"Green arc" for RPM or Manifold Pressure?

[Draker]

For those of us with EFIS's where you can set your gauge colors, did anyone bother to set a "green arc" for either RPM and/or Manifold Pressure? I have seen physical RPM and MP gauges on certified airplanes that have green arcs, but I see nothing in my engine (Lycoming) or prop (Hartzell) manuals that would indicate a "normal" range for either of these, or that would prohibit operation in any range. Just an RPM redline of course (in my case, 2700). Are there engines or props whose manuals specify either of these?

 

[RV6_flyer]

I do not have an EFIS but I do have a Dynon EMS-D10.

My Lycoming engine power chart does not have any restrictions on manifold pressure but there can be some MAP restrictions at certain RPMs. For the most part, I should not operate more than 6" of MAP over 100 of RPMs. (avoid settings that are more than 6" oversquared) I tend to not operate more than 3" oversquared.

Hartzell does not have any RPM restrictions for my prop on my engine that are below 2,700.

 

[jrs14855]

Limitations

The exact prop and engine are required as a starting point. Example angle valve 360 with hartzell prop on Piper Arrow with no crank counterweights
2000-2350 yellow arc.
There are various restrictions on some non certified props on certain engines.

 

[bjdecker]

For those of us with EFIS's where you can set your gauge colors, did anyone bother to set a "green arc" for either RPM and/or Manifold Pressure? I have seen physical RPM and MP gauges on certified airplanes that have green arcs, but I see nothing in my engine (Lycoming) or prop (Hartzell) manuals that would indicate a "normal" range for either of these, or that would prohibit operation in any range. Just an RPM redline of course (in my case, 2700). Are there engines or props whose manuals specify either of these?

Yes. While my propeller/engine/ignition has no restrictions aside from maximum RPM, I like the look of the green ARC for MAP (0 - 32"), RPM (0 - 2690, yellow at 2690-2699, red at 2700)

The Hartzell application guide, 193, shows the MAP *AND* RPM limitations of various combinations of engines and props. (https://hartzellprop.com/EXP-AIRCRAFT/Man-193-Vol-01.pdf) -- see tabular data on page 2-3 and beyond.

 

[RV7A Flyer]

For the most part, I should not operate more than 6" of MAP over 100 of RPMs. (avoid settings that are more than 6" oversquared) I tend to not operate more than 3" oversquared.

That's an interesting limitation. Where did that come from?

 

[rolivi]

Also depends on which certificated airplanes you're discussing.

On Cessnas there is a green arc for the tach that when you get ready to desend for landing you need to pull carb heat below the green. ~2000RPM

On Piper the arc goes all the way down to idle and carb heat is only mentioned in the POH as "as needed."

I've been told it has to do with the carb location on conti's vs lycoaurs and the icing potential involved. Not sure how technically accurate it is, but in a 172 carb heat always below the green, in a Cherokee don't touch it till you need it.

 

[RV6_flyer]

That's an interesting limitation. Where did that come from?

Lycoming Performance Curve chart.

 

[RV7A Flyer]

Lycoming Performance Curve chart.

Which one in particular? Looking at the IO-360-M1B, I see curves (lines, actually) for MAP from <14" to >28" for all RPMs from 1800 to 2700. E.g., 29"/1800 is perfectly within the chart.

Maybe your engine chart is different...but when people start talking about anything related to "oversquare" operations, I smell an OWT.

 

[pazmanyflyer]

For the MP I just have a green arch from 0- 30". No other markings.
The RPM I have a yellow band from 0 to the just below idle speed. Right now I have it at 700 as a start point. I'll dial that in when we do engine runs and idle adjustments. Then green from idle to 2650. Back to yellow from 2650 to 2700 and red from 2700 to 2750 for the redline.

 

[lr172]

That's an interesting limitation. Where did that come from?

It is in the manual right next to the limitation of not taking off before the oil temp reaches 100*. The mystery of finding that particular manual still remains

As brian mentions, the prop may have very real limitations on RPM/MAP combinations, but unlikely you can create alarming for them with discrete RPM or MAP alarms.

 

[rongawer]

but unlikely you can create alarming for them with discrete RPM or MAP alarms.

The G3X does have this functionality with v9.21. It is detailed in the Advanced Gauge Configuration Section 29.4.32.27. You can now have the RPM bands change based on manifold pressure, or oil temperature, or just about any other parameter available within the G3X. You can choose a yellow or red band with alerting as an option.

As noted by a poster in another thread, it is not a super simple thing to do, but by setting up the two examples shown in the manual, I've somewhat figured it out. Very powerful tool.