Internal combustion engine designers had to have a atmosphere from which to start there engine design! What is the standard temperature, barometric pressure and height above sea level from which to start their calculations? Assume a 7 cylinder radial engine, with normal carburation system.
The "Standard" atmosphere, from which all designs, both engine and aircraft, is: #1- Sea Level, 59 degrees Fahrenheit, 29.92 inches of barometric pressure! Any deviation of any of the three will effect both engine performance and aircraft performance. Example, at Denver's International airport, the elevation above sea level is 5,430 feet above sea level. You could still have a barometric pressure setting of 29.92 and the OAT of 59 degrees, but when compared to Miami, Fla airport, your aircraft and engine would only recognize the density altitude of the airport you are sitting on, at Denver. If you compared the takeoff at Denver to the takeoff in Miami, you would see real quick that because of the less dense air at Denver, your takeoff roll would be quite a bit longer. Now, if you were to also include the OAT of Miami, 92 degrees for example, and you had the same at Denver, you would really have a loooong takeoff roll in a piston type engine.
