poetpilot ,on the one i did the airtest on the fuel could be checked via a small round window in the side of the aircraft that views a sight tube......just !.
The whole thing was too micky mouse for the C of A airtest so we uplifted a known quantity of fuel into an empty aircraft.
It is of little surprize to me that some one has run out of fuel in the 115 as the sight tube is so poorly placed to be all most useless.