Principle of Flight

Lift ~~~ Lift is the force created by the interaction between the wings and the airflow. It always act upwards. It is considered to be the 'most important force' as without it, an aircraft cannot ascend from ground and maintain altitude.(不明白的話,請按上圖)

Weight ~~~ This force acts on an aircraft due to the interaction between the aircraft's body weight and Earth's gravity. Weight is a downward force.(不明白的話,請按上圖)

Thrust ~~~ This force is created by an aircraft's engine and is required for forward motion.(不明白的話,請按上圖)

Drag ~~~ This force acts in reverse direction to that of 'Thrust' and hinders forward motion. Drag is considered as a negative force and all engineers try their best to reduce drag.(不明白的話,請按上圖)

1.)In steady straight and level flight at constant altitude and speed, the amount of the Lift acting on an aircraft is equal to its Weight and its Thrust is equal to its Drag.

2.)The mechanism of flying is based on the wing of aircraft, which is so shaped that the speed of air flows over the top surface will be faster and therefore the pressure will be lower.

3.)Air around the lower surface of the wing will experience higher pressure and slower speed than the supper surface.

4.)Stalling is that when the angle of attack increases beyond about 15 degrees the airflow becomes turbulent and lift decreases rapidly and suddenly.

5.)Stalling can occur at any attitude and it is the angle of attack that determines the occurrence of a stall.

6.)The angle of attack is the angle between the incoming air (or path of the aircraft) and chord line of the wing.

7.)The movement of an aircraft in the rolling plane is about the Longitudinal axis, and is controlled by ailerons.(控制飛機的部分)

8.)When the left aileron move upwards, the right ailerons moves downwards and the aircraft roll to its left.

9.)The movement of an aircraft in the yawing plane is about the Vertical axis (or Normal axis), and is controlled by rudder. (The axis of rotation)

10.)When the rudder moves to the left, the aircraft nose will move to the left.

11.)The movement of an aircraft in the pitching plane is about the Lateral axis, and is controlled by elevator.

12.)When the elevator moves upwards the aircraft nose begins to move upwards.

13.)The feet of the pilot control rudder and the hands control ailerons and elevator.

14.)When the flaps on an aircraft are fully extended, lift will be increased and drag will also be increased.

15.)The drags acting on an aircraft are named as Form Drag, Skin Friction and Induced Drag.

16.)From drags and Skin Friction increase with air speed.

17.)Induced Drag decreases when air speed increase.

18.)Polishing all the surfaces over which the airflow passes can reduce skin friction.

19.)Streamlined shape of aircraft can reduce form drag.

20.)Flaps are hinged surfaces which are fitted to the trailing edges of the wings ---- inboard of the ailerons.

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