Property Trigger

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Property Triggers fire when one or more conditions are met. These conditions can be based on aircraft speed, altitude, failure of components, or a whole host of other simulation variables.


Fires when one or more conditions are met.

ConditionTimer Duration in which the condition has to be true, before it fires.
ResetTimer OnFailure This determines if the timer resets when the condition is false. If it set to false, the trigger will fire when the condition has been true for a total amount of time equal to the timer. Else, the trigger will only fire if the condition has been true for an uninterrupted period equal to the timer.
DisableIfIA HasControl
ReversePolish Condition MSFS's way of creating a condition with the Reverse Polish Notation.

Property Triggers are one of the more useful triggers. They can check a set of predefined properties of the player, or an AI, for being higher, lower, or equal to, a constant value or another property.



MSFS uses reverse polish condition. This is a kind of equation called This equation uses Reverse Polish Notation where the operators come after the operands.


MSFS script propertytrigger RPN example.jpeg

If the speed is less than or equal to 135kts, and the plane is on the ground, the condition will become:


Which works out to True, so the trigger fires.


In FSX, property trigger conditions are applied using the conditional editor.

Possible Uses

  • Checklists
  • Speed callouts
  • Out of bounds (coordinates)
  • Check engines off


See MSFS Mission Script - Triggers for an overview of triggers and more info about triggers in general.

Pages relevant to mission creation for MSFS.

Mission structure

Weather definitions
Flight file
Mission script
AirportLandingTrigger & AreaLandingTrigger · CounterTrigger · PropertyTrigger · ProximityTrigger · TimerTrigger
ObjectActivationAction · DialogAction · AdjustPayloadAction · ChangeAssistanceItemAction · FadeToColorAction · RandomAction · RequestTeleportAction · CountAction · ResetTimerAction · TimerAdjustAction · GoalResolutionAction & SubGoalResolutionAction · GrantRewardAction · PointOfInterestActivationAction · ActivateWaypointsAction · AITakeControlsAction · SendMessageToAIAction
Mission objects
Mission definition · Goal · LivingWorldExclusion · Camera
Flow states
Rectangle Area · Cylinder Area · Polygon Area · Corridor Area · InGameMarker
Library objects
Sim objects

Mission tools

MSFS Script Editor · BushTripInjector · BushMissionGen · MSFSLocalizer · SPB2XML · Little Navmap


Example mission files
Porting FSX Missions to MSFS
Click the links to access the topic pages (Default - Opens in same window).