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bobair8(at)msn.com
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 Posted: Mon May 12, 2008 6:53 pm Post subject: LycomingEngines-List Digest: 0 Msgs - 05/11/08 |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> I have a topped O-360-A1A (180 HP) in an experimental amateur-built that is ready for its first flight. The prop is fixed pitch and I don't have a manifold pressure gauge in the panel. I want to prepare a simple table of RPM at various pressure altitudes to yield 65% (117 HP) and 75% (135 HP) power so that I can set the power appropriately for the first few hours on the engine to set the rings properly.
I have the Lycoming Operator's Manual (Publication No. 60297-12, Revision -6/7th Edition). I'm trying to decipher Figure 3-17, Sea Level and Altitude Performance on Page 3-33. By my reading it seems like I can generate 75% power at less than 2000 RPM up to a pressure altitude of about 3000 feet and pull 65% power at 2000 RPM at 7500 feet pressure altitude. That RPM seems way too low to generate those power levels.
Do any of you have the right power settings for an O-360 180 HP fixed pitch set-up? The prop is a Sensenich 74" diameter and the pitch is 65" if I recall correctly (the pitch between climb and cruise).
Or can someone tell me how to properly interpret the table? My inclination is to run it at 2700 RPM for take-off and then reduce it to 2500 RPM from then on out and then vary the RPM +/- 100 RPM every half hour or so. I'll be operating at pressure altitudes of between sea level and 5000 feet.
Bob
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douglas.dodson(at)pobox.c
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| Posted: Tue May 13, 2008 6:22 am Post subject: LycomingEngines-List Digest: 0 Msgs - 05/11/08 |
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With a fixed pitch propeller, setting the throttle to 2000 RPM will result in a manifold pressure much less than atmospheric pressure. I don’t think those charts can be used without knowing the manifold pressure.
Douglas L. Dodson, Jr.
Glasair II-S FT
Flight Test Engineer, CFI-A/S&ME,I,G
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