breather tubes

[Mjg2011]

I fly a 172s and I noticed three tubes near the nose wheel. I know one is the battery acid drain and one is the crankcase breather. Is the last one an oil pressure relief or something? I was always under the impression that the crankcase breather and oil breather were the same thing.

 

[AKBill]

My Beech has 2 hoses off the battery box. One that goes out the bottom and one at the top of the battery box. One is acid drain and one is a vent for the battery box. Not sure if the 172 has the same set up, but it might.

 

[eman1200]

it's a 172? I think that's where the last remaining ounce of coolness leaks out onto the hangar floor. I'm guessing you rarely see any puddles under there?


I kid, I kid.

 

[Howard Wilson]

Maybe fuel sump drain??

 

[GRG55]

it's a 172? I think that's where the last remaining ounce of coolness leaks out onto the hangar floor. I'm guessing you rarely see any puddles under there?
...

I've noticed nothing ever leaks onto the hangar floor from a Mooney. I've been told that's because it just gets carried away in the slipstream as the airplane is doing 250 knots on 2 gallons an hour.

 

[eman1200]

I've noticed nothing ever leaks onto the hangar floor from a Mooney. I've been told that's because it just gets carried away in the slipstream as the airplane is doing 250 knots on 2 gallons an hour.

that's only if you're ROP

 

[Dan Thomas]

If it's a '96 or newer 172, the third line is a fuel pump drain. It's connected to the space between the two diaphragms in the pump, and will drain oil leaking past the inner diaphragm or gasoline leaking past the outer.

Some older 172s (like from around 'mid-1960s to 1986) have, or are supposed to have, a 1/4" drain tube from the fuel strainer drain.