Aviation Mechanic - General, Airframe, and Powerplant › I. General › Task A. Fundamentals of Electricity and Electronics

AM.I.A.S5

Skill

Test a switch or relay.

Practice questions Ask the tutor

Study note

Get a short, cited explanation of this element written from the FAA handbooks: the core idea, the numbers that matter, common test traps, and a quick self-check.

From the FAA library

Aviation Maintenance Technician Handbook - General p. 12-162
Chapter 12: Fundamentals of Electricity & Electronics › Three-Phase Alternator › Differential Relay Switch
Differential Relay Switch Aircraft electrical systems normally use some type of reverse current relay switch, which acts not only as a reverse current relay cut-out but also serves as a remote control switch by which the generator ... disconnected from the electrical system at any time. One type of reverse current relay switch operates on the voltage level of the generator, but the type most commonly used on large aircraft is the differential relay switch, which is controlled…
Aviation Maintenance Technician Handbook - General p. 12-163
Chapter 12: Fundamentals of Electricity & Electronics › Three-Phase Alternator › Overvoltage & Field Control Relays
differential coil, the differential relay contact closes and, thus, completes the main contractor coil circuit. The contacts of the main contactor close and connect the generator to the bus. When the generator voltage drops below the bus (or battery) voltage ... reverse current weakens the magnetic field about the temporary magnet of the differential relay. The weakened field permits a spring to open the differential relay contacts, breaking the circuit to the coil of the main contactor relay, opening its contacts…
Aviation Maintenance Technician Handbook - Airframe p. 17-19
Chapter 17: Fire Protection Systems › Fire Detection System Troubleshooting
resistance of the loop returns to its normal value. 5. Failure to obtain an alarm signal when the test switch is actuated ... caused by a defective test switch or control unit, the lack of electrical power, inoperative indicator light, or an opening in the sensing element or connecting wiring. When the test switch fails to provide an alarm, the continuity…
Aviation Maintenance Technician Handbook - Powerplant p. 9-12
Chapter 9: Engine Fire Protection Systems › Fire Detection System Troubleshooting
resistance of the loop returns to its normal value. 5. Failure to obtain an alarm signal when the test switch is actuated ... caused by a defective test switch or control unit, the lack of electrical power, inoperative indicator light, or an opening in the sensing element or connecting wiring. When the test switch fails to provide an alarm, the continuity…
Aviation Maintenance Technician Handbook - Airframe p. 13-65
Chapter 13: Aircraft Landing Gear Systems › Anti-Skid › Anti-Skid System Tests
failure occurs. An operational test can be performed before flight. The anti-skid control switch and/ or test switch is used in conjunction with system indicator light(s) to determine system integrity. A test is first done with the aircraft ... then in an electrically simulated anti-skid braking condition. Some anti-skid control units contain system and component testing switches and lights for use by the technician. This accomplishes the same operational verification but allows an additional degree of troubleshooting…