What is an aircraft? (BAK)

What is Air?

Air is a gas with many elements – nitrogen, oxygen and a mixture of other elements.

Aircraft can fly because air has mass (substance), weight (due to gravity), density (weight vs volume), temperature and pressure (both static and dynamic).

The aeroplane flies because the wings are shaped to compress the air underneath and to reduce the pressure of the air above. The combination of these effects lifts the plane into the air and makes it fly.

The engine functions by sucking in the air, mixing it with fuel, igniting the mixture and using this temperature rise to generate a force which turns the propellor.

Parts of an Aircraft

  • Cabin
  • Wings
    • Can be low-wing, mid-wing or high-wing
  • Fuselage
  • Vertical stabiliser (fin)
  • Tailplane
  • Undercarriage

How an Aircraft is lifted

It works by reducing the pressure of air above the wing and increasing the pressure of air below the wing. The difference between these pressures builds the cushion on which the wing is supported.

The air behind the wing is deflected downwards which causes a reaction.

This reaction has two elements:

  • Vertical force (called lift)
  • A rearward component called induced drag

The amount of lift and drag depends on four elements:

  • The thickness of the air (air density)
  • The speed of the wing through the air (airspeed)
  • The size of the wing (wing area)
  • The efficiency of the wing (lift coefficient) which is dependent on the angle of attack of the wing and the shape of the wing

The angle of attack in the angle between the airflow and the chord line of the wing.

What is Stability?

Stability is the natural tendency of the aircraft to maintain its direction through the air.

Stability vs Control

If we have too much stability we have too little control.

Control is the ability to change our flightpath.

Control Surfaces

The elevator controls the pitch of the aircraft.

The ailerons control the bank of the aircraft.

The rudder controls the balance of the aircraft.

The Cockpit

Where the pilot sits and controls the aircraft (obviously).

The pilot’s references are the attitude of the aircraft (the position of the nose in relation to the horizon) and the power that is set.

Attitude and power, together, control the flightpath and speed of the aircraft.


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