I need the help from someone involved in light aircraft instructing. In small aircraft like Cessna 172s or Piper 160s, the pilots' handbooks include, of course, takeoff performance charts. These charts indicate takeoff distances based upon gross weights, OATs and pressure altitudes. The charts are simple enough to interpolate from; however, I have doubts concerning their thoroughness. Can anyone tell me if the derived takeoff distances are based on the "implied" density altitudes based on the various temperatures given, or are the derived takeoff distances based solely on pressure altitudes? It does make sense that the distances would imply density altitude performance given that the charts include various temperatures. Nonetheless, the distances themselves seem pretty optimistic. Should a pilot formulate his takeoff distance from the chart and then refigure for density altitude, or should he expect that density altitude is already accounted for? In the larger aircraft that I instruct in we must figure both numbers and base our balanced field lengths and climb performances only upon density altitude. To those of you actively flying 172s and Piper Cherokees, do these numbers in the takeoff performance charts seem plausible? Are they fairly accurate?