Simon Smith a crit :
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>See http://www.europa-aircraft.biz/pdfs/914xs.pdf
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Simon,
Thank you for the link. Now I get it !
The behavior of your system is quite normal, considering the way it is
set up.
Normal operation (pump 1 is assumed to be primary pump)
Pump 1 draws fuel through filter 1, then pushes it through check valve 2.
Takeoff/landing : both pumps on
Pump 1 draws fuel through filter 1, then pump 2 adds pressure to the
already pressurize fuel downstream of pump 1.
Pressure downstream of check valve 1 is the same as downstream of pump
1, so the fuel has no reason to flow through check valve 1 and filter 2.
Emergency : pump 1 unserviceable
Pump 2 draws fuel via check valve 1 and filter 2.
This seems a bizarre setup, where filter 2 is only there for a ride,
except in the rare event of a primary pump failure. But there is nothing
wrong with it, provided you have a drainable sump in the tank, and a
drainable gascolator aupstream of the pumps.
By the way, the fuel pickup points appear to be at the front tank
bulkhead, whereas they would be much more wisely located at the REAR of
the tank, for the sake of nose-high fuel supply.
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
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