On Wed, 04 Feb 2004 21:54:41 -0600, "Curtis L. Olson" <[EMAIL PROTECTED]> wrote in message <[EMAIL PROTECTED]>:
> Andy Ross wrote: > > Curtis L. Olson wrote: > > > >>The real fun comes from practicing with only one engine running > >>[...] There are some real world effects that are important for > >>training which I don't think we model well on existing twins. > >> > >>The main one that comes to mind is that with an engine out there is > >>a minimum speed you must maintain > > > > > > That's no doubt true, but hopefully it's more a lack of tuning than > > it is a fundamental flaw. For the specific case of YASim: the > > asymmetric thrust effects should be more or less correct as-is, > > because it applies the force at the location of the engine. The > > blue line speed is almost certainly wrong, but should be relatively > > easy to find by tuning the rudder effectiveness only. > > > > If anyone with ME experience wants to take a few hops in the DC-3 or > > (YASim) C310 and provide feedback, I'd be happy to try tuning the > > models. > > It very well could be a model setup issue at which point it's probably > beyond my ability to debug, but with the JSBSim c310, I took off, > climbed to a comfortable altitude and speed, and chopped the throttle > on my right engine. Then I slowly pitched up to bleed off speed > little by little. As the speed bled off, I held my heading with > rudder and kept the wings level with aileron. > > From the readme: > > Minimum single-engine control speed (Vmca): 75 KIAS ..with or without the 5-ish degree bank towards the good engine? > However, I was able to fly right through this until I got the stall > horn, (about 60 kts?) and all the time, the rudder had plenty of > effectiveness to hold heading. In the real thing (assuming the README > is correct) at about 75 knots the rudder loses enough effectiveness to > hold heading against the one good engine at full throttle and you > begin an uncontrollable yaw. This doesn't happen right now in the > JSBSim C310 anyway. > > I'm sure this is just a matter of tweaking the configuration file. > But this is an important behavior to have reasonably correct in small > twins. > > I also tried this with the YASim C310. I see a definite yaw effect > from the engine, but I think I am getting to the stall point there too > before I'm getting to the point where the rudder looses effectiveness > against the engine. At about 80 kts (yasim version) the rudder can't > quite hold heading by itself, but I can add a bit of bank towards the > good engine with ailerons and hold my heading until I stall. At the > point of the stall in the real aicraft, the good engine would > definitely dictate the direction of the spin. I find in the yasim > model, the aircraft can stall/spin into the good engine about as > easily as the other way. > > In both cases it's probably just the models that need tweaking, but in > their current form, I don't think they are very useful for engine out > training. -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
