Aviation

Light Aircraft ( Part 2 )

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Light aircraft are small , relatively simple planes that are used for recreational and

business travel. They are usually powered by piston engines that drive propellers,

although some have jet engines. Unlike large, high-speed aircraft, which have

under-carriage (wheels) that retracts during flight for streamlining, light aircraft

usually have fixed under-carriage to save weight and cost. With the development

of new composite materials, aircraft have become stronger, lighter, and capable of

flying greater ranges.

Airliners ( Part 1)

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Modern airliners depend on the same aerodynamic principles as light aircraft. However, in order

to meet contemporary standards of safety and comfort and to carry much heavier payloads over

far greater distances, this medium of mass transportation has required huge developments in

instrumentation systems, wing and engine design, and in the material used in their construction.

Airliners ( Part 2 )

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The largest passenger-carrying aircraft under development is the Airbus A3XX, which will

carry up to 840 passengers. It will have a takeoff weight of 640 tons (580 tonnes) and a

range of up to 10,000 miles (16,000 km ). In order to propel an aircraft of this size, powerful

engines have been developed. These engines must be fuel efficient in order to meet

anti-pollution standards. The need for fuel economy is one reason why fuel-hungry

supersonic aircraft, such as Concorde, have not become more widely used. It has also

meant that modern aluminum alloys and carbon fiber composites are increasingly used in the

construction of aircraft because they markedly reduce weight and increase strength. Perhaps

the most significant innovation in airliner design has been in control systems. All modern

airliners rely on "fly-by-wire" technology that substitutes the mechanical linkages of traditional

control systems with electronic data lines, and enables complex aircraft to be flown by a crew

of two.

Turbojet Engine (Part 1 )

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Turbojet engines burn a mixture of air and liquid fuel, in the form of kerosene , to produce

a stream of fast-moving , hot exhaust gases that drives the engine forward. Although

turbojets consume large amounts of fuel and are very noisy, they are extremely powerful

and relatively lightweight, which makes them suitable for use on supersonic aircraft such

as Concorde.

Turbojet Engines ( Part 2 : Diagrams)

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Turbofan Engines ( Part 1 )

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Turbofan engines ( Part 2 )

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Jet engines are type of internal combustion engine that have been used to propel

power boats and cars to world speed records. They are most familiar, however, as

aircraft engines. Jet engines produce power by accelerating a mass of air through

the engine . Burning fuel in the combustion chamber produces hot, expanding

exhaust gases that are blasted out of the rear of the engine. Some jet engines

also drive a propeller, while others, called turbofans, gain most of their power by

pushing a "bypass" jet of cold air around the engine.

A jet engine produces thrust, force that drives the engine forward. This force is explained by the

principle of action and reaction. Hot, expanding gases are pushed out of the engine. This force ,

the action force, produces an equal and opposite reaction force from the exhaust gases to the

engine. This reaction force, called thrust, propels the engine and the attached aircraft forward.

Exactly the same principle operates when air escapes from an inflated balloon, propelling the

balloon through the air.

British engineer Dir Frank Whittle (1907 -- 1996 ) developed the jet engine in the 1930s and

his design, the turbojet , is still used today, mainly in military aircraft. Modifications of this

basic design include turboprop and turbofan engines. Turboprops couple a set of spinning

blades called a turbine to a propeller, usually at the front of the engine. The turbine uses the

exhaust jet's energy to drive the propeller, which provides most of the engine's thrust.

Turboprops are economical and suitable for small, low-speed passenger aircraft. Turbofans

use a turbine inside the engine to turn a large fan at the front that sucks in a huge volume

of air. This air is bypassed around the hot engine core and expelled at the rear, producing

most of the thrust. Turbofans are quieter but far more powerful than other jet engines and

are used in large airliners.

Helicopter (Part 1 : Body Diagram )

Helicopters are highly maneuverable aircraft that generate lift using rapidly-turning

wing-shaped rotor blades . In contrast, conventional aircraft flt by moving forward

at speed to force air over fixed wings. Since helicopters do not require forward

motion to product lift, they can take off and land vertically, hover, and fly in any

direction, even backward. The first practical helicopter was developed in 1939 by

the Russian-born engineer Igor Sikorsky (1889--1972).

