The output winding of the IF transformer feeds the input of the IF amplifier with a signal whose frequency is that to which the IF transformer is tuned.
intermittent-duty relay or solenoid. An electrically operated relay or solenoid that must be de-energized (the power to its operating coil must be turned off) at intervals to keep the coil from overheating. Starter relays and relays used to operate motors that run for only a short period of time can be intermittent-duty relays. Intermittent-duty relays cannot be used as master battery relays or light relays that must be energized for long periods of time.
intermittent fault. A fault which occurs in a system or circuit only at certain times and under certain conditions. Intermittent faults often do not follow a consistent pattern, and their cause is usually difficult to determine.
intermittent load (electrical load). An electrical load that is not continuously applied to the circuit. The landing gear retraction motor and the flap operating motor are both intermittent loads in that neither of them are operated continuously.
internal combustion engine. A form of heat engine in which the fuel and air mixture is burned inside the engine to heat and expand the air so it can perform work.
internal control lock (aircraft control system component). A device used to lock the flight controls of an
aircraft so they cannot be damaged by the wind. Internal locks hold the control stick or wheel and the rudder pedals, rather than clamping the control surfaces themselves.
internally wrenching bolt. A special type of bolt having a large, cylindrical head with a flat top and a hexagonal socket cut into it. Internally wrenching bolts are used for high-strength and high-temperature applications.
internal resistance (batteries). Opposition to the flow of current caused by the plates of a battery. The internal resistance of a lead-acid storage battery increases as the battery becomes discharged, and current flowing through the higher resistance causes a voltage drop that lowers the closed-circuit voltage of the battery.
internal supercharger (reciprocating engine component). A gear-driven centrifugal air pump installed inside a reciprocating engine. Fuel and air are mixed in the carburetor, and the mixture is compressed by the internal supercharger before it is distributed to the cylinders.
internal supercharger drain valve (reciprocating engine component). A pressure-operated valve in the bottom of the internal supercharger section of a reciprocating engine that is open when the pressures inside and outside the supercharger housing are the same. Excess fuel can drain from the engine through this valve if the engine is flooded during the starting procedure.
internal timing (aircraft magneto operation). Correctly meshing the gears and adjusting the breaker point clearance in an aircraft magneto so the breaker points begin to open when the rotating magnet is in the correct position relative to the pole shoes, in its E-gap position. When a magneto is correctly timed internally, it produces the hottest spark.
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