Vx vs Vy Comparison Calculator
Best angle or best rate? Compare gradient, time-to-altitude and position-at-altitude for both speeds — and see exactly what each choice buys and spends.
Vx wins where (steepest path), Vy wins when (quickest altitude). They converge with altitude and meet at the absolute ceiling — and the engine's cooling vote usually goes to Vy the moment the obstacle is behind you.
Formula
⚠️ For planning and education only. Weight & balance must be computed from YOUR aircraft's actual empty weight, arm and current equipment list, and verified against the POH/AFM envelope before flight.
Best angle or best rate? Compare gradient, time-to-altitude and position-at-altitude for both speeds — and see exactly what each choice buys and spends.
About Vx vs Vy Comparison Calculator
Vx versus Vy is taught as a definition pair and flown as a habit; this calculator turns it into visible geometry. Enter both speeds with their climb rates and a target altitude: out come the two gradients (Vx's steeper slope), the time difference (Vy's earlier arrival at altitude), and the along-track positions that explain the whole trade — the obstacle cares where you climb, the engine and schedule care when.
How to use Vx vs Vy Comparison Calculator
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula gradient = ROC×60/V; time = Δh/ROC; distance = V × time — two optima, one trade substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Vx vs Vy Comparison Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula gradient = ROC×60/V; time = Δh/ROC; distance = V × time — two optima, one trade with sources cited on the page
- ✓Vx wins where (steepest path), Vy wins when (quickest altitude). They converge with altitude and meet at the absolute ceiling — and the engine's cooling vote usually goes to Vy the moment the obstacle is behind you.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
What exactly do Vx and Vy each maximize?+
Vx maximizes altitude per unit of distance — excess thrust's domain — putting the most height between you and an obstacle at a fixed ground position. Vy maximizes altitude per unit of time — excess power's domain — reaching any altitude on the earliest clock. Same airplane, two different denominators, two different optima.
Why does the gap between Vx and Vy close with altitude?+
Thrust and power curves both sag with density, but they sag differently: Vx (true) creeps up while Vy (true) drifts down until the two meet at the absolute ceiling, where exactly one speed yields the airplane's last zero climb. Practically: at high density altitude the choice matters less aerodynamically — and more thermally, where Vy's airflow wins.
How long should I hold Vx after a short-field takeoff?+
Through the obstacle window and no longer: POH short-field procedures typically say Vx (often with flaps) until clear, then accelerate to Vy. Extended Vx climbs trade cooling margin, forward visibility and stall margin for a steepness no longer purchasing anything. The calculator's position outputs show how brief the Vx phase needs to be.
Are POH Vx/Vy values fixed numbers?+
They're max-gross sea-level placards that drift: both decrease a knot or two with weight below gross (≈ half the percentage of the weight reduction), Vx (indicated) rises slightly with altitude while Vy (indicated) falls — converging as above. The POH performance section notes the schedule where it matters; your type's numbers, today's weight.
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