Aviation Maintenance Terms beginning with E
E-gap angle
The position of the rotating magnet in a magneto when the breaker points are timed to open. The E-gap (efficiency gap) angle is several degrees of magnet rotation beyond the magnet’s neutral position. At this point, the magnetic field stress is the greatest, and the change in flux is the greatest, inducing the maximum voltage in the secondary winding.
Eccentric brushing
A special bushing used between the rear spar of certain cantilever airplane wings and the wing attachment fitting on the fuselage. The portion of the bushing that fits through the hole in the spar is slightly offset from that which passes through the holes in the fitting. By rotating the bushing, the rear spar may be moved up or down to adjust the root incidence of the wing.
Eddy current
Current induced into a conductor due to a mobbing or non-uniform magnetic field.
Eddy current damping (electrical instrument damping)
Decreasing the amplitude of oscillations by the interaction of magnetic fields. In the case of a vertical-card magnetic compass, flux from the oscillating permanent magnet produces eddy currents in a damping disc or cup. The magnetic flux produced by the eddy currents opposes the flux from the permanent magnet and decreases the oscillations.
Eddy current inspection
An inspection method where eddy currents are induced into the material to be tested. In aircraft manufacturing plants, eddy current is used to inspect castings, stampings, machine parts, forgings, and extrusions.
Edge distance
The distance between the center of a rivet hole and the edge of the sheet of metal.
Edge grain
Edge-grain lumber has been sawed parallel with the pith of the log and approximately at right angles to the growth rings; that is, the rings form an angle of 45 degrees or more with the surface of the piece.
Effective pitch
The actual distance a propeller advances in one revolution through the air.
Ejector
A form of jet pump used to pick up a liquid and move it to another location. Ejectors are used to ensure that the compartment in which the boost pumps are mounted is kept full of fuel. Part of the fuel from the boost pump flowing through the ejector produces a low pressure that pulls fuel from the main tank and forces it into the boostpump sump area.
Elastic limit
The maximum amount of tensile load, in pounds per square inch, a material is able to withstand without being permanently deformed.
Elastic limit
The maximum amount of tensile load, in pounds per square inch, that a material is able to withstand without permanent deformation.
Electrical energy
Electrical energy is converted to heat energy when an electric current flows through any form of resistance such as an electric iron, electric light, or an electric blanket.
Electrical potential
The electrical force caused by a deficiency of electrons in one location and an excess of electrons in another. Electrical potential is measured in volts.
Electrical steel
A low-carbon iron alloy that contains some silicon It is used as the core for transformers, field frames for generators and alternators, and the magnetic circuit of magnetos.
Electricity
One of the fundamental quantities in nature consisting of elementary particles, electrons and protons, which are manifested as a force of attraction or repulsion, and also in work that can be performed when electrons are caused to move; a material agency which, when in motion, exhibits magnetic, chemical, and thermal effects, and when at rest is accompanied by an interplay of forces between associated localities in which it is present.
Electromagnet
Temporary magnet which is magnetized by sending current through a coil of wire wound around an iron core.
Electromagnet
A magnet produced by an electrical current flowing through a coil of wire. The coil is normally wound around a core of soft iron which has an extremely low retentivity, allowing it to lose its magnetism as soon as the current stops flowing.
Electromagnetic radiation
A method of transmitting energy from one location to another. Current caused by high voltage in the secondary winding of a magneto produces electric and magnetic fields which oscillate back and forth at a high frequency and extend out into space in the form of waves. These waves of electromagnetic radiation are received as interference by the radio receivers in the aircraft.
Electromagnetic/Radio Frequency Interference (EMI/RFI)
Frequency spectrum of electromagnetic radiation extending from subsonic frequency to X-rays. This term should not be used in place of the term Radio Frequency Interference (RFI). (See radio frequency interference. ) Shielding materials for the entire EMI spectrum are not readily available.
Electromotive force
A force that causes electrons to move from one atom to another within an electrical circuit. An electromotive force, or EMF, is the difference in the electrical pressure, or potential, that exists between two points. An EMF may be produced by converting mechanical movement, pressure, chemical, light, or heat energy into electrical energy. The basic unit of EMF is the volt.
Electromotive force (EMF)
Difference of electrical potential measured in volts.
Electromotive force (EMF)
The pressure or force that causes electrons to flow in an electrical circuit.
Electromotive force (EMF)
The force that causes electrons to move from one atom to another within an electrical circuit. Electromotive force is an electrical pressure, and it is measured in volts.
