On 01/27/2009 12:15 AM, Martin Spott wrote: >> Alright, I've updated JSBSim now, including a number of engine files. >> The following files might need some attention though, since they are not >> in JSBSim CVS: > > Mmmmh, did you make a plan to take care for those models whose authors > don't regularly read this list ?
That seems like a reasonable question. I have some related questions. For one thing, in a Real World C182 at 2000 feet, at economy cruise with 18" MAP and 2100 RPM, the engine puts out 45% of rated power with a BSFC of 0.445 ± 0.010 lb/hp.hr or thereabouts. See e.g. the power setting table on page 5-17 of the POH. So the question is, why does the FlightGear model c182rg, with the new FGPiston, put out only 25% of rated power under the given conditions. And why is the BSFC up around 0.7? Pilots tend to notice when the power output is too low by almost a factor of 2, and when they can only fly 2/3rds as far as expected on a given amount of fuel. ================ The deeper question is, why are we playing whack-a-mole in FGPiston.cpp? That is, what's the point of replacing one wildly unphysical throttle model with another? Why not do it right? -- The old model was messed up with regard to power and RPM. -- The new model is messed up with regard to MAP and fuel flow. This suggests it may be a bit premature to run around changing all the .xml configuration files for the FG aircraft. Again: What's the point of replacing one wildly unphysical model with another ... especially given that a well-founded throttle model _that agrees closely with Lycoming factory data_ was worked out some time ago. http://www.av8n.com/fly/engine.htm The c++ code to implement this exists, too. It's only a few lines of code. ------------------------------------------------------------------------------ This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
