REFLECTOR: No management fuel systems
John Dibble
aminetech at bluefrog.com
Sat Jan 14 08:49:16 CST 2012
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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