wedge. A triangular body forced into an opening to enlarge the opening, or to separate the sides of the opening. A wedge is a form of inclined plane.
weft threads. See fill threads.
weighing points (aircraft weight and balance). Locations on an aircraft, designated by the manufacturer, for the placement of the scales or load capsules when the aircraft is being weighed.
weight. A measure of the force of gravity acting upon a body. Weight and mass are often used interchangeably, but they are not the same thing. Mass is the amount of material in a body and does not consider the effect of gravity acting on it. Weight does take into consideration the effect of gravity acting on the mass.
weight and balance record (aircraft record). The record kept in an aircraft that gives the pilot or flight engineer an accurate account of the total weight of the aircraft and the location of its center of gravity. If the aircraft weight is too great, or if the center of gravity falls outside the allowable limits, the aircraft is not safe to fly.
weld bead. The ridge of metal left along the seam where two pieces of metal are joined by welding. The ridge, caused by the metal from the welding rod, increases the strength of the joint.
welding. A method of joining pieces of metal by fusion. The pieces to be joined are placed next to each other, and the surfaces between the two pieces are melted and allowed to flow together. The heat used to melt the edges is produced by a gas flame, an electric arc, or an extremely hot stream of plasma (ionized particles that act as a gas).
Most welds are reinforced by adding filler metal to the puddle of molten metal to build up the area where the pieces are joined.
welding flux. A material that melts and flows over the surface of metal being welded. Flux produces an airtight seal which prevents oxygen reaching the surface of the hot metal and forming an oxide film. Oxides on the metal contaminate the weld.
Western Union splice (wire splice). A type of wire splice used to join two pieces of solid copper wire. The insulation is removed from the ends of the two pieces of wire, and the wires are scraped clean of all oxide coating. The wires are crossed and each end is wrapped around other wire; then the joint is coated with molten solder and insulated with tape.
wet-bulb temperature. Temperature measured with a thermometer enclosed in a cloth wick, saturated with water. Evaporation of the water lowers the temperature measured by this thermometer.
Relative humidity of the air is found by comparing the wet-bulb temperature with the dry-bulb temperature, which is not affected by evaporation.
wet-sump engine (lubrication system classification). An aircraft engine that carries its supply of lubricating oil in a sump, or compartment, which is part of the engine itself. After serving its lubricating functions, the oil drains back into the sump by gravity.
A dry-sump engine uses an external oil tank, and the oil, after flowing through the engine, is moved by scavenger pumps to the external tank where it is stored until it is pumped through the engine again.