.
- The Boeing 707 and Douglas DC-8 - The American-built jetliners that popularized the advantages of jet airliners
- The Airbus A320- Pioneer of fly-by wire
- The Concorde - Capable of flying at twice the speed of sound and operated from 1976 to 2003 by British Airways and Air France
- The Boeing 747 "jumbo jet" - the largest airliner between 1968 and 2005
- The Airbus A380 "superjumbo" - The world's largest airliner to date, featuring two full-length twin-aisle passenger cabins, is expected to start service with Singapore Airlines in mid 2007.
[edit] Airliner recycling
As airliners are very expensive, most are leased out for long periods of time (typically from 20 to 40 years) and very few go back into service after a long lease is up because evolving aerospace technology leaves older airliners unable to compete against newer machines that can be operated at a lower cost. Many end-of-service airliners end up in the Mojave Desert, at the Mojave Spaceport (also known as "The Airplane Boneyard"). From this, the term "Mojave" has come to refer to the temporary storage of aircraft, e.g. during decreased demand for air travel and between short-term leases. Another location to retire airliners is Marana, Arizona.
While eventually almost every airliner will be reduced to scrap (the exceptions end up as museum pieces or flown by collector groups) they may pass through many owners before they are finally retired. A well-maintained airliner can operate safely for decades, depending on how often it is flown, its operating environment, and whether damage and wear and tear is properly repaired.
What may end an airliner's working life is a lack of spare parts, as the original manufacturer and third manufacturers may no longer provide or support them. Corrosion and metal fatigue is another issue that becomes more expensive to deal with as time goes on. Eventually, these factors and advances in aircraft technology lead to older airliners becoming too expensive and inefficient to operate.
[edit] Cabin configurations
An airliner may have several classes of seating: first class, business class, and/or economy class (which may be referred to as coach class or tourist class, and sometimes has a separate "premium" economy section with more legroom and amenities). The seats in more expensive classes are wider, more comfortable, and have more amenities such as "lie flat" seats for more comfortable sleeping on long flights. Generally, the more expensive the class, the better the beverage and meal service.
Domestic flights generally have a two-class configuration, usually first or business class and coach class, although many airlines have switched to all-economy seating. International flights generally have either a two-class configuration or a three-class configuration, depending on the airline, route and aircraft type. Many airliners offer movies or audio/video on demand (this is standard in first and business class on many international flights and may be available on economy).
[edit] Seats
The types of seats that are provided and how much legroom is given to each passenger are decisions made by the individual airlines, not the aircraft manufacturers. Seats are mounted in "tracks" on the floor of the cabin and can be moved back and forth by the maintenance staff or even removed altogether. Naturally the airline tries to maximize the number of seats available in every aircraft to carry the largest possible (and therefore most profitable) number of passengers.
Passengers seated in an exit row (the row of seats adjacent to an emergency exit) enjoy substantially more legroom than those seated in the remainder of the cabin, while the seats directly in front of the exit row may have less legroom and may not even recline (for evacuation safety reasons). However, passengers seated in an exit row may be required to assist cabin crew during an emergency evacuation of the aircraft opening the emergency exit and assisting fellow passengers to the exit. As a precaution, many airlines prohibit young people under the age of 15 from being seated in the exit row [1].
The seats are designed to withstand strong forces so as not to break or come loose from their floor tracks during turbulence or accidents. The backs of seats are often equipped with a fold-down tray for eating, writing, or as a place to set up a portable computer, or a music or video player. Seats without another row of seats in front of them have a tray that is either folded into the armrest or that clips into brackets on the underside of the armrests. With increasing frequency, seatbacks now feature small color LCD screens for videos, television and video games. Controls for this display as well as an outlet to plug in audio headsets are normally found in the armrest of each seat.
[edit] Overhead bins
The overhead bins are used for stowing carry-on baggage and other items. While the airliner manufacturer will normally supply a standard product, airlines may choose to have bins of differing size, shape, or color installed. Over time, these bins evolved out of what were originally overhead shelves used for little more than coat and briefcase storage. As concerns about falling debris during turbulence or in accidents increased, enclosed bins became the norm. Bins have increased in size in order to accommodate the more numerous and larger carry-on baggage many passengers bring onto the aircraft. Many new bin designs include a handrail, useful when moving through the cabin when the airliner is in motion.
[edit] Passenger service units
Above the passenger seats are what are generically known as Passenger Service Units (PSU). This typically contains a reading light, "gasper" air vent, and a flight attendant call button. The units frequently have small "Fasten Seat Belt" and "No Smoking" illuminated signage installed and may also contain a speaker for the cabin public address system.
The PSU will also normally contain the drop-down oxygen masks which are activated if there is a sudden drop in cabin pressure. These are supplied with oxygen by means of a chemical oxygen generator. By using a chemical reaction rather than a connection to an oxygen tank, these devices supply breathing oxygen for long enough for the airliner to descend to thicker, more breathable air. Oxygen generators do generate considerable heat in the process. Because of this, the oxygen generators are thermally shielded and are only allowed in commercial airliners when properly installed - they are never loaded as freight on passenger-carrying flights.
[edit] Baggage holds
Airliners must have space on board to store baggage that will not safely fit in the passenger cabin. Designed to hold baggage as well as freight, these compartments are usually called "cargo bins", "holds", or occasionally "pits".
These compartments can be accessed through doors on the outside of the aircraft. Despite what is seen in many movies, access doors between passenger cabins and baggage holds are rare in current modern airliners.
Depending on the aircraft, baggage holds are normally pressurized just like the passenger cabin although they may not be heated. While lighting is normally installed for use by the loading crew, typically the compartment is unlit when the door is closed.
Baggage holds on modern airliners are equipped with fire detection equipment and larger aircraft have automated or remotely activated fire-fighting devices installed.
[edit] Narrow-body airliners
Most "narrow-body" airliners with more than 100 seats have space below the cabin floor, while smaller aircraft often have a special compartment separate from the passenger area but on the same level.
Baggage is normally stacked within the bin by hand, sorted by destination category. Netting that fits across the width of the bin is secured to limit movement of the bags. Airliners often carry items of freight and mail. These may be loaded separately from the baggage or mixed in if they are bound for the same destination. For securing bulky items "hold down" rings are provided to tie items into place.
[edit] Wide-body airliners
"Wide-body", or "jumbo jets", frequently have a compartment like the ones described above, typically called a "bulk bin". It is normally used for late arriving luggage or bags which may have been checked at the gate.
However, most baggage and loose freight items are loaded into containers called Unit Load Devices (ULDs), often referred to as "cans". ULDs come in a variety of sizes and shapes, but the most common model is the LD-3. This particular container has approximately the same height as the cargo compartment and fits across half of its width.
ULDs are loaded with baggage and are transported to the aircraft on dolly carts and loaded into the baggage hold by a loader designed for the task. By means of belts, rollers and drive wheels, an operator can maneuver the ULD from the dolly cart, up to the aircraft baggage hold door, and into the aircraft. Inside the hold, the floor is also equipped with drive wheels and rollers that an operator inside can use to move the ULD properly into place. Locks in the floor are used to hold the ULD in place during flight.
For consolidated freight loads, like a pallet of boxes or an item too oddly shaped to fit into a container, flat metal pallets that resemble large baking sheets that are compatible with the loading equipment are used.
