Landing distance calculator
Work out how much runway you need to land today.
Landing distance required
The flight manual figure times .
| Condition | Factor | Distance |
|---|---|---|
| Flight manual figure | 1.00 | |
The factors
From the UK's Safety Sense 09, Weight, Balance and Performance. They multiply together: wet grass with a 2% downhill slope is 1.35 × 1.10, not 1.45.
| Condition | Multiply by |
|---|---|
| Each 10% above the flight manual figure's weight | 1.10 |
| Each 1,000 ft of pressure altitude | 1.05 |
| Each 10°C above ISA | 1.05 |
| Paved, wet | 1.15 |
| Dry grass, up to 20 cm, firm soil | 1.15 |
| Wet grass, up to 20 cm, firm soil | 1.35 |
| Soft ground or snow | 1.25 |
| Each 2% downhill slope | 1.10 |
| Tailwind of 10% of the threshold speed | 1.20 |
| Safety factor, applied last | 1.43 |
Using the result
Use the flight manual's landing distance from 50 ft. If its chart already allows for altitude and temperature, leave those blank here.
The answer has to fit in the runway's landing distance available (LDA). A displaced threshold makes that shorter than the runway.
Cross the threshold at the speed and height the manual assumes. Faster or higher uses a lot more runway.
Pick your go-around point before you start the approach. If you're not down by then, go around.
Check the departure too, with the take-off distance calculator.
Straight answers
How do you calculate landing distance required?
Take the landing distance from 50 ft from the flight manual. Multiply it by a factor for everything worse than the manual assumes: weight, elevation, temperature, surface, slope and tailwind. Then multiply by 1.43. The answer has to fit in the landing distance available.
What is the 1.43 landing safety factor?
Room for a faster or higher approach than the test pilot flew, a late touchdown and less than perfect braking. The UK's Safety Sense 09 recommends it whenever the manual gives unfactored figures.
How much does wet grass add to the landing distance?
Wet grass up to 20 cm adds 35%, and dry grass 15%. A wet paved runway adds 15%, and soft ground or snow at least 25%.
Why does a downhill slope matter on landing?
Gravity works against the brakes. Each 2% downhill adds 10%, which is why sloping strips are usually landed uphill.
How much does a tailwind add?
A tailwind of 10% of your threshold speed adds 20%. At 60 kt, a 6 kt tailwind already means 20% more runway.
Is the calculator free?
Yes. It is free for any pilot, club or school, with nothing to sign up for, and nothing you enter leaves your browser unless you save it to a flight plan.
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