Section 5

The POH for Sally doesn't have a lot of information on performance. It provides data "that has been computed from actual flight tests in good conditions using average piloting techniques."

For Sally, the book says the takeoff run is 463' for concrete, 702' for grass. Landing distance is 1188' for concrete, 1109' for grass. The rate of climb (Vy) is 825fpm. But what if conditions are different than "good"?

Since aircraft engines combine air and fuel in their pursuit of power, air with lower density leads to less power. Airfoils also use air pressure for lift, so wings and propellers don’t work as well with air that is less dense. The result is that as temperature and altitude increase, performance decreases—sometimes at an alarming rate. Density altitude accounts for these factors and establishes a theoretical altitude at which the airplane performs. A Rule of Thumb is to increase takeoff distance 100' for every 1000' of density altitude. (It might be a good idea to listen to the ENTIRE ATIS/AWOS report.)  Have you heard of a Koch Chart?