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Fuel starvation on long down lines?

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Fuel starvation on long down lines?

Old 02-06-2009, 01:35 PM
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Default Fuel starvation on long down lines?

Can anyone help me with a solution to stop fuel starvation on long/extended down lines when the fuel tank is less than full? When the tank is less than full and in a nose down line position then the fuel pickup becomes uncovered. I have considered a smaller headder tank between the main fuel tank and the carb, is there another suggested method?

Using DA-50
Old 02-06-2009, 05:46 PM
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Default RE: Fuel starvation on long down lines?

so is the motor dead sticking on you on down lines?
Old 02-06-2009, 11:18 PM
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Default RE: Fuel starvation on long down lines?

Cut the throttle back.
Old 02-07-2009, 01:12 AM
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Default RE: Fuel starvation on long down lines?

80stars
Make sure of the following

Inlet fuel line is the same size as exit fuel line - meaning keep the ID of the fuel line the same a DA50R uses 3MM or 1/8 ID tubing.
Make sure you don’t have excessive fuel pickup line length - a DA 50R can draw fuel reliable over 11" but after that you might get weird problems
Make sure you double filter your fuel - You didn’t say what surface you fly off of. Grass fields cause more problems with fuel screens on gas engines than anything.
Make sure your fuel tank level is pretty even with the center line of the engine or you might create fuel siphon or draw problems. On start up does it take
allot of choke to get going. Do you find the fuel all the way to the carb, and then sit static for a few minutes and the line is clear. The fuel siphons back into
the tank. If so you might want to change the height of your tank in proportion to the carb center line.
I know this sounds silly but make sure your fuel is fresh. I know guys have these big 2 gallon Jersey or Abell fuel tanks and fuel can go stale and cause weird problems.
If you don’t fly allot and fuel sits in them try some octane booster just in case.
Recently I changed my style of tanks from Dubro and Great Planes to B&B Specialties. I build my tanks the way 3W recomends with Neoprene at both ends and a brass
tube center. This is very flexible and keeps the heavy Walbro or Tilloston felt clunk from falling forward. If you have not tried this you might see what you think.

I know we had quite a few DA50's in the club and they pretty much were a rock solid motor. But every once in a while some weird no start problem or motor out problem would creep up. Easily solved. Lately I have been flying a 3mm TOC 53 in a composite extra 330L and we have TRIED to kill this motor in the air with maneuvers and inverted waterfalls and anything else we can think of to fuel starve the motor and so far it runs like a champ. Don’t know what 3MM did but that motor sure runs great.


Good Luck

JDS

Old 02-07-2009, 06:04 PM
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Default RE: Fuel starvation on long down lines?


Doug,

You should be at idle on most down lines (very little throttle) and really not using Gas. Usually the amount of Gas in the line and Carb is enough to get you through the down-line and into your next maneuver. Maybe give us other details.
Old 02-07-2009, 09:31 PM
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Default RE: Fuel starvation on long down lines?

Sorry everyone, my post was a little mis-leading.

I have not had a flame out on an extended down line. I was going through my fuel lines and tank today because my last flight of the season (November) endend in a dead stick after an extended inverted flat spin. When I took the tank apart I found the culprit right away, the fuel line (tygon) to the clunk was all stiff and extended out horizontal. This by the way was after only 2 months of flying.

As I plumbed up the tank and clunk, the question about fuel starvation on a down line came to mind which generated this post. It sounds like gassers/pump and ignition eliminate this issue. Any thoughts about the ethanol blended in our fuel here in MN hardening the fuel lines???
Old 02-07-2009, 10:43 PM
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Default RE: Fuel starvation on long down lines?

80,
Glad you found the problem, I hate motor problems on my gas aerobats. Dead sticks are no fun out of a hover 50 feet off the ground. Especially in Texas where the wind blows all the time.

I asked a friend that drag races NHRA cars about ethanol in the gas. He said when you get outside the city limits they don’t sell that much blended gasoline, only in the city. I noticed that the local Exxon, Shell and Kroger Food Store stations all advertize that the gas you buy can be up to 10 % ethanol blended fuel. I was more worried about my ford F100 pickup than I was about my planes. I ran premium a few times and dumped in a couple cans of Berryman's in the tank and so far so good.

I too had my clunk fall off the hardened line (Dubro Yellow Tygon fuel line) after talking to Reza over at the QQ Aircraft thread he convinced me:

A. Don’t completely defuel the tank always leave a little in the bottom.
B. Switch to Aero Trend Blue line.

To make a long story short we could not get the blue line at that time, so I decide to get rid of all my Dubro tanks and switch over to B&B Specialties tanks and rebuild them with Hayes Products Medium Neoprene hose and the brass tubing with the little solder on barbs. So far this works much better that the fuel stopper tanks and they are easier to rebuild and maintenance. The lines in the tank stay pliable and don’t get hard the felt clunk catches allot of trash before it gets to my motor. Screens stay clean longer and restart after a long gap in flying are not the trouble they used to be.


Hope this helps
jds



Old 02-09-2009, 09:59 AM
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Default RE: Fuel starvation on long down lines?


ORIGINAL: cap10b

80,
Glad you found the problem, I hate motor problems on my gas aerobats. Dead sticks are no fun out of a hover 50 feet off the ground. Especially in Texas where the wind blows all the time.

