Definition
The flight instruments that back up and confirm what the primary instruments are showing during a given maneuver. They provide indirect indications of the aircraft's performance and help the pilot anticipate changes before they appear on the primary instruments.
Plain English
The instruments you cross-check to confirm what the main instruments are telling you. They give you supporting evidence that the airplane is doing what you want it to do.
Context Anchor
Seen in instrument failure and instrument cross-check discussions, especially when a pilot must keep control after losing or doubting a key instrument indication.
Derivation
Supporting' comes from Latin 'supportare,' meaning 'to carry' or 'to bear up.' Here, these instruments 'carry' or back up the readings of the primary instruments — they support the picture the primary instruments are giving.
Why Pilots Care
They enable continued safe attitude and performance control after instrument failure, reducing the risk of spatial disorientation or loss of control.
Grounding Statement
When one instrument does not look right, the supporting performance instruments help you answer, “What is the airplane actually doing?”
Intuition Check
Do not read “performance” here as engine power or aircraft capability. In this phrase, it means the airplane’s actual flight results, such as whether it is climbing, descending, turning, speeding up, or slowing down. Do not read “supporting” as unimportant. A supporting instrument may become critical when another instrument fails.
Example Sentence 1
During a level turn, the pilot used the attitude indicator as the supporting performance instrument to confirm a steady bank angle.
Example Sentence 2
During the instrument failure drill, the heading indicator and airspeed indicator served as supporting performance instruments for directional and speed control.