David Megginson wrote:
I noticed that the Piper Warrior II (pa28-161) YASim flight model is no longer converging. The model itself hasn't been touched since 2004, and it was working a couple of months ago, so I'll guess that recent YASim code changes have broken it. Here's what I get with --log-level=debug:WARNING: Legacy engine definition in YASim configuration file. Please fix. YASim solution results: Iterations: 10002 Drag Coefficient: 23.9359 Lift Ratio: 99.2994 Cruise AoA: -0.357463 Tail Incidence: 0.0942495 Approach Elevator: 0 CG: -2.475, -0.027, -0.076 YASim SOLUTION FAILURE: Solution failed to converge after 10000 iterations I'm going to try to debug the problem, but it would be helpful to know where I should start looking (i.e. where YASim has recently changed its behaviour). Any suggestions?
The biggest recent change was when we discovered that the wing incidence and twist was reversed between documentation and implimentation. We decided that the way it was documented made more intuitive sense so we reversed the sign of the incidence and twist values in the code.
What this means is that if someone previously *thought* they were specifying a positive 2 degree wing incident with a 2.5 degree washout (so the tips stall later than the inboard wing) then in reality yasim gave you negative 2 degree incidence with the washout going the wrong way (so the wing tips stalled before the inboard part of the wing.)
The yasim solver has some dead zones where it can't find a solution, so you may just need to nudge some numbers around by a small amount to get it working again? And it wouldn't hurt to give a quick sanity check to all the numbers in case you had to nudge things around previously to get it to fly right with the wrong incidence and washout/twist.
Regards, Curt. -- Curtis Olson http://www.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/ FlightGear Project http://www.flightgear.org Unique text: 2f585eeea02e2c79d7b1d8c4963bae2d ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=103432&bid=230486&dat=121642 _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
