JetCal analyzer (gas turbine engine test equipment). The registered trade name for a piece of test
equipment used to check the engine RPM and various temperatures and pressures inside an operating gas turbine engine. A JetCal also checks the accuracy of the instruments installed in the aircraft.
jet fuel. Fuel designed and produced to be used in aircraft gas turbine engines.
jet nozzle (gas turbine engine component). The opening at the rear of the exhaust duct of a gas turbine engine. A jet nozzle is also called an exhaust nozzle.
jet propulsion. A method of propulsion by thrust produced as a relatively small mass of air is accelerated through a large change in velocity.
jet pump (aircraft fuel system). A form of fluid pump that produces a low pressure by moving fluid at a high velocity through a venturi. A jet pump can be used to remove vapor from fuel before it enters a fuel control unit. Some of the fuel from the main fuel pump is returned to the tank through a venturi (the jet pump). The venturi is connected to the top of the chamber in which the vapors collect. The low pressure at the throat of the venturi pulls the vapors out of the chamber and returns them with the fuel back to the tank.
jet pump (environmental control system). A special venturi in a line carrying air from certain areas in an aircraft that need an augmented flow of air through them. High-velocity compressor bleed air is blown into the throat of a venturi where it produces a low pressure that pulls air from the area to which it is connected. Jet pumps are often used in the lines that pull air through galleys and toilet areas.

jet route. A route designated to serve flight operations from 18,000 feet MSL, up to and including flight level 450. The routes are referred to as “J” routes, with numbers to identify the designated route.
jet silencer. A noise suppressor used with a gas turbine engine. A jet silencer does not actually silence a jet engine; rather, it converts some of the low-frequency vibrations into higher frequency vibrations that are more easily dissipated as they mix with the surrounding air.
jet stream (meteorology). A high-velocity narrow stream of winds usually found near the upper limit of the troposphere. The jet stream normally blows from west to east, and the winds in the stream may reach velocities of up to 250 miles per hour.
jettison. To drop something from an aircraft or space craft in flight. Fuel is jettisoned when it is dumped from the aircraft fuel tanks to lower the weight of the aircraft to a weight approved for landing.
jet wake. The stream of hot, high-velocity gases that come from the exhaust of a gas turbine engine.
jewel bearing. A cup-type bearing in which a hardened steel pivot rides. Jewel bearings used in many types of indicating instruments are normally made of an extremely hard glass.
jeweler’s file. A small, fine-cut metalworking file used by instrument technicians to repair aircraft instruments. Jeweler’s files are available in many shapes.