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Post by ChiMike on Jul 28, 2018 1:27:24 GMT
I have a prop adjustment question for my P2008 with a 914. My prop is in ‘position 5’ which, as I understand it, is the most conservative setting. I typically get 124-127 ktas at cruise with a rpm of 5300-5400. With one pax and full fuel I’m right at the LSA max gross weight.
What settings do others have their prop?
Rpm and speeds at cruise? Pros and cons of going to a different prop setting?
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Post by Cluemeister on Jul 28, 2018 11:18:05 GMT
My prop is set to 5 as well. It was not fine tuned after that, so it probably could be tweaked more. My cruise numbers are about 5 knots shy of yours at those rpm levels.
My understanding is 5 gets you faster cruise speed, less climb. But with a 914, I can hardly notice the climb difference.
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Post by mackattack on Jul 28, 2018 19:29:24 GMT
These props can be tweaked past 5, to about 5.5. A good prop person can do that with the right tools. A dynamic balance helps too. I was able to hit 130 at 8-9000’ in my Astore.
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Post by MarkGregor on Jul 30, 2018 18:49:45 GMT
Mike,
I think your about as aggressive as I would go on pitch. Any more and the takeoff RPM gets lower than Rotax recommends.
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Post by ChiMike on Jul 30, 2018 23:25:13 GMT
Thanks, Mark—
A conversation with a local fellow here in Oklahoma had me wondering what other folks had done.
Mike
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Post by montanapilot on Aug 3, 2018 14:00:30 GMT
Mark-
What minimum takeoff rpm does Rotax recommend for the Astore?
Marshall
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Post by geobuff on Aug 20, 2018 18:03:54 GMT
On the 912IS you cannot get anything close to the Rotax recommended takeoff RPM, and get a decent cruise speed. Most of us will risk poorer take off performance for speed any day. You really need that 5650 WOT for good cruise performance as I see it. Perhaps on the 914 you can have both with that extra HP. Perhaps that is why the 914 is so popular.
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Post by montanapilot on Aug 20, 2018 21:02:40 GMT
What about the "5500 rpm no longer than 5 minutes" notation in the POH? Maybe that's only on the 914 and not on the 912. I'm getting 131 kts at 5400 rpm and climbout at Vy (which I don't normally do except to check the rate of climb at that airspeeed) is 1,000 fpm. I'm happy with the 131 kts, but as we all know, there's no such thing as fast enough. So, if you know something I don't (which could be quite a bit), I'm all ears. THX
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Post by geobuff on Aug 22, 2018 21:52:38 GMT
WOT is just a tool for testing engine loading. You get the correct RPM at WOT by adjusting pitch accordingly. Another thing to remember, is this WOT test must be at your most common cruise altitude. We must use a 'most common altitude' because we do not have variable pitch props. A real downside to LSA. The ideal WOT stays the same BUT the prop pitch technically changes for every 1000 feet altitude in order to achieve that ideal WOT. Hence WHY we need variable pitch props on LSA's.
Of course for cruise I never run continuous operation much past 5500. I have talked to folks who run higher however, and it does not seem to hurt anything. Another thing is on the IS engine, as you approach 5500, it automatically kicks out of ECO mode and gas flow increases almost 20% instantly. Yes, speed also increases significantly with max fuel flow, but you do pay for it at the pump. We hear a lot about higher speeds on this website, but I doubt the engine is consuming only 4 gph at those higher speeds. Many of you have indicated that Rotax fuel flow is so low anyway, so what. Yea, I sort of agree, but with the IS engine, it becomes a challenge to see how little fuel you can use in ECO mode. I have also spoken with some of you who get super low fuel flow, like 3 gph, but when I ask about your RPM, you are at 5000 RPM and cruising 100 kts. Retired folks often say "whats the hurry", but most of us have SPEED built into our DNA.
Remember, I have the 912IS, which only a very few in our TecnamTalk group have, so I often feel like what is the point of ever talking about the 912IS.
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Post by montanapilot on Aug 22, 2018 22:23:05 GMT
Way helpful and informative. Thanks! My 131 kts. isn't coming for nothing. I'm burning a bit north of 6gph. I also agree very much that the "extra speed" issue is more DNA than practical. At 5 kts less speed, you're only 15 miles farther away from your destination after a 3 hour flight, and that takes about 7 minutes extra. Still, we love seeing those larger numbers.
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Post by Flocker on Aug 23, 2018 20:10:35 GMT
I often feel like what is the point of ever talking about the 912IS. Because 4 gph is awesome! 
PS - Not retired yet, but I am in the "what's the hurry?" crowd.
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Post by Ed Midgley on Aug 23, 2018 23:38:39 GMT
Anyone want to race?  |
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Post by geobuff on Aug 24, 2018 1:55:23 GMT
Am I reading this correctly: 35.9" with IAS of 126, TAS of 150 and GS of 143? all at an altitude of 10,500. You MUST have the 914 turbo. No way to get that IAS at 10,500 without it. Impressive and a real advertisement for the turbo. You also must be pitched for speed. Are you at a 5-pitch?
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Post by skipper on Aug 24, 2018 10:26:00 GMT
Yes, please, more info. Those are impressive numbers and would make my decision to go LSA much easier. Does anyone else get that performance or is this unusual? Any advise appreciated. |
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Post by stroudj on Aug 24, 2018 15:39:30 GMT
Why are you flying with your generator off and why is your fuel pressure reading 51 psi? Just asking. Thanks, Jim |
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