REFLECTOR: No management fuel systems

Sat Jan 14 07:50:31 CST 2012

I an in contact with Terry Schubert now ( actually last night) and we 
agree that the key here is the left fuel line and right fuel line 
are*/T'eed together./*  This is not the same as the sump system the 
Velocitys have, and I also have, in my Cozy for 20 trouble free years 
now.  I have written to Burt asking for a more detailed explanation of 
his letter.
When he replies I will post it on the Reflector.

Vance Atkinson
EAA Tech and Flt Advisor
COZY N43CZ
VEZ  N3LV

On 1/13/2012 5:13 PM, Lou Stedman wrote:
> I am a member of CSA and received this notice today. Is this something 
> that we Velocity drivers should be concerned with? Does the sump tank 
> take away this problem?
>
> *CSA Article Correction*
> /Terry Schubert CSA Newsletter Editor/
> CSA # 105 January 2012, page 23, /_No Management Fuel System_/ article 
> correction.
> Subsequent to January 2012 CSA issue mailing, I received e-mails from 
> both Burt Rutan and Mike Melvill. They both felt the /_No Management 
> Fuel System_/ was potentially dangerous. The common sump fuel system 
> fed by both tanks simultaneously could only be safely used on a 
> gravity system without a fuel pump.
> I had no idea that this fuel system was viewed as being so dangerous. 
> I stand corrected. The /_No Management Fuel System_/ author is an IA 
> and has built two Long-EZs and flown a couple thousand hours in them. 
> Another highly experienced Cozy builder I checked with has about the 
> same time in his Cozy with a similar system.
> Communication from Burt and Mike follow and explain the reason for 
> concern.
> ***************
> *_Email from Burt Rutan_*
> Terry and Mike,
> I do read the CSA newsletters to stay in touch a bit, even in retirement.
> What I saw in #105 may represent a serious safety issue. A builder is 
> recommending a "No Management Fuel system" by teeing together both 
> fuel tanks. While this may work ok for a while, it would be dangerous 
> if a fuel cap is lost or is not installed after fueling OR if there is 
> a leak in a fuel cap seal. What happens is that all the fuel is 
> transferred in flight to one side and dumps out the cap that is 
> missing or is leaking. This can cause engine failure.
> For reference, the VariEze had the "both" fuel system, with a tee at 
> the bottom of the fuselage. It works ok on a Cessna 150 where the tee 
> is a full 4 ft below the tanks. However, if the tee is only several 
> inches below the tanks, a small difference in tank vent pressure can 
> put air to the tee and fail the engine. There were several Varieze 
> engine failures due to loss of fuel cap, or leak of a fuel cap. For 
> the LongEz I designed a much safer fuel system, with sumps that 
> assured a low amount of unusable fuel and made sure the fuel could not 
> swap sides or vent overboard.
> Burt
> ***********
> *_Email from Mike Melvill_*
> Terry,
> Burt is not kidding about this. In a Long-EZ/Cozy the fuel tanks MUST 
> be switched separately, and must separately feed the engine. Teeing 
> them together is dangerous as hell! This teeing idea only works on 
> gravity fed systems with no fuel pump, can you say Cessna 15, C172 
> etc. Look around---all GA planes with two or more fuel tanks plus an 
> engine driven fuel pump have a fuel tank selector valve just as the 
> RAF plans call out. Do not ever change this or you will eventually 
> find yourself out of gas with one tank full, and no way to get to that 
> fuel. It has happened before to several EZ folk! Why is it that we 
> never learn from lessons learned? Please put a stop to this stupidity!
> The big point really is this; Aside from high wing, gravity fed planes 
> like the Cessna 150, there are _NO_ certified aircraft with two fuel 
> tanks or more _PLUS_ a fuel pump, that don't use a fuel tank selector 
> valve! None! The reason the FAA insists on a fuel selector valve in 
> such a plane is this: if a fuel cap is accidentally left off or has a 
> leaky 'O' ring seal, or for some reason comes off in flight, the 
> result is always the same. You will run out of fuel with one tank full!!
> This is due to the fact that the fuel caps are generally on top of a 
> wing where there is low pressure in flight due to the airfoil 
> providing lift. When a fuel cap is missing the fuel is sucked out of 
> this fuel tank. With no fuel valve, the fuel in the tank _with_ a cap, 
> is drawn across the 'T' at the low point (where the fuel selector used 
> to be) into the tank without a cap. The engine continues to run until 
> the tank still equipped with a fuel cap is empty. Then _you are out of 
> gas_ and the engine quits in spite of the fact that you have an 
> essentially full tank of fuel in the tank with _NO_ cap!! The fuel 
> pump starts sucking air from the now empty tank with the cap, and the 
> low pressure above the tank with _NO_ cap won't allow the fuel pump to 
> deliver the remaining fuel (usually a full tank) to the engine. Having 
> a fuel tank selector valve in a Long-EZ (as well as in all Cherokees, 
> all Cessnas bigger than C150's & on and on) prevents this problem from 
> happening. The bottom line is this: If you have more than one fuel 
> tank AND you have a mechanical engine driven fuel pump, you must have 
> a fuel tank selector valve!
> This exact scenario happens to Cessna 150's as well as to Variezes if 
> they loose one fuel cap! In a gravity fed fuel system such as C150 & 
> Varieze with _no_ fuel selector, this problem can't be fixed. That is 
> why it is so important to remember to replace the fuel caps on gravity 
> fed planes!) Wes and Milly Gardner had this happen to them and I 
> believe we talked about this back then in the CP.
>
> Mike
>
>
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> __,_._,___
> Lou Stedman
> Velocity SEFG
> N7044Q
> Olean, NY
>
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