Types of helicopters - (1) Single-Rotor, (2)
Tandem-Rotor, and (3) Coaxial-Rotor Helicopter.
A heavily armed attack helicopter on a mission
A helicopter
hovering over a logging site
A transport
helicopter flying supplies to an oil rig
A business helicopter
landing on a city rooftop
Helicopters can do jobs that aeroplanes cannot do. Unlike planes, military attack
helicopters can turn instantly to fire weapons in almost any direction.
Helicopters can hover in midair and take off and land in small areas, such as
forest clearings, drilling platforms, and rooftops.
Helicopter rescue missions have saved the lives of thousands of people. A coast guard helicopter above
has picked up the crew members from a sinking ship.
Helicopter rescue missions have saved the lives of thousands of people. A coast guard helicopter above
has picked up the crew members from a sinking ship.
Crop-dusting by helicopter enables farmers to spray agricultural chemicals exactly where they are
needed. This specially equipped helicopter is spraying a field with
insecticide.
An antisubmarine helicopter, armed with torpedoes, takes off from a navy ship. Such helicopters carry
electronic devices to locate and track submarines.
A rotor blade's shape creates lift. As the blade moves, air flows faster over its curved upper
surface than under its flat lower surface. Air pressure is thereby reduced over
the blade but unchanged under it. This difference in pressure produces lift.
Greater lift can be created by increasing the angle of attack- the angle the
rotor blade makes with the air flowing past it. Increasing the angle causes air
to push against the bottom of the blade, which increases the air pressure and
thereby the lift.
Helicopter controls. Moving the collective pitch lever makes the helicopter climb,
hover, or descend. Tilting the control column causes forward, backward,
or sideways flight. Pushing the rudder pedals controls the direction the
helicopter points.
Piloting a helicopter - A pilot flies a helicopter by varying the pitch (angle) of the
rotor blades. The lift of the main rotor counteracts gravity. The force of the
tail rotor counteracts torque, a force that tends to spin the aircraft
in the direction opposite to that of the main rotor. In the diagrams below, the
pitch of the blades is indicated by the thickness of the circles showing the
area swept by the rotor.
The first practical single-rotor
helicopter was built and flown by Igor
Sikorsky. Its first flight, was in 1939.
Helicopters in combat were first used on a massive scale by United States armed forces during
the Vietnam War (1957-19751).
An experimental compound helicopter has coaxial rotors to provide lift. However, it uses jet engines for
forward movement. Such aircraft can fly much faster than regular helicopters.
What is a Helicopter?
Helicopter is a type of aircraft that derives both
lift and propulsion from one or more sets of horizontally revolving overhead
rotors. It is capable of moving vertically and horizontally, the direction of
motion being controlled by the pitch of the rotor blades.
Facts, History and Types. Helicopter, aircraft with one or more power-driven horizontal propellers
or rotors that
enable it to take off and land vertically, to move in any direction, or to
remain stationary in the air. Other vertical-flight craft include autogiros,
convertiplanes, and V/STOL aircraft of a number of configurations...
Helicopter is an aircraft that is lifted into the air and kept aloft by one or two
powerful whirling rotors. A helicopter rotor resembles a huge propeller that
is parallel to the ground. However, the rotor is actually a rotating wing. The
name helicopter refers to the
rotor. It comes from the Greek words helix,
meaning spiral, and pteron, meaning wing. Nicknames for the helicopter
include "chopper," "eggbeater," and "whirlybird."
A helicopter can fly straight up or
straight down, for- ward, backward, or-sideways. It can even hover (stay in one spot in the air).
Unlike most aeroplanes, helicopters need no runway. They can take off and land
in a very small space. In addition, helicopters can fly safely at much slower
speeds and lower altitudes than aeroplanes. However, they cannot fly as fast
as most planes. Most helicopters cannot exceed 320 kilometres per hour. At faster
speeds, strong vibrations develop that could damage the rotor blades.
Helicopters also use more fuel than aeroplanes to travel the same distance, and
so are less economical than aeroplanes. In general, helicopters can fly for
only two to three hours-or less than 1000 kilometres—without refuelling.
Aeroplanes can travel much further without refuelling.