Helicopter ( Part 2 : Rotor )

Most helicopters are powered by turboshaft engines, a type of jet engine in which

a turbine turns a driveshaft that powers the rotors. In order to produce lift, each

rotor blade must be pitched, or angled, upward relative to the oncoming air. The

pilot controls the blade pitch using two controls, the collective and cyclic pitch sticks,

which are connected to swash plates on the main rotor assembly. During takeoff,

the pilot increases the pitch of all the rotor blades by the same amount with the

collective pitch stick. The throttle is opened to speed up to the rotor until the amount

of lift produced exceeds the weight of the helicopter and it rises vertically. To hover,

the pilot reduces the collective pitch so that the lift becomes equal to the weight of

the helicopter. To descend, the collective pitch is reduced until the lift is less than the

weight.

Directional flight is achieved by tilting the swash plates with the cyclic pitch control,

which alters the pitch of each blade as it rotates, so that every blade produces

greater lift at a particular point. Although vertical lift is still produced overall, thrust

is also generated in the direction that the swash plates are tilted, which causes the

helicopter to lean and fly in that direction. Further directional control is obtained by

increasing or decreasing the thrust of the tail rotor that is fitted to most helicopters.

One significant advance in helicopter design in recent years has been the development

of no-tail-rotor (NOTOR) helicopters, which use fan-driven air circulation system in place

of tail rotors.



Helicopter ( Part 3 : Forward Flight )

To fly forward , the swash plates are tilted so that the rotor blades are pitched lower

in front of the rotor assembly than behind it. This creates more lift at the back of the

helicopter than at the front, and the net force pulls the helicopter forward.

Helicopter (Part 4 : Notar System )

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No-tail-rotor helicopters :

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A tail rotor not only prevents a helicopter spinning out of control, it also allows the helicopter

to be maneuvered in tight circles. It is, however, noisy and easily damaged, as well as being

hazardous to people on the ground when it is in use.

No-tail-rotor (NOTAR) helicopters provide a quieter , safer alternative. They allow a downwash

of air from the main rotors to enter the fuselage of the helicopter. This air is driven down the

tailboom by a large fan. Some of this air is forced out of slots along the side of the tailboom

and circulates around it. This creates a force that counteracts the effects of torque . Directional

control is provided by varying the amount of residual air that is expelled from the slot at the end

of the tailboom.

Helicopter ( Part 5 : Rotor Assembly )

The blades of a helicopter are rotated by one or more powered driveshafts, which are

linked to the main rotor shaft by a system of gears. The pitch (angle) of the blades is

controlled by the swash plate assembly. This consists of a non-rotating lower plate that

can be moved up and down or tilted by controls in the cockpit, and a rotating upper plate

that transfers this movement to the blades via control rods. The blades have an airfoil

section and are designed to withstand the extreme forces caused by rotation.

Navigation ( Part 1 )

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Navigation is the science of fixing a vehicle's position and charting an efficient route to a

destination. Until the advent of radio, navigation was once based on maps, charts, compasses,

clocks, and the position of Sun or stars. Ships and aircraft still use these techniques, but

today a range of ground- and space-based radio navigation aids enables accurate navigation,

even in conditions of zero visibility.

Navigation ( Part 2 : Landing Systems )

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Radio navigation :

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Two major radio navigation aids are LORAN and VOR .

1) LORAN (long-range navigation ) is widely used by ships and aircraft over sea.

2) VOR (Very High Frequency Omni-directional Radio Range ) beacons mark waypoints

on the air corridors (lanes) along which aircraft fly.

When landing, aircraft may use an ILS (Instrument Landing System), which enables landing

in zero visibility, or more advanced MLS (Microwave Landing System) and GPS-based systems.

Navigation (Part 3 : Air Traffic Control )

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As traffic has increased, navigation has become crucially linked with traffic control and the

maximization of the number of vehicles that can travel safely at the same time . Most modern

air and sea navigation system rely on various types of radio signals transmitted by fixed ground

stations. The main exceptions are the GPS (Global Positioning System), which is a very precise

satellite-based system, and IGS ( Inertial Guidance System), which is a self-contained onboard

system that works by recording every movement of a vehicle after it leaves a known starting point.

Ships and aircraft both rely on radar (radio detection and ranging), in which a transmitter sends

out radio waves and listens for echoes from other vehicles, surrounding terrain, and clouds. The

delay and intensity of the echoes enable a computer to image the surrounding area.