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JSBSim Thrusters: Difference between revisions
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→Starter speed
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</propulsion> | </propulsion> | ||
=== Starter speed === | === Starter speed (For piston engines) === | ||
There is a somewhat complex relationship among the power coefficient, the | There is a somewhat complex relationship among the power coefficient, the maxhp, and idlerpm. Both maxhp and idlerpm are set in the engine xml file. | ||
The power of the starter motor is | The power of the starter motor is equal to 0.4*sqrt(maxhp). The minimum RPM needed to start the engine is 80% of the idlerpm. The greater the power coefficient (for J near 0), the more power the propeller will require to spin when starting the engine with the aircraft at rest. | ||
If your propeller will not spin fast enough to start, you can try some combination of: | If your propeller will not spin fast enough to start, you can try some combination of: | ||
* Increase | * Open the throttle. Pulling a partial vacuum in the intake manifold takes some power. | ||
* Increase maxhp (increases the power of the starter motor) | |||
* Decrease idlerpm (decreases the minimum RPM needed to start the engine) | * Decrease idlerpm (decreases the minimum RPM needed to start the engine) | ||
* Decrease the power coefficient in the C_POWER table, for values of J close to (or equal to) 0. This will reduce the amount of power it takes for the propeller to spin at a given RPM where J is close to 0 (which is the typical situation when starting the engine and the aircraft is at a dead stop). | * Decrease the power coefficient in the C_POWER table, for values of J close to (or equal to) 0. This will reduce the amount of power it takes for the propeller to spin at a given RPM where J is close to 0 (which is the typical situation when starting the engine and the aircraft is at a dead stop). | ||
You can open the property tree and watch the value of J (/fdm/jsbsim/propulsion/engines/advance-ratio) to get an idea of which values you need to change in the C_POWER table. | You can open the property tree and watch the value of J (/fdm/jsbsim/propulsion/engines/advance-ratio) to get an idea of which values you need to change in the C_POWER table. | ||
''' Code is in upstream JSBSim, and should be in FG 2.7/2.8 to independently control the power of the piston starter motor, to include weak battery effects. ''' | |||
=== Development Tips === | === Development Tips === | ||