"Curtis L. Olson" said: > > > >The biggest tradeoffs seemed to be in trying to balance high end performance, > >(e.g. altitude, speed) against having enough drag to get reasonable behavior > >at lower power settings. It seems pretty common for yasim models to glide > >too > >much (excessive lift/insufficient drag) when cutting the power. > > > > > > Jim, > > I think this is more a factor of getting the right actual power output > from the engine. If the engine output is too low, you are going to get > up with a "slick" model that glides forever. If the engine output is > too high you are going to end up with a "draggy" model that slows down > too quickly. I remember you struggling with trying to model the complex > p51 engine gearing correctly in yasim and maybe that never came out > right and you ended up with a severely under powered model. > > If that is the case, yasim will reduce drag and make your wing lift > better so that you can still hit the performance numbers. > > For the Citation-II I felt like Yasim did a pretty good job. I haven't > really hit the validation end of it hard, but I was getting plausible > performance throughout the envelope. > > I think the big trick is to get the engine power output in the right > ball park, then everything else starts falling into place much better. >
Yes, I'm aware of the theory behind fixing these issues, but from the beginning I was compensating for them and getting reasonable thrust numbers (I think you are thinking of Vivian with the spitfire). On the last round Andy made some code changes, but I got stuck with solver issues when trying to crank up a little more power. Also I did not mention that there are some subtle problems that affect handling the aircraft during takeoffs that come into play when you start "tweaking". I vaguely remember a further problem with Yasim in connection with engine power, but it'll require getting my head back into it before I know for sure. Best, Jim _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
