Everything about Airliner totally explained
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 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.
History of airliners
If an airliner is defined as a plane intended for carrying multiple passengers in commercial service, the Russian
Sikorsky Ilya Muromets was the first official passenger aircraft. The Ilya Muromets was a luxurious aircraft. It contained an isolated passenger
saloon, comfortable wicker chairs, bedroom, lounge and a bathroom. The aircraft also had
heating and
electrical lighting. On
December 10,
1913, the Ilya Muromets was tested in the air for the first time, and on
February 25,
1914, took off for its first demonstration flight with 16 passengers aboard. From
June 21-
June 23, it made a round-trip from
St Petersburg to
Kiev in 14 hours and 38 minutes with just one landing. If it hadn't been for
World War I, the Ilya Muromets would have probably started passenger flights that same year.
The second airliner was the
Farman F.60 Goliath from 1919, which could seat up to 14 passengers, and was produced in a number of approximately 60. It was followed in 1923 by a less successful quad engine
Farman F.121 Jabiru.
The
Ford Trimotor was an important early airliner. With two engines mounted on the wings and one in the nose and a slabsided body, it carried 8 passengers and was produced from 1925 to 1933. It was used by the predecessor to
TWA as well as other airlines long after production ceased. In 1932 the 14 passenger
DC-2 flew and in 1935 the more powerful, faster, 21-32 passenger
DC-3. DC-3s were produced in quantity for WWII and sold as surplus afterward.
The first
jet airliners came in the immediate post war era.
Turbojet engines were trialled on piston engine airframes such as the
Avro Lancastrian and the
Vickers VC.1 Viking the latter becoming the first jet engined passenger aircraft in April 1948. The first purpose built jet airliners were the
de Havilland Comet (UK) and the
Avro Jetliner (Canada). The former entered production and service while the latter did not. The Comet was unfortunate in that metal fatigue caused crashes.
Jets didn't immediately replace piston engines and many designs used the
turboprop rather than the turbojet or the later turbofan engines.
Types of airliners
Wide-body jets
wide-body aircraft jets. 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,
Lockheed L-1011 TriStar,
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 include the
Boeing 787 and
Airbus A350.
Narrow-body jets
A smaller, more common class of airliners are the
narrow-body aircraft 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,
McDonnell Douglas DC-9 &
MD-80/MD-90 series,
Airbus A320 family,
Tupolev Tu-204,
Tu-214,
Embraer E-Jets 190&195 and
Tu-334. Older airliners like the
Boeing 707,
727,
McDonnell Douglas DC-8,
Fokker F70/
F100,
VC10,
Tupolev, and
Yakovlev jets also fit into 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
Embraer ERJ,
Bombardier CRJ series and "Q" (
DASH-8) series,
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.
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. Depending on local and national regulations, a commuter aircraft 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 don't carry a
flight attendant as an
aircrew member.
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 made by
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. Gas turbine engines operate efficiently at much higher altitudes, are far more reliable than piston engines, and produce less vibration and noise. Prior to the jet age it was common for the same or very similar engines to be used in
civilian airliners as in
military aircraft. In recent years, divergence has occurred so that it's now unusual for the same engine to be used on a military type as a civilian type. Usually military aircraft which share engine technology with airliners are transports or
tanker types.
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 DC-9), reconnaissance (
Embraer ERJ 145,
Saab 340,
Boeing 737), as well as for troop-carrying roles.
Layout
Modern airliners are usually low-wing designs with engines mounted in underwing pods (usually two of them). For airliners, multi-engine design is mandated by some national regulations. This feature is specified so that aircraft can continue to climb even in the worst case of power loss in one engine right after take-off. Another relevant regulatory demand is that aircraft are able to fly a mininum specified amount of time after one engine fails in flight (see
ETOPS).
The idea of mounting the engines underneath and to the fore of the wing was first implemented by Boeing with the
B-47 bomber of the 1950s, with the realization that this would provide for lesser efforts on the wings and therefore allow for a lighter wing structure. After this feature proved successful, Boeing introduced it to its 707 airliner design and it has been increasingly adopted since.
Mounting the engines in underwing pods also makes physical access for maintenance significantly quicker and easier compared to
tail-mounted engines.
Additionally, low wing design helps keep the engine nacelles and refueling valves closer to the ground to simplify access and the wing's surface acts as a sound barrier to prevent the engines' noise from reaching the fuselage in-flight.
