Landing Distance Calculator (Headwind/Tailwind, Grass, Slope, Density Altitude & Safety Factor)

How it works

headwind = wind × cos(wind − runway); crosswind = wind × sin(...) · corrections: density altitude ≈ +5% per 1,000 ft (if the chart was read at sea level), headwind −10% per 9 kt, tailwind +10% per 2 kt, grass +20% (dry) / +60% (wet) on the ground roll, slope ∓5% per 1% up/down, weight ∝ (W ÷ W_chart)² · required = corrected total × safety factor (1.43 or 1.67)

The POH landing chart is a starting point measured by test pilots in a new aeroplane on a dry paved runway. Real days add density altitude (higher true airspeed at the same indicated), tailwinds, grass, slopes and a less-than-perfect flare, and the published notes and national guidance give percentage corrections for each. Multiply them through, then apply a safety factor — 1.43 is the widely taught general-aviation figure — and compare with the runway you actually have. When the answer is close, the right decision is almost always a longer runway.

Worked example

A trainer's POH gives 575 ft ground roll and 1,335 ft over 50 ft at sea level. At 4,000 ft density altitude (+20%) with a 12 kt wind 30° off runway 27 (about a 10 kt headwind, −12%) on dry paved runway, the corrected landing is about 1,410 ft, or about 2,010 ft with the 1.43 factor — comfortable on a 2,600 ft runway. On wet grass the same day the ground roll grows by 60% and the requirement rises to about 2,550 ft — inside the 2,600 ft runway by only about 50 ft, which is a reason to go elsewhere.

Frequently asked questions