I found this topic quite interesting, and as I don't have the script you're looking for, I tried to mock up one of my own.
I ended up with:
#loop
_pos = getpos heli1
_x = _pos select 0
_y = _pos select 1
_z = (_pos select 2) -5
tank1 setpos [_x,_y,_z]
tank1 setvelocity [0,0,0]
_dir = getdir heli1
tank1 setdir _dir
~0.0001
_pos2 = getpos tank1
?(_pos2 select 2 >2): goto "loop"
exit
However, this isn't perfect.
It works with: any car and empty aircraft
Doesn't work with: mounted aircraft, armoured
Also, another bug is that depending on what is carrying and being carried, crashed sometimes occur. This could be fixed by chaging _z. Don't feel you need to use this, but this is a baisic versin of the script.
-=GC=-Fungus1999