Electron
A negative charge that revolves around the nucleus of an atom; a unit of a negative electrical charge.
Electron current
The actual flow of electrons in a circuit. Electrons flow from the negative terminal of a power source through the external circuit to its positive terminal. The arrowheads in semiconductor symbols point in the direction opposite to the flow of electron current.
Electron Volt (eV)
A unit of energy equal to the energy aquired by an electron falling though potential differences of one volt, approximately 1.602 x 10^19 joule.
Electronics
General term that describes the branch of electrical science and technology that treats the behavior and effects of electron emission and transmission.
Electrostatic field
A field of force that exists around a charged body.
Elevator downspring
A spring in the elevator control system that produces a mechanical force that tries to lower the elevator. In normal flight, this spring force is overcome by the aerodynamic force from the elevator trim tab. But in slow flight with an aft CG position, the trim tab loses its effectiveness and the downspring lowers the nose to prevent a stall.
Elevons
Movable control surfaces on the trailing edge of a delta wing or a flying wing airplane. These surfaces operate together to serve as elevators, and differentially to act as ailerons.
Empennage
The section of the airplane that consists of the vertical stabilizer, the horizontal stabilizer, and the associated control surfaces.
Empennage
The tail section of an airplane.
Empty weight
See standard empty weight.
Empty-weight center of gravity
The center of gravity of an aircraft when it contains only the items specified in the aircraft empty weight.
Empty-weight center of gravity range
The distance between the allowable forward and aft empty-weight CG limits.
Emulsion
A suspension of small globules of one material in another when the two materials will not mix. Oil and water will not mix, but they can be formed into an emulsion. An emulsion will separate into its components when it is allowed to sit.
Emulsion-type cleaner
A chemical cleaner which mixes with water or petroleum solvent to form an emulsion (a mixture which will separate if allowed to stand). It is used to loosen dirt, soot, or oxide films from the surface of an aircraft.
Enamel
A type of finishing material that flows out to form a smooth surface. Enamel is usually made of a pigment suspended in some form of resin. When the resin cures, it leaves a smooth, glossy protective surface.
Energizing brake
A brake that uses the momentum of the aircraft to increase its effectiveness by wedging the shoe against the brake drum. Energizing brakes are also called servo brakes. A single-servo brake is energizing only when moving in the forward direction, and a duo-servo brake is energizing when the aircraft is moving either forward or backward.
Energy
The capacity of a physical system to perform work. There are two types of energy, kinetic and potential.
Engine trimming
A maintenance procedure in which the fuel control on a gas turbine engine is adjusted to cause the engine to produce the required EGT or EPR at a specified rpm.
Enhanced Visual Acquisition (EVAcq)
This application is an enhancement for the outthe-window visual acquisition of aircraft traffic and potentially ground vehicles.
Entrained water
Water suspended in jet fuel. The amount of entrained water that can be held in the fuel is determined by the temperature of the fuel. When the fuel becomes cold, the water precipitates out and forms ice crystals on the fuel filter element.
Epicyclic reduction gears
A gear train in which a series of small planetary gears rotate around a central gear. More commonly called a planetary gear train.
Epoxy
One of various usually thermosetting resins capable of forming tight cross-linked polymer structures marked by toughness, strong adhesion, high corrosion, and chemical resistance, used especially in adhesives and surface coating.
Epoxy
A flexible, thermosetting resin that is made by polymerization of an epoxide. Epoxy has wide application as a matrix for composite materials and as an adhesive that bonds many different types of materials. It is noted for its durability and its chemical resistance.
Epoxy primer
A two-part catalyzed material used to provide a good bond between a surface and a surface coating.
Epoxy resin
A common thermosetting resin which exhibits exceptionally good adhesion, low cure shrinkage, and low water-absorption properties.
Equalizing resistor
A large resistor in the ground circuit of a heavy-duty aircraft generator through which all of the generator output current flows. The voltage drop across this resistor is used to produce the current in the paralleling circuit that forces the generators to share the electrical load equally.
Erosion
Loss of metal from metal surfaces by the action of small particles such as sand or water.
Erosion
Surface removal of material by mechanical action of grit, sand, water, etc., usually present on the leading edge close to the tip.
Estimation
The process of determining a track’s state based on new measurement information.
Ethanol
Alcohol made from cereal grains such as corn.