I asked a friend that drag races NHRA cars about ethanol in the gas. He said when you get outside the city limits they don’t sell that much blended gasoline, only in the city. I noticed that the local Exxon, Shell and Kroger Food Store stations all advertize that the gas you buy can be up to 10 % ethanol blended fuel. I was more worried about my ford F100 pickup than I was about my planes. I ran premium a few times and dumped in a couple cans of Berryman's in the tank and so far so good.

I too had my clunk fall off the hardened line (Dubro Yellow Tygon fuel line) after talking to Reza over at the QQ Aircraft thread he convinced me:

A. Don’t completely defuel the tank always leave a little in the bottom.
B. Switch to Aero Trend Blue line.

To make a long story short we could not get the blue line at that time, so I decide to get rid of all my Dubro tanks and switch over to B&B Specialties tanks and rebuild them with Hayes Products Medium Neoprene hose and the brass tubing with the little solder on barbs. So far this works much better that the fuel stopper tanks and they are easier to rebuild and maintenance. The lines in the tank stay pliable and don’t get hard the felt clunk catches allot of trash before it gets to my motor. Screens stay clean longer and restart after a long gap in flying are not the trouble they used to be.


Hope this helps
jds



Great info, thank you!!

I threw a similar post out on the gas forum and was told Viton line works even better than neopene, I haven't checked yet maybe that is what blue line is.
Old 02-09-2009, 10:08 AM
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Default RE: Fuel starvation on long down lines?





[/quote]

I was told Viton line works even better than neopene, I haven't checked yet maybe that is what blue line is.
[/quote]

Doug,

You can get the Viton through McMaster Carr, it works great and no brass insert needed. Get the same size as the tygon 1/4" OD X 1/8" ID
After one season, the line still looks good and is flexible.
Old 02-09-2009, 10:26 AM
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Default RE: Fuel starvation on long down lines?

ORIGINAL: 80stars

Can anyone help me with a solution to stop fuel starvation on long/extended down lines when the fuel tank is less than full? When the tank is less than full and in a nose down line position then the fuel pickup becomes uncovered. I have considered a smaller headder tank between the main fuel tank and the carb, is there another suggested method?

Using DA-50
Have you checked the filter screen in the carb? I have seen these over time build up trash in the small screen in the carb and then your engine will start acting strange and most guys start playing with the needle jets and then everything goes down hill from there. Take the four screws off the side of the carb that has the casting not the steal plate side where the diaphram is. Seperate the haves slowly as not to tear the gaskit. You will see a small round screen down in a small recesed area where the fuel line nipple comes into the carb. Use a small soft brush and clean the crap off it. It will have some junk on it no matter how many filters you have. Put it back togather and do not over thighten the four screws. I have have seen this many times and it allways seems to fix the problem if everything else is right.

I see you have found the problem. As a good practece I allways pull my tanks every year and put in all new fuel line. This may sound like over kill but you will never have a problem by changing out the fuel line every year. I use the XL Tygon on all my 40% birds and just buy the complete 50' roll. The felt clunks are the way to go for sure.

Old 02-09-2009, 10:40 AM
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Default RE: Fuel starvation on long down lines?

All,
Viton is a trade name for Florocarbon rubber. its used in Aircraft fuel systems where the temperature is low. So dont be laying your fuel line on your hot cylinder head.
Viton has excellent properties for Ethanol fuels (hence the fuel system in the truck probably has Viton seals and is not affected by ethanol.)

Viton is good for compression (hence the no need for barbs) in the turbine compression set fuel and oil tubes on various turbo prop engines
ala PT-6 and TPE 331.

Sounds good to me.

I got some other stuff I need from McMaster (hour Meter)

JDS



Old 02-19-2009, 05:41 AM
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Default RE: Fuel starvation on long down lines?


You did not mention if you bump up your throttle (move idle trim up 3 or 4 clicks) just before take-off or soon after.
I was taught to do that, and in the beginning of my Gas Flying, when I forgot to bump up, I'd end up with a dead stick.
When I build or rebuild a Gas Tank, I use at least on zip tie on the ends of the fuel lines. On the tank brass tubing inside
and out, I will use two, wheras, when the fuel line is over a nipple, I just use one. I have the Abell fuel Can. Filter in the
pick up line in the Can, Filter on top of the can and a filter between the tee fitting and the carb. I experience very little
fuel problems.

Gerald
Old 02-20-2009, 03:45 PM
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Default RE: Fuel starvation on long down lines?


ORIGINAL: Rockyaged


You did not mention if you bump up your throttle (move idle trim up 3 or 4 clicks) just before take-off or soon after.
I was taught to do that, and in the beginning of my Gas Flying, when I forgot to bump up, I'd end up with a dead stick.
When I build or rebuild a Gas Tank, I use at least on zip tie on the ends of the fuel lines. On the tank brass tubing inside
and out, I will use two, wheras, when the fuel line is over a nipple, I just use one. I have the Abell fuel Can. Filter in the
pick up line in the Can, Filter on top of the can and a filter between the tee fitting and the carb. I experience very little
fuel problems.

Gerald
Thanks Gerald, I do add a few clicks of throttle up trim after take off, I wish my transmitter had a throttle up feature (7CAP).

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