I am using particles for this effect and I have a hard time avoiding that the trail gets longer as speed increases. Any suggestion welcome
I don't know how your particle code looks like, but probably the issue is that you're shooting the particles 'at rest in world space' from a moving plane, so both the length and the spacing of the AB effect particles depend on airplane velocity. What you want to do instead is to shoot particles relative to your moving model, such that spacing and length remain independent of the airplane state of motion. The thing to do according to the Wiki seems to use
<attach>local</attach>
but if that doesn't do the trick, it seems the shooter speed can also be property-controlled, so you could use that to compensate if the shooter speed is a function of the airspeed.
With the particles effect, the plume will bend right out of the nozzle when pulling g's
Would it not do so in reality? I'm a hard time understanding why a volume of burning exhaust gas should not continue on a straight line trajectory and 'know' somehow that the plane changes trajectory. The curvature of the plume is just a function of exhaust velocity vs. airplane turning velocity, and that can be done in the particle system correctly with fast-moving particles with a short lifetime.
The particle system has a lot of physics in which begs to be used - it has probably better physics in than any Nasal you can come up with
(Not that I'm an expert in the particle system, I've just done a few waterfalls, but all you need seems to be there).