It very well could be a model setup issue at which point it's probably beyond my ability to debug, but with the JSBSim c310, I took off, climbed to a comfortable altitude and speed, and chopped the throttle on my right engine. Then I slowly pitched up to bleed off speed little by little. As the speed bled off, I held my heading with rudder and kept the wings level with aileron.
From the readme:
Minimum single-engine control speed (Vmca): 75 KIAS
However, I was able to fly right through this until I got the stall horn, (about 60 kts?) and all the time, the rudder had plenty of effectiveness to hold heading. In the real thing (assuming the README is correct) at about 75 knots the rudder loses enough effectiveness to hold heading against the one good engine at full throttle and you begin an uncontrollable yaw. This doesn't happen right now in the JSBSim C310 anyway.
I'm sure this is just a matter of tweaking the configuration file. But this is an important behavior to have reasonably correct in small twins.
I also tried this with the YASim C310. I see a definite yaw effect from the engine, but I think I am getting to the stall point there too before I'm getting to the point where the rudder looses effectiveness against the engine. At about 80 kts (yasim version) the rudder can't quite hold heading by itself, but I can add a bit of bank towards the good engine with ailerons and hold my heading until I stall. At the point of the stall in the real aicraft, the good engine would definitely dictate the direction of the spin. I find in the yasim model, the aircraft can stall/spin into the good engine about as easily as the other way.
In both cases it's probably just the models that need tweaking, but in their current form, I don't think they are very useful for engine out training.
Ok it seems we need a little definition of Vmc.
To do a Vmc demo you configure the aircraft as follows.
Altitude - 3500 MSL Gear and Flaps - UP Left engine - IDLE Right engine - Full Throttle Props - Full Forward Entry Speed - Blue line CG - farthest aft. Weight - Maximum 0 to 5 degrees of bank to the right.
Execute manuver -
pitch nose up to decrease airspeed by 1 kt / sec.
discontinue when you encounter any of the following
stall warning
stall buffet
lose of directional control
These will give you the worst possible situation to deal with.
Also remember that Vmc decreases as altitude increases in normally asperated twins.
I will play around with the 310 tomorrow to see if I see any other issues.
BTW, does FG currently simulate P-factor? This is very important in multi-engine aircraft because of the off-center nature of the thrust being created. This is why most US made ME aircraft consider the left engine to be the critical engine.
Ryan
_______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
