Definition
The throttle setting selected as the initial reference for a desired flight condition, used as the starting point from which power is then adjusted to achieve and maintain the target performance (such as a specific airspeed, climb rate, or descent rate).
Plain English
The first power setting you pick for what you're trying to do, then fine-tune from there to get the exact result you want.
Context Anchor
Seen in instrument flying when using an electronic flight display to decide which indication should guide pitch, bank, and power corrections.
Derivation
"Primary" comes from Latin primus, meaning "first." Here it means the first or initial power setting chosen — not the most important one, and not the only one used.
Why Pilots Care
Knowing a reliable starting power setting for each phase of flight reduces workload, especially under instrument conditions. Instead of hunting for the right power, the pilot sets a known value and trims it from there.
Intuition Check
Do not read “primary” as meaning the only power indication that matters. It means the first or most useful indication for power control in that specific moment.
Example Sentence 1
Leveling off at cruise altitude, she set primary power at 23 inches and then made small adjustments to settle on her target airspeed.
Example Sentence 2
Loss of primary power triggered the automatic switch to the standby battery for the electronic attitude indicator.