Actionscript 3 :: The Private Attribute May Be Used Only On Class Property Definitions - Flash CS5 Error

Here's my code:

[URL]

The errors are one line 123 and 128.I've googled the error, but I still can't fix it, it's got me baffled for an hour now! I've tried adding curly brace's but still same error. I left line 123 and 128 like this

function _update(e:Event):void
{
_helicopter.update(_mouseDown);
}
function onEnterFrame(e:Event):void
{'

But I'm getting an error stating that _update is not defined