There’s a performance chart for every basic phase of flight. Pilots use them to determine how fast they can fly, for how long and how much runway they’ll use doing it, among other things. The tables, graphs and charts in the performance section of your typical personal airplane’s flight manual or operating handbook purport to identify for you, beforehand, the answers to the how fast and how long questions. Which gets embarrassing when we run the numbers and roll off the end of the runway anyway.
When that happens, it might be pilot error—maybe you made a mistake tracing your pencil along a curve on a performance chart. It also could be because your calculations are all wrong, not because you made a mistake—did you interpolate when you should have extrapolated?—but because the numbers you came up with are more advisory than exact. How can this be? There are several reasons. What can you do about it? There are several answers. Let’s explore.
