Heliport the only fuel figure that should ever be written down anywhere is total fuel on board...as Tarten says it's the PIC's responsibility to know what proportion is deemed unusable.
So you're saying that the figure written in the tech log should be total fuel, and that I should subtract unusable fuel before every flight when making my W&B calculations? And I should subtract unusable fuel when setting the fuel totaliser, which I expect to read zero when there's no usable fuel left?
Isn't it rather more straightforward to record usable fuel and treat unusable fuel as part of the basic aircraft, as is done on W&B sheets? That strikes me as less error prone, given what I've seen of pilots' arithmetic skills after flight.