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912 ULS WOT RPM

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5 months 2 weeks ago #21470 by ZU-EEC
912 ULS WOT RPM was created by ZU-EEC
Hi Roger - I have read various other discussion topics regarding ideal RPM settings for 912 ULS engines. Just some clarity for me please.

It seems the "ideal" RPM to achieve you've described at 5650rpm at WOT (wide open throttle) in "straight and level" flight at my most common cruising altitude. Is this correct?

If this is correct, am I correct in assuming that putting the nose down on my Zodic 601XL while measuring this, which will increase the RPM above 5650rpm, results in a further RPM increase which "could" result in the RPM increasing over the max 5800rpm allowed if I'm not careful. However, would that then be the correct fixed pitch prop setup which I should keep?

Thanks! Kevin

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5 months 2 weeks ago #21474 by Roger Lee
Replied by Roger Lee on topic 912 ULS WOT RPM
Hi Kevin,
Quote:
"It seems the "ideal" RPM to achieve you've described at 5650rpm at WOT (wide open throttle) in "straight and level" flight at my most common cruising altitude. Is this correct?"

The 5600-5650 WOT rpm is in level flight and normal prop loading. Pitch nose high or low will change the rpm. You have no control over prop pitch with a ground adjustable prop so throttle becomes your avenue of choice. Yes lowering the nose will unload the prop and rpm will increase more. At this point lowering the nose (depends on how much the nose is lowered) at WOT for most will end up putting them over Vne (max aircraft speed) so reducing the throttle with a nose down pitch is wise at some point. You could go to idle and with enough nose down go over Vne.

Did this help?

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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5 months 2 weeks ago #21477 by ZU-EEC
Replied by ZU-EEC on topic 912 ULS WOT RPM
Hi Roger - yes helpful thanks!

So at WOT straight and level which I set to be 5600-5650rpm on ground adjustable - it would be possible to exceed the 5800rpm limit with the nose down correct? So something so be careful of if the case.

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5 months 2 weeks ago - 5 months 2 weeks ago #21478 by Roger Lee
Replied by Roger Lee on topic 912 ULS WOT RPM
Yes in a dive or nose down and at full throttle you could over rev. If you start to get to much rpm just back out of the throttle some. I've had my Flight Design CTSW to 160 mph (not Vne) at idle in a nose down attitude.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last edit: 5 months 2 weeks ago by Roger Lee.

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