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Mike Hoffman
Joined: 11 Mar 2006
Posts: 54
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 Posted: Wed Jun 04, 2008 2:34 am Post subject: Fuel return line on a 912 ULS |
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I just received my Home Built Help DVD and noticed the 912 ULS engine comes plumbed for a return fuel line. I believe they said it is meant to help remove air from the fuel lines.
Is anyone currently at that stage and if so where did you put the return line? The DVD just mentions to feed it back into the supply line (back behind the seat?)
Mike H
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txpilot
Joined: 26 Feb 2007
Posts: 87
Location: Houston, TX
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| Posted: Wed Jun 04, 2008 6:41 am Post subject: Re: Fuel return line on a 912 ULS |
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I noticed the deal about the return line also. I talked with my EAA tech advisor and he said it's to prevent vapor lock. He also indicated vapor lock is not very common with 100LL fuel (which I intend on using exclusively), so I did not install a return line.
I once talked to Caleb at ZAC about it. He thought a return line wouldn't be necessary, but if I did install one he recommended drilling into the top of the gascolator and installing the return line there.
I'm thinking it might be a good idea if you're planning on running autogas. The ethanol they're putting in autogas may cause a vapor lock issue (although I'm probably talking outside of my expertise here).
Dan Ginty
N787DG
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flyingmike9
Joined: 09 Dec 2006
Posts: 33
Location: England
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| Posted: Wed Jun 04, 2008 9:22 am Post subject: Re: Fuel return line on a 912 ULS |
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here in the UK the return line has to be used i am building 601 xl and the fuel return line goes directly back to the left fuel tank
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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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| Posted: Wed Jun 04, 2008 9:42 am Post subject: Fuel return line on a 912 ULS |
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At 10:22 AM 6/4/2008 -0700, Mike wrote:
| Quote: | here in the UK the return line has to be used i am building 601 xl and
the fuel return line goes directly back to the left fuel tank
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I'm building a 601XL/Jab 3300 with fuel pumps in the wings, so my issues
are different. But, Clayton, my EAA tech counselor insists that a return
line is important and can really help with restarting the engine if vapor
lock happens. I cannot seem to understand his reasoning, but, Clayton is a
very experienced, smart guy, so I'll probably put it in. I was going to use
1/4" aluminum for the return line, and plumb it into the end of the gas
tank, probably using something like the Earl's AT985064 fitting, possibly
augmented with an Earl's Stat-O-Seal washer on the inside of the tank. The
fitting would be installed on the end of the tank using a wrench inserted
through the fuel gage hole. I'm a bit nervous about using a bulkhead
fitting on the sheet metal of the tank, but I don't want to try welding a
connection onto the tank. How are you connecting to the tank, Mike? In the
engine compartment, Clayton suggests putting a tee in the fuel line just
upstream of the carb with the return line connected to the branch,
preferably pointed upwards. Then he suggests filling the branch of the tee
with solder and drilling a smaller than #60 hole for air to return to the tank.
This approach probably goes way beyond the need for the 912ULS. I would
greatly appreciate comments on the need for the return line, and on the
implementation I've suggested.
Terry
Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons
are done; working on the wings
http://www.mykitlog.com/N47TP/
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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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txpilot
Joined: 26 Feb 2007
Posts: 87
Location: Houston, TX
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| Posted: Wed Jun 04, 2008 10:20 am Post subject: Re: Fuel return line on a 912 ULS |
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| Quote: | I'm building a 601XL/Jab 3300 with fuel pumps in the wings, so my issues
are different. But, Clayton, my EAA tech counselor insists that a return
line is important and can really help with restarting the engine if vapor
lock happens. I cannot seem to understand his reasoning, but, Clayton is a
very experienced, smart guy, so I'll probably put it in. I was going to use
1/4" aluminum for the return line, and plumb it into the end of the gas
tank, probably using something like the Earl's AT985064 fitting, possibly
augmented with an Earl's Stat-O-Seal washer on the inside of the tank. The
fitting would be installed on the end of the tank using a wrench inserted
through the fuel gage hole. I'm a bit nervous about using a bulkhead
fitting on the sheet metal of the tank, but I don't want to try welding a
connection onto the tank. How are you connecting to the tank, Mike? In the
engine compartment, Clayton suggests putting a tee in the fuel line just
upstream of the carb with the return line connected to the branch,
preferably pointed upwards. Then he suggests filling the branch of the tee
with solder and drilling a smaller than #60 hole for air to return to the tank.
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I'm curious if you're also installing a check valve. One of the issues I contemplated was in the case of an engine fire. If you shut off the main line, is there a possibility of fuel backflowing from the tank through the return line to the engine.
