> The reason I wanted to add this feature was for aircraft fitted with > variable pitch props. As it is, its a bit too easy to set a given rpm > and manifold pressure for cruise. In the real world as the rpm is > changed by changing the prop lever the manifold pressure should > change very slightly, needing a slight adjustment of the throttle > again to get the desired settings, and thus possibly another slight > adjustment of the prop lever if its not a constant speed prop. Thats > what I would think anyway, IANAP.
The easy way is to model the throttle lever as a variable size hole and the engine as a volume flowrate that is proportional to RPM. The input to the throttle and the output from the engine are both the static pressure (as reported by the environmental module). Solving tells you immediately what the instantaneous MP should be. Given the MP, you have the energy required to crank the engine, due to the volumetric flow being pressurized from MP up to static. Combining the crank torque with friction and prop thrust tells you whether the engine will speed up or slow down. There is the same thing implemented in the steam for the vac pump. Oh, and the prop control is a pure integrator, complete with all the overshoot problems and the like you'd expect from control theory, with the gain term more or less proportional to oil temperature in fahrenheit (if you want a lazy way to model it) so that the time constant is about one second in normal operating modes. As a rule of thumb, changing altitude or any of the engine controls on a controllable prop aircraft will usually affect both RPM and MP. It is probably a good idea to detect overpressure-underspeed (on the C310) and cause an engine failure ... to encourage careful usage...! _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