Both
Airbus and
Boeing utilize this common layout for all of their passenger aircraft and emerging manufacturers (for example
Embraer and
Sukhoi Superjet) follow the same scheme.
In general, visual diversity of airliners has significantly decreased in the past decades, especially as
Eurowhite paint schemes became popular with airlines worldwide. Nowadays distinguishing an Airbus plane from a Boeing aircraft may require observing finite details, like the shape of wingtip devices (none, raked or fence) or assessing the tail designs (canoe versus conical).
In a few special cases, where engine proximity to ground is detrimental (for example rural airfields with risk of foreign object damage or dirt on the pavement), airliners will feature tail-mounted engines (for example
MD-80 or
Tu-334) or high-wing designs with underhung nacelles (for example
BAE-146). These planes become rarer every year as almost all newly-built airliners have underwing nacelles and the tail-engined designs are relegated to
business jet manufacture.
Future airliners may feature innovative delta-wing or
lifting body outlines, in case problems related to excessive noise levels and poor fuel economy of
supersonic (hypersonic) flight are solved.
Manufacturers
These include:
The international market for middle-sized and large-sized airliners is now divided between
Airbus and
Boeing. Smaller-sized aircraft manufacturers include, in addition to these two,
ATR,
Embraer and
Bombardier.
Notable airliners
Boeing 247 - first design to incorporate modern features
Douglas DC-3 - considered by many to be the first true airliner
Lockheed Constellation - Triple-tailed piston-engined airliner of the 1950s
De Havilland Comet - the first jet airliner in service
Tupolev Tu-104 - the first turbojet airliner successful at regular service
Vickers Viscount - the first turboprop airliner to enter service
Sud Caravelle - the first successful jet airliner.
Boeing 707 and Douglas DC-8 - the first American-built jetliners
Boeing 727 - one of the most successful airliners
Douglas DC-10 and Lockheed L-1011 TriStar - one of the first wide-bodies
Douglas DC-9 - more than 1000 built. Many still in service.
Boeing 737 - the best selling civilian jet airliner
Airbus A320- of fly-by-wire
Tupolev Tu-144 - the first supersonic transport aircraft constructed in Soviet Union
Concorde - flew at twice the speed of sound
Boeing 747 "jumbo jet" - the largest airliner between 1968 and 2005
Boeing 777 - the first airliner designed entirely by computer (no mockups were used)
Airbus A380 "superjumbo" - The world's largest airliner, featuring two full-length twin-aisle passenger cabins, started service with Singapore Airlines in October 2007.
Boeing 787 "Dreamliner" - Boeing's latest long haul jet.
Airliner recycling
As airliners are very expensive, most are leased out for times typically from 20 to 40 years. 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, for example during decreased demand for air travel and between short-term leases. Another common 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're retired. A well-maintained airliner can operate safely for decades, depending on how often it's 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 are other issues that become more expensive to deal with as time goes on. Eventually, these factors and advances in aircraft technology lead to older airliners becoming too expensive or inefficient to operate.
In order to protect the environment, the Airbus company has set up a special centre in France to decommission and recycle older aircraft. More than 200 airliners will finish active life each year, and will be dismantled and recycled under the newly established PAMELA Project.
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 instead offer 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). Cabins of any class are provided with lavatory facilities (see board toilets).
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 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) usually 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 (External Link
).
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's either folded into the armrest or that clips into brackets on the underside of the armrests. However, seats in premium cabins generally have trays in the armrests or clip-on trays, regardless of whether there's another row of seats in front of them. Seatbacks now often 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.
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 larger carry-on baggage passengers may bring onto the aircraft. New bin designs may include a handrail, useful when moving through the cabin.
Passenger service units
Above the passenger seats are Passenger Service Units (PSU). These typically contain a reading light, air vent, and a flight attendant call button. The units frequently have small "Fasten Seat Belt" and "No Smoking" illuminated signage 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's 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're not permitted to be loaded as freight on passenger-carrying flights. ValuJet Flight 592 crashed on May 11, 1996 as a result of improperly loaded chemical oxygen generators.
Baggage holds
Airliners must have space on board to store baggage that won't safely fit in the passenger cabin.
Designed to hold baggage as well as freight, these compartments are called "cargo bins", "holds", or occasionally "pits". Occasionally baggage holds may be referred to as cargo decks on the largest of aircraft. 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 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.
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're bound for the same destination. For securing bulky items "hold down" rings are provided to tie items 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 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 LD3. 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 and rollers 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.
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