этапы отбора и ответы. Этапы отбора и ответы. REV2. Этапы отбора в Аэрофлот
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The Equation of Continuity (уравнение неразрывности потока)A continuity equation in physics is an equation that describes the transport of some quantity. In fluid dynamics, the continuity equation states that the rate at which mass enters a system is equal to the rate at which mass leaves the system plus the accumulation of mass within the system. Airfoil chord line, Mean chord line, mean camber line, angel of attack, angel of incidence, washout, dihedralWingspan – is the shortest distance measured between the wing tips of an airplane. Airfoil chord line - is a straight line from the leading edge to the trailing edge of an airfoil. Mean chord line - is the wing area divided by the wingspan (sometimes referred to as the standard mean chord). Mean Aerodynamic Chord - is the chord line that passes through the geometric center of the plan area (the centroid) of an airfoil. A rectangular wing of this chord and the same span would have broadly similar pitching moment characteristics. The MAC is located on the reference axis of the aircraft and is a primary reference for longitudinal stability considerations. Mean camber line - is a line joining the leading and trailing edges of an airfoil, equidistant from the upper and lower surfaces. Angel of attack - is the angle between the chord line of an airfoil and the relative airflow. Angel of incidence - is the angle between the airfoil’s chord line and the aircraft’s longitudinal datum (axis). It is a fixed angle for a wing but may be variable for a tailplane. (It is sometimes called rigging incidence.) Sweep Angle – is the angle subtended between the leading edge of an airfoil and the lateral axis of an airplane. Washout - is a decrease in the angle of incidence from the wing root to the tip. This compensates for the early stall due to the higher levels of loading experienced at the wing tips. The root will tend to stall first. Dihedral - is the upward inclination of a wing from the root to the tip. The angle between the horizontal datum of an airplane and the plane of a wing. Точка стагнации, центр давления, центр тяжести, фокус крылаStagnation point - the point on an airfoil at which the approaching airflow becomes stationary and the airstream velocity is zero and the air pressure is greatest. It is located on the leading edge of the airfoil just below the maximum point of curvature and moves downward and aft along the lower surface of the airfoil profile as the angle of attack increases. A stagnation point exists where the air stream impacts (impinges) on the front of the airfoil’s surface and splits; some air goes over and some under. Another stagnation point exists at “B,” where the two airstreams rejoin and resume at identical velocities. Center of pressure. The point on the chord line where lift is considered to be concentrated. For this reason, the center of pressure is commonly referred to as the center of lift. The point on the chord line through which the resultant of all of the aerodynamic forces acting on the wing. Center of gravity (CG). It is the mass center of the airplane, or the theoretical point at which the entire weight of the airplane is assumed to be concentrated. It may be expressed in inches from the reference datum, or in percentage of mean aerodynamic chord (MAC). The location depends on the distribution of weight in the airplane. Aerodynamic center (AC) or Wing focus – is a stationary point on the chord line about which pitching moment remains constant. Pitching moment about the AC does not change with changes in angle of attack. The changes in magnitude of lift force due to changes in angle of attack, acting through the aerodynamic center (AC). It is a point situated on the wing chord where and at this point increment of the wing lift is applied in spite of AOA changes. Dynamic (positive, negative, neutral)/Static (positive, negative, neutral) stabilityStability is the tendency of an aircraft to maintain its attitude in flight and return to this attitude if displaced, without pilot intervention. Dynamic stability refers to the aircraft response over time when disturbed from a given AOA, slip, or bank. This type of stability also has three subtypes: Positive dynamic stability—over time, the motion of the displaced object decreases in amplitude and, because it is positive, the object displaced returns toward the equilibrium state. Neutral dynamic stability—once displaced, the displaced object neither decreases nor increases in amplitude. A worn automobile shock absorber exhibits this tendency. Negative dynamic stability—over time, the motion of the displaced object increases and becomes more divergent. Static stability refers to the initial tendency, or direction of movement, back to equilibrium. In aviation, it refers to the aircraft’s initial response when disturbed from a given AOA, slip, or bank. Positive static stability—the initial tendency of the aircraft to return to the original state of equilibrium after being disturbed. Neutral static stability—the initial tendency of the aircraft to remain in a new condition after its equilibrium has been disturbed. Negative static stability—the initial tendency of the aircraft to continue away from the original state of equilibrium after being disturbed. Longitudinal / lateral / directional stabilityDirectional (vertical) stability is the tendency for an aircraft to regain its direction (heading) after the aircraft has been directionally disturbed (e.g., an induced yaw) from its straight path. This is achieved naturally because the fin (vertical tailplane) becomes presented to the airflow at a greater angle of incidence, which generates a restoring aerodynamic force. Directional stability is about the normal axis (yawing). The area of the vertical fin and the sides of the fuselage aft of the CG are the prime contributors which make the aircraft act like the well known weather vane or arrow, pointing its nose into the relative wind. Stability around the normal axis is called directional stability, because it is concerned with the stability in the directional or yawing plane. Lateral stability is the tendency for an aircraft to return to a laterally level position around the longitudinal axis on release of the ailerons in a sideslip. Lateral stability is about the longitudinal axis (rolling). The most common procedure for producing lateral stability is to build the wings with an angle of one to three degrees above perpendicular to the longitudinal axis. The wings on either side of the aircraft join the fuselage to form a slight V or angle called “dihedral.” The amount of dihedral is measured by the angle made by each wing above a line parallel to the lateral axis. Stability around the longitudinal axis is known as lateral stability, because it is concerned with movement in lateral or rolling plane. Longitudinal stability is an aircraft’s natural ability to return to a stable pitch position around its lateral axis after a disturbance. Longitudinal stability is about the lateral axis (pitching). To obtain static longitudinal stability, the relation of the wing and tail moments must be such that, if the moments are initially balanced and the aircraft is suddenly nose up, the wing moments and tail moments change so that the sum of their forces provides an unbalanced but restoring moment which, in turn, brings the nose down again. A forward CG leads to the increased longitudinal stability and an aft CG leads to reduced LS. There are the specified limits for the CG position. Stability around the lateral axis is known as longitudinal stability, because it is concerned movement in longitudinal or pitching plane. An airplane is in a state of equilibrium when the sum of all the forces on it is zero and the sum of all the turning moments on it is zero. |