Definition
The airspeed that produces the greatest gain in altitude per unit of horizontal distance traveled. At VX, the airplane climbs at the steepest possible angle, clearing the most ground obstacles in the shortest forward distance. VX is published in the Pilot's Operating Handbook and varies with airplane weight and configuration.
Plain English
The speed that gives you the steepest climb -- the most height gained for the least distance covered across the ground. Use it when you need to climb over something close ahead, like trees off the end of a short runway.
Context Anchor
You will see VX in takeoff and obstacle-clearance discussions, especially when the airplane must climb away from the runway without staying low for long.
Derivation
The 'V' comes from the French 'vitesse,' meaning speed, used throughout aviation for defined airspeeds. The 'X' is simply the letter assigned to mark this particular speed in the standard V-speed system.
Why Pilots Care
Using VX gives the greatest vertical gain per horizontal distance, which is essential for obstacle clearance on short or obstructed runways.
Grounding Statement
Picture lifting off from a short runway with trees ahead: VX is the speed that gives the steepest path upward.
Intuition Check
VX is not just “a good climb speed.” It is specifically the best angle-of-climb speed, which is about climbing steeply over distance, not climbing fastest over time.
Example Sentence 1
With trees off the departure end of the short strip, the pilot rotated and climbed at VX until clear of the obstacle, then lowered the nose and accelerated to VY.
Example Sentence 2
In the short-field takeoff procedure, the airplane was climbed at VX until all obstacles were cleared.