Definition
A performance reference chart used to estimate the combined effect of high temperature and high airport elevation on an aircraft's takeoff distance and rate of climb. The pilot enters the chart with the outside air temperature and the airport pressure altitude, and reads off two correction factors: a percentage increase to add to the standard sea-level takeoff distance, and a percentage decrease to apply to the standard sea-level rate of climb.
Plain English
A simple chart that tells you how much hotter weather and higher airports will hurt your aircraft's performance. It gives you two numbers: how much longer your takeoff roll will be, and how much weaker your climb will be, compared to a cool day at sea level.
Context Anchor
Seen in density-altitude discussions, especially when comparing airport altitude, air temperature, takeoff distance, and climb performance before flight.
Derivation
Named after its developer. The chart is a planning tool, not a word with a hidden meaning, so the name itself is just an attribution.
Why Pilots Care
Allows quick assessment of whether an aircraft can safely depart from a high, hot airport without exceeding available runway or climb capability.
Grounding Statement
Picture a hot afternoon departure from a mountain airport: the Koch Chart helps show how much longer the takeoff roll may be and how much weaker the climb may feel.
Intuition Check
Do not treat the Koch Chart as the airplane’s official performance chart. It is a quick estimate of altitude-and-temperature effects; the aircraft’s approved performance data is still the controlling source.
Example Sentence 1
Before departing a 6,000-foot mountain strip on a 90 °F afternoon, the pilot used a Koch Chart and found that takeoff distance would increase by about 230 percent and climb rate would drop by roughly 75 percent.
Example Sentence 2
After checking the Koch Chart the pilot saw the expected rate of climb would drop by half and decided to wait for cooler temperatures.