Andy Ross said: > Jim Wilson wrote: > > What should I look for then when mucking with the cruise numbers from > > the prop definition? Or is there some way to just remove them? > > One thing to try would be to remove the variable pitch settings > entirely and nail the prop down at your specified cruise setting > (which should generally be low rpm, long range values). Verify that > you get the desired performance in that configuration, then add the > min/max settings back in to check that they don't break anything. > Doing it this way, the variable pitch tuning shouldn't be far off from > 1.0 in your cruise configuration.
I think I've run out of steam for this one. The current (in CVS) settings seem to be pretty good. This does sound like something that could be automated in YASim though, doesn't it? > > I've tried to get a little more thrust of this prop and haven't had > > much luck. One thing that just occurred to me, does this formula make > > any assumption about the number of blades? The P51D prop has four > > blades and I'm not clear on how that is accounted for. > > Doesn't matter. The big advantage to doing the modelling with an > efficiency curve is that you don't worry about details like this. The > engine provides input power, divide by current speed to get output > thrust. Plausibly perfect performance in all conditions. But hard to > tune. > > What thrust are you looking for, btw? You can get an actual value in > pounds out of the property tree. With some unit conversions, you can > multiply this by the true airspeed and divide by the engine power > output to work backwards manually to an efficiency value (maybe a > Nasal script would be good for this). If you are seeing something in > the range of 75-85%, then your problem is more likely engine power > than prop thrust. > Basically I've been trying to target the published initial climb rate of 3475. It seemed that the thrust would be the primary factor here. I reduced the fuel to 0.5 which helps some. Perhaps that published figure is with minimal fuel...that's the problem with these "published" values. Also I opted to overstate the engine horsepower by 100hp, and for now it seems pretty good. One thing I noticed was at lower rpm settings (and over 200mph speed) the thrust actually doubles when I turn the boost off. Is that normal, ie removing the cost of turbo/super charging? Best, Jim _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
