Airliner
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Image:Airliner.airjamaica.a340.arp.750pix.jpg An airliner is a large fixed-wing aircraft whose primary function is the transportation of paying passengers. Such aircraft are usually operated by an airline company which owns or leases the aircraft.
The official definition of an airliner varies from country to country, but the usual definition is that of an aircraft with seating for 20 or more passengers and/or and empty weight above 22,680 kg, and two or more engines.
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Types of airliners
Wide-body jets
The largest airliners are wide-body jets, commonly known as jumbo jets. A term frequently used by those in the aviation industry is twin-aisle aircraft because these aircraft are equipped with two separate aisles running from front to back of the passenger cabin. Typical aircraft in this category include the Boeing 747, Airbus A300/A310, A330/A340, Boeing 767, DC-10, MD-11, Ilyushin Il-86/96 and Boeing 777.
Narrow-body jets
A smaller, more common class of airliners are the narrow-body or single aisle aircraft. Typical aircraft in this category include the Boeing 717, 737, 757, DC-9, MD80 series, and the Airbus A320 family. Older airliners like the Boeing 727, DC-8, Fokker 70/100, VC10, and the Russian Tupolev and Yakovlev jets also fit this category.
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, the Embraer ERJ 145 family and Brasilia, the ATR 42/72 and Saab 340/2000.
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 so not be subject to the regulations that restrict the use of 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 typical aircraft in this category are the Fairchild Metro, Jetstream 31/41, 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 used as airliners. Twin piston-engined aircraft from Cessna, Piper, Britten-Norman, and Beechcraft are also in use as commuter aircraft.
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, since they operate efficiently at much higher altitudes, are far more reliable than piston engines, and produce less vibration and noise.
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 various military functions such as airborne tankers (for example, the Vickers VC-10, Lockheed L1011, and 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.
Manufacturers
Image:Turkmenistan.airlines.frontview.arp.jpg Historically, a few aircraft manufacturers have dominated the market for large airliners: American companies Boeing, Douglas Aircraft Company (now part of Boeing), and Lockheed Corporation (now part of Lockheed-Martin, and no longer involved in civil aviation); Soviet (now Russian) manufacturers Tupolev, Ilyushin and Antonov; and European multinational Airbus Industrie. Other major manufacturers include EMBRAER, De Havilland Canada (now part of Bombardier), ATR, and Fokker (now defunct), all concentrating on smaller "regional" airliners.
The airliner market is currently dominated by two main companies: Airbus (based in Western Europe) and Boeing (based in the United States). Since Airbus has emerged as a viable 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 been engaged in bitter quarrels, each side accusing the other of being subsidized by their government. Airbus can borrow money from European governments at low rates and without the need to refund them should the product result in losses; Boeing gets research and development contracts from NASA and the US Department of Defense, in addition to a large volume of military orders.
However, both Airbus and Boeing use subcontractors from many countries around the world. 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. So, while both major airliner-building companies may try to present themselves as "all Europe" or "built in the USA", in reality, all airliners are made up of components from across the globe.
Famous airliners
Image:Qantas.b747-400.vh-ojl.arp.jpg 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 Boeing 707 and Douglas DC-8 - the American-built jetliners that introduced much of the world to the advantages of jet airliners
- The Concorde - operated 1976 to 2003 by two airlines only, British Airways and Air France, and capable of flying at twice the speed of sound
- The Boeing 747 "jumbo jet" - the only airliner in the world with two passenger decks from 1968 to 2005
- The Airbus A380 "superjumbo", the world's largest airliner to date, featuring full-length dual passenger decks, is expected to start service with Singapore Airlines
Airliner recycling
As airliners are very expensive, most are leased out for long periods of time (20-40 years, typically) and very few go back into service after a long lease is up (the latter due to the fact that the gradually evolving aerospace technology leaves older airliners unable to compete against new machines with respect to operating economy). Many end-of-service airliners end up in the Mojave desert, at the Mojave Spaceport (aka "The Airplane Boneyard"). From this the term "Mojave" has come to refer to the temporary storage of aircraft, e.g. during recessions in airline industry activity and between short-term leases. Another notable location for this activity 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 for good. A well-maintained airliner can operate safely for decades, depending on how often it is flown (usually termed as "cycles" where one takeoff and one landing equal one cycle), what environment it operates in, and whether accidental damage is properly repaired.
Quite often, what ends an airliner's working life is not being able to obtain necessary spare parts as the original manufacturer may no longer provide or support them. Corrosion is another issue that gets more expensive to deal with over time. Eventually, the old airliner gets too expensive to operate.
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, and sometimes has a separate "premium" section with more legroom and amenities). Basically, for more money, you can book a seat in whatever class of service you can afford, the seats in each more expensive class becoming wider, more comfortable, and with more amenities such as free In-flight Entertainment systems and "lie flat" seats for more comfortable sleeping on long flights. Each successive increase in class of service will ordinarily improve the beverage and meal service as well.
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 (standard on first and business class international flights, may be available on economy).
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) load.
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.
The seats themselves are designed to withstand very high forces without breaking or coming 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 video programming and games. Controls for this display as well as an outlet to plug in headsets for any audio programming are also normally found in the armrest of each seat.
Overhead bins
Like the seats, the overhead bins used for storing carry-on baggage and other items may vary from airline to airline. 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 an integrated handrail, useful when moving through the cabin when the airliner is in motion.
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.
More importantly, 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 typically supplied with oxygen by means of a device called a chemical oxygen generator. Using a chemical reaction instead of connection to a big oxygen tank, these devices supply breathing oxygen for enough time 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 for use - they are never loaded as freight on passenger-carrying flights.
Baggage holds
Airliners must have space onboard to store baggage that will not safely fit in the passenger cabin. Designed to hold baggage as well as freight loads, 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 the action movies might have you believe, access doors to these areas from inside the passenger cabin are rare in 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 dark when the door is closed.
All baggage holds on modern airliners are equipped with fire detection equipment and all larger aircraft have automated or remotely activated fire-fighting devices installed.
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 and these may be loaded separately from the baggage or mixed in if they are bound for the same final destination. For securing bulky items "hold down" rings are provided to tie the item into place.
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 bags and bags which may have been checked at the gate.
However, most of their 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. However, the most common model is called 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 to be loaded into the cargo bin by a loader designed for the task. By means of belts, rollers and drive wheels, an operator can manoeuvre the ULD from the dolly cart, up to the aircraft cargo bin door and into the aircraft. Inside the bin, the floor is also equipped with drive wheels and rollers where an operator inside the bin controls the system to move the ULD properly into place. Locks in the floor are engaged 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 and are compatible with the loading equipment are used.
Despite portrayals in popular culture, wide-body cargo holds loaded with ULDs have no room for dramatic fistfights, that is, if they could get into it in the first place. Plus, it is normally dark inside and many wide-body cargo holds do not even have a solid floor in many places.