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fuel system suggestions

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airvair601(at)yahoo.com
Guest

Posted: Sat Apr 14, 2007 7:49 am Post subject: fuel system suggestions

 	  Quote: 	
		  Ok guys I have a questions for the group about fuel systems that my <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />EAA technical advisor (TA) asked us.  First some background.  Our advisor has built and flown behind many aircraft.  He has restored several classic aircraft, is a retired airline captain and currently spends his

 days flying corporate and running an airport.  He is the kind of guy who has, or will, fly behind everything he suggests..  Our project is a Zenith 601 HDS that has 2 ten gallon leading edge wing tanks.  It currently calls for a plain vanilla corvair engine and an MA3 carb.  TA has

 warmed to the idea of Corvair, although he is not crazy about it.  He has helped people in the past with other auto-conversion and was helpful, EAA technical advisor (TA) asked us.  First some background.  Our 	
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gboothe5(at)comcast.net
Guest

Posted: Sat Apr 14, 2007 8:12 am Post subject: fuel system suggestions

Phill,  

   

I would never question the wisdom of a TA, but not all TA’s look at things the same. Yours suggests the wisdom of a complicated fuel delivery system which exceeds the design of the manufacturer. That’s your choice.   

   

There is a common feeling that simplicity is the best answer. The most simple fuel delivery is with a header tank, gravity feeding to the carb. The classic Taylorcraft BC12-D had two 6 gallon wing tanks that gravity fed into the 12 gallon header tank. When the header tank got low you open the valve and drain from a wing tank. When the header tank was full, you closed the valve.  

   

The 601 HDS is similar as it is designed to use either an 8 or 18 gallon header tank. The only difference, obviously, is that you need the fuel pumps to deliver to it. Most 601 drivers that have planes with header tanks feel that the header tank is the only insurance they need to get to a safe place if the fuel pumps fail. The key factor being:  Keep your header tank full.  

   

The MA3 carb likes gravity pressure best. This is described in length by William Wynne. I am hoping that you plan on using a header tank. Whatever means of delivering to that tank is up to you.  

     

Gary Boothe 

 Cool, CA 

 601 HDSTD, WW Conversion 90% done, 

 Tail done, wings done, working on c-section       

  

From: owner-zenith-list-server(at)matronics.com [mailto:owner-zenith-list-server(at)matronics.com] On Behalf Of 601corvair

 Sent: Saturday, April 14, 2007 8:49 AM

 To: Zenith list

 Subject: fuel system suggestions  

  

    	  Quote: 	
		  Ok guys I have a questions for the group about fuel systems that my EAA technical advisor (TA) asked us.  First some background.  Our advisor has built and flown behind many aircraft.  He has restored several classic aircraft, is a retired airline captain and currently spends his days flying corporate and running an airport.  He is the kind of guy who has, or will, fly behind everything he suggests..  Our project is a Zenith 601 HDS that has 2 ten gallon leading edge wing tanks.  It currently calls for a plain vanilla corvair engine and an MA3 carb.  TA has warmed to the idea of Corvair, although he is not crazy about it.  He has helped people in the past with other auto-conversion and was helpful, but not overly enthusiastic.  All that being said, here is the issue.  During a conversation on fuel system design we showed him the William Wynne (www.flycorvair.com) design for the Zenith XL, using the 2 in series electrical pumps and no mechanical pump.  He recommended against it on the principle that we had placed all our eggs in the one basket, that being the electrical system.  His suggestion was to use one electrical pump and the corvair mechanical pump and fly it like a Cherokee using the electrical pump as a boost pump and only during take off and landing.  Alternatively, he suggested a header tank, pumping fuel to the header and gravity feeding the carb.  This would probably require a return line to the wing tank.   We discussed this for sometime and then he asked me this.  Could I name a certificated aircraft, low wing, that only had one type of pump to move fuel to the carb?  If not, why did I think that was?  Interesting question as the FAA guys “fly behind” lots of airplanes.  I would be interested in any help or suggestion I can get with fuel systems, especially flying airplanes and their different fuel systems.  Thanks phill 	
    

   

  

        

  

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 Check out [url=http://us.rd.yahoo.com/evt=48245/*http:/autos.yahoo.com/new_cars.html;_ylc=X3oDMTE1YW1jcXJ2BF9TAzk3MTA3MDc2BHNlYwNtYWlsdGFncwRzbGsDbmV3LWNhcnM-]new cars at Yahoo! Autos.[/url]    	  Quote: 	
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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Sat Apr 14, 2007 10:05 am Post subject: fuel system suggestions

Certificated aircraft use magneto ignition systems that don't rely on  

the electrical system to operate. With a mechanical pump, these  

engines can continue run if the entire electrical system fails.  