Dan
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Larry Hursh
Joined: 16 Feb 2008
Posts: 125
Location: Edwardsburg, MI (near Elkhart, IN)
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| Posted: Wed Jun 04, 2008 10:34 am Post subject: Fuel return line on a 912 ULS |
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| Quote: | | Quote: | This approach probably goes way beyond the need for the 912ULS. I would
greatly appreciate comments on the need for the return line, and on the
implementation I've suggested.
Terry Hi Terry,I've been flying a Tecnam Bravo with a 912 100 HP in it. It does have a mechanical fuel pump but also has an electric booster pump. We only turn it on during takeoffs and landings. The way the fuel system is routed in the aircraft, the boost pump takes fuel out of the right tank and if it's not being consumed, it is dumped into the left tank only (as the overflow). The pilot has to be careful to watch the fuel in the right tank so it doesn't go empty! |
01234567 |
[quote][b]
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_________________
Larry Hursh (N650LM Reserved)
"One rivet at a time......one day at a time.."
CH650 (Converted from CH601XL)
1/2 done with fuselage
will be Corvair Powered |
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cscsail(at)gmavt.net
Guest
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| Posted: Wed Jun 04, 2008 12:53 pm Post subject: Fuel return line on a 912 ULS |
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I think -- the fuel in the wing tanks has enough head pressure to bypass the mechanical pump and fill the carburetor bowls. At least that is what appeared to happen when I did my first test run of the engine (no wings attached) I put a 1 gal gas can on top of the fuselage. I drained fuel from both of my sumps and then cranked the engine and it came to life immediately. A couple of weeks ago when I moved the plane to the airport and assembled it, I put 5 gal of fuel in the right wing tank, the result was exactly the same. I believe any air that may developed in the system will be quickly vented out the top of the carburetor bowls.
701 912ULS 10hr. and having a great time
Gordon
---
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Mike Hoffman
Joined: 11 Mar 2006
Posts: 54
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| Posted: Thu Jun 05, 2008 2:13 am Post subject: Re: Fuel return line on a 912 ULS |
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Hi Terry and everyone that responded,
I am foo far along to pull a fuel tank and add a extra fitting to it. My original plan was to put a tee in one of the fuel lines, some where between one of the tanks and the gascolator. After reading everyone's remarks, I like the idea of drilling into the top of the gascolator and installing the return line there.
No, I do not have any check valve installed in my fuel lines and presently don't see a need for it.
Mike H
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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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| Posted: Thu Jun 05, 2008 6:26 am Post subject: Fuel return line on a 912 ULS |
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I hadn't thought of that, Dan, but that could be a concern. I'll have to
run that past Clayton. Thanks for the thought.
Off the top of my head, I think the risk would be minimal at least in a
normal A/C attitude, because the tank is at atmospheric pressure because it
is vented, the tank is pretty low in the system, and the <#60 orifice in
the tee would greatly restrict liquid flow.
I think I'm questioning the need for the return line because the boost pump
would pretty quickly push any air or vapor through the carb, and then the
motor would run again. Of course, if it stopped on takeoff, 200 ft above
the ground, the restart might be too late to do any good. Clayton is
supposed to visit (my 2 neighbor 601XL builders and) me on 6/14. I'll ask
him then and post any insight I get.
Terry
Terry
At 11:20 AM 6/4/2008 -0700, Dan wrote:
| Quote: | I'm curious if you're also installing a check valve. One of the issues I
contemplated was in the case of an engine fire. If you shut off the main
line, is there a possibility of fuel backflowing from the tank through the
return line to the engine.
Dan
> I'm building a 601XL/Jab 3300 with fuel pumps in the wings, so my issues
> are different. But, Clayton, my EAA tech counselor insists that a return
> line is important and can really help with restarting the engine if vapor
> lock happens. I cannot seem to understand his reasoning, but, Clayton is a
> very experienced, smart guy, so I'll probably put it in. I was going to
use
> 1/4" aluminum for the return line, and plumb it into the end of the gas
> tank, probably using something like the Earl's AT985064 fitting, possibly
> augmented with an Earl's Stat-O-Seal washer on the inside of the tank. The
> fitting would be installed on the end of the tank using a wrench inserted
> through the fuel gage hole. I'm a bit nervous about using a bulkhead
> fitting on the sheet metal of the tank, but I don't want to try welding a
> connection onto the tank. How are you connecting to the tank, Mike? In the
> engine compartment, Clayton suggests putting a tee in the fuel line just
> upstream of the carb with the return line connected to the branch,
> preferably pointed upwards. Then he suggests filling the branch of the tee
> with solder and drilling a smaller than #60 hole for air to return to
the tank.
>
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Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons
are done; working on the wings
http://www.mykitlog.com/N47TP/
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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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