Fuel tank vent
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
vented fuel caps
Is it OK to put a vented fuel cap on both wings? I am having fuel flow issues.....being I burn more out of the right wing (which has the vented fuel cap) than the left wing.
Sean
Sean
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Bruce Fenstermacher
- Posts: 10318
- Joined: Tue Apr 23, 2002 11:24 am
Yes it's OK to use 2 vented caps. I have 2 on my aircraft and it doesn't make a differece. Fuel still flows out the left tank faster than the right. Lot of discussion about this in older posts if you do a search. Basicly your probably stuck with what ever fuel flow youv'e got.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Well, when I bought my '52 it still had the original unvented caps on both sides and fuel flow was fine. When we complied with the AD and put one vented cap on the right side, my fuel flow got all unbalanced. When I went to two vented caps, everything evened out.
I'm fine, Bruce isn't... who knows.
I'm fine, Bruce isn't... who knows.
Doug
Here's a copy of a recent reply I sent to a member regarding his complaint that his right tank feeds faster than his left:
"Your airplane does not really feed fuel faster out of one tank more than
the other. Both tanks feed the engine equally when the selector is in Both.
But.....
....Your right tank (for several reasons noted below) feeds both the
engine...and replenishes fuel in your left tank at the same rate your left
tank feeds the engine...therefore it APPEARS that the right tank is doing
all the feeding.
The right tank is required by AD note to have a vented fuel cap. The
fuel in your right tank is also "weighted" towards it's overhead vent line
due to "P" factor during takeoff and climb (when your fuel consumption is at its highest rate), so fuel crosses over the vent line and refills the left
tank replenishing that which the left tank has sent to the engine. When the fuel level in the right tank drops sufficiently to create sufficient suction
differential with the left tank, then the vent line fills with air and the
siphoning action towards the left tank interrupts.
I have two vented caps and the problem still persists on my B model,
although not quite as badly as it once did.
I suggest you simply operate on Both, and not worry about it any longer.
You may be assured that both tanks are feeding your engine.
Very best regards,
George Horn
Parts/Mx TIC170A
"Your airplane does not really feed fuel faster out of one tank more than
the other. Both tanks feed the engine equally when the selector is in Both.
But.....
....Your right tank (for several reasons noted below) feeds both the
engine...and replenishes fuel in your left tank at the same rate your left
tank feeds the engine...therefore it APPEARS that the right tank is doing
all the feeding.
The right tank is required by AD note to have a vented fuel cap. The
fuel in your right tank is also "weighted" towards it's overhead vent line
due to "P" factor during takeoff and climb (when your fuel consumption is at its highest rate), so fuel crosses over the vent line and refills the left
tank replenishing that which the left tank has sent to the engine. When the fuel level in the right tank drops sufficiently to create sufficient suction
differential with the left tank, then the vent line fills with air and the
siphoning action towards the left tank interrupts.
I have two vented caps and the problem still persists on my B model,
although not quite as badly as it once did.
I suggest you simply operate on Both, and not worry about it any longer.
You may be assured that both tanks are feeding your engine.
Very best regards,
George Horn
Parts/Mx TIC170A
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
Re: Fuel Flow
Besides the items GH mentioned about fuel flow one other item is the aircraft trim; the most common thing that causes more feed out of one tank is an out of plumb turn and bank indicator.
One thing to double check is that the ball in the turn and bank indicator is leveled. Place a level in the aircraft so that the level line is running between the two doors. Then let air out of one tire to level the aircraft. Then adjust the ball in the turn and bank by loosening the instrument attachment screws to the panel so that the ball sits between the two marked lines. If it was out of plumb you should see a marked improvement in the fuel flows between the two tanks.
One thing to double check is that the ball in the turn and bank indicator is leveled. Place a level in the aircraft so that the level line is running between the two doors. Then let air out of one tire to level the aircraft. Then adjust the ball in the turn and bank by loosening the instrument attachment screws to the panel so that the ball sits between the two marked lines. If it was out of plumb you should see a marked improvement in the fuel flows between the two tanks.