What the Distance Numbers Are Telling You
Every takeoff and landing chart answers one question: given today’s air, today’s weight, and this runway, how much concrete does the airplane need? The chart gives it in two parts — the ground roll, and the longer distance over a 50-foot obstacle. The second number is the one to compare against the runway you have, because the airplane is still climbing (or still descending) through that first 50 feet whether or not anything is standing there.
Four inputs drive the result: pressure altitude, temperature, weight, and wind. The first two combine into density altitude — thin air lengthens the roll and flattens the climb at once. Weight comes out of weight and balance, and it is the lever you can still move on the day. Wind comes from the runway you pick, which is why the crosswind calculator feeds the headwind component straight into this page.
Where These Numbers Come From
FlightKit computes from digitized POH performance tables, and it tells you which one it used: when the figures come from a published chart, a Source line names the document — and the serial number too, for models whose limits are serial-dependent. When an aircraft has no digitized table, the page shows an amber “model estimates” card instead of quietly rendering physics-model numbers as if they were published ones. With no aircraft set at all, the figures are labelled generic trainer numbers.
That distinction matters more than it looks. A performance number with no provenance is indistinguishable from a number out of your own book until the day it is wrong, so the rule on this page is verified or visibly generic, with no silent middle. Either way, the POH in the airplane is the authority — Section 5 in most books — and 14 CFR 91.103 makes runway lengths and takeoff and landing distance data part of your required preflight action for every flight.
What the Charts Do Not Model
Published distances assume a dry, level, hard-surfaced runway, a new airframe and engine, and the technique described in the book, flown precisely. Grass, standing water, snow, an upslope, a soft field, a worn engine, a fast approach, or a long float all add distance that no chart correction covers. A multi-engine POH figure is an all-engines-operating number and says nothing about accelerate-stop or accelerate-go — compute those separately.
So treat the computed distance as a floor, not a plan. Decide in advance what margin you require over the book number, and decide it somewhere other than the run-up area, where the pressure to go is highest. Then take the whole picture into Go / No-Go and brief an abort point on the runway before you release the brakes.
Frequently Asked Questions
How do you calculate takeoff and landing distance?
Enter the POH performance chart with pressure altitude and temperature, read the ground roll and the distance over a 50-foot obstacle at your weight, then apply the chart’s correction factors for headwind or tailwind, runway surface, and slope. The calculator above does this from the digitized chart for your aircraft and shows both the ground roll and the 50-foot distance.
What is the difference between ground roll and the 50-foot distance?
Ground roll is the distance from brake release to liftoff (or touchdown to a full stop). The 50-foot distance also includes the air distance to clear a 50-foot obstacle on departure, or from 50 feet down to the stop on landing. Runway length must be judged against the 50-foot number, not the ground roll — obstacles do not have to be there for the extra distance to be real.
Where do FlightKit’s takeoff and landing numbers come from?
From your aircraft’s published performance charts where they have been digitized: the page shows a "Source:" line naming the POH or handbook document behind the figures, plus the serial number when the model’s numbers are serial-dependent. Where a chart has not been digitized, the page says so — an amber "Model estimates — POH not digitized" card — and where no aircraft is set, it labels the figures as generic trainer numbers rather than showing them silently.
Do POH distances assume a new airplane and a test pilot?
Effectively, yes. Published figures come from a new airframe with a fresh engine, flown by a manufacturer test pilot on a clean, dry, level, paved runway using the exact technique in the book. A worn engine, a soft or wet surface, an imprecise rotation, or a long float all cost you distance the chart never accounted for — which is why most operators add a margin to the book number rather than planning to it.
How much margin should I add to the book numbers?
There is no single regulatory factor for Part 91 piston operations, so it is a personal-minimums decision. Adding 50% to the computed 50-foot distance is a widely used habit, and requiring the runway to be substantially longer than that on a hot day, at high density altitude, or on grass is a reasonable place to draw the line. Pick a number, write it down, and hold to it when the day is tight.
Does a headwind help as much as a tailwind hurts?
No — and the charts show it. Corrections for a tailwind are far larger per knot than the credit for a headwind, because energy is being added to the ground roll rather than removed from it. Many POH charts also cap the tailwind they will model at all. Treat any tailwind takeoff or landing as a decision, not an adjustment.