REFLECTOR: No management fuel systems

Sat Jan 14 08:31:41 CST 2012

I respect mike Melville but the is a lot of miss information in his letter about there being no tee'd certified systems with fuel pumps.  Or maybe I read it wrong.

vance atkinson <nostromo56 at tx.rr.com> wrote:

>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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