Pitch is changed in this case by moving the entire horizontal surface of the tail. Craft capable of supersonic flight often have a stabilator, an all-moving tail surface. The system of a fixed tail surface and moveable elevators is standard in subsonic aircraft. In micro-lights and hang gliders the pitch action is reversed-the pitch control system is much simpler so when the pilot moves the elevator control backwards it produces a nose-down pitch and the angle of attack on the wing is reduced. The angle of attack on the wings increased so the nose is pitched up and lift is generally increased. By moving the elevator control backwards the pilot moves the elevator up (a position of negative camber) and the downwards force on the horizontal tail is increased. Pitch is controlled by the rear part of the tailplane's horizontal stabilizer being hinged to create an elevator. A precise combination of bank and lift must be generated to cause the required centripetal forces without producing a sideslip. Using yaw alone is not a very efficient way of executing a level turn in an aircraft and will result in some sideslip. On a large aircraft there may be several independent rudders on the single fin for both safety and to control the inter-linked yaw and roll actions. Since the force is created at a distance behind the centre of gravity, this sideways force causes a yawing moment then a yawing motion. The movement of the rudder changes the size and orientation of the force the vertical surface produces. In turning flight, lift exceeds weight and produces a load factor greater than one, determined by the aircraft's angle of bank. In addition, if the aircraft is not accelerating, thrust is less than drag. In straight descending flight, lift is less than weight.
In straight, climbing flight at constant airspeed, thrust exceeds drag. When flying straight upwards the aircraft can reach zero airspeed before falling earthwards the wing is generating no lift and so does not stall. This can be seen by considering an aerobatic aircraft in straight vertical flight (one that is climbing straight upwards or descending straight downwards). 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. When an aircraft is climbing at constant speed it is its thrust that enables it to climb and gain extra potential energy. At first, this seems incorrect because if an aircraft is climbing it seems lift must exceed weight. In straight climbing flight, lift is less than weight. In addition, if the aircraft is not accelerating, thrust is equal and opposite to drag. In straight and level flight, lift is approximately equal to the weight, and acts in the opposite direction. Weight acts through the aircraft's centre of gravity, towards the centre of the Earth. Drag acts parallel to the aircraft's velocity vector, but in the opposite direction because drag resists motion through the air. Lift acts perpendicular to the vector representing the aircraft's velocity relative to the atmosphere. 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. In flight a powered aircraft can be considered as being acted on by four forces: lift, weight, thrust, and drag. 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.įurther information: Steady flight § Steady Flight Maneuvers 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). An aeroplane ( airplane in US usage), is defined in ICAO 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". Please help improve this article by introducing citations to additional sources.įind sources: "Aircraft flight mechanics" – news Īircraft flight mechanics are relevant to fixed wing ( gliders, aeroplanes) and rotary wing ( helicopters) aircraft. Relevant discussion may be found on the talk page. This article relies largely or entirely on a single source.
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