The error message sometimes gives you a # to show where in the code the error is occurring.
Make sure you have named the heli correctly. Also make sure your Activation box is correct (eg east present) and that your chopper would otherwise activate it. (In this example it would be an East chopper) It shouldn't make any difference but move the brackets:
this and (not (heli in thislist))
a
and try that ... just a suggestion, may not work. The ; at the end is definitely wrong.