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I know that calculating takeoff and landing distance data is required by 14 CFR 91.103 but it states "runway lengths at airports of intended use." So of course as part of my preflight action I calculate takeoff and landing distances for the airport I'm departing and arriving at.

Let's say I'm doing a local flight and decide to do some pattern work at a local nontowered airport. Am I legally required to have calculated takeoff and landing distance for that airport?

Also for my landing data my school taught me just to use the same data I use in calculating takeoff distance (e.g. pressure altitude and temperature) but should I be using forecasted data? I don't even know where to find temperature forecasts besides winds aloft and using standard lapse rate down to the surface.

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"Intended use" is pretty clear. You need to know the runway length for every airport you intend to use. Short of an emergency or a mistake, you shouldn't be landing at any airport you don't intend to use, so effectively this means every airport.

The better you can predict the actual conditions, the better off you are. If the available landing distance may not be enough under certain weather conditions, you can decide on "go/no go" conditions beforehand. Perhaps the runway is suitable at 15°C with calm winds but not at 40°C with a 10 knot crosswind. If you aren't sure what the actual conditions will be, do your calculations with the values that give the longest takeoff and landing conditions.

The point isn't to estimate the distance exactly- it's to make sure you definitely have enough distance! So be liberal with "fudge factors," as long as they make the calculated distance longer. Many pilots add 50% to the calculation right off the bat as a safety margin.

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There is a difference between takeoff and landing distance, and runway length. You need to know both.

Suppose your plan is to launch from Romeo, Michigan, overfly Fair Haven, and then do some pattern work at Marine City.

Sectional chart excerpt showing Romeo and Marine City Link to above chart at SkyVector

You do your takeoff and landing distance calculation for Romeo and discover that you need 2,800 feet to take off and land. Winds are from 220 at 10 knots. No problem, the runway at Romeo is plenty long enough. You blast off and head to Marine City.

Arriving over the field, you glance down and notice that the paved surface of runway 4-22 is 3,070 feet long, but there's a 295 foot displaced threshold on runway 22. Now the available landing distance is less than what your airplane requires. Can you still land?

Hmm. What if you land on runway 04? You'll have the full 3,070 feet available to you...but you'll be landing with a 10 knot tailwind. Can you still land?


Obviously I've chosen these airports on purpose to illustrate the problem. Most of the time, if you can take off and land at your home airport, you can take off and land at nearby outlying airports using the same data - but not all of the time. You need to be aware of both how much runway your aircraft needs at a particular place, and how much runway you have at that place, before attempting a takeoff or a landing.

Otherwise, you're just crossing your fingers and hoping.

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