Ether
A volatile, highly flammable liquid that may be used to prime the cylinders of an aircraft engine when starting under extremely cold conditions.
Ethylene dibromide
A chemical compound added to aviation gasoline to convert some of the deposits left by the tetraethyl lead into lead bromides. These bromides are volatile and will pass out of the engine with the exhaust gases.
Ethylene dibromide
A colorless, poisonous liquid BrCH2CH2Br that is blended with leaded gasoline to help scavenge lead oxides.
Ethylene glycol
A form of alcohol used as a coolant for liquid-cooled engines and as an anti-icing agent.
Ethylene glycol
A form of alcohol used as a coolant for liquid-cooled aircraft engines. It is also used in automobile engines as a permanent antifreeze.
Eutectic
An alloy or solution that has the lowest possible constant melting point.
Eutectic material
An alloy or solution that has the lowest possible melting point.
Evacuation (air conditioning servicing procedure)
A procedure in servicing vapor-cycle cooling systems. A vacuum pump removes all the air from the system. Evacuation removes all traces of water vapor that could condense out, freeze, and block the system.
Evaporative cooling
See steam cooling.
Evaporator (air conditioning component)
The component in a vapor-cycle cooling system in which heat from the aircraft cabin is absorbed into the refrigerant. As the heat is absorbed, the refrigerant evaporates, or changes from a liquid into a vapor. The function of the evaporator is to lower the cabin air temperature.
Exceedance condition
A condition in which a parameter sensed by the EICAS exceeds the limits for which it is programmed.
Exciter
Small generator for supplying direct current to the alternator’s field windings.
Exfoliation corrosion
A form of intergranular corrosion that attacks extruded metals along their layer-like grain structure.
Exhaust cone
The fixed conical fairing centered in the turbine wheel. The exhaust cone straightens the flow and prevents the hot gases from circulating over the rear face of the turbine wheel.
Exhaust nozzle
The opening at the rear of the exhaust pipe.
Expandable sleeving
Open-weave braided sleeving used to protect wire and cables from abrasion and other hazards (commonly known by trade name EXPANDO).
Expander-tube brake
A brake that uses hydraulic fluid inside a synthetic rubber tube around the brake hub to force rectangular blocks of brake-lining material against the rotating brake drum. Friction between the brake drum and the lining material slows the aircraft.
Expansion wave
The change in pressure and velocity of a supersonic flow of air as it passes over a surface which drops away from the flow. As the surface drops away, the air tries to follow it. In changing its direction, the air speeds up to a higher supersonic velocity and its static pressure decreases. There is no change in the total energy as the air passes through an expansion wave, and so there is no sound as there is when air passes through a shock wave.
Expansion wave
The change in pressure and velocity of supersonic air as it passes over a surface that drops away from the flow. As the surface drops away, the air tries to follow it, and in changing its direction, the air speeds up to a higher supersonic speed, and its static pressure decreases. There is no change in the total amount of energy as air passes through an expansion wave.
Exploded view drawing
A pictorial drawing of two or more parts that fit together as an assembly. The view shows the individual parts and their relative position to the other parts before they are assembled.
Exponent (power)
A shorthand method of indicating how many times a number, called the base, is multiplied by itself. For example, in the number 43, the 3 is the power or exponent and 4 is the base. That is, 43 is equal to 4 × 4 × 4 = 64.
Extended Squitter
A long (112 bit) Mode S transmission that is spontaneously produced by the radio as opposed to a response to a Mode S Interrogation. Extended Squitter is the mechanism used to provide ADS-B messages from a Mode S transponder.
Extension lines
Used to extend the line showing the side or edge of a figure for the purpose of placing a dimension to that side or edge
External-combustion engine
A form of heat engine in which the fuel releases its energy outside of the engine. This released heat expands air which is used to perform useful work. Steam engines are a popular type of external combustion engine.
External-load attaching
The structural components used to attach an external load to an aircraft, including external-load containers, the backup structure at the attachment points, and any quick-release device used to jettison the external load.
Extrapolation
The process of predicting a track’s state forward in time based on the track’s last kinematic state.
Extreme pressure (EP) lubricant
A lubricant that reacts with iron to form iron chlorides, sulfides, or phosphides on the surface of a steel part. These compounds reduce wear and damage to surfaces in heavy rubbing contact. EP lubricants are specially suited for lubricating gear trains.
Extruded angle
A structural angle formed by passing metal heated to its plastic state through specially shaped dies.
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