Text in force at CS27-10: from CS27-0, effective 14 Nov 2003.
The fuel system must be designed and arranged to prevent the ignition of fuel vapour within the system by:
(a) Direct lightning strikes to areas having a high probability of stroke attachment;
(b) Swept lightning strokes to areas where swept strokes are highly probable; or
(c) Corona and streamering at fuel vent outlets.
ED Decision 2003/015/RM · Source