ashless dispersant oil. See AD oil.
ASM (air-to-surface missile). A missile carried on an aircraft and used against a surface target. The missile is guided to its target by an internal guidance system or by signals from the launch aircraft.
aspect ratio. The ratio of the length, or span, of an airfoil to its width, or chord. For a nonrectangular airfoil, the aspect ratio is found by dividing the square of the span by the area.
Aspect Ratio = Span2 / Area
asphalt. A heavy, brownish-black mineral found in crude oil. Asphalt is used as a base for some acid-resisting paints.
aspheric (optics). The characteristics of an optical element that contains one or more surfaces that are not spherical.
ASR (airport surveillance radar). Approach control radar used to detect and display an aircraft’s position in the terminal area. ASR provides range and azimuth information but does not provide elevation data. Coverage of the ASR can extend up to 60 miles.
assembly. The process of fitting together all the parts to form a complete structure or unit.
assembly break. A joint in the structure of an aircraft formed when two subassemblies are removed from their jigs and joined together to form a single unit.
assembly drawing. An aircraft drawing which shows a group of parts laid out in the relationship they will have when they are assembled.
assembly line (aircraft manufacturing). An arrangement of work stations in an aircraft factory that allows a certain function to be performed on all aircraft at a particular physical location.
Special tools and specially trained personnel stay in one location, and each aircraft is moved to this location for the function to be performed.
assigned frequency (radio communications). The frequency of the carrier signal produced by a radio transmitter.
This carrier frequency is assigned by the Federal Communications Commission (FCC) for the particular transmitter or the particular type of transmission.
astable. Not stable; “a” means not. An astable electronic device has two conditions of temporary stability, but no condition of permanent stability.
astable multivibrator. An electronic oscillator that has no stable condition. Astable multivibrators, also called free-running multivibrators, contain two devices such as transistors to control the flow of electrons. When one transistor is conducting, the other is not conducting. The two transistors alternate between conditions of conducting and not conducting.