Definition
The instrument scanning technique of checking the secondary instruments that back up a primary instrument to confirm the aircraft is holding the desired flight condition. For straight-and-level flight, the supporting instruments are those that indirectly indicate pitch, bank, and power — typically the airspeed indicator, vertical speed indicator, turn coordinator, and heading indicator — used in conjunction with the primary instruments to verify performance and trend.
Plain English
Glance at the backup instruments that confirm what the main instruments are telling you. They support the picture and let you catch small errors before they grow.
Context Anchor
Seen in instrument-scan training for straight-and-level flight, where the pilot uses some instruments as the main references and others to confirm the airplane’s performance.
Derivation
‘Cross-check’ comes from the idea of checking one source against another to confirm it is correct. ‘Supporting’ here means instruments that back up — or support — what the primary instruments are showing. Together: confirm the primary picture by looking at the instruments that reinforce it.
Why Pilots Care
Maintains accurate control and detects instrument errors when visual references are unavailable.
Intuition Check
Do not assume “supporting” means unimportant. A supporting instrument may not be the main reference at that moment, but it still helps confirm whether the airplane is doing what you intend.
Example Sentence 1
While holding altitude, the pilot included a cross-check of supporting instruments to confirm the vertical speed and airspeed were steady.
Example Sentence 2
During the instrument approach briefing, the instructor stressed the need to cross-check supporting instruments whenever the primary attitude indicator showed any change.