How does altitude affect engine performance?

As altitude increases, the engine performance generally decreases due to several factors primarily related to the reduced air density. At higher altitudes, the amount of air available for combustion is less because the atmosphere becomes thinner. This decrease in air density impacts the engine's ability to intake air, which is essential for the combustion process.

As a result, engines produce less power at higher altitudes because they cannot draw in as much air to mix with fuel. This loss of air density leads to a corresponding reduction in the mass flow of air entering the engine, which directly affects thrust in the case of turbojet engines or horsepower in reciprocating engines.

While temperature can also influence engine performance, its effects are secondary to the fundamental issue of air density at altitude. Understanding this relationship is key to predicting engine performance in various flight environments.