Definition
VY is the airspeed that produces the greatest gain in altitude per unit of time. At VY, the airplane has the largest excess power available — the difference between the power the engine is producing and the power required for level flight — which is what climbs the airplane fastest in terms of feet per minute.
Plain English
VY is the speed that gets you the most altitude in the shortest amount of time. Fly at VY and the airplane gains height quickly measured by the clock.
Context Anchor
You see VY in airplane performance charts, takeoff and climb procedures, and discussions of how the airplane trades speed for altitude.
Derivation
The 'V' comes from the Latin velocitas, meaning speed. The subscript 'Y' is simply the FAA's letter code for this particular climb speed — paired with VX (best angle of climb) so pilots can keep the two straight.
Why Pilots Care
Using VY lets the pilot reach a safe or assigned altitude quickly, which matters for obstacle clearance, traffic separation, and efficient transition to cruise.
Grounding Statement
If you hold VY in a steady climb, the airplane is gaining altitude as fast as it can for that situation.
Intuition Check
VY does not mean the steepest climb path over the ground. It means the fastest gain in altitude over time.
Example Sentence 1
After lifting off and clearing any obstacles, the pilot pitched for VY to reach cruise altitude as quickly as possible.
Example Sentence 2
Once clear of obstacles the pilot accelerated from VX to VY for a more efficient climb to pattern altitude.