Temp/Humidity

[Chris Fretz]

I flew on Saturday and it was hot and humid. I went out today and it was probably 10° cooler and not as humid.  But as soon as I fired up the engine the Rpm's were much higher than it was set at on Saturday. So I slowed the Rpm's down to where I was flying on Saturday, but then the airplane was doing slower lap times and I ran out of fuel in the pattern. I cranked the Rpm's back up to where it started at today and my lap time were normal and it took a little more fuel to get back where I was on Saturday. Does this sound like what happens when its cooler? How can you decide what set up to use at a competition when temp and humidity change? Now I'm wondering if I'm going to overrun or come up short at the contest.

2nd question, do temp and humidity changes also change your tank height set up or does that stay the same once you get it set?

Thanks
Chris Fretz

[bob whitney]

what part of the country

[Chris Fretz]

what part of the country

Pa. Hour away from Brodaks.

[Massimo Rimoldi]

Hi,
the best method to solve the problem is certainly to modify the percentage of nitro in the fuel.
+ humidity, + temperature, - pressure => + nitro
- humidity, - temperature, + pressure => - nitro

In any case, the changes of the weather conditions do not affect the location of the tank.

Regards, Massimo

[Eric Viglione]

Hi,
the best method to solve the problem is certainly to modify the percentage of nitro in the fuel.
+ humidity, + temperature, - pressure => + nitro
- humidity, - temperature, + pressure => - nitro

In any case, the changes of the weather conditions do not affect the location of the tank.

Regards, Massimo

I will only add to the excellent reply above to say that while it doesnt change the effective tank height, that running richer will magnify an existing asymmetry in your tank height. Lean and fast covers a multitude of sins. Also worth noting that if the plane starts running different inverted with NO atmospheric changes and you note that turning the needle in on the ground has little effect in the air, I woud almost guarantee you have a plug growing a tater or going bad in some fashion.
EricV

[Chris Fretz]

Thanks for the good info guys!

Chris