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williamtsullivan(at)att.n
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 Posted: Tue Sep 16, 2008 4:40 am Post subject: Kolb List Re: fuel line |
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On my 447 I had clear fuel line- Tygon- and a clear fuel filter. I also questioned the bubbles in the line, and air in the filter. I had tried bleeding the system, but always ended up with a visible flow of bubbles. No apparent leaks or loose clamps. John H. advised ignoring it, and it didn't seen to affect engine rpm. Possibly it was cavitation, as the pulse pump was quite close to the engine, and the "lift" was over a foot. Dana's last comment was that a pulse pump (Mikuni) could only be located a limited distance away from the engine. How far can it be located from the engine? Mine was bolted near the base of the engine, and it was very close to being hit by the aileron control horn when folded.
Bill Sullivan
[quote][b]
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pj.ladd(at)btinternet.com
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| Posted: Tue Sep 16, 2008 6:19 am Post subject: Kolb List Re: fuel line |
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I am fascinated by all the discussion about fitting an extra fuel pump.
Has anyone actually checked to see what percentage of fuel pumps have failed. It seems to me, ignorant as I am, that all the complications of setting up a back up pump merely increase the risk of something going wrong.
What about doubling up on the control cables? If they part you really do have trouble. Whatever happened to simple, slow, cheap flying..
puzzled
Pat
[quote][b]
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lucien
Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM
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| Posted: Tue Sep 16, 2008 7:54 am Post subject: Re: Kolb List Re: fuel line |
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| pj.ladd(at)btinternet.com wrote: | I am fascinated by all the discussion about fitting an extra fuel pump.
Has anyone actually checked to see what percentage of fuel pumps have failed. It seems to me, ignorant as I am, that all the complications of setting up a back up pump merely increase the risk of something going wrong.
What about doubling up on the control cables? If they part you really do have trouble. Whatever happened to simple, slow, cheap flying..
puzzled
Pat
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From most field experience with the Rotax motors that I'm aware of, fuel pump failures are very rare compared to other things that tend to go wrong. Even the pneumatic pumps for the 2-strokes very rarely give problems.
I've never felt the need for a backup electric pump in any of my planes because of this. I try to keep the system as simple as possible so that the backup pump isn't needed for fuel flow reasons.
My experience with engine trouble and engine outs is generally that you don't want to try to debug a quit or sagging engine in the air anyway. I muchly prefer to get the plane on the ground first and ignore that until I'm down. By the time I could diagnose that it was actually the fuel pump that's bad the prop would likely be already stopped anyway and continued fiddling would only hinder my chances at a good emergency out-landing.
That's just what works for me and I'm not suggesting that for anyone else. I just don't like long checklists when trouble with the fan starts; at that point I'd rather make the landing field choice and start setting up the approach rather than going through some long procedure.
The engine out I had in my trike was the very best lesson on this for me that I ever had in my flying career.
So, MHO is that the addition of the backup electric pump where it's not needed for fuel flow reasons isn't worth the extra complexity, wiring etc. that it adds, due to the very low chances it'd ever be needed with the Rotax pumps.
Again only MHO and not a suggestion for others,
LS
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LS
Titan II SS |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Sep 16, 2008 8:23 am Post subject: Kolb List Re: fuel line |
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> So, MHO is that the addition of the backup electric pump where it's not
needed for fuel flow reasons isn't worth the extra complexity, wiring etc.
that it adds, due to the very low chances it'd ever be needed with the Rotax
pumps.
| Quote: |
Again only MHO and not a suggestion for others,
LS
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Lucien:
Boost pump doesn't really increase complexity of the system; a Facet pump, a
little wire, and a switch. I put the boost pump in line.
All the aircraft I have flown prior to getting into ultralights had boost
pumps. It is automatic for me to flip the switch if I have an engine
problem. Flipping the boost pump switch to the on position, or doing
nothing if the switch is already on during take offs, landings, and low
level flying.
In addition to filling the float bowl prior to engine start, (eliminates the
primer bulb), it is a little insurance to keep you going should your main
engine pump fail.
That's why I use mine...
john h'
mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Tue Sep 16, 2008 9:11 am Post subject: Kolb List Re: fuel line |
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At 08:39 AM 9/16/2008, william sullivan wrote:
| Quote: | On my 447 I had clear fuel line- Tygon- and a clear fuel filter. I
also questioned the bubbles in the line, and air in the filter. I had
tried bleeding the system, but always ended up with a visible flow of
bubbles. No apparent leaks or loose clamps. John H. advised ignoring
it, and it didn't seen to affect engine rpm. Possibly it was cavitation,
as the pulse pump was quite close to the engine, and the "lift" was over
a foot. Dana's last comment was that a pulse pump (Mikuni) could only be
located a limited distance away from the engine. How far can it be
located from the engine? Mine was bolted near the base of the engine,
and it was very close to being hit by the aileron control horn when folded.
|
The Cuyuna manual says the pulse line should be 6 inches long or
less. Also the pump should always be located above the pulse line
connection on the crankcase, so that any fluid that gets into the pulse
line can drain back down into the engine.
