- Industry: Aviation
- Number of terms: 16387
- Number of blossaries: 0
- Company Profile:
Aviation Supplies & Academics, Inc. (ASA) develops and markets aviation supplies, software, and books for pilots, flight instructors, flight engineers, airline professionals, air traffic controllers, flight attendants, aviation technicians and enthusiasts. Established in 1947, ASA also provides ...
An instrument that shows in a visual form the value it is sensing. There are two basic types of indicating instruments: instruments that give their indication in an analog form, and instruments that have a digital readout.
An analog instrument has a dial and one or more pointers. The position of the pointer on the dial is an analog, or representation, of the value the indicator is sensing. A digital instrument uses numbers to indicate the value it is sensing. An ordinary clock is a form of analog indicating instrument. The number of degrees the hands have moved past their straight-up position relates to the number of hours, minutes, or seconds that have passed since noon or midnight. A digital clock uses just numbers to indicate the seconds, minutes, and hours that have passed since noon or midnight.
Industry:Aviation
An instrument used for nondestructive inspection. A fluorescent screen is used in place of photographic film, to display the shadows which form when X-rays penetrate the structure being inspected.
Industry:Aviation
An instrument used in an aircraft to show the rotational speed of the engine crankshaft. A flexible shaft, or cable, turned at one-half crankshaft speed, spins a permanent magnet inside the tachometer.
An aluminum drag cup rides over the spinning magnet, but does not touch it. A pointer shaft is mounted on the center of the cup, and the tachometer pointer is pressed onto the end of the shaft. A flat, coiled hairspring attached to the shaft holds the cup against a stop so the pointer rests on zero when the magnet is not spinning.
When the engine is running, the magnet spins, and its lines of flux cut across the aluminum drag cup and generate a voltage in it. This voltage causes eddy currents to flow in the aluminum cup where they produce a magnetic field. The magnetic field caused by the eddy currents opposes the field of the spinning magnet. The faster the magnet spins, the more the cup is pushed against the restraint of the hairspring.
Most magnetic-drag tachometers incorporate an hourmeter, similar to the odometer in an automobile speedometer. The hourmeter is a gear-driven counter which counts the revolutions of the drive shaft and displays the number of hours the engine has run on the hourmeter wheels. The hours shown are correct only at a specific RPM, which is normally the cruising speed of the engine. This speed is stamped on the tachometer case.
Industry:Aviation
An instrument used to analyze the chemical composition of the exhaust gas released by a reciprocating engine. One type of analyzer measures the conductivity of the exhaust gas and indicates the ratio of fuel and air in the mixture that produced the exhaust gas.
An exhaust gas temperature (EGT) system is not the same as an exhaust gas analyzer.
Industry:Aviation
An instrument used to collect and measure the amount of rain which has fallen at a given location.
Industry:Aviation
An instrument used to determine the frequency of alternating current. The frequency of an accurately calibrated internal oscillator is varied and compared with the frequency being measured.
When the two frequencies are mixed, a third frequency, called the beat frequency, is produced. This beat frequency is the difference between the two.
The variable frequency is changed until the beat frequency disappears. When it disappears, the frequency being measured is the same as that being produced by the oscillator.
Industry:Aviation
An instrument used to determine whether or not something is level, or perpendicular to a line that points directly toward the center of the earth. A spirit level is a curved glass tube partially filled with liquid. Enough liquid is left out of the tube so there is a bubble in it. The tube is mounted in a long, straight metal or wood bar in such a way that when the bar is level, the bubble in the liquid is in the center of the tube. Spirit levels are also called bubble levels.
Industry:Aviation
An instrument used to draw circles or portions of a circle. A compass is made of two legs, hinged in the center. One leg is fitted with a sharp point to hold it at the center of the circle, and the other leg can be fitted with a lead holder or ink pen to draw the circle.
Industry:Aviation
An instrument used to examine the inside of a structure through a very small hole. The inside of a turbine engine and the inside of the cylinder of a reciprocating engine, for example, can be examined by inserting the probe of the borescope through a small inspection hole or through a spark plug hole.
A borescope furnishes its own light, and some borescopes have different ranges of magnification. Some borescopes are fitted to a camera to photograph the inside of the structure. A modern trend in borescopes is to place a video pickup on the borescope tube and display the results on a small television screen.
Industry:Aviation
An instrument used to measure a value by comparing it with a known variable value. The known value is compared with the unknown and is changed until the null detector determines that there is no difference between the two. The known value is now exactly the same as that of the unknown.
Industry:Aviation
