Citabria Fuel-Flow Problem

On May 8, 7:39*pm, Bertie the Bunyip wrote:

another useful clue

The deflector business is something nobody else has mentioned yet;
I'll pass it on to the A&P. He's got a couple planes needing
attention to their engines and the Citabria, being under-utilized and
still flyable in the pattern, isn't a high priority, so resolving this
may take until next week. I'll post what's been found after the whole
system's been gone through thoroughly. Thanks.

quietguy writes:



The deflector business is something nobody else has mentioned yet;
I'll pass it on to the A&P.

I can't see the deflector being it, considering it does not drain back
while tied down...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

I use to own a 1968 7ECA. The fuel never drained equally. Sometimes,
one tank would not start to drain until the other was fairly low. Not
only did I replace the cap gaskets, I replaced the fuel caps completely.
It seemed to help a little. Do you have fuel gauges in each wing
root? Mine only had a gauge on one side so you knew which side was
flowing if the gauge was dropping faster or slower than it should. At
cruise I burned 6 gallons an hour or hopefully 3 gallons per side but
many times I'd fly for an hour and the gauge would never move or I'd fly
for an hour and the gauge would indicate 1/2 (13 gallon tanks) instead
of 3/4. I was thinking that you may not in fact have a problem but my
tanks would tend to equalize overnight. There's a pretty active
citabria group on yahoo that I used to participate in. I'd ask over
there but it does sound like a soft fuel line.
Dave
1960 M35

quietguy wrote:
The A/C in question is a 1974 Bellanca 7ECA, re-engined with an O-320
so it's effectively a 7GCAA. It belongs to the Offutt AFB Aero Club
and has seen very little use, often sitting for weeks at a time until
a week ago when I began taking dual in it 2-3 times a week to get my
tailwheel endorsement. The fuel system is not for inverted flight, so
no header tank -- two 18-gallon wing tanks with check valves to a
single vent on the left, crossflow pipes to the aft fuel manifold
under the baggage compartment and crossflow pipes to the forward fuel
manifold on the firewall. Caps are non-vented and the gaskets are
like new.

This A/C is drawing 3-4 times as much fuel from the left tank as from
the right and it's not crossflowing on the ground, even overnight.
We've made right patterns as well as lefts -- makes no difference. We
haven't done any extended S&L flight, just 11 NM to Plattsmouth, NE
for pattern work. The club's A&P has blown out the feed and vent
lines and got a good blast into the right tank from both. We're
getting a free flow of clean gas out of all four drains.

So what's our next move? Anybody had this problem?

On Wed, 7 May 2008 11:17:24 -0700 (PDT), quietguy
wrote:

The A/C in question is a 1974 Bellanca 7ECA, re-engined with an O-320
so it's effectively a 7GCAA. It belongs to the Offutt AFB Aero Club
and has seen very little use, often sitting for weeks at a time until
a week ago when I began taking dual in it 2-3 times a week to get my
tailwheel endorsement. The fuel system is not for inverted flight, so
no header tank -- two 18-gallon wing tanks with check valves to a
single vent on the left, crossflow pipes to the aft fuel manifold
under the baggage compartment and crossflow pipes to the forward fuel
manifold on the firewall. Caps are non-vented and the gaskets are
like new.

This A/C is drawing 3-4 times as much fuel from the left tank as from
the right and it's not crossflowing on the ground, even overnight.
We've made right patterns as well as lefts -- makes no difference. We
haven't done any extended S&L flight, just 11 NM to Plattsmouth, NE
for pattern work. The club's A&P has blown out the feed and vent
lines and got a good blast into the right tank from both. We're
getting a free flow of clean gas out of all four drains.

So what's our next move? Anybody had this problem?

does the fuel situation change if you swap the caps to the other tank?

On May 8, 8:18 pm, quietguy wrote:

The deflector business is something nobody else has mentioned yet;
I'll pass it on to the A&P. He's got a couple planes needing
attention to their engines and the Citabria, being under-utilized and
still flyable in the pattern, isn't a high priority, so resolving this
may take until next week. I'll post what's been found after the whole
system's been gone through thoroughly. Thanks.

