Definition
Two modes of flying solely by reference to instruments. Full panel means all primary flight instruments are working and available for use. Partial panel means one or more primary instruments have failed or been lost, and the pilot must control and navigate the aircraft using the instruments that remain.
Plain English
Full panel is flying on instruments when all of them are working. Partial panel is flying on instruments when one or more have failed and you have to manage with the rest.
Context Anchor
Seen in inadvertent IMC training, instrument proficiency checks, and emergency practice where a pilot may need to keep control of the aircraft in cloud or poor visibility.
Derivation
"Panel" refers to the instrument panel in front of the pilot. "Full" and "partial" describe how much of that panel's information is available -- all of it, or only some of it after a failure.
Why Pilots Care
Allows continued safe flight and landing when instruments are lost in clouds or at night.
Intuition Check
Full panel does not mean the whole flight is flown on instruments; it means the normal instrument set is available. Partial panel does not mean partly visual; it means some instrument information is missing or unusable.
Example Sentence 1
During the checkride, the examiner covered the attitude indicator and heading indicator to test partial panel flying.
Example Sentence 2
After the attitude indicator failed, the pilot switched to partial panel and used the turn coordinator and altimeter to stay level.