When the nut is screwed down tight against the washer, the twisted teeth flatten out, and their spring action holds the nut tight against the threads of the screw and prevents its backing off.
An external-tooth lock washer is also called a Type-B shakeproof lock washer.
extra-flexible control cable. Aircraft control cable made up of seven strands of wire with each strand containing 19 individual wires. Extra-flexible cable, normally called 7 by 19 cable, is used in all locations where the cable must pass over a pulley.
extratropical low (meteorology). Any cyclone that is not a tropical cyclone. It usually refers to the migratory frontal cyclones found in the middle or high latitudes.
extrusion. A form of structural material made by passing metal heated to its plastic state through specially shaped dies. The extruding process is used to make long, continuous lengths of such structural shapes as angles and channels.
eye (meteorology). The roughly circular area of calm or relatively light winds and comparatively fair weather at the center of a well-developed tropical cyclone. Wall clouds mark the outer boundary of the eye.
eyebolt. A bolt having a blade-like head with a hole in it. An eyebolt is used to attach a cable to a structure.
eyebrow lights. Small lights placed in a shield over the two top corners of an instrument installed in an aircraft instrument panel. Eyebrow lights illuminate the dial of the instrument, but do not shine in the pilot’s eyes.
F
FAA (Federal Aviation Administration). The division within the Department of Transportation of the United States government that has the responsibility of promoting safety in the air, by both regulation and education. Aircraft and the airmen who operate them are licensed by the FAA, and the FAA maintains the airways along which the aircraft fly. The FAA is headed by a civilian, the Administrator of Federal Aviation.
FAA Form 337. The Major Repair and Alteration form that must be completed when a major repair or major alteration has been completed on an FAA-certificated aircraft or engine.
fabric. A cloth produced by interlacing two yarns at right angles to each other.
fabricate. A term that means to build or to manufacture something.
fabrication. The process of assembling parts to make a complete unit or structure.
fabric punch test (aircraft maintenance test). A maintenance test performed by a technician to determine the condition of the fabric used to cover an aircraft. A special spring-loaded punch with a sharp point is pressed into the fabric, and the amount of force needed to cause the punch to make a specific size hole in the fabric is measured. The stronger the fabric, the more force is needed to make the hole.
A color-coded scale is used to indicate the condition of the fabric. Green means the fabric is good, yellow means that the strength of the fabric is questionable, and red means that the fabric is too dead to pass an airworthiness test. A fabric punch test is not an absolute indication of the strength of the fabric, but it is quick and accurate enough to determine the basic condition of the fabric.
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