Definition
To remove electrical power from a circuit, component, or system, causing it to stop operating. A de-energized relay, solenoid, or coil returns to its at-rest position once current is no longer flowing through it.
Plain English
To switch off the electrical power going to something so it stops working and returns to its normal off-state.
Context Anchor
Seen in aircraft maintenance procedures, electrical system checks, and safety instructions before working on powered equipment.
Derivation
The prefix 'de-' comes from Latin meaning 'remove' or 'reverse,' and 'energize' comes from Greek 'energeia' meaning 'activity' or 'in work.' So de-energize literally means to remove the working power from something.
Why Pilots Care
Many aircraft systems behave differently when de-energized. For example, some relays are 'normally open' and some are 'normally closed' when de-energized, which affects how a system fails or resets. Understanding this helps when reading wiring diagrams or troubleshooting electrical issues.
Intuition Check
Do not read de-energize as meaning the part is broken or removed. It means the part or circuit is still there, but its electrical power has been taken away.
Example Sentence 1
Before working on the starter circuit, de-energize the bus by turning off the master switch.
Example Sentence 2
During shutdown the pilot de-energized all nonessential systems to conserve battery power.