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EB3

My Cruise RPM Today

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Today we finally had the opportunity to take a nice XC in the CTLSi - the first since I flew it home from Tulsa in 2018 as a new owner.  Today was a 4-hour flight to Conroe, TX.

The flight was great, but had an annoying issue with throttle setting. I wanted to cruise between 5200-5300 RPM, but the throttle refused to land in that bracket. I'll use a shirt size analogy: I wanted to wear a L, but all I could find was M and XL.

It would cruise at approx 5150, then as I'd advance the throttle in micro-movements, it would suddenly jump to 5270-5300 and then slowly increase, settling in between 5380-5450. It wasn't a smooth transition to higher RPM, either; you could hear the engine roar as the RPM suddenly increased. Micro-movement pull it back, and it would fall back to about 5150. We fiddled with the throttle the whole trip, first me and then my wife - same result every time. 

There is gap in throttle/power setting, and I have no clue as to why. Anyone? Anyone? 

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The 912is has a "Economy" setting and a "Power" setting that transitions at a throttle percentage.  Depending on how the prop is pitched that transition will occur a various rpm's, sounds like you were operating at that range.  If you watch the Dynon engine display you should see a text of "Eco" or "Pwr" depending on which side you are.  "Eco" will trim the fuel flow down to 3.8-4.0 gph usually which slows you down a bit but your range goes way up.

 

Hope that helps

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Coppercity, that must be it! I noticed the Dynon doing just as you say with the Eco and Pwr. Between the two settings, GPH went from 4 to 5.2 - a pretty big jump. Is there any way to adjust that? Prop pitch? Or should I just run at one or the other and quit fussing with it? I guess I'm good either way - maybe I just need to get used to cruising around 5400.  If I'm out boring holes in the sky, I usually keep it 5000-5100, so I never noticed this issue before. 

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21 minutes ago, EB3 said:

Coppercity, that must be it! I noticed the Dynon doing just as you say with the Eco and Pwr. Between the two settings, GPH went from 4 to 5.2 - a pretty big jump. Is there any way to adjust that? Prop pitch? Or should I just run at one or the other and quit fussing with it? I guess I'm good either way - maybe I just need to get used to cruising around 5400.  If I'm out boring holes in the sky, I usually keep it 5000-5100, so I never noticed this issue before. 

413L had the same issues before the sport upgrade. After the sport upgrade the throttle movement was linear with the power and there was no “bump” as before the upgrade. Can you confirm you have had the “sport” upgrade?

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2 hours ago, Duane Jefts said:

413L had the same issues before the sport upgrade. After the sport upgrade the throttle movement was linear with the power and there was no “bump” as before the upgrade. Can you confirm you have had the “sport” upgrade?

No, sir - do not know off-hand. It's a 2017 CTLSi. 

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EB,

521JW's engine was Sport upgraded by Rotax before installation at the FD factory... my throttle action is totally linear... 

The long flight with your wife must have been a blast, hopefully she was comfortable.

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2 hours ago, AGLyme said:

EB,

521JW's engine was Sport upgraded by Rotax before installation at the FD factory... my throttle action is totally linear... 

The long flight with your wife must have been a blast, hopefully she was comfortable.

Yes, it was a fun and COMFY flight for both of us! Having autopilot is such a luxury - it frees me up to concentrate on my communication with ATC and spend more time looking outside the plane. 

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Why not cruise at the higher RPM? For a 4 hour flight and given the CT sips fuel anyway - why not go as fast as possible?

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RU kidding?  I would have to dive to get those kind of RPM's.  He must have better seats than I do too, I need a cushion for those long ones.

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37 minutes ago, Ben2k9 said:

Why not cruise at the higher RPM? For a 4 hour flight and given the CT sips fuel anyway - why not go as fast as possible?

Cruising at the higher RPM is fine, but it's annoying not to have linear control through all throttle settings. 

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10 hours ago, SportFlyer1 said:

RU kidding?  I would have to dive to get those kind of RPM's.  He must have better seats than I do too, I need a cushion for those long ones.

Youd have to dive to hit what RPM?  The highest RPM mentioned was 5450rpm...if you can’t hit that in level flight then your prop is set too coarse.  You should adjust it to achieve 5600-5700rpm in level flight at your normal cruise altitude.

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I've got 2008 CTLS with the ULS and at 5500 ft I level out at 5600 rpm which is just in the yellow range.  What is the max rpm that the engine should be run for a long trip?

 

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1 hour ago, okent said:

I've got 2008 CTLS with the ULS and at 5500 ft I level out at 5600 rpm which is just in the yellow range.  What is the max rpm that the engine should be run for a long trip?

 

5,500 for continous.  When you set to higher you cannot cruise continuous at best speed.

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Flew home today, and the jump between throttle settings wasn't as acute. It actually settled in +/-5300 RPM, which was fine by me.

This is such a great traveling machine!  Comfy, economical, fast enough, and the auto-pilot is spoiling me. Also love the ADS-B. Even with flight following, ATC never called out the traffic heading directly toward us at +500 ft, but it showed up on the Dynon, so I quickly lost about 300 feet. Within seconds, a twin passed us overhead going the opposite direction.  Had I not had ADS-B and not made the descent, only 500-feet separation would've been a bit too close for comfort.

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I agree EB3.  Flying to Oshkosh this year flight following went away just past Chicago and ADS-B was very useful.  Really makes spotting traffic a lot easier.

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Our 2014 CTLSi will go into ECO mode below 98% power, which is about 5200 to 5300 rpms while burning about 4.8 gph.  That is what I consider wide open in ECO mode.  As soon as you bump the power up to 99% power the fuel burn goes up to about 6.5 gph.  If I am going on a cross country trip, I run it as close as I can get to wide open in ECO mode.  Also, I find it virtually impossible to keep the RPMs at a constant rate during the summer in South Carolina.  The RPMs normally fluctuate about a hundred RPMs up or down.  The updrafts and downdrafts really change the RPMs in the summer.  

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I had the same issue coming back from Wisconsin with my ULS model.  I had to fiddle with the throttle the whole time(5 hours).  I shot for 5300 rpm which gave me 115 knots  and 5.5 gallons per hour.

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5 minutes ago, okent said:

I had the same issue coming back from Wisconsin with my ULS model.  I had to fiddle with the throttle the whole time(5 hours).  I shot for 5300 rpm which gave me 115 knots  and 5.5 gallons per hour.

Any airplane with a fixed pitch prop will require constant adjustment to maintain a fixed RPM.  When I'm flying on autopilot in smooth air, basically all I'm doing is monitoring gauges and tweaking the throttle.

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 I'm accustomed to normal RPM fluctuation during normal operations. I'm now sure that my situation was due to what others have mentioned: The jump from ECO to PWR mode.  I wasn't expecting it and didn't understand it. I'm grateful for the informative replies! 

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