Whenever I put items in the helicopter grid they just disappear when I pickup the helicopter as opposed to other vehicles such as gunships, (I am playing space exploration). Is there a fix for this?

This is a known issue, but unfortunately I hadn't managed to get around to fixing it...
It's pretty much the reason why it was omitted in the original version, and my attempt to bodge it in yielded a mixed result.

Helicopter when you pick it up retains its inventory; you can see that by hovering a mouse over it. However, when you plop it back onto the ground, it pretty much creates a new instance of the grid helicopter and grid.

So, the temporary "solution" would be: "Don't pick it up."