Definition
A small set of independent, traditional flight instruments installed in aircraft equipped with electronic flight displays, used as a backup if the primary electronic display fails. Typically includes an attitude indicator, an altimeter, and an airspeed indicator, each powered and driven independently of the main electronic system.
Plain English
A separate, simple set of backup instruments that keep working if the main glass-cockpit screens fail, so the pilot can still see attitude, altitude, and airspeed.
Context Anchor
Seen in electronic flight display operations, especially when the main screen fails, loses information, or omits needed flight indications.
Derivation
Stand-by comes from the old maritime and military sense of someone or something held ready to step in when needed. The instruments are not the main reference in normal flight, but they stand by, ready to take over if the primary display quits.
Why Pilots Care
They allow continued controlled flight and safe landing after a primary display failure.
Intuition Check
Stand-by does not mean optional or unimportant here. It means ready for immediate use if the primary flight information is lost or cannot be trusted.
Example Sentence 1
After the primary flight display went blank, the pilot transitioned to the stand-by instruments and continued the approach.
Example Sentence 2
During the approach the instructor covered the electronic displays so the student could fly using only the stand-by instruments.