There's always a bit of air visible in my clear glass fuel filter. When I
start the engine, some bubbles move through the fuel line toward the pump,
and a few more when I first go to full throttle. However, I never see them
downstream of the pump, which is why I'm fairly certain they're minor
cavitation, or dissolved air coming out of solution. The time I had the
blockage in the [now removed] primer bulb, there were bubbles downstream of
the pump as well, indicating that there _was_ a leak.
-Dana
--
Resist militant "normality" -- A mind is a terrible thing to erase.
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Tue Sep 16, 2008 9:21 am Post subject: Kolb List Re: fuel line |
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At 10:17 AM 9/16/2008, pj.ladd wrote:
| Quote: | I am fascinated by all the discussion about fitting an extra fuel pump.
Has anyone actually checked to see what percentage of fuel pumps have failed. It seems to me, ignorant as I am, that all the complications of setting up a back up pump merely increase the risk of something going wrong.
What about doubling up on the control cables? If they part you really do have trouble. Whatever happened to simple, slow, cheap flying.. |
The previous owner of my plane had an engine failure on his very first solo flight when a new (but sitting on the shelf for several years) Mikuni pump failed... the diaphragm was shot. (He got it down on the airport with only a broken landing gear). I'll simply replace or rebuild the pump every winter... it's cheap insurance.
I also installed a fuel pressure gauge, not because I really need it, but because I had it laying around. The pressure is pretty constant, so if I see it drop I'll know it's time to poke around a bit.
I'd be a lot less worried about control cables which are far stronger than they need to be, and which I can see during my preflight, than I am about hidden rubber flaps and diaphragm vibrating madly inside a fuel pump.
-Dana
--
Resist militant "normality" -- A mind is a terrible thing to erase. [quote][b]
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Sep 16, 2008 10:25 am Post subject: Kolb List Re: fuel line |
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Dana:
How does the little mikuni pump do, pressure-wise?
Will is maintain 3 to 5 psi?
Just curious.
How do you inspect your control cables?
Can't remember for sure, but do no think there are any fairleads on the US. I have some on my mkIII, and can not remember if there were any on the original Firestar. Normal aging process..............
john h
mkIII - With fresh Shell Rotella T Full Synthetic 5W40 diesel oil and a Fram TG3614. Good for another 25 to 50 hours.
[quote] I also installed a fuel pressure gauge, not because I really need it, but because I had it laying around. The pressure is pretty constant, so if I see it drop I'll know it's time to poke around a bit.
I'd be a lot less worried about control cables which are far stronger than they need to be, and which I can see during my preflight, than I am about hidden rubber flaps and diaphragm vibrating madly inside a fuel pump.
-Dana
[b]
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Tue Sep 16, 2008 2:30 pm Post subject: Kolb List Re: fuel line |
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At 02:25 PM 9/16/2008, John Hauck wrote:
| Quote: | Dana:
How does the little mikuni pump do, pressure-wise?
Will is maintain 3 to 5 psi? |
3-4 psi, a bit less at idle. Another good check (of the pump check valves as well as the float needle) is that it holds pressure for awhile after shutting down the engine.
| Quote: | How do you inspect your control cables?
Can't remember for sure, but do no think there are any fairleads on the US... |
Just a visual check, with particular attention to where they go around the pulleys, the most likely point of failure, and look for any signs of slippage at the nicopress swages (highly unlikely if they were done correctly and survived this long). Security of clevis and cotter pins and turnbuckle wiring, and any unusual feel or noise when the controls are moved. No, no fairleads... the nice thing about the US is that everything is out in the open and visible; I even can (and do) peer down the inside of the boom tube before putting the gap seal on.
-Dana
--
What has four legs and an arm? A happy pit bull. [quote][b]
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Sep 16, 2008 4:27 pm Post subject: Kolb List Re: fuel line |
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Dana:
We used to have problems with the sides of the micarta pulleys wearing if they were a little out of alignment. Not a big problem, but something I liked to keep my eye on.\
john h
mkIII
[quote] Just a visual check, with particular attention to where they go around the pulleys,
-Dana
[b]
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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