Definition
The instrument that gives the most direct indication of the aircraft's pitch attitude for the maneuver being flown. In straight-and-level flight at a constant altitude, the altimeter is the primary pitch instrument because it shows immediately whether the nose is holding the altitude. The primary pitch instrument changes depending on the maneuver — for example, in a constant-airspeed climb, the airspeed indicator becomes the primary pitch instrument.
Plain English
The one instrument the pilot watches most closely to see whether the nose is in the right position for what they are trying to do. Which instrument that is depends on the maneuver.
Context Anchor
Seen in instrument flying when learning which instrument is the main reference for pitch, bank, or power during a specific maneuver.
Derivation
"Primary" comes from the Latin primus, meaning "first" — in this context, the first instrument to look at for pitch information, not the only one. "Pitch" refers to the up-or-down angle of the aircraft's nose.
Why Pilots Care
Correct use prevents altitude and airspeed deviations by giving immediate pitch information without outside visual references.
Intuition Check
Primary does not mean the same instrument is always used first. Here it means the main pitch reference for this particular maneuver.
Example Sentence 1
While holding altitude in cruise, the altimeter is the primary pitch instrument, so any movement of its needle calls for an immediate pitch correction.
Example Sentence 2
When transitioning to a climb, the pilot references the primary pitch instrument to set the correct nose-up attitude.