the Aviation Dictionary

circling approach . class
instrument approach is not possible or desirable. This
maneuver is made only after ATC authorization and
the pilot has established the required visual reference to
the airport.
circling approach - See circle-to-land maneuver.
circumscribed circle - A circle drawn around the
outside of another figure in such a way that all of the
points touch the circumference of the circle.
cirriform - High altitude clouds made up mostly of
small ice crystals.
circling maneuver - See circle-to-land maneuver.
cirrocumulus (Cc) - Cirroform clouds, elements of
which appear as small puffy clouds sometimes aligned
circling minima - A statement of MDA and visibility in rows.
required for the circle-to-land maneuver.
Note: Descent below the established MDA or DH is not
cirrostratus (Cs) - Layer of cirroform clouds that
authorized during an approach unless the aircraft is in a
appear as thin white or light-gray sheets.
position from which normal approach to the runway cirrus (Ci)- Detached cirroform clouds that appear as
of intended landing can be made and adequate visual white feathers or filaments.
reference to required visual cues is maintained.
cistern -A container used to store a liquid.
circuit - The complete path in which electrical current
flows. ~t must contain a source of electrical energy, a 'IT sensor - A device that sends an duct
load to absorb this energy, and conductors to carry the
temperature signal to the fuel control as a scheduling
elcctron flow.
parameter.
circuit breaker - A circuit-protecting device that opens
civil aircraft - Aircraft other than public aircraft.
the circuit in case of excess current flow. A circuit civil twilight - The period of time before sunrise or after
breaker differs from a fuse in that it can be reset sunset when the sun is not more than 6" below the
without having to be replaced.
horizon.
circuit diagram - An electrical drawing that uses
conventional symbols to show how the components in
an electrical system are interconnected.
clad aluminum - An aluminum alloy with a coating of
pure aluminum rolled onto both sides for corrosion
protection.
circuit protector - A device that opens an electrical cladding - A method of protecting aluminum alloys
circuit in the event of an excessive current flow.
from corrosion by rolling a coating of pure aluminum
circular inch - The area of a circle whose diameter is onto the surface of the alloy. Although cladding
1." protects the alloy, it also reduces its strength.
0;::
circular mil (CM) - A clamp - Any device used to exert pressure to
measurement of area equal to
temporarily hold objects together.
0.00f
that of a circle having a
clamp-on ammeter - A hand-held ammeter that clamps
0.7~~4
diameter of 'll,~o," 1 mil., or
around a current-carrying wire that is to be measured.
0.001 ." The changing magnetic field around the wire induces a
circular motion - The motion of an object along a voltage in the jaws of the ammeter proportional to the
curved path in which the object stays a constant amount of current flowing in the line.
distance from the center of the motion.
clamshell doors - Two doors that open on the opposite
circular saw - A power saw driven by an electric motor sides of the center line similar to the way the shell of a
that uses a circular blade.
clam opens.
circular rule - A rule having scales arranged clamshell thrust reverser - A thrust reverser, clamshell
in circles on the surface of a disk. Transparent runners door system that fits in the exhaust system of a turbojet
attached at the center of the disk can be moved over the engine. When the reverser is deployed for thrust
scale to perform various mathematical operations.
reversing, the doors move into position to block the
normal tailpipe and duct the exhaust gases around so
circulation - In meteorology, the organized movement that they flow forward to oppose the forward
of air. Also called an eddy.
movement of the aircraft.
circumference of a circle - The linear distance around a
circle. The circumference of a circle is always 3.1416
times the length of the diameter of the circle.
circumferential frame - A circular or oval frame. It
gives shape to a fuselage or nacelle. Also referred to as
a belt or transverse frame.
74
Aircraft Technical Book Company
P.O. Box 270
Tabernash, CO 80478
http:llw.ACTechbooks.com
class - 1. AS used with respect to the certification,
ratings, privileges, and limitations of airmen, means a
classification of aircraft within a category having
similar operating characteristics. Examples include:
single engine; multiengine; land; water; gyroplane;
helicopter; airship; and free balloon. 2. As used with
respect to the certification of aircraft, means a broad