Definition
A symbol on a head-up display or primary flight display that shows the aircraft's actual trajectory through the air -- the direction it is truly going, not the direction the nose is pointing. The symbol's position on the display indicates where the aircraft will be a few seconds in the future if current conditions are maintained.
Plain English
A small symbol on the flight display that shows where the aircraft is actually heading, which can be different from where the nose is pointed. If you place that symbol on the runway, that's where you're going to land.
Context Anchor
Seen on a head-up display or on some glass cockpit flight displays, especially during approaches, climbs, descents, and crosswind operations.
Derivation
A 'vector' in physics is a quantity with both direction and magnitude -- it points somewhere. So the flight path vector is literally the arrow showing the path the aircraft is flying along, as opposed to where it is merely facing.
Why Pilots Care
Lets the pilot precisely manage the aircraft's actual trajectory and energy state, especially on approaches and in low-visibility conditions.
Grounding Statement
If the nose is pointed one way but the airplane is drifting or descending another way, the flight path vector shows the real movement.
Intuition Check
Do not assume the flight path vector shows where the nose is pointed. It shows where the aircraft is actually going.
Example Sentence 1
On final approach, she placed the flight path vector on the runway numbers and let the aircraft track itself to touchdown.
Example Sentence 2
With the flight path vector aligned to the glide path, the aircraft maintained a stable descent without further power changes.