After reading the SDK about FSX effects, I am under the impression that the following is true: * Effects (.fx) can only be triggered either by being tied to a light circuit in aircraft.cfg for user control, or if attached to geometry in the model, randomly, continuously, or based on time or time of day. * Effects can not be triggered programatically (unless tied to a light circuit that is triggered)In other words, there is currently no way to turn an effect on/off programmatically without using a light circuit for this purpose.Anyone know different?

AFAIK, that is correct...However, there is absolutely nothing that prevents you from Linking the node to which the .fx is Attached to another node which itself has its controlled by any variable... ;)For example, for the GPU that I've added to the CJ1 and CII FSX versions, I have a "smoke .fx" applied to a node at the exhaust stack of the little diesel engine.I have that node Linked in the model to a control node. That node's is controlled by a custom L:var (L:GPU Running,bool)...As it happens, that node is itself Linked to other nodes in the heirarcy that specify additional conditions. I don't want the pilot to be dragging the GPU along while taxiing, for example. ;)... // controls , show if = 1...... // controls , show if = 1.......... // controls of the object............. // controls L:GPU_Running,bool) 1 ==............... // smoke.fx Attached to this nodeBefore anyone asks... Yes, I could have "simplified" this arrangement by placing all conditions in a single modeldef.xml entry......but, using this arrangement is (a) more flexible and (:( reduces the number of XML code entries in the modeldef.xml file.By "more flexible" I mean that I may have many objects that depend only on the condition being TRUE, but yet are not dependent on the condition.

Thanks Bill.This will help alot.