On Sunday 04 December 2005 11:27 am, Joacim Persson wrote: > I couldn't help but notice that the JSB version of the 747 has a lift-ratio > which would make a sailplane pilot envious. One can glide about with full > flaps, gear out etc with AoA at 30--40° in 80 kias and keep it level. ;) > ... > The testbed being used here is a fresh cvs version.
The first thing I would change is the idle thrust factor at 0 speed and 0 altitude. The value of 0.0836 was an old typo that got copied into several turbine config files. A value of 0.0317 looks better, and is what I'm using in the CFM-56 config. Also, there is no gear drag included. I would copy the gear drag coefficient out of the 737 config and paste it into the 747 config. Also, the newer turbine model allows one to knock off some thrust due to bleed/accessory/installation losses. I would knock off 4 percent. See the 737's CFM-56 config. As far as the drag values go, the CD0 looks good, and matches aeromatic well. The induced drag is calculated a different way than I do it, and I'd have to get the calculator out to compare results with the aeromatic method, which I hope to get to some time. I'm not a fan of the method used in the 747 config, even if the numbers turn out to be good. The flap drag looks good. Dave _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
