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Aircraft flight mechanics
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Aircraft flight mechanics
Aircraft flight mechanics are relevant to fixed wing (gliders, aeroplanes) and rotary wing (helicopters) aircraft. An aeroplane (airplane in US usage), is defined in ICAO defined by bala from Erode Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
Note that this definition excludes both dirigibles (because they derive lift from buoyancy rather than from airflow over surfaces), and ballistic rockets (because their lifting force is typically derived directly and entirely from near-vertical thrust). Technically, both of these could be said to experience "flight mechanics" in the more general sense of physical forces acting on a body moving through air; but they operate very differently, and are normally outside the scope of this term.
A heavier-than-air craft (aircraft) can only fly if a series of aerodynamic forces come to bear. In regard to fixed wing aircraft, the fuselage of the craft holds up the wings before takeoff. At the instant of takeoff, the reverse happens and the wings support the plane in flight.
In flight a powered aircraft can be considered as being acted on by four forces: lift, weight, thrust, and drag. Thrust is the force generated by the engine (whether that engine be a jet engine, a propeller, or -- in exotic cases such as the X-15 -- a rocket) and acts in a forward direction for the purpose of overcoming drag. Lift acts perpendicular to the vector representing the aircraft's velocity relative to the atmosphere. Drag acts parallel to the aircraft's velocity vector, but in the opposite direction because drag resists motion through the air. Weight acts through the aircraft's centre of gravity, towards the centre of the Earth.
In straight and level flight, lift is approximately equal to the weight, and acts in the opposite direction. In addition, if the aircraft is not accelerating, thrust is equal and opposite to drag.
In straight climbing flight, lift is less than weight. At first, this seems incorrect because if an aircraft is climbing it seems lift must exceed weight. When an aircraft is climbing at constant speed it is its thrust that enables it to climb and gain extra potential energy. Lift acts perpendicular to the vector representing the velocity of the aircraft relative to the atmosphere, so lift is unable to alter the aircraft's potential energy or kinetic energy. This can be seen by considering an aerobatic aircraft in straight vertical flight (one that is climbing straight upwards or descending straight downwards). Vertical flight requires no lift. When flying straight upwards the aircraft can reach zero airspeed before falling earthwards; the wing is generating no lift and so does not stall. In straight, climbing flight at constant airspeed, thrust exceeds drag.
In straight descending flight, lift is less than weight. In addition, if the aircraft is not accelerating, thrust is less than drag. In turning flight, lift exceeds weight and produces a load factor greater than one, determined by the aircraft's angle of bank.
There are three primary ways for an aircraft to change its orientation relative to the passing air. Pitch (movement of the nose up or down, rotation around the transversal axis), roll (rotation around the longitudinal axis, that is, the axis which runs along the length of the aircraft) and yaw (movement of the nose to left or right, rotation about the vertical axis). Turning the aircraft (change of heading) requires the aircraft firstly to roll to achieve an angle of bank (in order to produce a centripetal force); when the desired change of heading has been accomplished the aircraft must again be rolled in the opposite direction to reduce the angle of bank to zero. Lift acts vertically up through centre of pressure which depends on the position of wings. The position of the centre of pressure will change with changes in the angle of attack and aircraft wing flaps setting.
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Aircraft flight mechanics
Aircraft flight mechanics are relevant to fixed wing (gliders, aeroplanes) and rotary wing (helicopters) aircraft. An aeroplane (airplane in US usage), is defined in ICAO defined by bala from Erode Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
Note that this definition excludes both dirigibles (because they derive lift from buoyancy rather than from airflow over surfaces), and ballistic rockets (because their lifting force is typically derived directly and entirely from near-vertical thrust). Technically, both of these could be said to experience "flight mechanics" in the more general sense of physical forces acting on a body moving through air; but they operate very differently, and are normally outside the scope of this term.
A heavier-than-air craft (aircraft) can only fly if a series of aerodynamic forces come to bear. In regard to fixed wing aircraft, the fuselage of the craft holds up the wings before takeoff. At the instant of takeoff, the reverse happens and the wings support the plane in flight.
In flight a powered aircraft can be considered as being acted on by four forces: lift, weight, thrust, and drag. Thrust is the force generated by the engine (whether that engine be a jet engine, a propeller, or -- in exotic cases such as the X-15 -- a rocket) and acts in a forward direction for the purpose of overcoming drag. Lift acts perpendicular to the vector representing the aircraft's velocity relative to the atmosphere. Drag acts parallel to the aircraft's velocity vector, but in the opposite direction because drag resists motion through the air. Weight acts through the aircraft's centre of gravity, towards the centre of the Earth.
In straight and level flight, lift is approximately equal to the weight, and acts in the opposite direction. In addition, if the aircraft is not accelerating, thrust is equal and opposite to drag.
In straight climbing flight, lift is less than weight. At first, this seems incorrect because if an aircraft is climbing it seems lift must exceed weight. When an aircraft is climbing at constant speed it is its thrust that enables it to climb and gain extra potential energy. Lift acts perpendicular to the vector representing the velocity of the aircraft relative to the atmosphere, so lift is unable to alter the aircraft's potential energy or kinetic energy. This can be seen by considering an aerobatic aircraft in straight vertical flight (one that is climbing straight upwards or descending straight downwards). Vertical flight requires no lift. When flying straight upwards the aircraft can reach zero airspeed before falling earthwards; the wing is generating no lift and so does not stall. In straight, climbing flight at constant airspeed, thrust exceeds drag.
In straight descending flight, lift is less than weight. In addition, if the aircraft is not accelerating, thrust is less than drag. In turning flight, lift exceeds weight and produces a load factor greater than one, determined by the aircraft's angle of bank.
There are three primary ways for an aircraft to change its orientation relative to the passing air. Pitch (movement of the nose up or down, rotation around the transversal axis), roll (rotation around the longitudinal axis, that is, the axis which runs along the length of the aircraft) and yaw (movement of the nose to left or right, rotation about the vertical axis). Turning the aircraft (change of heading) requires the aircraft firstly to roll to achieve an angle of bank (in order to produce a centripetal force); when the desired change of heading has been accomplished the aircraft must again be rolled in the opposite direction to reduce the angle of bank to zero. Lift acts vertically up through centre of pressure which depends on the position of wings. The position of the centre of pressure will change with changes in the angle of attack and aircraft wing flaps setting.