Aeronautical Terms beginning with E
Electrical Bus
A Bus Bar. An electrical power distribution point to which several circuits may be connected. It is often a solid metal strip having a number of terminals installed on it.
Electrohydraulic
Hydraulic control which is electrically actuated.
Elevator
The horizontal, movable primary control surface in the tail section, or empennage, of an airplane. The elevator is hinged to the trailing edge of the fixed horizontal stabilizer.
Emergency Locator Transmitter
A small, self-contained radio transmitter that will automatically, upon the impact of a crash, transmit an emergency signal on 121.5, 243.0, or 406.0 MHz.
Empennage
The section of the airplane that consists of the vertical stabilizer, the horizontal stabilizer, and the associated control surfaces.
Energy Balance equation
According to this equation, the net transfer of mechanical energy into and out of the airplane (a function of thrust minus drag) is always equal to the change in its total mechanical energy (a function of altitude and airspeed).
Energy Distribution error
An energy error where the total mechanical energy is correct, but the distribution between potential (altitude) and kinetic energy (airspeed) is not correct relative to the intended altitude-speed profile. When this error occurs, the pilot will observe that altitude and airspeed deviate in opposite directions (e.g., higher and slower than desired; or lower and faster than desired). An example would be an airplane on final approach that is above the desired glide slope and at a slower airspeed than desired.
Energy Error
An altitude and/or airspeed deviation from an intended target expressed in terms of energy. Depending on the airplane’s total amount of energy and its distribution between altitude and airspeed, energy errors are classified as total energy errors, energy distribution errors, or a combination of both errors.
Energy Exchange
Trading one form of energy (e.g., altitude) for another form (e.g., airspeed).
Energy Height or total specific energy (ES)
Measured in units of height (e.g., feet), it represents the airplane’s total energy per unit weight. It is found by dividing the sum of potential energy and kinetic energy by the airplane’s weight. It also represents the maximum height that an airplane would reach from its current altitude, if it were to trade all its speed for altitude.
Energy State
The airplane’s total mechanical energy and its distribution between altitude and airspeed.
Energy System
A flying airplane is an open energy system. That means that the airplane can gain energy from some source (e.g., fuel) and lose energy to the environment (e.g., surrounding air) . In addition, energy can be added to or removed from the airplane’s total mechanical energy stored as altitude and airspeed.
Engine Pressure Ratio (EPR)
The ratio of turbine discharge pressure divided by compressor inlet pressure that is used as an indication of the amount of thrust being developed by a turbine engine.
Environmental Systems
In an aircraft, the systems, including the supplemental oxygen systems, air conditioning systems, heaters, and pressurization systems, which make it possible for an occupant to function at high altitude.
Equilibrium
A condition that exists within a body when the sum of the moments of all of the forces acting on the body is equal to zero. In aerodynamics, equilibrium is when all opposing forces acting on an aircraft are balanced (steady, unaccelerated flight conditions).
Equivalent Shaft Horsepower (ESHP)
A measurement of the total horsepower of a turboprop engine, including that provided by jet thrust.
Exhaust
The rear opening of a turbine engine exhaust duct. The nozzle acts as an orifice, the size of which determines the density and velocity of the gases as they emerge from the engine.
Exhaust Gas Temperature (EGT)
The temperature of the exhaust gases as they leave the cylinders of a reciprocating engine or the turbine section of a turbine engine.
Exhaust Manifold
The part of the engine that collects exhaust gases leaving the cylinders.
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