EICAS. Engine indicating and crew alerting system. An electronic instrumentation system that monitors airframe and engine parameters and displays the essential information on a video display on the instrument panel. Only vital information is continually displayed, but when any sensed parameters fall outside of their allowable range of operation, they are automatically displayed. 

Elastic limit. The maximum amount of tensile load, in pounds per square inch, that a material is able to withstand without permanent deformation. 

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. 

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. 

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. 

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. 

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. 

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. 

EPR.  Engine pressure ratio. The ratio of the turbine discharge total pressure to the compressor inlet total pressure. EPR is normally used as the parameter to determine the amount of thrust an axial-flow turbojet or turbofan engine is producing. 

ESHP. Equivalent shaft horsepower. A measure of the power produced by a turboprop engine. ESHP takes into consideration both the shaft horsepower delivered to the propeller and the thrust developed at the engine exhaust. Under static conditions, one shaft horsepower is approximately equal to 2.5 pounds of thrust. 

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 colorless, poisonous liquid BrCH$_{2}$CH$_{2}$Br that is blended with leaded gasoline to help scavenge lead oxides. 

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. 

Evaporative cooling.  See steam cooling. 

Exceedance condition. A condition in which a parameter sensed by the EICAS exceeds the limits for which it is programmed. 

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. 

