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Rotax 912iS idle fuel flow
- Thread starter wcmorgan
- Start date
1650 RPM
Your idle seems to be set correctly.
It's hard to prove a negative, but I'm not sure there is evidence of anything actually being wrong. The fuel flow is a calculated value provided by the Rotax EMS. Rotax does not actually publish a minimum value. The various warnings and color ranges are custom (or default) parameters that are triggered by the EFIS comparing the EMS value to it's programmed range. Put another way, this is not your engine reporting an actual problem...it's your EFIS having been programmed to see .5gph as an arbitrary lower limit and flagging any time it drops below that value.
I don't want to speak for the Dynon guys because I am more familiar with Garmin, but I think if you were to ask around you might find this is not uncommon.
It's hard to prove a negative, but I'm not sure there is evidence of anything actually being wrong. The fuel flow is a calculated value provided by the Rotax EMS. Rotax does not actually publish a minimum value. The various warnings and color ranges are custom (or default) parameters that are triggered by the EFIS comparing the EMS value to it's programmed range. Put another way, this is not your engine reporting an actual problem...it's your EFIS having been programmed to see .5gph as an arbitrary lower limit and flagging any time it drops below that value.
I don't want to speak for the Dynon guys because I am more familiar with Garmin, but I think if you were to ask around you might find this is not uncommon.
I suspect it is not a Dynon/Garmin issue. The red range is set to 0 to .5 Red for the Dynon. The Garmin is probably set to the same. Its normal for my FF to be less than .5 GPH (hence red) when at idle on the ground (1650 RPM for my aircraft.)
It never really botherd me - When I first noticed, I thought that really is an issue for normal flying, so let it be red.
From a purist point of view - Red means crew action needed, Yellow means Crew awareness needed, so since there is a period (approach with throttle closed) where awareness is not required, the high end of the red should be set so it is not red at idle, only below (engine stopped?)
Or you could not color it at all - FF is not an issue that needs correction as long as the engine is developing the required power. At cruise - all you are doing is flagging a gross instrmention error, any other time you are probably not using FF to set power.
It never really botherd me - When I first noticed, I thought that really is an issue for normal flying, so let it be red.
From a purist point of view - Red means crew action needed, Yellow means Crew awareness needed, so since there is a period (approach with throttle closed) where awareness is not required, the high end of the red should be set so it is not red at idle, only below (engine stopped?)
Or you could not color it at all - FF is not an issue that needs correction as long as the engine is developing the required power. At cruise - all you are doing is flagging a gross instrmention error, any other time you are probably not using FF to set power.
I have raised the ground idle to 1750. I still have the same issue.
I don’t think adjusting a different parameter to be out of spec., in an attempt to correct the one you started this thread for, is a very good idea.
Especially since the higher idle speed will effect flight characteristics.
As a former EFIS engineer for part 25 aircraft and a RV-12 pilot, I'll echo Scott's comments. You do not want to affect the flight characteristics of the aircraft (in this case the ability to dump residual thrust during the landing) just to get rid of a warning. Set the warning to the proper level or get rid of it.
With apologies to Vans engineering - its probably best to get rid of it. It is supposed to indicate a parameter that is out of range - but .5 GPH is not out of range. That is normal when the engine is at idle. The result is that there is a red indication that is a nuisance during decent and landing and an indication of a sensor failure during the other phases of flight. Not really required. The other way to look at it is there should be a section in the POH that describes the action when the fuel flow is too low, there isn't & it would be hard to imagine what that section would say.
For the Dynon that I have the setting is in the rotax settings file. The range is red below .5, green from .5 to 8GPH, yellow & red above that. I would just extend the green to 0, and leave the upper red and yellow.
With apologies to Vans engineering - its probably best to get rid of it. It is supposed to indicate a parameter that is out of range - but .5 GPH is not out of range. That is normal when the engine is at idle. The result is that there is a red indication that is a nuisance during decent and landing and an indication of a sensor failure during the other phases of flight. Not really required. The other way to look at it is there should be a section in the POH that describes the action when the fuel flow is too low, there isn't & it would be hard to imagine what that section would say.
For the Dynon that I have the setting is in the rotax settings file. The range is red below .5, green from .5 to 8GPH, yellow & red above that. I would just extend the green to 0, and leave the upper red and yellow.
I have reset my idle back to 1650 RPM.
I extended the green band to zero as recommended.
The indication is now NORMAL at "Flight Idle".
Thank you for the advice.
