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Fuel Systems

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b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Wed Jun 11, 2008 6:33 pm Post subject: Fuel Systems

Since 1995 I fly a plan built 701 with a R912 and kit built Z 950 amphib

floats. I have 490 hrs on wheel, skis, and floats. For my needs the 701 has

been a great aircraft, given me much pleasure, both while building and

flying. I made a number of modifications while building and over the years

added others, some cosmetic, others I consider essential for my particular

use and safety. A number of these were to the fuel system which has been the

subject of discussion on this list recently.



Originally I had the large collector/nose tank and two optional 22 litre

wing tanks feeding parallel lines in the engine compartment.The main line

fed through the engine pump, the emergency through an electric boost pump.

They had filters and met at a cross at the top rear of the engine to feed

the carbs. This was a popular and common configuration in the mid 90s.

Except for minor feed issues from the wing tanks this system worked well.

However, even with the battery at the extreme rear, the CofG was too far

forward making power-off landings challenging and with the addition of

floats dangerous. In addition I was not trilled with sharing the cockpit

with 30+ litres of fuel.Hence one of my first major mod was getting rid of

the nose tank and moving  the battery forward to the firewall. To feed all

the wing fuel safely I added  a collector to the back of the baggage

compartment.

The shape of the collector is important. First the tank only holds 8.5

litres and is high and narrow so when it starts to empty the two fuel level

warning switches at the top activate promptly to announce 30 minutes fuel

left. To enhance this feature the warning switches are located in a ridge

across the top. The bottom of the tank is conically shaped to form a

sump/gascolator connected to a drain on the bottom of the fuselage. The fuel

feed with a finger screen attached is 2"off the bottom to minimize picking

up debris/water. It uncover with about 1/2 litre remaining in the collector.

The front of the tank has the wing feed connection and a sight gage with a

black cork float to monitor the depletion of the last 8 litres available.

Finally the top ridge has one of the warning switches (the other is on the

right top side) and the connection for the vent which connects to the top of

the right wing tank. (I've attached a couple of photos of the tank and its

location).

Management is simple. Fuelling is done over the wing; I usually only use the

right tank. Additional ground checks are to start with the wing tanks OFF

and check the low fuel warning light operation. It comes ON in about 3-4

minutes after start. I then turn one wing tank ON and confirm it is feeding

(low fuel warning goes out) and visually check the collector is full before

T.O. In smooth flight the low level warning activates pretty sharply when a

wing tank empties. In rough air it will start to flash 20 or so minutes

before it comes ON steady. In a steep descent while feeding a low wing tank

it will come ON  within 30 seconds indicating an interrupted feed.

This system has worked well for me and friends that have copied it. I am

confident flying down to a couple of litres (1/2Gal) if need be without

danger of interrupting the feed.

I'll tell you about a more recent mod to my fuel system due to the

increasing amount of Ethanol in our mogas here in the "land of the

freeze".I'll save that for my next post. Also att pic of my a/c 2006.

Smooth landings.

Carl

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kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Thu Jun 12, 2008 5:29 am Post subject: Re: Fuel Systems

Thank you  for the info and pics. This is similar to what I was thinking of. My version came from the Brazilian STOL site, but the added volume of your "fuselage ?"  tank with warnings and quasi gasolator is a better idea. A little known safety margin and added range, depending on size of tank, I was thinking 3 gallons and about 1/3 gallon left in sump when port to pump is uncovered.



Let me know but I think picture that I'm attaching is pretty close to what you have.



Kevin

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_________________
â€œAlways do what you are afraid to do.â€
R.W. Emerson (1803-1882)

"Real freedom is the sustained act of being an individual." WW - 2009

"Life is a good deal...it's worth it" Feb 1969
Dorothy McCune

b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Thu Jun 12, 2008 1:21 pm Post subject: Fuel Systems

Kevin,

Three gallons should be fine.

I make your wing fuel 160 litters, or about 10 hrs in cruise for the R912; I 

presume you are using a bigger engine?

Carl

---

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Thu Jun 12, 2008 6:16 pm Post subject: Re: Fuel Systems

No, sorry the drawing is from the Brazilian list and I guess that they had dual wing tanks sown as one! No, I was just asking if this basic layout is what you were describing? The drawing shows way too much fuel, unless your thinking about flying around the globe by yourself.

The 3 gallons was a safe weight wise, amount to increase the range a little and to give better low fuel warnings with the tank.



Kevin

b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Thu Jun 12, 2008 7:17 pm Post subject: Fuel Systems

Kevin

It was a lot of fuel for a 701, an ocean crossing did come to mind. 

