Oil Additive
Certainly a partially open overflow valve would cause some fuel loss and misting, the spectacular fuel spillage of the subject report arises from a different failure mode......finger trouble.
If the fuelling control panel power remains on, the wing tank Fuelling Shut off Valve solenoids are deenergised. During CWT fuel transfer pump ops this will cause fuel pressure to build up in the servo line to the wing tank overflow valves causing them to open and allow the fuel spillage during T/O and climb.
Usually caused by closing the access panel for the fuelling control panel and relying on its nylon baulk to turn the fuel control panel off. Sometimes it doesnt work.
This known problem has been addressed via SED and SB action but the fix is to use your fingers to physically operate the power sw and observe that the panel does indeed power down;
before you close the access panel.
Learnt the hard way a few years back......
