On 12/13/2008 06:16 PM, Jon S. Berndt wrote: > The manual should allow some fairly thorough testing.
OK, good. I reckon thorough testing would be helpful. As several others have mentioned, before delving too deeply into the Cessna-specific details, it might be worthwhile to vet the engine and prop models. Here are some specific hints about where to look: 1) Under standard sea-level conditions, I observe the c172p model (from rc2) developing 120% of its rated power at _zero_ kias. That is peculiar, to say the least. Usually the static power is significantly less than the rated power ... not more. 2a) I observe the engine putting out 90% of its rated power at 60 kias at 10,000 feet. Based on my experience, that seems "optimistic" to say the least. http://www.av8n.com/fly/fgfs/engine-power.png It is also "optimistic" for the engine to put out more than 100% of its rated RPM at 10,000 feet at modest airspeeds. 2b) Also I observe a trend: At 10,000 feet, as the airspeed goes down, the engine rotation rate goes down (as expected) but the shaft power output goes _up_. http://www.av8n.com/fly/fgfs/engine-power.png This power trend is not only unexpected based on experience, it defies the laws of physics as I understand them. How can the engine produce more power at less RPM and constant manifold pressure? I suspect these engine anomalies are /masking/ various anomalies in the aircraft FDM. So, ironically, fixing the engine will make some things look worse in the short run. Sometimes exposing a bug is the best way to start fixing it. ------------------------------------------------------------------------------ SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. The future of the web can't happen without you. Join us at MIX09 to help pave the way to the Next Web now. Learn more and register at http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
