Definition
Cockpit instruments and indicators that support, confirm, or supplement the primary flight instruments by providing additional information about aircraft systems, performance, or flight condition. They are not the main reference for controlling pitch, bank, power, or trim, but they assist the pilot in cross-checking and managing the flight.
Plain English
Gauges and displays that back up or add to the main flight instruments. The pilot uses them to confirm what the primary instruments are showing and to monitor things like engine and system status.
Context Anchor
Seen in discussions of airplane mechanical factors, cockpit indications, and how a pilot monitors the airplane while flying.
Derivation
‘Secondary’ comes from the Latin secundarius, meaning ‘of the second rank or order.’ In aviation it doesn’t mean less important — it means used in a supporting role rather than as the main reference.
Why Pilots Care
Allows continued safe aircraft control and navigation during primary system malfunctions, directly affecting emergency decision-making and accident prevention.
Grounding Statement
If the engine-driven vacuum pump fails, the electrically powered standby attitude indicator continues to show pitch and bank so the pilot can keep the wings level.
Intuition Check
Do not read secondary as “not important.” Here it means supporting the main flying references, not replacing them.
Example Sentence 1
During level cruise, the altimeter is the primary pitch instrument and the vertical speed indicator serves as secondary instrumentation.
Example Sentence 2
The preflight checklist confirmed that the secondary instrumentation was powered and indicating correctly before takeoff.