REFLECTOR: No management fuel systems
Scott Derrick
scott at tnstaafl.net
Sat Jan 14 09:14:18 CST 2012
I've flown without a fuel cap, for 45 minutes, no loss of fuel, no problem except my utter surprise when putting the plane away and seeing the missing cap.
John Dibble <aminetech at bluefrog.com> wrote:
>Maybe that's why the builder of my plane installed over flow vents in
>each tank that face forward which pressurizes the tanks. Of course
>valves are not entirely safe either (John Denver). Doesn't the
>alternate vent prevent this problem? Anyone have experience with a
>leaking fuel cap?
>
>John
>
>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 RutanTerry 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 MelvillTerry, 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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