Structure of an aeroplane(1)

by alan200994 Thu Nov 06, 2008 9:19 pm

STRUCTURE OF AN AIRPLANE
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Most aircraft are composed of the following parts:

Fuselage (body)
Wings (airfoil)
Empennage (tail)
Landing Gear
Power Plant

Now let's take a closer look at each of these parts that make up an airplane.

FUSELAGE

The body of the airplane is called the fuselage. The fuselage must be strong and streamlined, to enable it to withstand the forces that are created in flight.
The fuselage serves several functions. It is the attachment point for the other major components. It houses the cabin, the flight crew, passengers, and cargo.

WINGS (The Airfoil)

The wing is a framework made up of spars, ribs and (possibly) stringers. Structure of an aeroplane(1) Spar

Sparsare the main strength members of the wing
and run along the length of the wing.
Ribs run from the leading edge to the rear of the
wing and support the covering and provide the airfoil
shape (camber) that allows the wing to create lift.
Wings generally have two types of control surfaces:
Ailerons extend from about the midpoint of each wing outward to the tip. They move in opposite directions; when one aileron goes up, the other goes down.
Flaps have two purposes: when they are lowered they increase lift and drag allowing the airplane to fly at slower speeds. They are used for landing and in some airplanes also for takeoff. They extend outward from the fuselage to the midpoint of each wing. They always move together. If one flap is down, the other is down.
EMPENNAGE (Tail Assembly)

The empennage, commonly called the tail assembly, is the rear section of the body of the airplane. Its main purpose is to give stability to the aircraft. It consists of:

Horizontal Stabilizer -- fixed part that prevents the airplane from pitching up or down.
Elevator -- moveable control surface attached to the rear (aft) of the horizontal stabilizer used to control the up-and-down motion of the aircraft's nose.
Vertical Stabilizer -- fixed part that prevents the aircraft from yawing back and forth.
Rudder -- movable control surface attached to the rear of the vertical stabilizer. Used to counter adverse yaw when turning the aircraft.

LANDING GEAR
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Three common types of landing gear:

Conventional has two wheels forward and a third small wheel at the tail. Most often seen on older light aircraft and commonly known as a "taildragger".

Tricycle has two main wheels and a nosewheel. Most modern light aircraft use this arrangement.

Tandem, used for large aircraft, has two sets of wheels located one behind the other on the fuselage. The B-52 shown below uses tandem landing gear, as do most large airliners like the Boeing 747, 767, 777 and the DC-10.

Structure of an aeroplane(1) Convengear1

Conventional

Tandem

POWERPLANT
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The powerplant can be an engine and propeller combination, a jet engine, or a combination of a jet engine with a propeller attached, called a turboprop. The C-130 cargo aircraft with four jet engines with attached propellers is an example of a turboprop aircraft. The F-16 is an example of a "pure" jet powerplant. The ram jet and the rocket engine are also powerplants.

In the engine/propeller combination powerplant the engine drives the propeller which pulls the aircraft through the air.

A jet powerplant produces thrust from its exhaust gases which push the aircraft through the air.

A turboprop powerplant uses a jet engine to drive a propeller to pull that aircraft through the air. A turboprop also produces a small amount of thrust (push) from its jet exhaust.

All powerplants usually also drive attached accessory components to produce electrical power.

STRESS
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Five types of stress act on the aircraft in flight:

Tension tends to pull things apart.
Compression tends to push materials together
Bending is a combination of tension and compression.
Shear is caused by forces tending to slip or slide one part of a material in respect to another part.
Torsion tends to distort by twisting.

CHARACTERISTICS OF THE FLIGHT ATMOSPHERE
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The atmosphere is composed of a mixture of gases, mostly Nitrogen (78%) and Oxygen (21%). All gases have certain characteristics: weight, density, temperature, pressure, and mass.

COMPARING TEMPERATURE AND DENSITY

As temperature decreases the density of air increases.

As the temperature of air increases the density decreases.

HUMIDITY
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Relative humidity is the ratio of the amount of water vapor a sample of air holds to the amount it can hold when saturated.

TEMPERATURE
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Celsius and Fahrenheit

On the Celsius scale water freezes at 0 degrees and boils at 100 degrees.

On the Fahrenheit scale water freezes at 32 degrees and boils at 212 degrees.

FOUR FORCES OF FLIGHT
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During flight the four forces acting on the airplane are:

Lift is the upward force created by the effect of airflow as it passes over and under the wings. It supports the airplane in flight.
Weight is a downward force caused by the pull of gravity. It opposes lift.
Thrust is the forward force generated by the propeller and engine which propels the airplane through the air.
Drag is the rearward force that limits the speed of the airplane.

AIRFOILS
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An airfoil is any part of an airplane that is designed to produce lift.

Leading Edge or front of an airfoil is the portion that meets the air first.
Trailing Edge is the rear of the airfoil.
Chord of an airfoil is an imaginary straight line drawn through the airfoil from its leading edge to its trailing edge.
Camber of an airfoil is the characteristic curve of its upper or lower surface. It is the camber that gives the airfoil the ability to create lift.

BERNOULLI'S PRINCIPLE Page 1-10

Bernoulli's principle: As the velocity of a fluid increases, its pressure decreases.
The increase in velocity of air (a fluid) across the top of the wing produces a decrease in pressure on the top of the airfoil. This decrease in pressure on the top of the airfoil causes lift.

RELATIVE WIND
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Structure of an aeroplane(1) Relativewind

Relative wind is the airflow produced by the aircraft moving through the air. As diagrammed above, the relative wind stays constant for any given airspeed, regardless of weather the airplane is climbing, descending, or in level flight.

Angle of Incidence is permanently fixed when the aircraft is designed

Angle of Incidence is the angle between the chord line and the longitudinal axis of the aircraft. It is part of the aircraft design and never changes, regardless of flying conditions.