Performance Landing Calculator

Landing distance from the POH is only valid at the exact conditions it was tested under, so this calculator layers correction factors onto your reference ground roll and total distance (over a 50-foot obstacle) to match your actual day. It first derives pressure altitude from field elevation and altimeter setting, then density altitude from pressure altitude and the deviation between actual outside air temperature and the ISA-standard temperature at that pressure altitude — this density altitude drives a 5% distance increase per 1,000 feet, a gentler penalty than the corresponding takeoff correction because landing performance is less sensitive to reduced air density than the power-limited climb-out phase. Weight is corrected linearly (landing distance scales directly with weight, unlike takeoff distance which scales with weight squared, since kinetic energy on rollout is the dominant factor rather than lift-off speed squared), and Vref is adjusted for weight via a square-root relationship for the same aerodynamic reason best-glide speed scales that way. Wind correction is intentionally asymmetric: headwind shortens distance by about 3% per knot (floored so it can never reduce distance below 30% of the unwinded figure), while tailwind lengthens it by about 5% per knot, reflecting how much more tailwind hurts landing distance than headwind helps it.

Runway surface applies a further multiplier — 1.0 for dry pavement, 1.15 for wet, 1.45 for grass — to both ground roll and total distance over 50 feet. Runway gradient is handled more narrowly: it only adjusts ground roll (uphill shortens it, downhill lengthens it), since it changes deceleration during the rollout rather than the air distance flown down to the obstacle — the total distance over 50 feet and the factored distance carry no gradient correction. The factored distance applies the FAA's 1.67 safety multiplier to unfactored POH total distance — the dry-runway factor set out in Advisory Circular 91-79B, Aircraft Landing Performance and Runway Excursion Mitigation (which superseded the now-cancelled AC 91-79A in 2023 but carried the same 1.67 figure forward); compare that factored number, not the raw total, against available runway length, but add your own margin for a sloped runway since neither the total nor the factored distance accounts for gradient.