Definition
An automatic internal check that an avionics system performs on itself to verify that its components, sensors, and logic are functioning correctly before being used. In a flight director or autopilot system, the self-test runs at power-up or on pilot command and confirms the unit is serviceable; if a fault is detected, the system flags it and typically inhibits engagement.
Plain English
It's the system checking itself to make sure it's working properly before you trust it to fly the airplane. If something is wrong, it tells you and won't let you turn it on.
Context Anchor
Seen during preflight or before using the flight director or autopilot, often as a message, light, or alert on the panel.
Why Pilots Care
A successful self-test confirms the system is safe to engage; a failure means the autopilot or flight director should remain off until the fault is corrected.
Intuition Check
A self-test does not mean the system is guaranteed perfect. It means the system ran its built-in check and either passed or reported a problem.
Example Sentence 1
After turning on the avionics, the pilot waited for the autopilot self-test to complete before engaging the flight director.
Example Sentence 2
A red warning light after the self-test indicated the flight director should not be used for the flight.