Helicopters range in size from tiny,
single-seat models to huge transports that can carry two trucks in their cargo
hold. The heaviest helicopter is the Mil Mi-26, built by the Soviet Union. It
weighs 28 metric tons and can carry 20 metric tons of cargo.
Uses of helicopters
Helicopters can be used for many tasks
that cannot be performed by other types of aircraft, because they are able to
hover in midair and take off and land in small areas. They are particularly
useful (1) for rescue missions, (2) for aerial observation, (3) for
transportation and construction work, (4) for agricultural and forestry operations,
and (5) for military missions.
For rescue missions. Many early developers of helicopters intended them to be used for
saving lives. A helicopter can hover above the scene of a disaster. A sling or
harness can then be lowered from the craft to endangered people below. They
are then pulled up and flown to safety. Helicopters have been used to pluck
people from burning skyscrapers, sinking ships, and rising floodwaters. They
have flown stranded mountain climbers and injured skiers to safety. Serving as
flying ambulances, helicopters can land near car or aeroplane crashes and rush
the injured to hospitals. Helicopters can also deliver food and medicine to
areas that other vehicles cannot reach because of earthquakes, floods, or
storms.
For aerial observation. In many cities, police use helicopters to trail fleeing suspects and
direct police cars on the ground. Law enforcement agents in helicopters look
for lost people and escaped convicts. They may patrol national borders on the
lookout for smugglers and illegal immigrants. Helicopters are also used to
patrol motorways and identify speeding cars.
Many radio and television stations use
helicopters to cover news events from the air. In large cities, helicopter
pilots observe the flow of traffic and broadcast radio reports warning drivers
of traffic jams. Film companies often film from helicopters to give audiences a
bird's- eye view of a scene. Helicopter pilots fly low along pipelines,
railway tracks, and power lines to inspect them for damage.
Helicopters are used to explore wilderness
areas, to survey land, and to help locate oil and other resources. From
helicopters, scientists count wildlife populations and chart the migration
routes of wild animals. Some fishing fleets use helicopters to spot schools of
tuna.
For transportation and construction work. Helicopter transportation is expensive. However, the convenience of
helicopter flight makes "choppers" ideal transport vehicles for
certain uses. The flexibility, security, and speed of helicopter travel have
made it a major method of transportation for political leaders in many
countries. Helicopter travel saves business executives time that they otherwise
might waste in using slow-moving ground transportation. From heliports (airports for helicopters) on
city office buildings, business executives may fly directly to nearby cities
for meetings.
Helicopter service is essential to many
offshore oil-drilling operations. Numerous offshore wells are in rough ocean
waters that make it hazardous to bring in replacement crews and supplies by
ship. However, helicopters can land on the drilling platforms and so provide
much faster and safer delivery than ships.
Helicopters are often used to transport
cargo that is too large or awkward for other vehicles to haul. The cargo is
carried in a sling hanging below the craft.
Powerful helicopters are used in
construction work as "flying cranes." Workers in helicopters install
aerials and huge air conditioners on top of tall buildings and erect
preassembled electric power transmission towers. Workers also use helicopters
to pour concrete in hard- to-reach places and to put long bridge sections in
position.
For agricultural and forestry operations. Farmers use helicopters to spread seeds, fertilizers, weedkillers, and
insecticides over large areas. Instead of building roads, some companies that
manufacture forest products depend on helicopters to transport logging crews
into and out of forests and to carry out logs.
For military missions. In the armed forces, helicopters serve as flying ambulances and as troop
transports. Powerful military helicopters carry artillery to key battle
positions and fly jeeps, tanks, and other equipment wherever they are needed.
Helicopters equipped with electronic gear pick up and disrupt enemy communications
signals. The armed forces also use helicopters to observe the movements of
enemy troops and ships. Many naval helicopters have devices to locate and track
submarines. They may also be armed with depth charges, missiles, or torpedoes.
Army attack helicopters may
carry bombs, cannons, machine guns, or missiles. Their main targets are enemy
tanks.
