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Fuel system with 4 tanks?!

Started by Rais, March 28, 2024, 07:32:17 AM

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Rais

Colleagues, I am the owner of Helio H-395, originally this plane had two tanks. But the previous owner bought fenders with 4 tanks and installed them. Now my Helio has four tanks. But they were not connected correctly. Now I have them combined in two tanks - the external tanks are combined with each other and the internal tanks are combined with each other. A selector with three positions is responsible for selecting the tank - internal, external and off. Thus, I can fly either on internal tanks or on external tanks. This is bad, because gasoline is constantly pouring from the tanks on the left wing and they overflow.(
I want to return it to the original design. In the Manual I found two diagrams for connecting four tanks. Tell me which scheme is preferable?!

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Rais

There is also this diagram:
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Louis

What is a fenders ?

Some remarks:  A four tank wings doesn't have the same spar.  The pickup is longer.  Hope it was changed when the mods was made. 

The first two drawing looks like the military version.  They were converted to the third drawing once for civil use.  For civil 295 with four tanks , 700 and 800

Rais

Quote from: Louis on April 01, 2024, 06:18:44 PMWhat is a fenders ?


Some remarks:  A four tank wings doesn't have the same spar.  The pickup is longer.  Hope it was changed when the mods was made. 

The first two drawing looks like the military version.  They were converted to the third drawing once for civil use.  For civil 295 with four tanks , 700 and 800

Thank you for your responses. I speak English poorly and use Google translator.

What is a fenders ? - I wrote about wings with 4 fuel tanks.

Some remarks:  A four tank wings doesn't have the same spar.  The pickup is longer. - What do you have in mind?! I cannot accurately translate this phrase.

I don't know who installed the wings with 4 fuel tanks. And how he did it.

What to do to check that everything is ok.

Thank you very much!




Louis

Ok, the previous owner had installed four tank wings.  As opposed to install an additional tank to a one tanks wing.  This is good news.  I got it wrong at the first reading, thinking he might had converted a one tank wing to two tanks.  Wich is a process that involves strengthening the spar if you want to make it as good as a factory two tank wing.  Mainly it ask to drill and remove the part near the fuselage.  I have never really believed that it can be done safely.  Drilling  some holes into a spar.  And as we know, we don't have a strut in a Helio.  The strenght of the spar is like something very important.  So i am happy that your Helio had it's wing swapped for factory made four tanks wings.  Swapping wings is something that does not involved any work that could have remove some strenght from the wing.  Good news !!

Louis

Now the selector.   You mentioned a three position selector valve.  Exterior, interior , and off.  Wich seems to look like the schematic A, B, B3.   As you can see on that schematic, there is no way fuel from external tank can transfer into the other tanks if the selector is OFF. 

When do you see that transfer that result is some fuel going out as an overflow ?  On the ground ?  In the air ? External tanks only ?

Because i am not familiar with schematic ABB3.  But i see there is a valve called interconnect emergency shutoff valve.  That does whatever between the two inside tanks.  And that there is no connection between the two outside tanks ( except by the feed to engine tubing )

There is some reason that they changed to electric pump between the outside pumping to the inside tank.  But if there is a way to keep it without a transfer pump, i would surely choose it.  Even if it does involved a better understanding from the pilot to manage fuel transfer between all the four tank.  Post a picture of those valve, including the emergency one.  Post also a picture of the top vent so we can determine which schematic you might have, even if it was changed partially when the wings were swapped.


Rais

Thank you very much for your answers. Yes, wings from another aircraft with 4 tanks were installed. But the tanks were not connected to each other correctly. The external tanks - right and left - were combined with each other, and the internal ones were connected to each other. Selector for two positions - external tanks and internal tanks. Now I want to make a standard diagram. I like the third scheme with transfer pumps. It will be on my plane.) Now I'm choosing fuel pumps and check valves. I like these pumps: https://www.aircraftspruce.com/catalog/eppages/facetgoldflo.php
But I can't find check valves for them.

Louis

I have that kind of pumps on my Helio 4 tank.  They do have internal check valve inside the pump

Louis

Louis

#8
How will you arrange the necessary fuel vent ?

On the pump equipped 4 tanks, the original Helio had an underwing fuel vent for each of the external tanks.  Don't know why they didn't put it on top of the wing.  When the flaps are deployed, fuel is coming out the underwing tanks.  Not really a problem.  But wonder why they didn't put it on top.  On the external tanks of the Pilatus, they did put a vented fuel cap.  Not sure how it works to keep the rain outside.  Looks like there is a spring to prevent rain water coming in, and not strong enough to prevent air under negative pressure.   

It will be interesting to see how you will arrange the external fuel vent