Electronic

Electronic

1. Electronic fundamentals

   • Semiconductor theory
     • The properties of most semiconductor devices are profoundly affected by temperature.
   • Diodes
     • In the freely conducting forward-biased state, the diode acts rather like a closed switch. In the reversebiased state, the diode acts like an open switch.
   • Transistors
     • The characteristics of a bipolar junction transistor are usually presented in the form of a set of graphs relating voltage and current present at the transistors terminals.
   • Integrated circuits
     • Integrated circuits contain large numbers of individual components fabricated on a single slice of silicon

2. Digital fundamentals

   • Logic gates
     • Logic circuits involve signals that can only exist in one of two mutually exclusive states. These two states are usually denoted by 1 and 0, ‘on’ or ‘off ’, ‘ high’ and ‘low ’, ‘closed’ and ‘open’, etc.
   • Decoders
     • Unfortunately, there has been at least one case when the failure of a single data line in a Gillham interface has generated erroneous altitude data which has caused an aircraft’s Traffi c Alert and Collision Avoidance System ( TCAS) to guide an aircraft into a near miss situation.
   • Bus systems
     • Modern aircraft use multiple redundant bus systems for exchanging data between the various avionic systems and sub-systems

3. Generators and motors

   • Generator and motor principles
     • An e.m.f. will be induced across the ends of a conductor when there is relative motion between it and a magnetic fi eld.
   • AC generators
     • AC generator the magnetic fi eld is rotated rather than the conductors from which the output is taken
   • AC motors
     • The principle of all AC motors is based on the generation of a rotating magnetic fi eld. It is this rotating fi eld that causes the motor’s rotor to turn.

4. Batteries

   • The main battery provides autonomous starting for the engine(s) or auxiliary power unit (APU) when external ground power is not available.
     • Storage cells
       • The basic function of any electrical cell is the conversion of chemical energy into electrical energy.
     • Lead-acid batteries
     • Nickel-cadmium batteries
     • Lithium batteries
     • Nickel-metal hydride batteries

5. Airframe monitoring, control and indicating systems

   • Landing gear
     • The landing gear comprises two or more wheels and shock absorbers, or oleo legs ; these can be fi xed in position or retractable
   • Trailing edge flaps
     • The flap drive motor is a reversible DC motor that drives the fl ap control mechanism through a gearbox.
   • Control surfaces
     • Different aircraft types have a variety of control surface position indicators
   • Electronic indicating systems
     • The two systems used on the majority of passenger aircraft are EICAS and ECAM.

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