Definition
An attitude instrument flying method in which the pilot identifies, for each maneuver, one instrument that gives the most direct indication of a desired performance value (the primary instrument) and other instruments that back up and refine that indication (the supporting instruments). The primary instrument for a given parameter is the one that shows the value being held constant most directly; supporting instruments confirm the trend and help the pilot maintain the value precisely.
Plain English
A way of flying on instruments where, for each thing you're trying to hold steady (like altitude, heading, or airspeed), one gauge is your main reference and the others are there to back it up.
Context Anchor
Seen in instrument flying when learning how to scan the cockpit instruments without giving every instrument equal attention at every moment.
Derivation
Primary' comes from the Latin primus, meaning 'first' — the first instrument you look at for a given value. 'Supporting' simply means the other instruments are there to back up what the primary is telling you. The pairing reflects how the method works in practice: one lead reference, several confirmations.
Why Pilots Care
Allows precise aircraft control in instrument conditions by directing attention to the right reference first and avoiding over-correction from scattered instrument scans.
Grounding Statement
The primary instrument leads your attention for the task; the supporting instruments help confirm that the picture is still correct.
Intuition Check
Do not read primary as meaning permanently most important. In this context, the primary instrument can change depending on whether the pilot is holding altitude, turning, climbing, descending, or changing speed.
Example Sentence 1
In straight-and-level flight, the altimeter is the primary instrument for altitude, while the attitude indicator and vertical speed indicator are supporting.
Example Sentence 2
For heading control in a turn, the heading indicator is primary and the turn coordinator provides supporting information on rate and coordination.