航空术语词典Dictionary of Aeronautical Terms 中

时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次

life-limited part. An aircraft part whose service life is limited to a specified number of operating hours or operating cycles.
life-support systems. Systems in an aircraft which make it possible for the occupants to operate in an environment that does not support life. Oxygen systems and pressurization systems are examples of life-support systems.
lift (aerodynamic force). An aerodynamic force caused by air flowing over a specially shaped surface called an airfoil. The airfoil is curved in such a way that the air flowing over the upper surface finds the surface falling away from it. The air is being pressed onto the surface by the air above it, and in order for it to remain on the surface, it must speed up. As the air speeds up, its pressure drops, and the air above it flows down to fill the low-pressure area.
The air below the airfoil finds the surface rising into its flow path, and this slows the air. As the air slows down, its pressure rises, and it forces the surrounding air away from it. The combination of the low pressure pulling air down to the airfoil and the high pressure forcing air away from the airfoil causes the air to be deflected downward. When an airfoil forces air downward, a force equal to the weight of the deflected air forces the airfoil upward. This force is called lift.

lift coefficient (aerodynamic parameter). A dimensionless number used in the formula for aerodynamic lift that varies with the shape of the airfoil and the angle of attack. The lift coefficient (CL) is obtained from
wind tunnel data and is plotted on a set of airfoil characteristic curves.
lift fan. A special type of turbofan engine installed on an aircraft in such a way that it can be pivoted to direct its thrust in a vertical direction. Lift fans are used on some types of V/STOL (vertical, or short takeoff and landing) aircraft.
lifting body (aerodynamic shape). The shape of the fuselage of an aircraft that produces lift. Such a device can fly without wings.
lifting condensation level (meteorology). The level at which a parcel of unsaturated air lifted dry-adiabatically becomes saturated.
lift wires (airplane structural components). Wires installed between the wings of a biplane to support the wings against the forces of lift. Lift wires run from the inboard end of the lower wing to the interplane struts on the upper wing. Lift wires are also called flying wires.
light. The portion of the electromagnetic spectrum that produces waves visible to the naked eye. The wavelengths of visible light range from 3,800 to 7,800 Angstroms.
light aircraft. As defined by the Federal Aviation Administration, a light aircraft is one having a maximum certificated takeoff weight of less than 12,500 pounds.
light chopper (optoelectronic device). An optoelectronic device that interrupts a beam of light being shone on a photoelectric cell. The chopper changes the steady DC output of the photoelectric cell into pulsating DC that can be easily amplified.

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