Troubleshooting & Repair Practices Flashcards

Before using an ohmmeter to check continuity in an aircraft circuit, what must the technician do?

Answer: Remove all power from the circuit

An ohmmeter supplies its own current, so external voltage can damage it and give false readings.

With a circuit energized and the load not operating, a voltmeter across a closed switch reads nearly full system voltage. What is the most likely fault?

Answer: The switch contacts are open or have very high resistance

A good closed switch has near-zero voltage drop, so full voltage across it means the contacts are not conducting.

An ohmmeter connected across both ends of a wire reads infinite resistance. This indicates:

Answer: An open circuit

Infinite resistance means no current path exists through the conductor.

Which troubleshooting technique repeatedly checks a system at its midpoint to isolate a fault quickly?

Answer: Half-split method

Testing at the midpoint eliminates half of the remaining system with each check.

Per AC 43.13-1B, the maximum resistance of a typical bonding jumper connection used for current return should not exceed:

Answer: 0.003 ohm

AC 43.13-1B specifies 0.003 ohm for bonding connections that carry current.

Which instrument is used to check the insulation resistance of aircraft wiring?

Answer: Megohmmeter (megger)

A megger applies high voltage to measure insulation resistance in megohms.

A lead-acid aircraft battery requires frequent water additions and shows signs of spewing. What is the most likely cause?

Answer: Voltage regulator set too high, overcharging the battery

Overcharging causes excessive gassing and water loss, usually from a high regulator setting.