David Megginson wrote: > Andy Ross writes: > > Basically, if I understand the request, it should be sufficient to set > > the takeoff-rpm value to 2100 or so, while leaving the cruise value > > alone. That should do what you want. > > I'm not sure that's right. By the time the plane is moving fast > enough to take off, the propeller should be at full RPM.
That's exactly what it does. The core problem is that the propeller's aerodynamic "drag" (more strictly, counter-torque), when matched to a cruise performance, ends up being much too high at zero speed. The reason for this is that the propeller at takeoff is essentially in a stalled condition -- the AoA on the blades results in separated flow, and much less induced drag. YASim handles this by providing a "cap" on the drag and thrust coefficients that works at high AoAs (real torque and thrust curves really do look like this, btw). That cap is specified as a takeoff RPM which it will attempt to match. The takeoff-rpm value you specify will only be matched, though, at takeoff. As you speed up, you'll see the RPMs grow appropriately, until they match the cruise-rpm value you specified (presuming you end up at cruise conditions, obviously). Andy -- Andrew J. Ross NextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com "Men go crazy in conflagrations. They only get better one by one." - Sting (misquoted) _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
