Power requirement of propeller

by Alberto Aragones in 912 / 914 Technical Questions 12 years ago

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Re: Power requirement of propeller

by Roger Lee » 12 years ago

Roger Lee

125 5.11k 4.52k

Hi Mike,

Any of my post on WOT is in the air flat and level flight. In all the props that I have tested the static rpms have all been a little different. I only use static ground rpm at the shop when I have an aircraft and a prop for the first time setup to just get into the ballpark. To accurately dial it in it needs to be flown since all aircraft have different characteristics. In my latest test with Sensenich (5 different props)the 2 blade static rpm was needed to be much higher than the 3 blade prop static rpm. That's no big deal, but just shows not all static rpms and props are equal for the finished WOT setting. I also recommend to people to make the finished WOT rpm setting to their average altitude. Doesn't do any good to set the prop up for sea level flight if you always fly at 9K'.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: Power requirement of propeller

by DUANE HILL » 12 years ago

DUANE HILL

3 9 0

My understanding is that the 912ULS should be flown at cruise close to but not over 5500RPM, as that is how the engine was designed. Some people flying this engine have told me that they never cruise close to 5500 as they think this could hurt the engine.

So what is the recommended RPM at cruise? Is is OK to use lower to gain fuel efficiency?

Thanks

Thank you said by: YEN NIEN YU

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Re: Power requirement of propeller

by Roger Lee » 12 years ago

Roger Lee

125 5.11k 4.52k

Hi Duane,

The constant rpm can be up to 5500 rpm. Yes it was designed for that if that needed to be the case, but the huge majority of us probably runs between 5000-5300 rpm for cruise. I'm happy at 5150-5200 for my cruise with a WOT rpm setting of 5600 flat and level. That put me in my plane about 130-135 mph with a 68" 3 blade adjustable Sensenich composite prop. Something you need to consider is whether you have an in flight adjustable prop, a ground adjustable prop or just a fixed pitch. The majority here probably have a ground adjustable. Personally I don't see a need for 5500 full throttle rpm. It isn't fuel efficient and the speed difference between 5200 and 5500 is small.
The best of all worlds is an in flight adjustable prop, but most don't have one so balancing your needs for flight characteristics and the Rotax engine requirement is just that, something that needs balance.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Power requirement of propeller

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