how should I vent my header tank ?

[EDMO 1078]

Paul S.,

      "Am I missing something?"

Yes Paul, you are missing FLAPS!  With good flaps, you don't need to slip except for a crosswind.    But I get your point about no fuel from tank to engine from the low wing.

I really don't want to find out the hard way, but I wonder what happens if you get a large air bubble going to the fuel pump - I don't think they pump air very well.

 On our diesel engines, if we got an air bubble in the lines to the cylinders we had to loosen all the fittings and bleed the air out to get them started - you could run down the battery cranking the starter and no fuel would ever get to the engine without getting the air out.

EDMO

[marksires 484]

Ed, it was on the ground, not flying, but after having the engine overhauled, I didn't have anything but air in the lines (and the header tank - I drained everything while the engine was off).  The electric fuel pump with the 1 tank and inline header tank cleared the air just fine.

I did find in the Avid newsletters an update on the header vent that is pretty much what you described, except they changed it from a forward facing vent to an upside down 'U' shaped, so there would be neither negative or positive pressure from the vent.

 

I also found that hangar I picked my plane up from was the president and owner of Avid (Charlie) at the time they bought the kit in built it.  The two guys that built it lived in the same area as Charlie, and after they bought the kit from him he let them rent hangar space from him.  That explains why there was so much Avid stuff in that hangar!

 

Mark

[marksires 484]

Here is the page from the April 1992 newsletter with the vent update.

Mark

 

April_1992_page4_ventdiagram.pdf

[1avidflyer 1983]

Just looked at that file, and see they show a filter in the fuel line between the wing tank and the header tank.  I had to land in a neighbors field one time with my MK IV and when I talked about it on the list, Steve Winder said that it was a big no no to put a fuel filter in that line.  It's just gravity feed at that point, and a filter doesn't have to be very plugged to restrict the flow to the header tank.  I had a filter in the line, and it started to plug  and when the header tank started to run empty at 450', the engine would only maintain about 4500 RPM.  That got the adrenalin going!  More trees than fields around my strip.  Header tank works as a good filter/gascolator and if one puts a filter in between it and the fuel pump, you have all you should need for filters.   Jim Chuk

[EDMO 1078]

Mark,

     Thanks for the fuel pump info.

The vent you talked about was posted from someone else.   I only know about the kind of vent that Kitfox uses that goes back to the upper part of the fuel tank.   I know it works well, and can double as a sight tube in level flight - also as a "Panic Tube" as you do a slip and watch the fuel level going down fast and knowing there is no fuel coming from the wing and you only have what is in the header tank.

EDMO

[EDMO 1078]

I wanted to get dramatic, and say that you are doing a side slip to get into your landing spot since you have gotten too high on final, and there are trees on the left, wind from the right, and only a narrow canyon with all right turns as you miss your approach - But, that wouldn't be realistic - Would it....?

Maybe I should have said "Deep Valley" instead of canyon, for us flatlanders and Hill-Williams - Canyon conjures up pictures of steep rocky sides, and the deep valleys are more like grass and tree covered hills - either would be the same scenario of only having access to the gas in the header tank.

EdMO

Edited 14 Oct 2014 by Ed In Missouri