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Need advice for prop pitch 912uls float flying application

  • Brody602
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1 week 2 days ago #20256 by Brody602
Hello everyone, I’m seeking advice on the best rpm range to have for best overall performance on floats, cruise/takeoff distance.

I have a Bushcaddy R-80 with the 912ULS, I’m running a 69” three blade ground adjustable “KOOLprop” which is very similar to the kievprops.

I currently have it set as follows;

5600RPM firewalled when static on the ground

In straight and level flight I can overev the engine if I firewall, it went up to 6000 and I immediately pulled back power a bit.

At 5200rpm I’m seeing cruise speeds of 75mph which seems to be about 10-15mph slower than reported numbers from other people running the same plane/engine on floats.

I know fine pitch is better for takeoff performance and coarse is better for cruise, but I’m actually wondering, is it possible to be pitched too fine that you’re actually hindering performance? Would I potentially see improved takeoff distance with a coarser adjustment?

I’m open to suggestions on what I should be aiming for with static rpm firewall on the ground and rpm when firewall in straight and level,

Again, i’m on floats would like to keep takeoff distance to a minimum to get in and out of small lakes.

Thanks in advance.

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1 week 2 days ago #20259 by alananpat
Hi Brody.

It seems you have already answered your question. Since your engine should never exceed 5800rpm you need to increase the blade pitch to compensate for this. Drop the static rpm to no more than 5400 and try the level flight WOT again. 5800 WOT in level flight should give you the very best takeoff performance for float type activities and won't damage your engine accidentally.

Alan

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1 week 2 days ago #20260 by Brody602
Thank you, just figured it was best to ask to make sure.

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1 week 1 day ago - 1 week 1 day ago #20273 by Roger Lee
I agree that too fine a pitch will cost you performance and the possibility of over revving. Some of this may be personal preference.Usually a good place to be for normal operations is 5600-5650 (ground adjustable props) in level flight at WOT. Since you're using floats and a little heavier and have more drag you may want to try 5700 -5800. I would try both rpm ranges as mentioned and see what works best for you specific circumstances. The 5600 range will certainly get you more cruise speed over your current setup, but might prefer a tad better climb (5700-5800) depending on your weight and elevation where you operate.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
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Last edit: 1 week 1 day ago by Roger Lee.
The following user(s) said Thank You: Brody602

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