912iS Prop Pitch Considerations

The 912is certainly benifits from a Variable Pitch Prop.

The Power/ECO change is like having another gear-set that shifts as it sees fit.

The engine goes into Power Mode above 97% power.

This usually means "Climbing" but at higher altitudes, you may very well need 100% power to do what you want.

This does not mean you are asking for 100hp, just >97% of what is available in the ambient conditions.  This might only be 80 hp but it is still 100% of what is available and if you ask for the whole 100% the engine is going to try and give you all that it can by going into Power mode.

It doen't know if you are trying to clear a ridge to save your life, or just trying to get home before the game starts, it will give you all that it can at the cost of economy.

It will up to the pilot to pull back a little throttle if it is determined that absolute Full Power is not justified.

I can see how a variable pitch prop would work well on the iS engine.  However, without that option I’m still a lot happier with the plane now with the prop at a lower pitch.  I flew a couple hours today at various altitudes through 10.5k, with the plane heavy and OAT above standard.  Finding a good power setting is much easier and the RPM dead zone between ECO and POWER modes is reduced.  Maybe as the injection systems evolve the transition between modes will be more seamless. 

I suggest you discuss your issues with DUC. They may well tell you that flattening the pitch more is okay. It could be that their limits are more guidelines than rules. What Bill said about staying in ECO below 5500 rpm makes a lot of sense. Another degree might get you there with no harm done.

I looked at the instructions for the DUC Prop and suspect the advice is more for protecting the user from himself than protecting the Propeller.

The prop is rated for 3400 Propeller RPM which is over 8000 Engine RPM, so we are never going to come close to that limit.

You will need to be diligent about NOT over-speeding the engine in level flight but as I have stated before, This "Ain't" an Air-Race.

If you can run the engine up to the Max Continuous Power point of 5500 RPM and be just barely under the 97% Power point, you wil finally be allowing the engine to be "All that it can Be" knowing that the next knotch on the throttle will result in "Full Military Power!!!"   

Well, even the thought of having a “full military power” throttle position is reason enough to give it a go. DUC allows for down to 20 degrees for the standard 912 with the same gearbox.  I think at 21 degrees I would get most of the 5500 in ECO.  Stay tuned.