In rec.aviation.student Stan Prevost wrote:

"Alan Gerber" wrote in message
...

Right. People forget why they're doing this. It's not "how much runway
do I need", it's "is the runway long enough".

There's a difference?

Sort of. It's not like you're going to go out and buy a runway that's
1,542 feet long. You're trying to figure out if you can safely use,
say, a 2,000 foot runway.

So if you're looking at an answer that's in the 1,500-foot range, you
don't need to get it exactly. And if the answer is in the 2,500-foot
range, you need to do something drastic.

So you don't need to interpolate from the tables. Round everything up,
and if it still fits, great. If it doesn't fit, but it's close, MAYBE you
should go back and do a more precise calculation. Or maybe you should
think about reducing fuel, or cargo, or waiting for a colder day.

If the rounded-up answer is 1,700 feet, and the "right" answer is 1,461
feet, it's not like you're going to pay extra for the "extra" 239 feet.
You might relax a little more, but either way you'll get off the runway
OK.

.... Alan
--
Alan Gerber
PP-ASEL
gerber AT panix DOT com