CS-VLA 975 Fuel tank vents and carburettor vapour vents
ED Decision 2003/18/RM
(a) Each fuel tank must be vented from the top part of the expansion space. In addition -
(1) Each vent outlet must be located and constructed in a manner that minimizes the possibility of its being obstructed by ice or other foreign matter;
(2) Each vent must be constructed to prevent siphoning of fuel during normal operation;
(3) The venting capacity must allow the rapid relief of excessive differences of pressure between the interior and exterior of the tank;
(4) Airspaces of tanks with interconnected outlets must be interconnected;
(5) There may be no undrainable points in any vent line where moisture can accumulate with the aeroplane in either the ground or level flight attitudes;
(6) No vent may terminate at a point where the discharge of fuel from the vent outlet will constitute a fire hazard or from which fumes may enter personnel compartments; and
(7) Vents must be arranged to prevent the loss of fuel, except fuel discharged because of thermal expansion, when the aeroplane is parked in any direction on a ramp having a 1% slope.
(b) Each carburettor with vapour elimination connections and each fuel injection engine employing vapour return provisions must have a separate vent line to lead vapours back to the top of one of the fuel tanks. If there is more than one tank and it is necessary to use these tanks in a definite sequence for any reason, the vapour vent line must lead back to the fuel tank to be used first, unless the relative capacities of the tanks are such that return to another tank is preferable.
Summary: EASA regulations mandate VLA fuel tank venting to prevent obstructions, siphoning, and pressure build-up. Interconnected tanks need airspace connections. Vent lines must avoid moisture accumulation and fire hazards. Carburettor vapour vents must return to the primary fuel tank, preventing fuel loss on sloped surfaces.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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