Definition
A condition in which one or more primary flight instruments are inoperative or unreliable, requiring the pilot to fly using the remaining functional instruments. The term most often refers to the loss of gyroscopic instruments (such as the attitude indicator and heading indicator) due to a vacuum or electrical system failure, leaving the pilot to control the aircraft using the remaining pitot-static and supporting instruments.
Plain English
Flying when some of your cockpit instruments have failed, so you have to manage with the ones still working.
Context Anchor
Encountered during instrument training, instrument failure practice, and discussions of mechanical problems that can leave the pilot without a full instrument display.
Derivation
"Partial" means incomplete, and "panel" refers to the instrument panel in front of the pilot. Together: an instrument panel that is only partly working.
Why Pilots Care
Allows continued safe control of the aircraft when critical gyroscopic instruments fail.
Grounding Statement
Partial panel means the airplane may still be controllable, but the pilot must ignore failed information and rely on what is still reliable.
Intuition Check
Partial panel does not mean part of the physical panel is missing. It means some instruments are unusable, so the pilot must fly using the instruments that still work.
Example Sentence 1
When the vacuum pump failed in cloud, the pilot transitioned to partial panel flying using the turn coordinator and altimeter.
Example Sentence 2
The pilot maintained altitude and heading on partial panel by using the turn coordinator and altimeter together.