Definition
A cockpit annunciator light that shows the operating status of the aircraft's standby battery system. It typically illuminates to indicate the standby battery is armed, active, or in a fault condition, alerting the pilot that the standby battery is supplying or ready to supply emergency power to essential instruments if the main electrical system fails.
Plain English
A small light on the panel that tells the pilot whether the backup battery is ready, working, or has a problem.
Context Anchor
Seen on the instrument panel during electrical system checks and during operation on standby battery power.
Derivation
Standby comes from the older nautical sense of being ready to take over if needed. Indicator comes from the Latin indicare, meaning to point out or show. Together the term simply means a light that points out the status of the standby system.
Why Pilots Care
Confirms the backup power source is active so the pilot can continue instrument flight safely after primary electrical loss.
Intuition Check
Do not read standby indicator light as a spare light bulb. Here, standby means backup electrical power, and indicator light means the cockpit light that shows its status.
Example Sentence 1
During the preflight check, the pilot pressed the test button and confirmed the standby indicator light illuminated, showing the standby battery was ready.
Example Sentence 2
During the electrical systems check the pilot verified that the standby indicator light came on when the standby battery switch was selected.