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I agree with Jim about this. I've had similar problems with a Lyc powered RV-4. Anything over about 800 prop rpm caused a lot of float. I'd be interested to see the calculations on whether a really highly pitched cruise prop is producing thrust at 800-850 rpm & 60-70mph. I think that it's at least safe to say that the airflow isn't driving the prop disc & producing drag like a climb or c/s prop.
I wonder what engine-stopped glide angle would look like compared to the angle we get used to while being pulled along by the engine on final. This could be a significant safety issue if there's an engine failure when we have become acclimated to unknowingly carrying power (thrust) on final.
Charlie
Jim Sower wrote:
<... I need to get the idle speed way down ...>
You sure do. I've regaled you several times about my EZ with an O-235 idling at 800-900 rpm that could NEVER be slowed down enough to land - floated 1000' or more down every damned runway I encountered. Landed fine when I set the idle down to 500-600 rpm. Ran rough as a cob at that speed on the ground (which is why it had been set so high), but I could advance it to 800 for ground ops, and go to the idle stop on final. With all your power, I would emphatically recommend that you back the idle down till it will just barely idle on the ground. You can always taxi above the idle stop, but you can never land below it. I would also strongly recommend a shutdown switch (injectors? pumps?) near the throttle quadrant for convenient shutdown on final. A guarded switch (guarded ON) would satisfy safety considerations, and be convenient enough that you could shut down nearly as easily as pulling the mixture.
That way, you have all the bases covered ... Jim S.
John Slade wrote:
Last week we had some discussion on idle speeds, and I think the consensus
was to keep it around 2000 or a little under. Just for information for other
canard pusher people, I think 2000 is going to be a real problem for me. At
the current 1850 setting with the big 3 66/84 prop I have on she's pushing
hard against the brakes. I think I could taxi the length of the runway at
idle and be doing 30/40 kts at the end. On a short (3400) runway the only
way to stop might be kill the engine once on the ground, or even on short
final. So I need to get the idle speed way down.
John Slade (more power than I know what to do with)
>> Homepage: http://www.flyrotary.com/
>> Archive: http://lancaironline.net/lists/flyrotary/List.html
-- Jim Sower ... Destiny's Plaything
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T
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