Everything looks fine and very close to my set-up. Transport Canada 

recommends 3/8" fuel lines as minimum, they claim 1/4" is too easy to block 

especially in winter.

do not archive

Carl

---

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Thu Jun 12, 2008 10:13 pm Post subject: Re: Fuel Systems

Carl,

       A few weeks ago I looked at adding tall cylinder style header tanks to the baggage area on each side, where my fuel lines currently run down to my fuel selector located on the seat backrest between the seats.



Possibility for safety and ease of construction was to use irrigation tubing 5" dia. and with the top end plate and bottom end plate set at a suitable angle 15 - 30 degs. with an intake pipe and outlet pipe welded in at the apex of each end. This to take care of the need to have as little air pocket / water trap as possible and not require separate vents.



with height restricted to around 10" and this type of tubing I would get around 4.5 litres each side, this should alleviate the occasional unported low fuel wing tank situation I have experienced when doing steep descents or uncoordinated turns. It does get your attention!



I haven't gone ahead with this mod yet, is there a perceived problem with not providing separate venting, as my plan was to avoid the fuel lines changing direction, should be going down all the way from tanks to the gascolator aft and below the seat level thence upwards towards the carb? This is how I was told a fuel system should be, no siphon / airlock traps.



Regards, Ralph

_________________
Ralph - CH701 / 2200a

dougsnash

Joined: 14 Apr 2008
Posts: 281

Posted: Fri Jun 13, 2008 2:48 am Post subject: Fuel Systems

Kevin, is this fuel system design from the guy who ran

afoul with Transport Canada a few years ago while

trying to fly around the world in a 701 rip off?  



Seems to me that he couldn't get approval to take off

from Newfoundland with full fuel or some such thing. 

Took off anyway, had to return for weather or a minor

mechanical issue (can't rememberexactly) and then

crashed on landing because he was so overweight due to

all of the fuel.  Seems to me that he got hit with ten

plus thousand dollars in fines.  



Sad end to an interesting sounding adventure.



Doug MacDonald

NW Ontario

--- kmccune <kmccune(at)somtel.net> wrote:



 	  Quote: 	
		   

 <kmccune(at)somtel.net>

 

 No, sorry the drawing is from the Brazilian list and

 I guess that they had dual wing tanks sown as one!

 No, I was just asking if this basic layout is what

 you were describing? The drawing shows way too much

 fuel, unless your thinking about flying around the

 globe by yourself.

 The 3 gallons was a safe weight wise, amount to

 increase the range a little and to give better low

 fuel warnings with the tank.

 

 Kevin

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Fri Jun 13, 2008 2:48 am Post subject: Re: Fuel Systems

My next problem is figuring out the fuel return from the pump. As long as the   

small collector tank is vented back to the wing tanks, I think I can return to the collector tank.  The 3/8" lines do make more sense and they would flow more readily too.



Actually back to reality now, my next problem is getting more material, And reinforcing my brake! I need to get something to hang all this fuel stuff in first!



Thanks again



Kevin

b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Fri Jun 13, 2008 6:46 am Post subject: Fuel Systems

Ralf

Your design is interesting. I have a couple of questions.

    1. If air is sucked into your columns how will it escape and let feed 

resume? I see only two ways, to the engine or fight its way back through the 

fuel stream from the tanks. Either may cause fuel starvation.

    2. If air gets trapped in your columns/lines (air lock) how will you 

detect the problem in time to prevent fuel starvation?



 I strongly recommend collector tanks be vented to prevent airlocks and aid 

feeding, and fitted with reliable sensor(s) to alert the pilot when he is 

running low on fuel or feed is interrupted.

A final comment. I am not sure what irrigation pipe is made of. I made my 

collector out of .063 alum. so it could take knocks in case of an accident. 

Maybe overkill, .040 probably would suffice and save weight.

Hope this helps

Carl

Original Message ----- 

From: "jetboy" <sanson.r(at)xtra.co.nz>

To: <zenith701801-list(at)matronics.com>

Sent: Friday, June 13, 2008 2:13 AM

Subject: Re: Fuel Systems

 	  Quote: 	
		   



 Carl,

       A few weeks ago I looked at adding tall cylinder style header tanks 

 to the baggage area on each side, where my fuel lines currently run down 

 to my fuel selector located on the seat backrest between the seats.



 Possibility for safety and ease of construction was to use irrigation 

 tubing 5" dia. and with the top end plate and bottom end plate set at a 

 suitable angle 15 - 30 degs. with an intake pipe and outlet pipe welded in 

 at the apex of each end. This to take care of the need to have as little 

 air pocket / water trap as possible and not require separate vents.



 with height restricted to around 10" and this type of tubing I would get 

 around 4.5 litres each side, this should alleviate the occasional unported 

 low fuel wing tank situation I have experienced when doing steep descents 

 or uncoordinated turns. It does get your attention!



 I haven't gone ahead with this mod yet, is there a perceived problem with 

 not providing separate venting, as my plan was to avoid the fuel lines 

 changing direction, should be going down all the way from tanks to the 

 gascolator aft and below the seat level thence upwards towards the carb? 

