Prop pitch - myth

[Roger Lee]

Hi Ed,

 

With my testing I'm faster at 5650 rpm WOT than a guy is at 5500. Tested side by side with other CT's and that was when I tested a total of 8 different props. I set all my guys to around the 5600 mark now and it helps a little with cooling. We (formation of 2-6) typically cruise around 5100-5250 rpm. The 5600 +/- rpm is balance point between prop settings for us. You may loose on one side or the other with a prop setting favoring a too high or too low a pitch setting.

 

Balance is the best key for us with ground adjustable props.

 

Ed,

 

Does your plane have a Dynon D120 with a fuel flow transducer?

[Ed Cesnalis]

Hi Ed,

 

With my testing I'm faster at 5650 rpm WOT than a guy is at 5500...

 

 

I don't doubt it Roger but I bet it depends on altitude. For you guys cruise or 75% power is achieved with a partial throttle but I'm generally above a critical altitude to where full throttle is required to even approach 75%.

 

Above that critical altitude fastest becomes 5,500 @ WOT.

 

I bet I'm pitched the same as you guys or close, or is it the other way around?

[Roger Lee]

Your right altitude absolutely plays into our prop pitch selection. I would bet if we had the same props yours would be a flatter pitch than my down here in Tucson and your right that more throttle is needed to perform at your altitudes. When I fly at those altitudes like you which is rare I need a lot more throttle to maintain altitude and keep speed up. Our carbs do okay and help with altitude adjustment, but they will never be as good as the fuel injection with a FADEC and has the sensors to help make better calculations for the engine and in making adjustments for those altitude. At fairly high altitudes it may help to reduce flap pitch from -12 or -6 to zero. Of course this will all depend on aircraft weight, prop pitch and altitude.

[C ICEY]

Another advantage of the variable...... maintaining 5500 (I usually settle into 5350-5400) at almost any throttle setting less than WOT.

sip a bit less fuel, fly just a bit slower, but still maintain optimal, low vibration, rpm.

I find the flexibility of control essential in mountain flying, where I do lots of climb and descent, exploring the peaks and valleys and changing the altitude perspective.

[207WF]

Still, a constant speed prop would be great because it ... could maintain a constant rpm. Mountain and summer bumps mean lots of throttle jockying if you are flying at a high rpm, in order to keep if off the redline. I use 5200, in part because I can let the rpm drift up and down without needing to jockey the throttle so much. WF