That's why they have mechanical pumps. They have electric pumps to  

push the air out of the lines and get fuel to the mechanical pump and  

carb to allow the engine to start and continue to run in the nose  

high attitude during climb.



I assume you have an automotive type ignition system that relies on  

electrical power to drive it. In that case, it doesn't matter that  

both of your pumps are electric. If you lose the electrical system,  

and that's about the only way you could lose both pumps, you are a  

glider pilot anyway.



Electric fuel pumps are more reliable than mechanical pumps. With  

electric pumps, you can locate them so that you are always pushing  

fuel up to the engine. Mechanical pumps must be mounted to the engine  

where they will be sucking fuel up to the engine from the low-wing  

mounted tanks. If you can avoid drawing a vacuum on the fuel lines,  

you have a very low risk for vapor lock, especially with auto fuel.  

You can always install a backup battery to run the pumps and ignition  

if the main system fails.



Personally, I would put the pumps in parallel using a couple of Tees  

just so you aren't pushing (or sucking) fuel through the inoperative  

pump.

On Apr 14, 2007, at 11:48 AM, 601corvair wrote:



 	  Quote: 	
		     He recommended against it on the principle that we had placed all  

 our eggs in the one basket, that being the electrical system.

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

larry(at)macsmachine.com
Guest

Posted: Sat Apr 14, 2007 10:50 am Post subject: fuel system suggestions

Hi Phil,

Wing tanks are good in the HDS. The header tank does cause you to think 

about current range as you use

and refill it from the wing tanks. You have to be comfortable with the 

tank being in front of you and it should

be built of .040 or better. I prefer a smaller 9-1/2 gal header for 

space behind the instrument panel.

Fuel pump issues are easily resolved with two pumps on the firewall in 

parallel and using one during cruise.

A pump on each wing tank simplifies selective filling with a 

left-right-both-off valve at the center console.

I wouldn't put a mechanical pump on the Corvair as I've replaced too 

many mechanical pumps, but not

one electric pump. You shouldn't need a return line to the wing tanks 

unless you're going high pressure

for fuel injection. I don't recommend it for the complexity it 

represents. Carburetors are just simpler.

The Corvair is a good engine and won't let you down if you keep fuel 

delivery simple and adhere to WWs

crank recommendations etc. Auto conversions can be extremely reliable if 

you stay with current best practice.

I disagree on electrical pumps placed in series as one could either 

starve or clog the second one. In parallel

they are each free to feed or not selectively. My HDS is set up this way 

and has nearly 100 hours

running without problems. You'll find most of this is well covered in 

the archives.



Good luck,



Larry McFarland 601HDS at www.macsmachine.com

do not archive





601corvair wrote:

 	  Quote: 	
		     Our project is a 

 Zenith 601 HDS that has 2 ten gallon leading edge wing tanks.  It 

 currently calls for a plain vanilla corvair engine and an MA3 carb.  TA has

  

 warmed to the idea of Corvair, although he is not crazy about it.  He has 

 helped people in the past with other auto-conversion and was helpful, 

 but not overly enthusiastic.  All that being said, here is the issue.  

 During a conversation on fuel system design we showed him the William Wynne (www.flycorvair.com) design

  

 for the Zenith XL, using the 2 in series electrical pumps and no 

 mechanical pump.  He recommended against it on the principle that we

  had placed all our eggs in the one basket, that being the electrical 

 system.  His suggestion was to use one electrical pump and the corvair 

 mechanical pump and fly it like a Cherokee using the electrical pump as 

 a boost pump and only during take off and landing.  Alternatively, he 

 suggested a header tank, pumping fuel to the header and gravity feeding 

 the carb.  This would probably require a return line to the wing tank.   

 We discussed this for sometime and

  then he asked me this.  Could I name 

 a certificated aircraft, low wing, that only had one type of pump to 

 move fuel to the carb?  If not, why did I think that was?  Interesting 

 question as the FAA guys “fly behind” lots of airplanes.  I would be 

 interested in any help or suggestion I can get with

  fuel systems, 

 especially flying airplanes and their different fuel systems.  Thanks phill

  

 *



 *

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