 This is how I was told a fuel system should be, no siphon / airlock traps.



 Regards, Ralph



 --------

 Ralph - CH701 / 2200a





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=187698#187698

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jun 13, 2008 8:59 am Post subject: Re: Fuel Systems

Go to www.summitracing.com and look at fuel cells, they have a bunch

that would be suitable for use as header tanks at reasonable prices. They

range from 2 quarts to 30+ gallons. They have fittings, and mounting tabs 

all ready to go.



Header tanks typically vent to one of the fuel tanks.



Fuel injection return lines to the header require a check valve so don't

forget that item. 



As follows:



[fuel tank]---->[header]---(fuel shutoff)----->Engine driven pump feed

[fuel tank]---->[header]---<check valve<----<Engine driven pump return

[tank ret.]<-----[header vent]



Good idea to put strainers in the tank lines to the header, and shutoff

valves from each tank.

Jeff

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Fri Jun 13, 2008 1:12 pm Post subject: Re: Fuel Systems

I don't know if it is or not, but 40 gallons is the approximate fuel capacity with the optional 2nd wing tanks so I assumed the guy for simplicity just drew one tank knowing the the pairs had to be plumbed together. That was the reason for my comment about flying around the globe by yourself. By the time you put a couple clean pairs of underwear and a cooler of evening refreshments  in the back, your about over weight. 

But for myself, from time to time I would like to be able to slightly extend the range safely.  I like the idea of knowing that when you hit empty you have a little more, but just don't depend on it. It also like said will help the potential fuel starvation problem and it seems to me that it would help the wing tanks empty more evenly? 



Kevin

 	  dougsnash wrote: 	
		  Kevin, is this fuel system design from the guy who ran

afoul with Transport Canada a few years ago while

trying to fly around the world in a 701 rip off?  



Seems to me that he couldn't get approval to take off

from Newfoundland with full fuel or some such thing. 

Took off anyway, had to return for weather or a minor

mechanical issue (can't rememberexactly) and then

crashed on landing because he was so overweight due to

all of the fuel.  Seems to me that he got hit with ten

plus thousand dollars in fines.  



Sad end to an interesting sounding adventure.



Doug MacDonald

NW Ontario

--- kmccune <kmccune> wrote:



 	  Quote: 	
		   

 <kmccune>

 

 No, sorry the drawing is from the Brazilian list and

 I guess that they had dual wing tanks sown as one!

 No, I was just asking if this basic layout is what

 you were describing? The drawing shows way too much

 fuel, unless your thinking about flying around the

 globe by yourself.

 The 3 gallons was a safe weight wise, amount to

 increase the range a little and to give better low

 fuel warnings with the tank.

 

 Kevin

ch701builder

Joined: 07 Feb 2006
Posts: 119
Location: N38.9947,W105.1305,ALT. 9,100'

Posted: Fri Jun 13, 2008 1:55 pm Post subject: Fuel Systems

There is a guy flying here in Colorado, that has both the 10-gallon tanks and the header tank (I think the original 9-gallon?). The header gets filled from both wing-tanks. I have thought about this idea, but use a smaller (2-3 gallon) header tank.  (more room  for electronics)

 

 I'm not understanding his fuel level warning, is it just a probe that detects if it is emersed in fuel or not?

 

 The extra 120+ lbs does cut down on your payload, but if I were to fly using the extended fuel (extra wing tanks) , I would be by myself also. I would rather have the tanks and not use them instead of needing them and not having them.

 

 My 2 cents (0.00518 gallons worth)

 Keith

 ************************************************************************************************

 

 

 kmccune wrote:

  	  Quote: 	
		    	  Quote: 	
		  --> Zenith701801-List message posted by: "kmccune" <kmccune(at)somtel.net> (kmccune(at)somtel.net)



I don't know if it is or not, but 40 gallons is the approximate fuel capacity with the optional 2nd wing tanks so I assumed the guy for simplicity just drew one tank knowing the the pairs had to be plumbed together. That was the reason for my comment about flying around the globe by yourself. By the time you put a couple clean pairs of underwear and a cooler of evening refreshments  in the back, your about over weight. 

But for myself, from time to time I would like to be able to slightly extend the range safely.  I like the idea of knowing that when you hit empty you have a little more, but just don't depend on it. It also like said will help the potential fuel starvation problem and it seems to me that it would help the wing tanks empty more evenly? 



Kevin



dougsnash wrote:

    	  Quote: 	
		  Kevin, is this fuel system design from the guy who ran

afoul with Transport Canada a few years ago while

trying to fly around the world in a 701 rip off?  



Seems to me that he couldn't get approval to take off

from Newfoundland with full fuel or some such thing. 

