Capillary action causes a piece of blotting paper to pick up a liquid, and the lack of capillary action causes a drop of water to form into a ball on a waxed surface.
capillary tube. A metal or glass tube with such a small inside diameter that capillary action causes liquid to move in the tube.
A soft copper capillary tube is used with a vapor-pressure thermometer connecting the temperature-sensing bulb to the Bourdon tube. The tube is protected from physical damage by enclosing it in a braided metal wire jacket.
cap screw. A threaded fastener whose shank passes through a clear hole in one piece of material and screws into threads cut into the second piece.
The head of the cap screw, which is turned with a wrench, clamps the two pieces of material together.
capstan (aircraft controls). A device in the control system of an aircraft that allows the automatic pilot to move the control surfaces.
The capstan is a grooved drum-like wheel mounted on the automatic pilot servo motor. A bridle of control cable is wound around the capstan, and the ends of the bridle are attached to the aileron, elevator, or rudder control cable. When the servo motor turns, it winds the bridle around the capstan, and the bridle moves the main control cable.
capstan screw. A form of machine screw whose head has several radial holes, holes that go across the head, through it. A bar can be passed through these holes and used to turn the screw.
cap strip. The main top and bottom members of a wing rib. The cap strips give the rib its aerodynamic shape.
capsule (aircraft instrument component). A flat container made of thin disks of corrugated metal soldered together and used to sense changing pressure.
When the pressure inside the capsule changes, the capsule expands or contracts, and the change in its physical dimensions is proportional to the change in the pressure.
captive balloon. A lighter-than-air device anchored to the ground with a steel cable. Captive balloons were used in the American Civil War as aerial observation platforms. In both World War I and World War II, captive balloons were used as obstructions to keep low-flying airplanes from bombing and strafing vital ground installations.
captive screw. A screw that has a section of the threads on its shank next to its head cut away. A captive screw is free to turn in the body in which it is mounted, but it will not drop out when it is unscrewed from the part it is holding.
carbide. A chemical compound of carbon and a metallic element. Carbides are normally very hard materials.
carbide tool (machine tool). A metal-cutting machine tool whose cutting faces are surfaced with tungsten carbide, tantalum carbide, or titanium carbide. These carbides keep their hardness and cutting ability even when they are extremely hot.
Carboloy. The registered trade name for certain cutting tools and dies that have tungsten carbide bonded to their cutting or wearing surfaces.
carbon. An abundant, nonmetallic chemical element that occurs in all organic compounds and in many inorganic compounds. Carbon’s symbol is C, its atomic number is 6, and its atomic weight is 12.01115.
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