Cessna 152 fuel vents

RyanB

RyanB

Super Administrator
Management Council Member
PoA Supporter
Joined
Jul 21, 2010
Messages
16,232
Location
Chattanooga, TN
Display Name
Display name:
Ryan
Supposedly a possible question for my oral exam tomorrow. How many vents are in the fuel system of a 152. All I can think of is the fuel overflow that comes off the wing, what others?
Thanks!
 
All the answers of the systems can be found in the POH. If I remember correctly, there is only 1 on the left wing by the strut
 
jordane93 said:
All the answers of the systems can be found in the POH. If I remember correctly, there is only 1 on the left wing by the strut
Click to expand...

Thats all I thought there was too, I'll have to take a look at it before i head out.
Thanks!
 
There's the single vent tube under the left wing.

I am unsure if the caps are vented or not.
 
Hi Ryan.

The fuel overflow you mentioned is actually a vent. Also, the caps are vented (at least on our C-150) also. I think some 150's only have one vented fuel cap, but most (like ours) have likely had replacements so that both are vented.

Good luck on your test!
 
somorris said:
Hi Ryan.

The fuel overflow you mentioned is actually a vent. Also, the caps are vented (at least on our C-150) also. I think some 150's only have one vented fuel cap, but most (like ours) have likely had replacements so that both are vented.

Good luck on your test!
Click to expand...

Answers my question, and thank you!
 
The only active vent is the one on the left wing. It goes to the tank on that side and there's a crossfeed vent to the other. The right fuel cap should have a check vent in it, but that should only let air in if the underwing vent (or the cross line) somehow clogs.
 
Blackhawk said:
Funny, I assumed the fuel cap AD applied to all Cessna 100 series airplanes, but no 152.

http://www.airweb.faa.gov/Regulator...225F45DF0B489ACE86256A34006AB0A2?OpenDocument
Click to expand...

Probably because the AD is from 1979, and the 152 showed up in 1978, IIRC, and probably had the vented caps already. The AD only required a vented cap on the right tank, but there should be very few unvented caps anymore. They haven't made them in many years. The vented cap on the right tank will vent both tanks if the underwing vent ices up or a big bug or mud wasp gets into it. I've never heard of a crossventing tube clogging up. Leaking, yes. The short bits of rubber hose that couple each end of it to the tanks get old and hard and crack and shrink. Bad deal if it starts leaking in flight. Cessna wants them checked every 100 hours and replaced every ten years. The 100 hours is a bit wild, but a ten-year replacement is perfectly good advice. They're up there in the ceiling where it gets hot in the sun.

The vented cap has a rather fragile red silicon rubber check valve to let air in but prevent fuel leaking out.

Dan
 
Last edited:
The DPE wants you to know about the single vent, the cross-over feed that is "supposed" to keep your tanks balanced while on both, as well as if you have vented fuel caps.

They also use it as a teaching moment, as mine years ago then stated that if flying a low wet wing and the vent was clogged, the wing at the tank would begin to suction in on the effected side (which you can't see on a 152).
 
danhagan said:
The DPE wants you to know about the single vent, the cross-over feed that is "supposed" to keep your tanks balanced while on both, as well as if you have vented fuel caps.

They also use it as a teaching moment, as mine years ago then stated that if flying a low wet wing and the vent was clogged, the wing at the tank would begin to suction in on the effected side (which you can't see on a 152).
Click to expand...

To suck the wing skins in you'd need a good pump. A 152 doesn't have any fuel pump. Gravity feed only.

Low wing airplanes also don't have a "Both" position on the fuel selector. Since the fuel is being pulled uphill by the engine-driven pump, if one tank ran dry on "Both" the pump would just suck air instead of fuel from the other side, just like having a leaking standpipe above the waterline in a water well where the pump is up top.

Dan
 
Dan Thomas said:
Low wing airplanes also don't have a "Both" position on the fuel selector. Since the fuel is being pulled uphill by the engine-driven pump, if one tank ran dry on "Both" the pump would just suck air instead of fuel from the other side,
Click to expand...
Most low wing airplanes don't have a "BOTH."

The Navion fuel selector is entirely analogous to the Cessna 150. ON and OFF.

This is accomplished however by having the two wing tanks drain to a common accumulator which is where the pump draws from.
 
Dan Thomas said:
Probably because the AD is from 1979, and the 152 showed up in 1978, IIRC, and probably had the vented caps already. The AD only required a vented cap on the right tank, but there should be very few unvented caps anymore. They haven't made them in many years. The vented cap on the right tank will vent both tanks if the underwing vent ices up or a big bug or mud wasp gets into it. I've never heard of a crossventing tube clogging up. Leaking, yes. The short bits of rubber hose that couple each end of it to the tanks get old and hard and crack and shrink. Bad deal if it starts leaking in flight. Cessna wants them checked every 100 hours and replaced every ten years. The 100 hours is a bit wild, but a ten-year replacement is perfectly good advice. They're up there in the ceiling where it gets hot in the sun.

The vented cap has a rather fragile red silicon rubber check valve to let air in but prevent fuel leaking out.

Dan
Click to expand...
I discovered that the short bits of rubber hose in my 172 cross vents were shot while doing spins a couple years ago. Put a big stain in my headliner. Those old and hard tubes are a royal PITA to remove & replace. I no longer wonder why my A&P was eager to have me remove them before he stepped in to assist with the reinstall.

I would think it easier to do every 5 years or so before the rubber gets so hardened but I'm in no hurry either.
 
Took the Oral portion of my check ride yesterday and the DPE did indeed ask this question and the answer was correct. One being on the left wing as a fuel overflow, and at least the passengers side fuel cap is vented!
 
Dan Thomas said:
To suck the wing skins in you'd need a good pump. A 152 doesn't have any fuel pump. Gravity feed only.

Low wing airplanes also don't have a "Both" position on the fuel selector. Since the fuel is being pulled uphill by the engine-driven pump, if one tank ran dry on "Both" the pump would just suck air instead of fuel from the other side, just like having a leaking standpipe above the waterline in a water well where the pump is up top.

Dan
Click to expand...

You don't need a pump just a vacuum forming. Thisis why Cessnas have the AD.
 
You must log in or register to reply here.
Back
Top