The helicopter already emits pollution in its wake, you realize. I don't recall if it's emitted from the main helicopter entity or one of the auxiliary flight entities, though.
Yes, let's discuss that. I have a number of flying vehicles that I'd like to add functionality for. I thought I should code something like this since I studied physics, but have been making other mods first... it's been on the back burner. But from a quick glance at your code, it at least looks clean and readable, which is always a good sign, so if you're down to be the keeper, I will both help you and use it in my vehicles.
Right now, I have the helicopter and the blimp (sort of like the blimp on the mod portable already, but much larger), but for a good flight library we have more ideas. I'd like to conquer just a vertical takeoff and landing first, though, on these vehicles. Here's my current position...
Adamo Clicker has an autopilot function. For a car, it'll crash right through your buildings; we don't want that. :P But for the blimp or the helicopter already in flight it'll fly them over your buildings. If the blimp is always in the air (as it is now), then there's no issue. For the helicopter, the autopilot needs a remote access function to tell the helicopter to "lift off" before flying anywhere. Reaching this point is where I realized the right path forward is a standard flight library, with a couple important remote calls. Once this works for sure with hovering mechanics, then I think it will only be a couple steps to make it work for linear take off mechanics, provided the airplane is left in the right position/space, but for landing it will be harder... however, I think I know how to make landings work in my autopilot, so if we get to that point then I think it'll be a solvable problem.
Does that give you an idea of where I'm headed? I'll take a look through what you have so far, and let me know what you think.
How are you handling shadows?