From: Lee E. <le...@sp...> - 2006-02-21 19:09:56
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On Tuesday 21 February 2006 02:40, Dave Perry wrote: > Some questions concerning YASIM and constant speed props (from > flying the pa24-250): > > 1. At manifold pressures below 20 in. hg, the pa24-250 has > much too much power compared to the real AC. I normally use > 16 in of manifold pressure in procedure turns and then with > the gear down and 15 deg. of flaps, the descent and airspeed > fall in place at the outer marker. I can't even carry 10 in > MP in the yasim model in an approach. 2. A likely related > issues is that with the prop all the way "forward" (normal > landing procedure), the RPM stays high at 85 mph and no > throttle as I flare out. In the real AC, the engine cannot > keep the prop at high RPM in this situation. This makes > taxiing require a lot of braking or you can pull the prop > back, again not real. Also, parked, with the prop "forward" > and no throttle, the RPM builds to perhaps 1800 RPM. The > normal engine run-up is to 2000 RPM and getting it there > requires nearly 20 in. hg MP. Again not realistic. Any > suggestions form others using yasim with a constant speed > prop. > 3. The cruise speeds are very nearly correct if I lean at > altitude to the proper fuel flow. If I leave the mixture > rich, the speeds at altitude are too high. The egt does not > help me peak lean as leaning does not change the egt value. > Have I tied the egt to the wrong property? > > I have thought that yasim did not handle constant speed props > well before when I could not get the p51 to slow up with the > prop forward and little or no throttle. I don't know if I can > help tweak this. I have done only a little little C++ > programing. Most of my programming has been numerical > analysis in Fortran and C. > Willing to try, > Dave Perry Hello Dave, I don't know if this helps but while messing around with the TU-114 I found that if I omitted the control _input_ axis for the prop pitch I could then see the prop pitch changing as airspeed increased. Unfortunately though, the pitch seemed to start at 0.48 and dropped to 0.0 by a couple of hundred knots ias. This is most likely due to me mis-configuring the props as it's not something I know much about. If I included the control input for the prop pitch then the pitch seemed to stay set at whatever was specified - no constant-speed effect. LeeE |