An
airliner (also called a commercial transport)
is a large
fixed-wing aircraft
for transporting passengers and cargo. Such planes are owned by
airlines.The definition of an airliner varies from country to
country, but the common definition is an
aircraft with an empty weight above , with two or
more engines.
History
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 with an isolated passenger
saloon, wicker chairs, bedroom, lounge and
a bathroom. The aircraft also had
heating
and
electrical lighting. The Ilya Muromets
first flew on December 10, 1913. On February 25, 1914, it took off
for its first demonstration flight with 16 passengers aboard.
From
June 21 June 23, it
made a round-trip from Saint Petersburg
to Kiev
in 14 hours
and 38 minutes with one intermediate landing. If it had not
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.
Approximately 60 were built. It was followed in 1923 by a less
successful quad-engine
Farman F.121
Jabiru.
The third airliner was the little-known Buttcrack Flier. It was
manufactured by B&B Aero in November 1919, but was quickly
discontinued.
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 eight 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
Douglas DC-2 flew and in 1935 the more
powerful, faster, 21–32 passenger
Douglas
DC-3. DC-3s were produced in quantity for WWII and sold as
surplus afterward.
UAL DC-6 at Stapleton Airport, Denver,
in September 1966
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 did not immediately replace piston engines and many designs
used the
turboprop rather than the
turbojet or the later turbofan engines.
Types
Wide-body jets
The largest airliners are
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 and
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, air
taxis, or
feederliners, 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 do not 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 is 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 so
that aircraft can continue to climb even in the worst case of power
loss in one engine right after take-off. Another regulatory demand
is that aircraft are able to fly a minimum 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 Messerschmitt with the
Me-262 Schwalbe (Swallow) fighter of the 1940s, and
later used 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 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 barrier to prevent the engines' noise from
reaching the fuselage in-flight.
Both
Airbus and
Boeing
use this common layout for all of their passenger aircraft and
emerging manufacturers (e.g.
Embraer and
Sukhoi Superjet) follow the same
scheme.
In a few special cases, where engine proximity to ground is
detrimental (e.g. rural airfields with risk of foreign object
damage or dirt), airliners will feature tail-mounted engines (e.g.
MD-80 or
Tu-334) or
high-wing designs with underhung nacelles (e.g.
BAE-146). These planes become rarer as almost all
newly built airliners have underwing nacelles. Tail-engined designs
are mostly used by
business jet
manufacturers.
Future airliners may feature innovative delta-wing or
lifting body outlines.
Manufacturers
These include:
The international market for middle-sized and large-sized airliners
is now divided between
Airbus and
Boeing, though Russian/former Soviet manufacturers
still sell significant numbers of airliners to their traditional
markets. Smaller-sized aircraft manufacturers include, in addition
to these two,
ATR,
Embraer and
Bombardier.
Notable airliners
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, e.g. during decreased demand for air travel
and between short-term leases.
Another airliner retirement location is
Marana,
Arizona
.
While 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 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 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.
To
protect the environment, the Airbus company
has set up a 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 and features
An airliner will usually 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 have 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
[8215].
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. However, seats in premium cabins
generally have trays in the armrests or clip-on trays, regardless
of whether there is 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 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 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.
Cabin pressurization
Airliners developed since the 1940s have had pressurized cabins (or
more accurately, pressurized hulls including baggage holds) to
enable them to carry passengers safely at high altitudes where low
oxygen levels and air pressure would otherwise cause sickness or
death. High altitude flight enabled airliners to fly above most
weather systems that cause turbulent or dangerous flying
conditions, and also to fly faster and further as there is less
drag due to the lower air density. Pressurisation is applied using
compressed air, in most cases bled from the engines, and is managed
by a
environmental control
system which draws in clean air, and vents stale air out
through a valve.
Pressurization presents design and construction challenges to
maintain the structural integrity and sealing of the cabin and hull
and to prevent
rapid
decompression. Some of the consequences include small round
windows, doors that open inwards and are larger than the door hole,
and an emergency oxygen system.
To maintain a pressure in the cabin equivalent to an altitude close
to sea level would, at a cruising altitude around 10,000 m
(33,000 feet), create a pressure difference between inside the
aircraft and outside the aircraft that would require greater hull
strength and weight. Most people do not suffer ill effects up to an
altitude of 1800–2500 m (6000–8000 feet), and maintaining
cabin pressure at this equivalent altitude significantly reduces
the pressure difference and therefore the required hull strength
and weight. A side effect is that passengers experience some
discomfort as the cabin pressure changes during ascent and descent
to the majority of airports, which are at low altitudes.
Cabin climate control
The air bled from the engines is hot and requires cooling by
air conditioning units. It is also
extremely dry at cruising altitude, and this causes sore eyes and
dry skin and
mucosa on long flights. Although
humidification technology could raise its
relative humidity to comfortable
middle levels, this is not done since humidity promotes
corrosion to the inside of the hull and risks
condensation which could
short electrical systems, so for safety
reasons it is deliberately kept to a low value, around 10%.
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
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 inside the
hull and are therefore 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 are bound for the same destination. For
securing bulky items "hold down" rings are provided to tie items
into place.
Wide-body airliners
"
Wide-body" airliners 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.
See also
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External links and references
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(formerly Soviet
-controlled)
)
, now defunct)
, no longer
manufactures civilian aircraft)
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