On Friday 10 February 2012 04:08:32 Torsten Dreyer wrote: > Hi all, > > for our release of version 2.6.0 next week, we have a few open items on > our checklist and I am kindly asking for support to get them done: > > 1. How are our release candidates performing? Are there any release > blocking bugs that should be taken care of?
I found and fixed a potential NaN and Segfault in the JSBSim propeller code yesterday. It could be considered a blocking bug for 2.6 to me. The property /fdm/jsbsim/propulsion/engine/prop-induced-velocity_fps gives wrong answers, and can become NaN under certain conditions. When thrust is negative and forward velocity is small we can take the square root of a negative number. This could occur, for example, when using reverse thrusters on landing. The value comes out much too high when alpha is near 180, such as taxing with a tail wind. Thanks, Ron http://jsbsim.cvs.sourceforge.net/viewvc/jsbsim/JSBSim/src/models/propulsion/FGPropeller.cpp?r1=1.42&r2=1.43&view=patch --- FGPropeller.cpp 2011/12/22 22:13:59 1.42 +++ FGPropeller.cpp 2012/02/11 15:14:27 1.43 @@ -228,8 +228,16 @@ // Induced velocity in the propeller disk area. This formula is obtained // from momentum theory - see B. W. McCormick, "Aerodynamics, Aeronautics, // and Flight Mechanics" 1st edition, eqn. 6.15 (propeller analysis chapter). - Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area))); - + // Vinduced = 0.5 * (-Vel + sqrt(Vel*Vel + 2.0*Thrust/(rho*Area))) + // Since Thrust and Vel can both be negative we need to adjust this formula + // To handle sign (direction) separately from magnitude. + double Vel2sum = Vel*abs(Vel) + 2.0*Thrust/(rho*Area); + + if( Vel2sum > 0.0) + Vinduced = 0.5 * (-Vel + sqrt(Vel2sum)); + else + Vinduced = 0.5 * (-Vel - sqrt(-Vel2sum)); + // P-factor is simulated by a shift of the acting location of the thrust. // The shift is a multiple of the angle between the propeller shaft axis // and the relative wind that goes through the propeller disk. ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
