The V-n (velocity vs. load factor) diagram is the chart every aerospace and structures engineer learns first — it defines the flight envelope an airframe must be strong enough to survive. This tool draws a real, physics-based V-n diagram from your inputs: adjust gross weight, maximum lift coefficient (CLmax), never-exceed speed (VNE), and certification category (normal, utility, or aerobatic) and watch the parabolic stall-limit curves, the limit load factor lines, and the VNE boundary redraw instantly. Hover or tap any corner point for a plain-language explanation of what that specific structural design case means.
The vertical axis is load factor n — the ratio of aerodynamic lift to aircraft weight, expressed in g. The horizontal axis is equivalent airspeed. At any given speed, the maximum load factor the wing can generate is limited by CLmax (the wing stalls before generating more lift) — that produces the parabolic stall-limit curve, since lift grows with the square of airspeed. At higher speeds, the limiting factor switches from aerodynamic stall to structural strength: the airframe is only certified to a fixed maximum positive and negative load factor (the limit load lines), and a maximum placard speed VNE beyond which flutter or other high-speed structural risks become unacceptable.
Aircraft structures are not designed for "average" flight loads — they are sized for the worst-case corners of this envelope. Maneuvering speed VA is the speed above which an abrupt full control deflection can overstress the airframe before the wing stalls (below VA, the stall itself protects the structure). The corner where the positive limit load factor meets VNE combines maximum speed with maximum g and is often the single most critical case for wing spar bending. The negative-g corners mirror this for downward gusts and pushovers. This tool labels all of these so you can see exactly which flight condition drives which part of the structural design.
FAR/CS-23 defines three normal-category-family certification categories with different limit load factors: Normal category aircraft (most touring and training aircraft) are limited to roughly +3.8g/−1.52g; Utility category (permitting some aerobatic maneuvers like spins and steep turns) is limited to about +4.4g/−1.76g; Aerobatic category aircraft are built to a much larger envelope, roughly +6.0g/−3.0g, to survive intentional aerobatic maneuvers. Selecting a category in this tool instantly rescales the limit load lines and recomputes the maneuvering speeds that follow from them.
Gross Weight changes wing loading (W/S) directly, which shifts the stall-limit parabola and therefore the maneuvering speeds — heavier aircraft stall at a higher speed at any given g, so VA increases with weight even though the limit load factor itself does not change. CLmax represents how much lift the wing can generate before stalling (raised by flaps or high-lift devices) — a higher CLmax steepens the stall curve and lowers stall speed. VNE sets the right-hand structural speed boundary of the whole diagram. All three redraw the chart live, and the computed-values panel shows the resulting stall speed, maneuvering speeds, and limit load factors numerically.
No. This tool is an educational, physics-based approximation using simplified sea-level standard atmosphere conditions, a fixed reference wing area, and representative FAR/CS-23 category limit loads. It illustrates the correct shape and physics of a real V-n diagram, but a certified aircraft's actual flight envelope comes from its type certificate data sheet and flight manual, not from a generic web tool.
VA is the airspeed at which the wing reaches its maximum lift coefficient (stalls) exactly at the limit load factor. Since the stall speed at any load factor scales with the square root of wing loading (W/S), a heavier aircraft must fly faster to stall at the same g — so VA rises with weight. This is also why real flight manuals list a lower maneuvering speed for lighter operating weights: the protection VA provides against overstressing the airframe is only valid at or below the weight it was computed for.
Aircraft spend the overwhelming majority of their flight time under positive g (supporting their own weight against gravity), so the structure is optimized to carry much larger positive loads efficiently. Negative-g maneuvers (pushovers, inverted flight) are rarer and typically less extreme in normal operation, so certification standards require a smaller negative limit load factor — commonly around 40% of the positive limit for normal and utility category, rising closer to 50% for aerobatic category aircraft that are expected to fly inverted.
Exceeding the limit load factor (the outer boundary of this diagram) risks permanent deformation of the structure — bent spars, popped rivets, or wrinkled skin — even if the aircraft does not immediately break. Ultimate load, typically 1.5 times limit load, is the point at which structural failure is expected. Flying outside the envelope, especially near the VNE corners where dynamic pressure is highest, is why abrupt control inputs at high speed are one of the most dangerous things a pilot can do to an airframe.