Types of helicopters
Single-rotor helicopters are the most common type of helicopters. A single-rotor helicopter has
one main rotor mounted above its body. Although such an aircraft is called a
single-rotor helicopter, it also has a second, smaller rotor mounted on its
tail. The main rotor may have from 2 to 8 blades. It provides the helicopter's
lifting power. The tail rotor has from 2 to 13 blades. It is mounted vertically
on either side of the tail and so spins at a right angle to the main rotor. The
tail rotor is used to control direction. It also overcomes the tendency of the
helicopter to spin around in the direction opposite to that of the main rotor.
Twin-rotor helicopters have two main rotors. The rotors turn in opposite directions and so
eliminate the need for a tail rotor. Two basic types of twin-rotor helicopters
are widely used: tandem-rotor helicopters
and coaxial-rotor helicopters.
A tandem-rotor helicopter has a main rotor mounted above each end of its body.
A co-axial-rotor helicopter has one rotor above the other. The rotors are
mounted above the middle of the helicopter's body. The shaft of the upper rotor
turns inside the shaft of the lower rotor.
How helicopters fly
Lift is the force that causes an aircraft
to overcome gravity, climb into the air, and stay aloft. Most aircraft rely on
wings to produce lift. An aeroplane has fixed
(immovable) wings that create lift as the aeroplane moves forward. Helicopter
rotor blades are rotary wings.
An engine turns the rotor, and the blades generate lift as they whirl through
the air.
The special shape of wings helps them
create lift. A wing's upper surface is curved, and its lower surface is less
curved or flat. As a wing moves or whirls through the air, air flows over and
under the wing. In the same amount of time, the air flowing over the curved
upper surface travels farther than the air flowing under the wing. The air thus
flows faster over the wing than under it. This difference in air speed creates
a difference in air pressure above and below the wing. There is less pressure
on the upper surface than on the lower surface. Because air is pushing more
strongly against the bottom of the wing than against the top, lift is created.
For additional information, see the article Aerodynamics (Principles
of aerodynamics).
Helicopter pilots, like aeroplane pilots,
can control the amount of lift by changing the angle that the wings make with
the airflow. This angle is called the angle
of attack. You can demonstrate the relation between lift and the
angle of attack by using a kite to serve as a simple wing. Hold the kite flat
and point it into the wind. If you then slightly raise the front of the kite,
you increase the angle of attack. You will feel a force trying to push the kite
upward. This force is the lift created by the wind as it pushes against the
bottom surface, if you decrease the angle of attack, the force becomes weaker.
Piloting a helicopter. The pilot of a single-rotor helicopter operates three basic controls
inside the cockpit.
(1) The collective pitch lever makes the helicopter climb, hover, or
descend. (2) The control column,
also called the cyclic pitch control,
causes it to fly forward, backward, or sideways. (3) The rudder pedals swing the tail around so
that the helicopter can turn. Each control varies the pitch (angle) of the main rotor or tail
rotor blades.
A system of cables, rods, and other
devices leads from the controls in the cockpit to the rotor blades.
Climbing, hovering, and descending. The pilot's left hand moves the collective pitch lever up and down. By
raising the lever, the pilot increases the pitch of all main rotor blades
equally. The increased pitch, in turn, increases the lift generated by the
spinning rotor. When lift exceeds the force of gravity, the helicopter goes
straight up. After reaching a particular altitude, the pilot may want to hover.
The pilot then lowers the lever to decrease the pitch of the rotor blades and
so reduce the amount of lift. When the rotor's lifting force has been reduced
just enough to counteract the pull of gravity, the craft will maintain a
constant altitude. To descend, the pilot lowers the collective pitch lever
farther, thereby decreasing the lift. When lift becomes weaker than the force
of gravity, the craft descends.
Flying forward, backward, and sideways. The pilot's right hand operates the control column. The control column
is a stick between the pilot's knees. It can be tilted in any direction. The
helicopter moves in whatever direction the pilot tilts the column.
When the control column is tilted, the
pitch of the main rotor blades alternately increases and decreases as they
sweep through opposite sections of their circular path. To fly forward, the
pilot pushes the column ahead. This causes the pitch to be greatest just before
the blades pass over the tail. The blades have the least pitch just before they
reach the nose. These changes in pitch cause the rotor blades to rise slightly
in the rear. The rotor then tries to pull the helicopter both upward and ahead.