Took off anyway, had to return for weather or a minor

mechanical issue (can't rememberexactly) and then

crashed on landing because he was so overweight due to

all of the fuel.  Seems to me that he got hit with ten

plus thousand dollars in fines.  



Sad end to an interesting sounding adventure.



Doug MacDonald

NW Ontario

--- kmccune  wrote:

      	  Quote: 	
		   

 

 

 No, sorry the drawing is from the Brazilian list and

 I guess that they had dual wing tanks sown as one!

 No, I was just asking if this basic layout is what

 you were describing? The drawing shows way too much

 fuel, unless your thinking about flying around the

 globe by yourself.

 The 3 gallons was a safe weight wise, amount to

 increase the range a little and to give better low

 fuel warnings with the tank.

 

 Kevin

      	
 	
 



--------

Mark Twain: Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=187785#187785



ics.com/Navigator?Zenith701801-List">http://www.matronics.com/Navigator?Zenith701801-List

ronics.com">http://forums.matronics.com

ics.com/contribution">http://www.matronics.com/contribution





  	
 	
 

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************************************* 

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ITT Industries 

Advanced Engineering & Sciences 

5009 Centennial Blvd. 

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                      80919 

(719) 599-1787 -- work 

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keith.ashcraft(at)itt.com (keith.ashcraft(at)itt.com) 

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jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Fri Jun 13, 2008 2:08 pm Post subject: Re: Fuel Systems

Carl,



      Irrigation pipe is 1/16" wall for the thinnest grade.



If air goes down to the columns it should also bubble back up into the wing tanks where it came when further fuel sloshes down. This is no different to when you drain the gascolator (another cylinder type tank) and later replenish the fuel tanks above. I dont see any gascolators, Zenair type or GA type, that have a vent line running up above the tanks. The columns are effectively an inline expansion of the diameter of a piece of vertically run fuel line. In fact my original idea was to construct a much taller Zenair gascolator that runs from a level in the baggage shelf below the fuel line entry, all the way to the fuselage floor. 

If air is in the columns there is no fuel above so they will run till exhaustion but the fuel supply will be continuous for that time rather than the on/off sloshing of 5 litres in the tank trying to find the one outlet in the rear inboard corner.



Open to reasoning if this is not a viable method, adding vent lines for me would add more fuel lines in the cabin and require opening up the wings and tanks, If I were to do that I'd rather add the extra pair of longrange tanks instead. Further, if my aircraft was constructed to plans there would be no fuel selector ahead of the dual inlet gascolator/tee and therefore the ability to unport a tank and get starvation would not be a feature. I like using the Andair left/right/both/off selector because it lets me park on uneven ground and manage the balance.



Ralph



[quote="b.carl(at)sympatico.ca"]Ralf

Your design is interesting. I have a couple of questions.

    1. If air is sucked into your columns how will it escape and let feed 

resume? I see only two ways, to the engine or fight its way back through the 

fuel stream from the tanks. Either may cause fuel starvation.

    2. If air gets trapped in your columns/lines (air lock) how will you 

detect the problem in time to prevent fuel starvation?



 I strongly recommend collector tanks be vented to prevent airlocks and aid 

feeding, and fitted with reliable sensor(s) to alert the pilot when he is 

running low on fuel or feed is interrupted.

A final comment. I am not sure what irrigation pipe is made of. I made my

_________________
Ralph - CH701 / 2200a

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Fri Jun 13, 2008 4:08 pm Post subject: Re: Fuel Systems

My reason for not wanting the extra wing tanks is the extra wiring, plumbing, panel space and weight, even empty they weigh something. With the G13 or BMW engine the flying hours are quite a few more per tank due to lower fuel burn. How much more, time will tell and so will I when I find out. But until then its all BS

(baloney sausage, of course   )  



Kevin

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Fri Jun 13, 2008 4:35 pm Post subject: Re: Fuel Systems

This is a pic of a highlander sub-tank. It  has two inputs from the wing tanks on top and one on the bottom. There is no vent to the wing tanks. But it is a carburated engine so the pump is not returning fuel to the tank all the time.



Kevin

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b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Fri Jun 13, 2008 8:09 pm Post subject: Fuel Systems

Ralf

Try it without. Make sure your feeds are down hill all the way and you may 

want to use bigger than 1/4" lines to aid air moving up through the fuel. If 

you have feed issues you don't have to vent to a tank you can vent to 

atmosphere.

Do not archive

Carl

---

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Mon Jun 16, 2008 5:43 am Post subject: Re: Fuel Systems

In general you should vent the header to a tank, if you don't and you

get a pressure differential across the vents between the tank and the

header,  you can end up feeding fuel out the lower pressure vent.

This is not very likely, but it is possible. Also if you don't vent the 

header you can develop an enormous bubble in the header which

simply will not go away so you definitely should vent the header.



Jeff

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