C152 question?

swisspilot said:
I flew a C152 yesterday, anybody know why it only has the fuel vent on one side?
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Same with just about every 100/200 series Cessna. CPA (Cessna Pilot Association), has a pretty good article on it. It is the major reason there is an AD requiring vented fuel caps on all fuel tanks for these aircraft.
 
Like blackhawk said the fuel tank caps are vented. On the 152 both fuel tanks are connected via a t connection, the third line from that is gravity fed to the engine. I have always understood the vent under the wing cantilever is an overflow, in addition to an extra vent. Much like the overflow on the bottom of the Diamond DA20
 
Blackhawk said:
Same with just about every 100/200 series Cessna. CPA (Cessna Pilot Association), has a pretty good article on it. It is the major reason there is an AD requiring vented fuel caps on all fuel tanks for these aircraft.
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Don't 182's have a vent on both sides?
 
The 182s have the vents begining in 1979 I think. The entire process Cessna went through in attempts to get even fuel flows from each tank is quite a study in engineering and aviation. It seemed that every attempt to fix one problem introduced another problem. Putting secondary vented fuel caps was the easiest and cheapest solution.
Frankly, having one fuel vent is not really an issue. Cheaper? Sure it is. But who wants to pay more for flight training? Come on now, raise your hands. I know everyone on this board only wants to pay top dollar for the finest equipment, best maintenance, and most experienced instructors.
 
Pilotforhire587 said:
Like blackhawk said the fuel tank caps are vented. On the 152 both fuel tanks are connected via a t connection, the third line from that is gravity fed to the engine. I have always understood the vent under the wing cantilever is an overflow, in addition to an extra vent. Much like the overflow on the bottom of the Diamond DA20
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I had been told that too, but more recently, I've been told that there's supposed to be a check valve to prevent fuel from going overboard. I haven't talked to a mechanic to see if I can determine which is correct yet.
 
msmspilot said:
I had been told that too, but more recently, I've been told that there's supposed to be a check valve to prevent fuel from going overboard. I haven't talked to a mechanic to see if I can determine which is correct yet.
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There is a check valve, but it doesn't work that great usually and it's a pain in the ass to change... so as a result it usually drips when it's topped off.
 
unlike many c172, you can only select "both" or "off," meaning there is always a path for air and fuel to flow between tanks, essentially making them like one tank. Because of this only one tank needs to have that vent. The caps are vented so when the fuel drains out no "vacuum" will develop leading to a loss of flow. The vent that is at the bottom of the left wing is for expansion of fuel and fuel vapor that occurs as the temperature heats up and vapors expand. Because of this there is a valve that should only allow fuel to vent at this under-the-wing-location when positive pressure is building in the tanks. (or when you over fill it) ; )
 
The C172 has a vent only on the left side and a left/right/both/off fuel valve. There's a cross vent just like the C152.
 
Yeah but in a 172 it is possible to run on only one tank, necessitating the need for those bottom-of-the-tank vents, unlike the 152.
 
sorry Landis, I should have read what you said before I replied. You are right! Both the 152 and 172 have only one vent and a cross over tube on top! So the one vent vents both tanks.
 
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