Für die 152 kann ich es nicht sagen, nur für die Beech, aber: Die Tanks sind Gummiblasen, die an der Vorder- und Oberseite des Flügels befestigt sind. Die Kraftstoffleitung zum Motor führt über einen Schwimmer. Wenn die Tankbelüftungen verstopft sind, entsteht durch das Ansaugen des Kraftstoffes durch den Motor / Kraftstoffpumpe zunächst ein Vakuum und die Tankblase kollabiert nach oben, so daß die Tankanzeige voll anzeigt, obwohl der Tank leer geht, bis zu dem Zeitpunkt, wo die Ansaugkraft nicht mehr ausreicht und gar kein Sprit mehr zum Motor gelangt. Grundsätzlich können diese natürlich auch vereisen, das Ergebnis ist das Gleiche, und kann beheizt werden. Ob es mal zu einem Absturz führte, weiss ich nicht. Ich habe bisher immer nur von fuel icing gelesen, aber who knows.
Wie gesagt, ich kann es für die Hochdecker nicht sagen, kopiere hier aber mal eine wie ich meine sehr gute Erklärung aus dem Beech Forum hinein, leider auf englisch, die die Funktionsweise der Tankbelüftungen und die Gefahren der Verstopfung gut erklärt. Ich kann halt nur Beech :)
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"Air enters the tank at the outside top aft location so that as fuel is consumed, air replaces the fuel and the tank bladder does not collapse upward. The tank bladder is held in place on the top side with snaps that engage all along the upper inside surface of the wing leading edge, where the tank sits. The bottom of the tank is not secured, so if air doesn't replace the fuel consumed, suction will cause the tank bladder to collapse upwards. Since the fuel transmitters float on the fuel surface or the bottom of the tank, they will be held at the top of the tank if the air is not replacing the fuel.
The air line makes its way to the three vents, first a T provides air to a check valve that attaches to a flush anti-siphon vent in the lower wing surface in the vicinity of the tie down ring. In the event that fuel enters the vent line from the tank, the purpose of the check valve is to allow a bubble of air to enter the line and breaking the suction. When this gets clogged or the check valve fails, you can lose an entire tank of gas thru the vent line, especially if the airplane is out on the ramp on a hot day,
The vent line continues from the area of the T that feeds the check valve to another T located close to the inboard side of the landing gear. One side of the T goes to a recessed vent opening on the bottom of the wing near the wing root. The other side of the T goes to the vent located at the wing root with the few inch pipe protruding from the bottom surface of the wing. This tube often gets bent, but is supposed to be angled forward 10 to 15 degrees with the end cut off at a 45 degree angle. There is a hole on the back side of the vent tube that is drilled near the top of the tube, I forget its purpose, but if the tube gets bent, often if you try to bend it back to where it should be, it will break off at the location of the hole. The main purpose of the vent being angled forward is to pressurize the air going to the fuel tank. Since it is a relatively small diameter, it is subject to being blocked by icing conditions. However, since the line is T'd to the ice free vent that is recessed on the bottom surface of the wing, it will pick up the venting duty under those circumstances.
Bugs and mud daubers can get up into the vent system and defeat its operation, depending on how far they get. If they just block the line from the vent tube to the T, the ice free vent will still allow venting to take place. If they go beyond the first T, no venting will occur and the tank will collapse upward during flight and the fuel indication will remain high even as fuel is consumed. You will also hear a noticeable Whoosh when the tank cap is opened as air enters the tank. Also you will likely see the bottom of the tank staring you in the face.
If Bugs and or mud daubers climb up into the anti-siphon vent hole, it will not be able to break a siphon once it starts. This will also be the case if the check valve sticks in the closed position. You can easily lose an entire tank of fuel on the ramp under hot sun conditions. Since the check valve is only supposed to allow air to enter the line to break the suction for fuel in the line, and it is not supposed to allow fuel to exit thru the check valve, any fuel stains in the area of the vent will indicate that the check valve is stuck in the open position.
As an aside, when I fuel my V35A, I always point the nozzle slightly towards the inboard side as if you point it outboard, you will tend to pressurize and fill the vent line with fuel. If the anti-siphon check valve and vent are working, the fuel in the air vent line will eventually stop, but why pump good fuel overboard thru the vent tube near the wing root and onto the ground.
See the attached picture for the anti-siphon vent line, it is the hole just forward of the tie down ring and in the leading edge near the two rivet lines. The inspection panel gets you access to the outboard T and the check valve.
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