Gravity counteracts the upward pull, however, and so the aircraft moves forward
in level flight.
To fly backward, the pilot pulls back on
the control column. This gives the blades the most pitch as they approach the
nose and the least pitch as they approach the tail. The nose rises, the tail
dips, and the helicopter flies backward. The aircraft can be made to fly
sideways in a similar manner.
Turning. As a helicopter's main rotor spins in one direction, it creates a
force that pushes against the body of the craft in the opposite direction. This
twisting force is called torque.
It must be overcome or the helicopter will be out of control and simply turn in
circles.
The main rotor of a single-rotor
helicopter spins in a counterclockwise direction, and so the push of the torque
is clockwise. The pilot of a single-rotor craft uses the tail rotor to
counteract torque and to change direction. The pilot controls the tail rotor
by stepping on two rudder pedals. If neither pedal is depressed, the tail rotor
blades spin at just the right pitch to produce exactly enough sideways force
to counteract the torque. The helicopter then points straight ahead. To swing
left, the pilot steps on the left rudder pedal, thereby increasing the pitch
of the tail rotor blades. The increased force of the rotor pushes the tail in
the direction opposite to the clockwise push of the torque. The helicopter then
turns to the left. To turn right, the pilot depresses the right rudder pedal
and so decreases the pitch—and thus the force—of the tail rotor blades. The
torque itself then swings the tail in a clockwise direction, which turns the
helicopter to the right.
On a twin-rotor helicopter, one main rotor
turns clockwise and the other turns counterclockwise. As a result, the torque
generated by one rotor cancels out that generated by the other. The pilot turns
the craft by changing the pitch of the main rotors.
Development of the helicopter
Early designs and experiments. The earliest known mention of a rotor-powered flying machine appears in
a Chinese text written about A.D. 320. The design of this machine may have been
based on a Chinese toy called the flying
top. Such toys flew by means of feather rotors. In 1483, the great
Italian artist and scientist Leonardo da Vinci
sketched a design for a helicopter. It had a large screwlike wing made of
starched linen. In 1784, two Frenchmen named Launoy and Bienvenu built the
first model helicopter in Europe that could fly. Based on the Chinese flying
top, it had two rotors made of feathers. Throughout the 1800's, inventors in
Europe and the United States experimented with model helicopters. The steam
engines and electric motors of that time were too weak or too heavy to power a
full-sized helicopter.
By the early 1900's, small, powerful
petrol engines had been developed that made manned helicopter flight possible.
The first manned flight took place in 1907. The craft was a four-rotor
helicopter built by Louis Breguet, a French inventor. The helicopter lifted one
of Breguet's assistants 61 centimetres into the air for a minute. Assistants
on the ground steadied the helicopter during the flight. Later in 1907, a
French mechanic named Paul Cornu made the first free flight in a helicopter.
Fie flew his tandem-rotor aircraft to a height of about 2 metres for about 20
seconds.
The first practical helicopters. Early helicopters were difficult to control, and their flight was
wobbly. In 1935, Breguet and another Frenchman, Rene Dorand, built a
coaxial-rotor helicopter that was easier to control and flew far more steadily.
In 1936, Heinrich Focke, a German inventor, built a twin-rotor helicopter that
was even further advanced. The following year, it reached a speed of 122
kilometres per hour and an altitude of about 2,400 metres. It could stay aloft
for 1 hour and 20 minutes.
The first flight of a practical
single-rotor helicopter took place in the United States in 1939. The craft was
built and flown by Igor I. Sikorsky, a Russian engineer who had moved to the
United States in 1919. The British and the U.S. armed forces used an improved
version of Sikorsky's helicopter during World War II (1939-1945).
Further improvements. During the mid-1900's, the military use of helicopters began to increase
greatly, which led to major improvements in their design. Helicopters had been
used mainly for patrol and rescue missions in World War II. New tasks for the
helicopter during the Korean War (1950-1953) included armed observation of
enemy positions and strength and transporting troops and supplies to
hard-to-reach areas. During the Vietnam War (1957-1975), thousands of armed
U.S. attack helicopters flew combat missions.