The deflector does nothing more than keep bugs and ice out of the
vent. Cessna places theirs behind the lift strut to do the same thing.
When the airplane isn't in flight it makes no difference whatever, and
older Champs and Citabrias didn't have it.
I would still suspect rotten hoses, on both the fuel and vent
lines. Especially if they're old or have been run on Mogas. Or if some
mechanic installed the wrong MIL-Spec hose the last time they were
replaced. It's the only thing short of a blocked aluminum fuel line
that would do this, especially if it won't crossflow overnight to the
lower wing or equalize between tanks if the airplane is level. It
doesn't take much slope to make it run from one side to the other,
BTW.


Dan

wrote in news:429fbca0-f93a-4b0e-a37f-
:

On May 8, 8:18 pm, quietguy wrote:

The deflector business is something nobody else has mentioned yet;
I'll pass it on to the A&P. He's got a couple planes needing
attention to their engines and the Citabria, being under-utilized and
still flyable in the pattern, isn't a high priority, so resolving
this
may take until next week. I'll post what's been found after the
whole
system's been gone through thoroughly. Thanks.

The deflector does nothing more than keep bugs and ice out of the
vent. Cessna places theirs behind the lift strut to do the same thing.
When the airplane isn't in flight it makes no difference whatever, and
older Champs and Citabrias didn't have it.

Not so, according to my friend, but I agree, if it's not draining back
whilst sitting, it's unlikely to be the cause.

I would still suspect rotten hoses, on both the fuel and vent
lines. Especially if they're old or have been run on Mogas. Or if some
mechanic installed the wrong MIL-Spec hose the last time they were
replaced. It's the only thing short of a blocked aluminum fuel line
that would do this, especially if it won't crossflow overnight to the
lower wing or equalize between tanks if the airplane is level. It
doesn't take much slope to make it run from one side to the other,
BTW.

Yeah, gotta be, really. I have to say, i wouldn't consider the airplane
airworthy in this state, though.


Bertie

"Maxwell" luv2^fly99@cox.^net wrote in
:


"Bertie the Bunyip" wrote in message
...

OK, talked to my guy. He had several suggestions. One is to drain it
all dry and then blow some air (carefully!) into the right tank and
see if you can hear it coming across into the left tank by listening
at the filler cap.
Possible problems he came up with were a crushed or swollen fuel line
downstream of where you tested previously, or, he thought more
likely, incorrect placement of the little plastic fuel vent deflector
and/or the location of the fuel vent itself. There are specs for the
location of these if you look in the manuals. But for the fact that
the fuel doesn't migrate when parked, I would have said this is
definitely your problem For instance, Cessnas with bent or
incorrectly positioned vents are chronically out of balance.


Bertie

Oh yeah, that's a lot of help.


I know.


Where did you find this wanna boi,
Wikipedia?




Said where i found it wannabe boi.


Aren't we the little prankster!


Bertie

Stealth Pilot wrote in
:

On Wed, 7 May 2008 11:17:24 -0700 (PDT), quietguy
wrote:

The A/C in question is a 1974 Bellanca 7ECA, re-engined with an O-320
so it's effectively a 7GCAA. It belongs to the Offutt AFB Aero Club
and has seen very little use, often sitting for weeks at a time until
a week ago when I began taking dual in it 2-3 times a week to get my
tailwheel endorsement. The fuel system is not for inverted flight, so
no header tank -- two 18-gallon wing tanks with check valves to a
single vent on the left, crossflow pipes to the aft fuel manifold
under the baggage compartment and crossflow pipes to the forward fuel
manifold on the firewall. Caps are non-vented and the gaskets are
like new.

This A/C is drawing 3-4 times as much fuel from the left tank as from
the right and it's not crossflowing on the ground, even overnight.
We've made right patterns as well as lefts -- makes no difference. We
haven't done any extended S&L flight, just 11 NM to Plattsmouth, NE
for pattern work. The club's A&P has blown out the feed and vent
lines and got a good blast into the right tank from both. We're
getting a free flow of clean gas out of all four drains.

So what's our next move? Anybody had this problem?

does the fuel situation change if you swap the caps to the other tank?


Citabria caps aren't vented.


Bertie

"Bertie the Bunyip" wrote in message
...


Yeah, gotta be, really. I have to say, i wouldn't consider the airplane
airworthy in this state, though.


Bertie

Yeah buddy, like ANYONE would be stupid enough to give a rat's ass what you
think.

"Bertie the Bunyip" wrote in message
...

Citabria caps aren't vented.


Bertie

No, but your head is wannaboi.