Antonio wrote:
I see, so a similar purpose as a standard boost pump, only manual
Yes, but with a separate filter.
I think the Christen 844 wobble pump commonly used on Pitts and the like does the same thing.
Frank Christensen did this and his inverted oil system before he developed and marketed the Eagle aircraft.
I see, so a similar purpose as a standard boost pump, only manual
Antonio wrote:
So there is no selector valve on the Savannah, just a permanent “both” ?
Or ON and OFF 
Both at the same time yes.
Antonio wrote:
As to the handpump, well, it seems to have a third enigne-driven pump so it should only be necessary for emergencies and perhaps to prime the carburetor if dry for startup…right?
There’s only one engine driven pump, number 6 in the picture. Number 9 is two filters, one with the hand pump. You can se it better (and explained) below. The fuel lever is main, reserve, off. The hand pump is used to pump up the fuel pressure when starting, and in an emergency if the engine pump should stop.
So you notice you are ready for reserve when your engine stops, just like your moped!
What works on a motorcycle with a similar reserve arrangement is two fuel valves installed on the same tank, each independently supplying only a portion of the engine’s cylinders. That way it doesn’t ever quit completely and you switch both fuel valves to reserve as half the engine starts to misfire. With experience you can do it before anybody else would notice any misfire, a beautiful thing 
A friend of mine was once flying a passenger in a biplane out of a small polo field in a built up area when the carburetor decided that it would a good time to fall off the engine. He made it back and landed using the hand primer pump to keep the high inertia prop turning with bursts of power. After landing the passenger jumped out and said it was a great ride. He said nothing.
So there is no selector valve on the Savannah, just a permanent “both” ?
LeSving wrote:
Main and reserve. As can be seen from the drawing, it’s the same tank, only the main inlet is further up, just like a moped
That is a good one! So you notice you are ready for reserve when your engine stops, just like your moped! Thinking again, not that different, functionally, from your garden variety Piper or our Cessna 210!
As to the handpump, well, it seems to have a third enigne-driven pump so it should only be necessary for emergencies and perhaps to prime the carburetor if dry for startup…right?
Antonio wrote:
Also interesting the shroud around the tank …this is very much like large aircraft, but is it really useful in the Decathlon?
I’m not sure why it’s there. Crash resistance I guess? I know the Piper Pawnee had something similar. It started with a glass fiber tank in front of the cockpit. Due to fires at crashes, they installed a vinyl bladder. Later it got wing tanks. I flew this vinyl bladder empty ones
The check valve is to prevent fuel from draining out through the vent line when inverted. The drawing is really bad though. The exit to the engine is as shown, as a pipe from the middle of the tank. When upside down the fuel lines become the vent lines, but it doesn’t look like that in the drawing. The standard RV inverted system is a floppy tube in one of the tanks. A bit simpler than the header tank arrangement (one less tank and a hole bunch of fittings and fuel tubes less).
The standard Rotax arrangement is always with a fuel return line to (one of the) tank(s). This is the fuel system of the Savannah It has a “header” tank of 6l and the engine return line to the right tank. The header tank also work as a reserve. It’s connected to a warning light. When it is lit, there is precisely 6l left, which is good for 1/2 h on moderate power.
The fuel system on the Saab Safir is also cool. Dead simple, but works like nothing else. It has “two” tanks. Main and reserve. As can be seen from the drawing, it’s the same tank, only the main inlet is further up, just like a moped. It also has a hand pump. If the main pump fails, then hand pump can be used (or so manual say, I have never tried it )
Well, in this case a header tank is a must if you want to maintain power and altitude in negative g!
Interesting that there is also a check valve in the hdr tank vent line. Also interesting the shroud around the tank …this is very much like large aircraft, but is it really useful in the Decathlon?
LeSving wrote:
up/down/sideways is not clear
I also got my LH/RH reversed on the 210 diagram but we get the idea: don’t use a BOTH fuel selector on your RV6!
Interesting these fuel systems. This is the Super Decathlon inverted (for a minute or two at least ) The drawing is a bit awkward, up/down/sideways is not clear, but the basics are OK. It’s a header tank that is (also) used as an inverted tank.