The ever-expanding military use of
helicopters encouraged the development of faster, larger, and more powerful
craft. In the 1940's and 1950's, engineers adapted the jet engine for use in
helicopters. Jet engines were lighter and more powerful than the previous engines
used to turn the rotor shafts. They enabled helicopters to fly faster and
higher and to carry heavier loads. In addition, the use of new construction
materials made helicopters lighter, safer, and stronger. For example, metal or
wooden rotor blades were replaced by longer-lasting plastic blades. Such
improvements also made helicopters suitable for more civilian uses.
Recent developments include efforts by manufacturers to simplify the complicated operation
of helicopters and to increase their speed. One manufacturer has developed a
single-rotor helicopter that needs no tail rotor. Instead, the craft uses jets
of air to counteract torque and to change direction. Attempts to increase the
speed of helicopters have led to the development of experimental compound helicopters. These vehicles do
not depend entirely on rotors to provide forward movement as well as lift.
Instead, compound helicopters also have jet or propeller systems to help push
or pull them ahead. One compound helicopter has reached the speed of 555
kilometres per hour. Related articles: Aerodynamics, Sikorsky, Igor I; Autogiro;
Cayley, Sir George; and V/STOL
Outline:
Uses of helicopters: For rescue missions; For aerial observation; For agricultural and forestry
operations; For transportation and for construction work; and For military
missions
Types of helicopters: Single-rotor helicopters; and Twin-rotor helicopters
How helicopters fly: Lift, and Piloting a helicopter
Development of the helicopter
Questions
What kind of wings does a helicopter have?
How are helicopters used in the
construction industry?
What is a tandem-rotor helicopter?
A coaxial-rotor helicopter? Who built and flew the first practical
single-rotor helicopter? What are some military uses of the helicopter?
Why does a single-rotor helicopter have a
tail rotor?
What is a compound helicopter?
In what ways can a helicopter fly that an
aeroplane cannot?
What happens when a helicopter pilot
raises the collective pitch lever?
Why is helicopter service essential to
many offshore oil-drilling operations?
Helicopter Crash
A Skagway
helicopter pilot is dead following a crash outside Skagway Friday evening. The
pilot was 59-year-old Christopher Maggio of Skagway. Maggio was the only person
on board. According
to an Alaska State Trooper report, the U.S. Coast Guard contacted troopers
Friday evening around 8:30 to report that a helicopter had gone down near the
upper portion of the Denver Glacier, 6 miles east of Skagway.
BBC - Apr 29, 2016 - Thirteen
people are presumed dead after a helicopter crashed west of
the Norwegian city of Bergen, rescuers say. ... Meanwhile, Norway's civil
aviation authority has imposed a flight ban on the type of helicopter that crashed - the
Eurocopter (EC) 225L Super Puma. ... The aircraft was ...
The Straits
Times - 2 days ago - KUCHING (THE
STAR/ASIA NEWS NETWORK) - The fifth body from ahelicopter
crash in Sarawak which killed a deputy Cabinet minister has been
recovered on Saturday (May 7). ... Four bodies including that of Deputy
Plantation Industries and Commodities Minister Noriah Kasnon had already ...
The Straits
Times - 20 hours ago - KUCHING (THE
STAR/ASIA NEWS NETWORK) - New debris believed to be from the Sarawak helicopter that crashed and
killed a Malaysian ...
CNN - Apr 29, 2016 - (CNN) A helicopter carrying
workers from an oil platform to the mainlandcrashed off the
coast of Hordaland, Norway, on Friday, most likely ...
Alaska
Dispatch News - 1 day ago - A pilot for a
Southeast Alaska charter and flightseeing company was killed when the helicopter he was
flying crashed near a glacier in Skagway ...
WBAY‑TV: 4 days ago - A pilot
helping with the installation of transmission lines was killed when the helicopter
crashed in Manitowoc County Wednesday morning.
Pinal County
Sheriff Paul Babeu said the helicopter was
returning to Globe from Phoenix-Mesa Gateway Airport when it crashed in very
rugged terrain in the ...
A French
reality series has suffered a devastating accident. On Monday,
10 people died when two helicopters collided
into one another during the creation of the ...
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