Simple planes is a flight sim and engineering game but there is one problem... no start up sequence . You as a pilot want it to be realistic and if you are a builder then you need to know how to make it and get more downloads and upvotes. I am currently working on my own project my second model of my custom commercial airliner RGA121.Here is the instruction to make it:
1. Activate overload mod
2. From the bottom right, click on the last third button with a box and a "x" in it. this is the variable setter.
add some switches and buttons and open the overload mod after hovering on them , go to input controller and change the input to anything you like. say "bat1" save the settings
3.open the variable setters and make a variable named Bat.1(say) and in the expression put "bat1".
4. if you want to this to an engine do the same but with this: variable name"Eng1" expression:"clamp01(eng1*Bat.1)" MAKE SURE TO MAKE THE VARIABLE NAME FOR THE ENGINE

explanation: You make a input named bat1 which activates when you click the switch
you make a variable which turns true if your expression (input) is true
if you anything about coding, you many use && which is wrong for simple planes XML file. the AND expression is represented by *.
In the expression for the engine, you want both the Bat.1 and eng1 switch to be true so you use * as a AND equation.

I am taking leave on this post because my fingers are tired. Watch this video to know more if you didn't understood my explanation OR wait till i upload the RGA121.
watch all the three https://youtu.be/j34cNZSNagE?si=-yu3qaMmKZ5eVxL3 parts of this guy to know more