I tried flying my Xtra Easy 2 today right after a line of storms went through. The humdity levels jumped up to 97%. I was just wondering if anyone has ever had any problems flying in high humidity , for example the Engine Cutting out or performing poorly...... because after a few great flights, the engine starting cutting out, and losing power, spitting and sputtering, etc..... all i could think of is that since the engine is so small, any air that was being introduced into it was so water latent that it was causing problems.... if anyone can confirm this it would make me feel much better about the problems i had. Thanks !

High humidity will definitely affect performance. The engine is unable to produce as much power due to the air being less dense as well as the prop being less efficient.

Large changes in temperature or humidity require a little retuning of the carburetors on our engines. Same goes for any performance, naturally aspirated engine.

I'm not sure but i'll take a shot at it,with the higher humidity i would think you need to readjust,it might be burning a little lean,if the engine was hotter than normal it would be a good sign for a richer mixture but this is my opinion,hope others will jump in on this.

That makes sense ..... i'll have to check the setting tomorrow and see if its still acting up ... thanks everyone !

I was typing first but i'm slow.

High humidity, high temperatures, higher altitude,and low pressure systems all make the air less dense. So you need to run leaner to keep the fuel/air ratio right. Low humidity, low temperatures, lower altitudes and high pressure systems make the air denser so you need to run richer to get the proper fuel/air ratio. Air density also affects prop performance, airplane performance, and engine cooling, so treat the previous statements as incomplete, but useful to think about.

Jim

The air is denser,yes. But one of the biggest things is more available oxygen. You need to richen it up a coupla clicks due to the air density and extra oxygen.

Mark Shuman

PS: Drag racers love to run after thunderstorms. You can go a heck of a lot faster with the dense o2 rich air.

Just to clarify, Jim is correct. Air is LESS dense with high humidity, high temp, high altitude and lower barometric pressure. Changes in air density effect the quantity of O2 that is pulled into the chamber during each cycle, so fuel mixture needs to be adjusted accordingly. I.E, you will need to lean your mixture on hot humid days and you will need to richen your mixture on cool dry days. To a certain extent, this is why engines make less power on hot humid days, i.e. you had to lean the mixture so you are buring less fuel per cycle so you are making less power. I don't know drag racing, but what Phread said makes sense. After a TStorm, humidity typically drops and the rain probably cooled the air too. This would make for cool and dry air (i.e. dense air) after the storm, which means richer mixtures and more power.

Densisty Altitude Calculator
http://www.wahiduddin.net/calc/calc_da_rh.htm

I live in where its hot and humid all year round. The best I can squeeze out of my TT46 on 25% Tornado car fuel, which is good stuff, on a Bolly 10.6 x 7 is only 13,100 RPM. Never tached more than 13,200. Again, you not only loose engine power and prop efficiency but also less lift on your wings.

i have been having problems with my engine. normally it runs great and did last time i had it in the air, but when i took it out today it ran fine untill i idle down for landing and it cuts out. i never thought about the high humidity being a factor oh well i guess i will have to just play around with it some more

Air pressure, air temp and humidity plays a big role ... try the 1/10 scale gas powered cars, the engine is only 12 sized but screams all the way to 40K RPM. The Italian job ones are fussy like hell and when the air pressure or temp changes (about to rain, evening etc) you will have to retune the engine. Even certain brands of fuel makes it easier to tune.

Yes, but performance is not affect that much. Even saturated air has a lot less moisture than you might think. However high temperatures affect engine performance a great deal. Often high humidity is accompanied with high temperatures.

Higher temps definitely require a leaner mixture, cooler temps require a richer mixture.
Dennis-

Its kind of a moot point for me. I adjust it every trip to the field regardless of weather.