Fuel transfer
CONFiture
How much of an aircraft's flying is done with the Trim Tank "inoperative"?
Is it a Return to Base item, or does it need a Major Check, somewhere, to be fitted into a schedule before it can be rectified ?
Of course " It depends...!")
That used to be called " an Engineers' Hour.." ( IE , never less than...!)
Not having it available, costs money. (Ask your bean counter !)