Do planes fly better when it is hot, or, cold outside?
Seems to me it would be better when the air is cool due to the density.
Just wondering..

A friend of mine had this question too on his mind, he told me that here in my country, Enya is not popular it is used mostly in europe or in cold countries, my city gets pretty hot in summer, scorching hot, Im not expert but my common sense tells me that atmospheric temperature does effect on your engine, but what if the ground temperature which is hot, and when plane goes higher like 2,000 feet or more, upper atmospheric temperature is much cooler, but engine still seems to run good? Irvine its british engine, its not popular here. Here in my city people prefer, TT, O.S. Magnum & ASP, magnum and ASP are my favorite. in 4 strokes they prefer O.S. and YS, not saito I wonder why but Im sure somebody would come up with better answer than mine.

Mody

Here in Florida I don't notice any difference in engine performance but definately in battery life. When we get a cold snap and you have to wear gloves and a hat the battery voltage drops like crazy. The biggest effect the weather has is on me though. When it is scorching hot or freezing cold I don't fly well. I loose my concentration and am uncomfortable especially in the heat. Hey but don't let the weather stop you from flying.

They fly better when it's cold because the air is more dense which helps both the aerodynamics (lift) and the engine has more power. Also cold air can't hold as much moisture as warm air which means even more oxygen getting into the engine.

Downunder has it right. Under normal circumstances, your airplane will have noticeably more "power" on a cool dry day than a hot humid one.

Planes fly best when you have time to get to the fly field.[8D]

Del

I'll 2nd the comments by DownUnder. More air molecules = more lift. That's also why they fly better the closer to sea-level you are. Planes that fly into airports at higher elevations like Denver have to allow for this. It's called Density Altitude.

Humid air is lighter than dry air as water vapor, H2O is lighter than air. NO2. When it is hot AND humid your plane and engine will not perform as well.

Technically, it's not about weight. It's about density. Temperature, humidity, and elevation are the main variables that control air density.

I believe something that is more dense weighs more, but who really cares?

Given the same temperature and pressure, humid air is less dense than dry air. As mentioned, equal volumes of gas contain equal numbers of molecules, and air molecules (Primarily Nitrogen Gas and Oxygen Gas) are heavier than water molecules, so if you start substituting water molecules for air molecules, as in humidity, the density goes down. Cold air is more dense than hot air. Bottom line, cold dry air would seem to give you the best performance.

When the airplane is underpowered it'll fly better when the day is cold. When powerful enough or overpowered, it won't matter.

Engine power changes more and has more effect than "aero power".

Forget about densities with humid air. The engine needs oxygen from the air to run, the more oxygen the more fuel can be burned for more power. Water vapour in the air displaces some of the oxygen (and nitrogen) so less useable air gets into the engine. Hot air can hold a lot more water vapour than cold air before it becomes a fog which is why you only see a fog on cold days.

In some areas of the world, pilots find when they do the performance charts for the day, the aircraft can carry more than the gross weight of it.